Listen

In recent years industrialization has caused magnificent leaps in the high profitable growth of pharmaceutical industries, and simultaneously given rise to environmental pollution. Pharmaceutical processes like extraction, purification, formulation, etc., generate a large volume of wastewater that contains high chemical oxygen demand (COD), biological oxygen demand, auxiliary chemicals, and different pharmaceutical substances or their metabolites in their active or inactive form. Its metabolites impart non-biodegradable toxic pollutants as a byproduct and intense color, which increases ecotoxicity into the water, thus this requires proper treatment before being discharged. This study focuses on the feasibility analysis of the utilization of ultrasound cavitation (20 kHz frequency) together with a persulfate oxidation approach for the treatment of complex pharmaceutical effluent. Process parameters like pH, amplitude intensity, oxidant dosage were optimized for COD removal applying response surface methodology-based Box–Behnken design. The optimum value observed for pH, amplitude intensity and oxidant dosage are 5, 20% and 100 mg/L respectively with 39.5% removal of COD in 60 min of fixed processing time. This study confirms that a combination of ultrasound cavitation and persulfate is a viable option for the treatment of pharmaceutical wastewater and can be used as an intensification technology in existing effluent treatment plants to achieve the highest amount of COD removal.

Listen

  • Synergistic effect of ultrasonication and persulfate oxidation studied on pharma wastewater.

  • Box–Behnken method applied for process parameter optimization.

  • Significant reduction in the COD from the pharma wastewater within one hour of the reaction.

  • Potential choice for the implementation of the process as a pre-treatment option for wastewater treatment.

Box–Behnken design, cavitation, optimization, persulfate, pharmaceutical wastewater, ultrasound
Listen

Environmental pollution is one of the global challenges of today's world (Spina et al. 2012; Singh & Prashant 2017). Industrial effluent and other hazardous discharges from industries are one of the prime concerns for developing countries like India. In India, one-third of water pollution in natural water bodies and marine pollution are induced by industrial wastewater (Kansal et al. 2013; Singh & Prashant 2017). At this time, high amounts of pharmaceutical substances are used for the protection and cure of diseases for humans and animals, which lead to the generation of huge quantities of wastewater from pharmaceutical industries (Mohapatra et al. 2014; Ghafoori et al. 2015). The USEPA reported the daily effluent produced from the pharmaceutical unit as 1.0068 × 109 L (Adishkumar et al. 2012). These effluents contain highly biologically active compounds which can cause damage to health in humans and animals, as well as promoting the development of antibiotic resistance genes, and interrupts the ecological balance of the aquatic environment by initiating irreversible transformation to aquatic fauna (Ng et al. 2014; Tiwari et al. 2020). Industrial wastewater quality is estimated, based on the amount of organic matter present, as COD, total carbon, BOD, and wastewater quality parameters. The wastewaters produced from pharmaceutical sectors are complex and hazardous with high COD, BOD, solids containing supplementary chemicals, and pharmaceutical secondary metabolites leading the wastewater to be classified under the ‘red category’ (Gadipelly et al. 2014; Changotra et al. 2017, 2019; Martínez et al. 2018).

Pharmaceutical wastewater contains a large amount of recalcitrant or bio-refractory molecules which are very difficult to degrade through conventional treatments. Hence, most is converted into other complex by-products as fluoxetine and endocrine disruptors, which has resulted in a multitude of undesirable problems like harm to reproduction and metabolism of aquatic organisms and feminization of fish populations (Ford & Fong 2016; Huang et al. 2016; Thanekar & Gogate 2019). Thus it is necessary to treat pharmaceutical wastewater efficiently before discharging it into any water bodies to avoid further damage to the environment and ecosystem, it also pollutes water bodies (Gadipelly et al. 2014; Changotra et al. 2017, 2019; Singh & Prashant 2017; Martínez et al. 2018).

Treatment processes like biological oxidation require longer time because they have a slower reaction rate (Crini & Lichtfouse 2019). Chemical coagulation is useful for removal of pollutant in the form of colloidal or suspended particles that do not settle rapidly, it requires a longer retention time and more sludge production (Verma et al. 2012). Adsorption reactors rapidly becomes less effective due to clogging and their regeneration are not cost-effective, hence, this decreases the acceptance of a certain type of metal molecule (Crini & Lichtfouse 2019). These demerits of treatment, make it not efficient to remove all hazardous compounds effectively from pharmaceutical wastewater (Jeworski & Heinzle 2000; Ayare & Gogate 2019). In recent times advanced oxidation processes (AOP) such as Fenton oxidation (Singh et al. 2013), ozonation (Cortez et al. 2010), ultraviolet/hydrogen peroxide (Hu et al. 2011), and ultrasound cavitation (Gągol et al. 2018) have been considered as a useful process for treatment of bio-refractory pollutants (Yang et al. 2015). Among the different AOP the ultrasound cavitation-based process has been seen as a promising process for the oxidation of various pollutants in industrial wastewater. The principle behind the ultrasonication process is the pressure variation in liquid caused by inducing ultrasound which produces cavitation for the treatment of wastewater (Thanekar & Gogate 2019). Cavitation occurs due to pressure difference in the outer flow and the pressure induced inside the system by sound waves as system pressure decreases or increases in flow velocity, which produces small cavities; with time these start to grow longer compared with higher system pressure (Dular et al. 2016). Furthermore, variation in pressure leads to cavity formation, growth, and collapse at the micro-scale duration. These three stages occur during the ultrasound cavitation process which leads to the generation of free radicals and releases a large amount of energy. This energy can be up to 5,000 K temperature and 1,000 Atm pressure in wastewater known as a ‘local hotspot’ which can be extremely suitable for the oxidation of pollutants (Leighton 1995; Thanekar & Gogate 2019). The main advantage behind this treatment is it does not require any chemicals to promote oxidation, no sludge formation, no visible light requirement (Vega & Peñuela 2018) and it breaks up the agglomerates (Jordens et al. 2016; Dong et al. 2020). In the same way, the presence of reactive nitrogen such as NO3, NO2, NO or degradation of other organic pollutants that contain nitrogen species forms nitrate radicals (⁠⁠), nitrite radicals (⁠⁠), and nitrogen oxide radicals (⁠⁠), etc. These reactive nitrogen radicals participate in redox reactions as well and help in the nitration reaction of the pollutants (Rayaroth et al. 2022). Ultrasound cavitation is useful for the treatment of active pharmaceutical compounds (Tran et al. 2015; Serna-Galvis et al. 2019; Estrada-Flórez et al. 2020), such as carbamazepine, diclofenac, ciprofloxacin (Beckett & Hua 2001; Rayaroth et al. 2016), and the tetracycline antibiotic (Soltani et al. 2019). Ultrasound cavitation accelerates the degradation of pollutants in combination with other oxidation processes like Fenton's reagent (Zhang et al. 2016), zinc oxide, the zinc oxide nanotube catalytic process (Soltani et al. 2019), hydrogen peroxide (Chandak et al. 2020), carbon tetrachloride, and persulfate ions (Anipsitakis & Dionysiou 2003) to generate radicals (Rayaroth et al. 2016). The persulfate dissociation can also occur due to high localized temperature developed by the ultrasound system (Wei et al. 2017). The combination of persulfate oxidation with the ultrasound cavitation system has been less studied by other research groups (Monteagudo et al. 2015, 2018; Wang & Zhou 2016). An alternative to hydrogen peroxide, persulfate ion has gained more attention due to the increased interest in the higher redox potential of sulfate radicals (2.5–3.1 V) compared with hydroxyl radicals. The hydroxyl radicals prefer to react by addition, hydrogen atom abstraction, as well as through electron transfer mechanisms, while prefer to react through electron transfer mechanisms, which makes them selective towards electron-donating groups such as amino (-NH2), hydroxyl (-OH), alkoxy (-OR), amino (-NH2), alkoxy (-OR), π electrons of aromatic compounds, and unsaturated bonds (Fedorov et al. 2020):
(1)

The formation of sulfate radical occurs by breakage of the O-O bond of persulfate ions using different activation methods like heat (Tan et al. 2012), transitional metals (Liu et al. 2016), ultraviolet light (Xie et al. 2015; Arvaniti et al. 2020), ultrasound (Zou et al. 2014; Yang et al. 2019), and other means as shown in Equation (1) (Arvaniti et al. 2020). The homogeneous and heterogeneous catalytic activation of persulfate by using cobalt or manganese oxides, etc., has been studied by many researchers (Liang et al. 2012; Yuan et al. 2020). Among them, activation by ultrasound acts as an emerging method and is typically used for pharmaceutical wastewater treatment (Zou et al. 2014; Yang et al. 2019). The synergistic effect of combined cavitation and the persulfate process has been studied by Fedorov et al. (2022) and has computed the synergistic index for different combined process. The synergistic index of combined cavitation and persulfate varied from 1.52 to 4.43 for different pollutants (Fedorov et al. 2022). Therefore, it is significant to use a combined process for the treatment of pharmaceutical wastewater to achieve increased removal.

In the combined process multiple operating parameters influence or affect the removal efficiency. For complex systems governed by several parameters, generally, use of one parameter optimization at a time could provide misinterpretation due to lack of interaction effects, thus the Design of Experiment (DoE) is an effective tool for optimization. There are various DoEs available for optimization of parameters by reducing the number of experiments and cost (Dopar et al. 2011) like the Box–Behnken method for response surface methodology (RSM) which is a powerful design tool for modeling complex conditions (Tak et al. 2015). This tool estimates the relation between manageable input parameters and response variables (Khorram & Fallah 2018).

This study focuses on the combined effect of ultrasound cavitation and persulfate oxidation on the treatment of pharmaceutical wastewater. The synergistic effect of the combined process was investigated along with the effect of biodegradability of the combined process. The major process influencing factors of the combined ultrasound–persulfate process like pH, amplitude intensity, persulfate dosage, reaction time were investigated for their individual and the combined effects by using Box–Behnken design as an RSM for the treatment of pharmaceutical wastewater. The effect of reactive radicals on the removal of pollutants was investigated through scavenging tests.

Listen

Industrial wastewater

Listen

A wastewater sample of 40 L was collected from the pharmaceutical industry from Bharuch, Gujarat, India. Collected samples were stored in a refrigerator at 4 °C to avoid further biodegradation.

Chemicals

Listen

In this study, chemicals of analytical grade were used for the entire experimental process: potassium persulfate purity 98% purity, potassium dichromate 99% purity, mercury sulfate 98% purity, silver sulfate 98% purity, ammonium ferrous sulfate 99% purity, manganous sulfate 98% purity, ferric chloride 98% purity, di-potassium hydrogen phosphate 99% purity, potassium iodide 99% purity, potassium hydroxide 85% purity, sodium thiosulfate 98% purity were procured from M/s Merck India. Sulfuric acid of 98% purity, ferroin indicator, calcium chloride 96% purity, magnesium sulfate 99% purity, starch as an indicator were procured from M/s Finar India. All the required reagents were prepared using double-distilled water. For ultrasonic cavitation, a 20 kHz frequency probe-type sonicator made of Ti6Al4V titanium alloy with maximum power output of 750 W was used with a microprocessor-based programmable probe (Model No. VCX 500 with 17 mm solid probe diameter) and procured from Sonics Vibracell, USA.

Design of experiment (DoE)

Listen

Design-expert software was used to prepare DoE. The removal of organic matter from pharmaceutical wastewater was optimized using Box–Behnken design as RSM. Table 1 represents its coded and real value for lower level (−1), mid-level (0), high level (+1) for removal of organic matter as COD. Table 2 provides the details of a different combinations of experimental runs for the considered parameters pH (A), amplitude intensity% (B), persulfate dosage (C). The experimental range for the parameters was decided based on published literature.

Table 1

Coded and real values of the factors selected for Box–Behnken design

FactorsLow levelMid-levelHigh level
− 101
pH (A) 2 5 8 
Amplitude intensity % (B) 20 50 80 
Dosage (mg/L) (C) 100 250 400 
FactorsLow levelMid-levelHigh level
− 101
pH (A) 2 5 8 
Amplitude intensity % (B) 20 50 80 
Dosage (mg/L) (C) 100 250 400 
View Large
Table 2

Box–Behnken design

Experimental runspHAmplitude (%)Persulfate dosage (mg/L)COD remaining (mg/L)
1 2 50 100 11,200 
2 2 50 400 12,480 
3 5 80 100 10,944 
4 2 80 250 10,880 
5 5 50 250 9,440 
6 5 50 250 9,440 
7 5 20 100 8,320 
8 8 50 100 12,640 
9 8 80 250 12,640 
10 5 20 400 12,800 
11 8 20 250 12,800 
12 5 80 400 11,680 
13 8 50 400 12,960 
14 5 50 250 12,320 
15 2 20 250 11,200 
Experimental runspHAmplitude (%)Persulfate dosage (mg/L)COD remaining (mg/L)
1 2 50 100 11,200 
2 2 50 400 12,480 
3 5 80 100 10,944 
4 2 80 250 10,880 
5 5 50 250 9,440 
6 5 50 250 9,440 
7 5 20 100 8,320 
8 8 50 100 12,640 
9 8 80 250 12,640 
10 5 20 400 12,800 
11 8 20 250 12,800 
12 5 80 400 11,680 
13 8 50 400 12,960 
14 5 50 250 12,320 
15 2 20 250 11,200 
View Large

Mathematical representation of selected process parameters to the estimation of the dependent response y (COD removal) by coded terms is as mentioned below, by general model regression Equation (2):
(2)
where, y is a response, β0 is the linear, quadratic and regression constant, βj, βjj and βij represent the coefficients for linear, quadratic, and second-order interaction effects, respectively. xj and xi represent the coded independent process variables.

Experimental procedure

Listen
All experiments were conducted in a cylindrical batch glass reactor with 250 mL of working volume (capacity of 500 mL). The schematic diagram of the experimental process reactor is shown in Figure 1. The temperature of the sample was maintained at 50 ± 10 °C for the heat-based activation of persulfate (Ahmadi et al. 2019), with ultrasound and the pH was adjusted using nitric acid (1 N) and sodium hydroxide (1 N). Ioannidi et al. (2022) reported an acceleration in degradation of pollutant when the temperature of the wastewater was increased from 40 °C to 60 °C, whereas in the current study the external heating of wastewater was not done, instead the temperature of the water was maintained within the 50 ± 10 °C range through a water circulation method. The addition of sulfate ions in the advanced oxidation process will convert the ion to sulfate radicals. The sulfate radicals generated through the addition of sulfate ion may oxidize the organic matter over the persulfate-generated sulfate radical. Thus, to study the efficiency of persulfate radicals on wastewater treatment, the addition of sulfate ions (sulfuric acid) was restricted and instead nitric acid was used. The persulfate dosage was added according to the real value of factors suggested by DoE. All 15 experimental runs were conducted according to values suggested by DoE. All the experiments were duplicated twice to check their reproducibility, a ±10% change in results was accepted and the experiments were repeated when the deviation in results was beyond ±10%. Treated samples were withdrawn during the experiment at a time interval of 15, 30, and 60 min and analyzed for COD. The COD of the sample was analyzed as per the standard method using the closed reflux method. The synergistic effect of the combined process (ultrasound cavitation and persulfate oxidation) was analyzed using Equation (3) (Rokhina et al. 2008; Li & Zhu 2016). The synergistic index of the combined process can be determined by comparing the removal efficiency of the stand-alone process (RRultrasoundcavitation, RRpersulfate oxidation) with that of the removal efficiency of the combined process (RR):
(3)
where,
Figure 1
Schematic diagram of the experimental process.
View largeDownload slide

Schematic diagram of the experimental process.

Figure 1
Schematic diagram of the experimental process.
View largeDownload slide

Schematic diagram of the experimental process.

Close modal

RR – Removal rate of COD for the combined process

RRultrasound cavitation – Removal rate of COD for stand-alone ultrasound cavitation treatment

RRpersulfate oxidation – Removal rate of COD for stand-alone persulfate oxidation treatment.

If the synergistic index of the combined process is equal to one (SI = 1), the effect is called an additive effect. If SI > 1 the combined process effect is much greater than the sum of the sole process effect, this is called a synergistic effect and if SI < 1 the effect is termed as antagonism (Li & Zhu 2016).

Listen

Characteristics of pharmaceutical wastewater

Listen

Characterization of the pharmaceutical wastewater was done as per the APHA standard methods (Rice et al. 2012) and given in Table 3. The COD and BOD of the wastewater were 13,760 mg/L and 5,500 mg/L respectively with a BOD/COD ratio of 0.4.

Table 3

Characteristics of pharmaceutical wastewater

ParameterConcentration in mg/L (except pH)
pH 7.6–7.8 
Chloride 174.9 
Total solids 25,570 
Total organic carbon 2,815 
Biological oxygen demand 5,500 
Chemical oxygen demand 13,760 
BOD/COD 0.4 
ParameterConcentration in mg/L (except pH)
pH 7.6–7.8 
Chloride 174.9 
Total solids 25,570 
Total organic carbon 2,815 
Biological oxygen demand 5,500 
Chemical oxygen demand 13,760 
BOD/COD 0.4 
View Large

Analysis of variance (ANOVA)

Listen

The ANOVA in Table 4, provides the details of various coefficient values of process parameters and other details for COD removal from pharmaceutical wastewater with ultrasound cavitation treatment. The table shows that the model (Fischer test value) F-value is 9.42 and it shows the model value is significant as the P-value is less than 0.05, which implies that the model is significant. The significance of the P-value fixes the error probability of the regression co-efficient as significant. For optimized conditions of parameters quadratic and some of the interaction terms are significant, the parameter pH (A) is slightly significant, another parameter persulfate dosage (C) is significant, an interaction effect of amplitude intensity (B) and persulfate dosage (C), is also significant concerning model terms. According to the ANOVA, if the P-value of selected parameters is less than 0.05 (i.e. P < 0.05) then selected parameters are significant for the process efficiency, and when the P-value of parameters is greater than 0.05 (P > 0.05) then selected parameters are insignificant for the process efficiency. Table 5 gives the comparison of results between the predicted and experimental under different test conditions. The experimental results are comparable with the predicted with an error percentage variation of 0–30% under different parametrical conditions.

Table 4

ANOVA results for the obtained regression equations

SourceSum of squaresdfMean squareF-valueP-value
Model 3.115E + 07 9 3.461E + 06 9.42 <0.050 Significant 
A – pH 1.843E + 06 1 1.843E + 06 5.02 0.0652 Slightly significant 
B – Amp (%) 1.191E + 05 1 1.191E + 05 0.3241 0.5938  
C – Dosage 3.942E + 06 1 3.942E + 06 10.73 <0.050 Significant 
AB 4.096E + 05 1 4.096E + 05 1.11 0.3393  
AC 6.400E + 05 1 6.400E + 05 1.74 0.2441  
BC 5.345E + 06 1 5.345E + 06 14.55 <0.050 Significant 
A² 1.726E + 07 1 1.726E + 07 46.98 0.0010  
B² 1.150E + 06 1 1.150E + 06 3.13 0.1371  
C² 1.903E + 06 1 1.903E + 06 5.18 0.0719  
Residual 1.837E + 06 5 3.674E + 05    
Lack of fit 1.837E + 06 3 6.123E + 05    
Pure error 0.0000 2 0.0000    
Cor total 3.299E + 07 14 R2 = 94.43%    
SourceSum of squaresdfMean squareF-valueP-value
Model 3.115E + 07 9 3.461E + 06 9.42 <0.050 Significant 
A – pH 1.843E + 06 1 1.843E + 06 5.02 0.0652 Slightly significant 
B – Amp (%) 1.191E + 05 1 1.191E + 05 0.3241 0.5938  
C – Dosage 3.942E + 06 1 3.942E + 06 10.73 <0.050 Significant 
AB 4.096E + 05 1 4.096E + 05 1.11 0.3393  
AC 6.400E + 05 1 6.400E + 05 1.74 0.2441  
BC 5.345E + 06 1 5.345E + 06 14.55 <0.050 Significant 
A² 1.726E + 07 1 1.726E + 07 46.98 0.0010  
B² 1.150E + 06 1 1.150E + 06 3.13 0.1371  
C² 1.903E + 06 1 1.903E + 06 5.18 0.0719  
Residual 1.837E + 06 5 3.674E + 05    
Lack of fit 1.837E + 06 3 6.123E + 05    
Pure error 0.0000 2 0.0000    
Cor total 3.299E + 07 14 R2 = 94.43%    
View Large
Table 5

ANOVA analysis results

Coded factors
COD removal
Experimental runspHAmplitudePersulfate dosage (mg/L)Experimental (%) removalPredicted (%) removal
1 2 50 100 19% 22% 
2 2 50 400 8% 6% 
3 5 80 100 20% 20% 
4 2 80 250 21% 19% 
5 5 50 250 31% 32% 
6 5 50 250 31% 32% 
7 5 20 100 39% 36% 
8 8 50 100 7% 9% 
9 8 80 250 8% 7% 
10 5 20 400 7% 8% 
11 8 20 250 7% 10% 
12 5 80 400 21% 26% 
13 8 50 400 8% 5% 
14 5 50 250 31% 32% 
15 2 20 250 10% 12% 
Coded factors
COD removal
Experimental runspHAmplitudePersulfate dosage (mg/L)Experimental (%) removalPredicted (%) removal
1 2 50 100 19% 22% 
2 2 50 400 8% 6% 
3 5 80 100 20% 20% 
4 2 80 250 21% 19% 
5 5 50 250 31% 32% 
6 5 50 250 31% 32% 
7 5 20 100 39% 36% 
8 8 50 100 7% 9% 
9 8 80 250 8% 7% 
10 5 20 400 7% 8% 
11 8 20 250 7% 10% 
12 5 80 400 21% 26% 
13 8 50 400 8% 5% 
14 5 50 250 31% 32% 
15 2 20 250 10% 12% 
View Large

A mathematical representation of the independent variable to the dependent response by coded terms shown by this Equation (4):
(4)

From the above equation, it is noticed that there is a positive effect of linear terms on COD removal except persulfate dosage (C). With the change in linear terms, the COD removal changes according to its coefficients. The quadratic terms with a negative sign show a negative impact on COD removal. This means that an increase in the values of the quadratic coefficient will decrease the removal of the COD removal. Other interaction terms (AB, AC, BC) have mixed responses on the COD. The term with interaction (BC and AC) with persulfate dosage (C) will increase COD removal. Negative quadratic terms in Equation (2) indicate that the reduction in COD removal has been quadratic.

For the identification order of each process parameter and its effect while keeping the other process parameters constant indicated in perturbation plots, Figure 2 then factors sensitivity on COD removal, which is indicated by the nature of the curve for each process parameter and the factor with more slope has more noticeable effects on COD removal (Muthukumaran et al. 2017; Milano et al. 2018). The plot shows that factor B has a prominent effect on COD removal followed by A and C, similar to that reflected in the table for ANOVA.
Figure 2
Profile of perturbation plot showing significant parameters affecting COD removal with factors pH (curve A) 2–8, amplitude (curve B) 20–80%, persulfate dosage 100–400 mg/L (curve C) with middle level values. Temperature 50 ± 10 °C.
View largeDownload slide

Profile of perturbation plot showing significant parameters affecting COD removal with factors pH (curve A) 2–8, amplitude (curve B) 20–80%, persulfate dosage 100–400 mg/L (curve C) with middle level values. Temperature 50 ± 10 °C.

Figure 2
Profile of perturbation plot showing significant parameters affecting COD removal with factors pH (curve A) 2–8, amplitude (curve B) 20–80%, persulfate dosage 100–400 mg/L (curve C) with middle level values. Temperature 50 ± 10 °C.
View largeDownload slide

Profile of perturbation plot showing significant parameters affecting COD removal with factors pH (curve A) 2–8, amplitude (curve B) 20–80%, persulfate dosage 100–400 mg/L (curve C) with middle level values. Temperature 50 ± 10 °C.

Close modal
The individual effect of each parameter plot is shown in Figure 3(a)–3(c), which indicates the effect of parameter pH, amplitude intensity, and persulfate dosage, respectively. These plots are made by taking one factor as a variable and the other two factors fixed at constant levels and the experimental results are shown at three different levels compared to predicated plots that are discussed in the following section.
Figure 3
Profile of an individual parameter plot with two reference curves based on ANOVA for process parameters. (a) pH from 2 to 8, with a fixed parameter amplitude of 50%, and persulfate dosage of 250 mg/L. (b) Amplitude from 20% (18 W) to 80% (78 W) with fixed parameter pH of 5, and persulfate dosage of 250 mg/L at mid-level. (c) Persulfate dosage 100–400 (mg/L) with fixed parameter of pH 5 and amplitude of 50%, on removal of COD with 95% of confidence interval band. Temperature 50 ± 10 °C.
View largeDownload slide

Profile of an individual parameter plot with two reference curves based on ANOVA for process parameters. (a) pH from 2 to 8, with a fixed parameter amplitude of 50%, and persulfate dosage of 250 mg/L. (b) Amplitude from 20% (18 W) to 80% (78 W) with fixed parameter pH of 5, and persulfate dosage of 250 mg/L at mid-level. (c) Persulfate dosage 100–400 (mg/L) with fixed parameter of pH 5 and amplitude of 50%, on removal of COD with 95% of confidence interval band. Temperature 50 ± 10 °C.

Figure 3
Profile of an individual parameter plot with two reference curves based on ANOVA for process parameters. (a) pH from 2 to 8, with a fixed parameter amplitude of 50%, and persulfate dosage of 250 mg/L. (b) Amplitude from 20% (18 W) to 80% (78 W) with fixed parameter pH of 5, and persulfate dosage of 250 mg/L at mid-level. (c) Persulfate dosage 100–400 (mg/L) with fixed parameter of pH 5 and amplitude of 50%, on removal of COD with 95% of confidence interval band. Temperature 50 ± 10 °C.
View largeDownload slide

Profile of an individual parameter plot with two reference curves based on ANOVA for process parameters. (a) pH from 2 to 8, with a fixed parameter amplitude of 50%, and persulfate dosage of 250 mg/L. (b) Amplitude from 20% (18 W) to 80% (78 W) with fixed parameter pH of 5, and persulfate dosage of 250 mg/L at mid-level. (c) Persulfate dosage 100–400 (mg/L) with fixed parameter of pH 5 and amplitude of 50%, on removal of COD with 95% of confidence interval band. Temperature 50 ± 10 °C.

Close modal

Effect of pH on COD removal

Listen

One of the important parameters that affects the process efficiency is pH. It plays a vital role in the generation of intermediate oxidants for the oxidation of various compounds it can also affect their condition during the cavitation process (Keenan & Sedlak 2008; Barik & Gogate 2017; Thanekar & Gogate 2019). Effects of pH on the degradation of organic pollutants were studied by varying pH from 2 to 8 with a fixed amplitude intensity of 50% and persulfate dosage of 250 mg/L and is shown in Figure 3(a). As shown in Figure 3(a), the maximum COD removal of 39% at pH 5 at a reaction time of 60 min was observed. Increasing pH from the lower level at pH 2 to mid-level pH 5, the removal efficiency also increased, further increasing the pH to 8 decreased the removal efficiency of COD. Maintaining the mid-level value of factors amplitude intensity of 50% and persulfate dosage of 250 mg/L at pH 2 and pH 8 corresponded to a predicated removal efficiency of 19 and 21% respectively.

The degradation of organic pollutants from the wastewater depends on the radicalization of the reactive compounds. The possible radicalization reactions of persulfate with respect to ultrasound as the activator are given below, in Equations (5)–(12). The significant radicals formed during the persulfate reaction are sulfate radicals and hydroxyl radicals. The radical compounds react with the organic compounds and are oxidized to by-products, carbon dioxide and water (see Li et al. 2013; Wang et al. 2015):
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
Excessive loading of persulfate dosage above 250 mg/L has proven a scavenger for the process under the acidic and non-acidic conditions as given in Equations (13)–(15) (Peyton 1993; Wei et al. 2018).
(13)
(14)
(15)
The observed results show near acidic conditions as more effective compared to alkaline conditions for the degradation of pollutants under a similar kind of analysis as shown in the published literature (Thanekar & Gogate 2019). Due to this, removal was low at a higher levels of pH 8. Mid-level pH 5 showed maximum removal efficiency compared with the highly acidic pH 2, which was due to a higher amount of cavitation yield and effective generation of sulfate radicals by persulfate oxidant (Romero et al. 2010; Sarath et al. 2016). At pH 2 more numbers of protons are present in the form of which decreases effective decomposition of persulfate oxidant while increasing the pH, quantity of ions decreases in solution which leads to effective generation of sulfate radicals from persulfate as shown in given Equations (16)–(17) (Romero et al. 2010; Sarath et al. 2016):
(16)
(17)

Effect of amplitude on COD removal

Listen

Effect of power dissipation is one of the important influences in the ultrasound cavitation process, variation in amplitude generates more violent collapse of bubbles (Vega & Peñuela 2018). In this study, the effect of power dissipation on COD removal was studied by varying amplitude intensity from 20 to 80% (power dissipation 18–78 W) with fixed pH of 5 and persulfate dosage of 250 mg/L. The plot Figure 3(b) shows the variation in amplitude intensity at different levels and its effect on COD removal. The COD removal at 20, 50 and 80% of amplitude intensity is 27, 32 and 30% respectively. Maximum removal of 32% was observed at the mid-level of 50% (48 W), because Gaussian distribution probability of the cavitation bubble at the generation of cavitation is higher at lower amplitude (50%) and lower at higher amplitude (Feng et al. 2002). The amplitude intensity variation shows least significant by ANOVA as shown in Table 4. For higher power intensity at lower frequency, the decoupling effect occurs between sample solution and transducer. Thus bubble cloud formation occurs at the surface of the horn or transducer, resulting in a reduction in sound waves in the solution, hence at a lower frequency (20 kHz) the lower power cavitation becomes more effective (Sunartio et al. 2007).

Effect of persulfate oxidant on COD removal

Listen
Persulfate (⁠⁠) is one of the strong oxidizing agents (Yang et al. 2019) for the degradation of organic matter. It becomes activated in the presence of ultrasound (Yang et al. 2019) as given in Equation (18) and produces sulfate radicals with an oxidation potential of 2.40 V. The persulfate radical is a more stable radical compared to hydroxyl radicals (Romero et al. 2010). Persulfate oxidation has strong oxidation ability and efficient performance in a wide range of pH (Amor et al. 2019):
(18)
In this study, the effect of combined ultrasound activated persulfate oxidation on COD removal was studied by varying the persulfate dosage from 100 mg/L to 250 mg/L with fixed factors pH 5 and amplitude intensity of 50%, as shown in Figure 3(c). Maximum COD removal of 32% was observed at a lower level of persulfate dosage of 100 mg/L. Predicted removal at a mid-level of 250 mg/L dosages and a higher level of 400 mg/L dosages of persulfate was 31 and 21% respectively. The increase in persulfate dosage from 100 to 400 mg/L decreases the removal efficiency of COD. It shows that an increase in persulfate concentration leads to the existence of excess persulfate in the system with which sulfate radicals in the system react and produce sulfate ions, and also extra sulfate radicals react themselves, as given in Equations (19) and (20) (Vu et al. 2004; Wei et al. 2018) . The additional persulfate loading under particularly acidic solutions are reported as a scavenger, thus the rate of reaction slightly decreases with an increase in dosage (Peyton 1993; Wei et al. 2018):
(19)
(20)
Figure 4 shows the comparison of COD removal with stand-alone ultrasound, persulfate process compared with the combined ultrasound and persulfate process under optimum conditions. The combined process is more effective with a rate constant of 0.0094 min−1 and removal efficiency of 39.5% compared with the stand-alone ultrasound cavitation process with 8% COD removal under the optimum conditions of pH 5, amplitude 20% provide and persulfate oxidation process with 5% COD removal under 100 mg/L dosage. A similar effect was observed by Yang et al. (2019) for the removal of pollutant from the wastewater. The combined effect leads to a higher amount of cavitation yield production and effective generation of sulfate radicals by persulfate, it also improves the degradability through degradation of polysaccharides ions to monomer ions by a combined ultrasound–persulfate oxidation process (Zhou & Ma 2006; Chen et al. 2021).
Figure 4
Profile of percentage COD removal with individual treatment; ultrasound at pH 5, amplitude 20%; persulfate of 100 mg/L; temperature 50 ± 10 °C. Combined effect of ultrasound with persulfate at pH 5 and persulfate dosage of 100 mg/L, amplitude of 20%, temperature 50 ± 10 °C within 60 min reaction time.
View largeDownload slide

Profile of percentage COD removal with individual treatment; ultrasound at pH 5, amplitude 20%; persulfate of 100 mg/L; temperature 50 ± 10 °C. Combined effect of ultrasound with persulfate at pH 5 and persulfate dosage of 100 mg/L, amplitude of 20%, temperature 50 ± 10 °C within 60 min reaction time.

Figure 4
Profile of percentage COD removal with individual treatment; ultrasound at pH 5, amplitude 20%; persulfate of 100 mg/L; temperature 50 ± 10 °C. Combined effect of ultrasound with persulfate at pH 5 and persulfate dosage of 100 mg/L, amplitude of 20%, temperature 50 ± 10 °C within 60 min reaction time.
View largeDownload slide

Profile of percentage COD removal with individual treatment; ultrasound at pH 5, amplitude 20%; persulfate of 100 mg/L; temperature 50 ± 10 °C. Combined effect of ultrasound with persulfate at pH 5 and persulfate dosage of 100 mg/L, amplitude of 20%, temperature 50 ± 10 °C within 60 min reaction time.

Close modal

The synergistic index for the combined process has been computed based on the removal efficiency observed for the stand-alone process and for the combined process. When the wastewater was treated with ultrasound cavitation alone the maximum removal efficiency observed was 8% and that of persulfate oxidation was 5%. Whereas, when the persulfate process was activated with sonication the observed removal efficiency was almost 39.5%. Accordingly, the computed SI for the combined process was 3.038, which indicates there is a significant synergetic effect occurs when the ultrasound cavitation is combined with persulfate process as the reported synergetic index for the same process with different pollutants varies from 1.52 to 4.43 (Fedorov et al. 2022).

Effect of pH and amplitude on COD removal

Listen
The interaction effect of pH (A) and amplitude intensity (B) on COD removal is not significant based on ANOVA as shown in Table 4, its P-value is higher than 0.05 (P > 0.05). The combined effect of pH and amplitude on COD removal was studied by maintaining other parameters constant and the results are as shown in Figure 5(a). With the increasing amplitude at pH 2, removal of COD increased to 31% and, on the other hand, middle level pH 5 with amplitude up to 50% removal efficiency increased further as a result of the generation of effective cavitation and effective decomposition of persulfate (Sarath et al. 2016). By further increasing the amplitude to 80% at pH 5, this reduces removal due to reduction in the cavitation yield, thus increasing or decreasing amplitude beyond or below 50% under near acidic conditions has no significant impact on the removal efficiency (Thanekar & Gogate 2019).
Figure 5
Profile of the interaction effect plot for process parameters. (a) pH 2–8 to amplitude 20–80% (AB) maintaining persulfate dosage (mg/L) at middle level. (b) Amplitude 20–80% to persulfate dosage 100–400 (mg/L) (BC) maintaining pH at middle level. (c) pH 2–8 and persulfate dosage 100–400 (mg/L) (AC) maintaining amplitude % at middle level. Temperature 50 ± 10 °C.
View largeDownload slide

Profile of the interaction effect plot for process parameters. (a) pH 2–8 to amplitude 20–80% (AB) maintaining persulfate dosage (mg/L) at middle level. (b) Amplitude 20–80% to persulfate dosage 100–400 (mg/L) (BC) maintaining pH at middle level. (c) pH 2–8 and persulfate dosage 100–400 (mg/L) (AC) maintaining amplitude % at middle level. Temperature 50 ± 10 °C.

Figure 5
Profile of the interaction effect plot for process parameters. (a) pH 2–8 to amplitude 20–80% (AB) maintaining persulfate dosage (mg/L) at middle level. (b) Amplitude 20–80% to persulfate dosage 100–400 (mg/L) (BC) maintaining pH at middle level. (c) pH 2–8 and persulfate dosage 100–400 (mg/L) (AC) maintaining amplitude % at middle level. Temperature 50 ± 10 °C.
View largeDownload slide

Profile of the interaction effect plot for process parameters. (a) pH 2–8 to amplitude 20–80% (AB) maintaining persulfate dosage (mg/L) at middle level. (b) Amplitude 20–80% to persulfate dosage 100–400 (mg/L) (BC) maintaining pH at middle level. (c) pH 2–8 and persulfate dosage 100–400 (mg/L) (AC) maintaining amplitude % at middle level. Temperature 50 ± 10 °C.

Close modal

Effect of amplitude and persulfate dosage on removal

Listen

The interaction effect of amplitude intensity (B) and persulfate dosage (C) on COD removal is significant as indicated by ANOVA outputs shown in Table 4, its P-value is lower than 0.05 (P > 0.05). The interaction effect of amplitude intensity and dosage of persulfate on COD removal is shown in Figure 5(b). For an amplitude intensity of 20% and persulfate dosages of 100 mg/L, the COD removal is significant due to the high availability of activation energy at low amplitude which was required for breakage of O-O bond and generation of sulfate radicals (Wacławek et al. 2017). Under higher amplitudes of 50 and 80% the persulfate amount of 250 and 400 mg/L became excessive for the system, leading to scavenger reactions, which reduced the removal (Wei et al. 2018) compared to 20% amplitude and 100 mg/L of dosage.

Effect of pH and persulfate dosage on COD removal

Listen

The interaction effect of pH (A) and persulfate dosage (B) on COD removal was not significant as indicated by ANOVA (Table 4), its P-value is higher than 0.05 (P > 0.05). The interaction effect of pH and dosage of persulfate on COD removal at 50% amplitude intensity is shown in Figure 5(c). Under an acidic pH of 2 and 5 with 100 mg/L dosages, there is more significant COD removal efficiency when compared to the removal achieved at 250 mg/L and 400 mg/L dosages. Excessive loading of persulfate leads to less utilization of persulfate ions under acidic conditions (Wei et al. 2018), persulfate loading above some extent acted as a proven scavenger under acidic conditions (Peyton 1993; Wei et al. 2018). Increasing dosage under near neutral condition of pH 8 did not have a significant effect on COD removal.

The comparison of removal efficiency of combined persulfate process with sonication with other similar advanced oxidation processes is given in Table 6. It is apparent that the removal efficiency of the present combined process is comparable with that of other similar processes. The present work was done with real wastewater containing a very high COD of 13,760 mg/L and with a BOD/COD ratio less than 0.4. Also, it has been observed that the reaction time considered for the similar AOP process for the treatment pharmaceutical wastewater was very high compared to that of the present study.

Table 6

Comparison of combined persulfate and ultrasound processes with other similar processes for the treatment of pharmaceutical wastewater

Treatment technologyPollutantOperating conditionsEfficiencyReference
Photo Fenton COD pH – 3
COD – 8,370 ± 190
[Fe2+] = 0.05 mol/L
[H2O2] = 0.25 mol/L
Reaction time – 120 min 		58.4% Changotra et al. (2019) 
Electro-Fenton COD Batch experiment
Current density – 17 mA/cm2
Initial pH – 3
Fe2+/Fe3+/Co2+ – 1:1:2
Oxygen flow rate – 0.5 L/min
Reaction time – 2 h 		93% Quang et al. (2022) 
Electro-Fenton (EF) + photocatalytic oxidation (PcO) COD EF
Current density – 5 mA/cm2
Reaction time – 1 h
PcO
[TiO2] = 1.5 g/L
Reaction time – 4 h 		70.2% Başaran Dindaş et al. (2020) 
Aerobic biological treatment + Photo-Fenton COD pH –1 2.7 ± 0.25
COD – 8,370 ± 190 		62.2% Changotra et al. (2019) 
Aerobic biological treatment + electro-fenton COD pH – 12.7 ± 0.25
COD – 8,370 ± 190 		44.6% Changotra et al. (2019) 
Photocatalytic oxidation COD COD = 1,900 mg/L
pH = 4.5, catalyst dosage – 2 g/l
[H2O2] = 0.32 mM 		72.7% Berkün Olgun et al. (2021) 
Ultrasound + persulfate COD COD 13,760 mg/L, pH 5, amplitude 20%, persulfate dosage 100 mg/L and reaction time 60 min 39.5% Present study 
Treatment technologyPollutantOperating conditionsEfficiencyReference
Photo Fenton COD pH – 3
COD – 8,370 ± 190
[Fe2+] = 0.05 mol/L
[H2O2] = 0.25 mol/L
Reaction time – 120 min 		58.4% Changotra et al. (2019) 
Electro-Fenton COD Batch experiment
Current density – 17 mA/cm2
Initial pH – 3
Fe2+/Fe3+/Co2+ – 1:1:2
Oxygen flow rate – 0.5 L/min
Reaction time – 2 h 		93% Quang et al. (2022) 
Electro-Fenton (EF) + photocatalytic oxidation (PcO) COD EF
Current density – 5 mA/cm2
Reaction time – 1 h
PcO
[TiO2] = 1.5 g/L
Reaction time – 4 h 		70.2% Başaran Dindaş et al. (2020) 
Aerobic biological treatment + Photo-Fenton COD pH –1 2.7 ± 0.25
COD – 8,370 ± 190 		62.2% Changotra et al. (2019) 
Aerobic biological treatment + electro-fenton COD pH – 12.7 ± 0.25
COD – 8,370 ± 190 		44.6% Changotra et al. (2019) 
Photocatalytic oxidation COD COD = 1,900 mg/L
pH = 4.5, catalyst dosage – 2 g/l
[H2O2] = 0.32 mM 		72.7% Berkün Olgun et al. (2021) 
Ultrasound + persulfate COD COD 13,760 mg/L, pH 5, amplitude 20%, persulfate dosage 100 mg/L and reaction time 60 min 39.5% Present study 
View Large

In order to assess the effect of the oxidizing species in the present study, the radical scavenger tert-butyl alcohol was added. Tert-butyl is considered to be hydroxyl scavenger and has the effect of hydroxyl radicals in the electrolytic cell reaction (Li et al. 2017; Popat et al. 2019). At the optimum condition of pH 5, amplitude 20%, persulfate dosage of 100 mg/L, 1 mL of tert-butyl alcohol was added and the results are shown in Figure 6. From the figure it is very clear that the addition of tert-butyl alcohol did not cause any significant removal of COD, which shows that the hydroxyl and sulfate radicals have been scavenged. Whereas, without the addition of scavenger, significant removal of COD has been reported, which indicates the main oxidizing agents causing degradation of pharmaceutical waste water are hydroxyl radicals and persulfate radicals. A similar effect was observed by Popat et al. (2019) for the degradation of mixed industrial wastewater.
Figure 6
Effect of tert-butyl alcohol in the combined ultrasound and persulfate process (optimum condition: pH 5, amplitude 20%, persulfate dosage 100 mg/L, temperature 50 ± 10 °C and reaction time 60 min).
View largeDownload slide

Effect of tert-butyl alcohol in the combined ultrasound and persulfate process (optimum condition: pH 5, amplitude 20%, persulfate dosage 100 mg/L, temperature 50 ± 10 °C and reaction time 60 min).

Figure 6
Effect of tert-butyl alcohol in the combined ultrasound and persulfate process (optimum condition: pH 5, amplitude 20%, persulfate dosage 100 mg/L, temperature 50 ± 10 °C and reaction time 60 min).
View largeDownload slide

Effect of tert-butyl alcohol in the combined ultrasound and persulfate process (optimum condition: pH 5, amplitude 20%, persulfate dosage 100 mg/L, temperature 50 ± 10 °C and reaction time 60 min).

Close modal
Listen

The synergetic index of the combined persulfate sonication process was computed for the treatment of pharmaceutical wastewater. The synergetic index was found to be 3.038, which is higher than 1, indicating the high synergetic effect of the combined process. It can also be concluded that ultrasound can be a better activator for the persulfate process. At the optimum condition of parameters pH 5, amplitude intensity of 20%, and persulfate dosage of 100 mg/L, the maximum COD removal of 5,440 mg/L (39.5%) was observed at 60 minutes of reaction time. The observed results concluded that process parameters like pH and persulfate oxidant dosage are very significant parameters for COD removal from pharmaceutical wastewater. The removal efficiency of the persulfate process, sonication and the combined persulfate sonication is in the following order 5 < 8 < 39.5%, respectively. The BOD/COD ratio of the treated wastewater increased from 0.4 to 0.53, thus the biodegradability of the treated wastewater had increased. The synergistic effect of ultrasound cavitation and persulfate oxidation was more effective for the degradation of organic matter from pharmaceutical wastewater compared with the effects of the stand-alone processes under optimum conditions. The major parameters that affect economic feasibility are chemical cost and energy consumption for sonication, which comes under the operational cost, and the cost of the sonicator and the reactor are the initial investments.

Listen

The authors would like to thank the Centre for Biofuels and Bioenergy Studies (CBBS) in PDEU for providing laboratory facilities for performing characterization and property estimation. The authors are thankful to the Director, Pandit Deendayal Energy University, Gandhinagar, India and Director, National Institute of Technology, Calicut, India for providing encouragement and kind permission for publishing the article.

Listen

Karan Pandya: Methodology, Formal analysis, Writing – original draft, Writing – review and editing.

Thankappan Saraswathy Anantha Singh: Conceptualization, Methodology, Formal analysis, Supervision, Writing – original draft, Writing – review and editing.

Pravin Kodgire: Conceptualization, Methodology, Formal analysis, Supervision, Writing – original draft, Writing – review and editing.

Saji-Simon: Additional experimentation, Writing the revised article – review and editing.

Listen

Not applicable.

Listen

Not applicable.

Listen

Not applicable.

Listen

Not applicable.

Listen

Not applicable.

Listen

All relevant data are included in the paper or its Supplementary Information.

Listen

The authors declare there is no conflict.

Adishkumar
S.
,
Sivajothi
S.
 &
Rajesh Banu
J.
2012
Coupled solar photo-fenton process with aerobic sequential batch reactor for treatment of pharmaceutical wastewater
.
Desalination and Water Treatment
48
(
1–3
),
89
–
95
.
https://doi.org/10.1080/19443994.2012.698799
.
Google Scholar
 
Ahmadi
S.
,
Igwegbe
C. A.
 &
Rahdar
S.
2019
The application of thermally activated persulfate for degradation of Acid Blue 92 in aqueous solution
.
International Journal of Industrial Chemistry
10
(
3
),
249
–
260
.
https://doi.org/10.1007/s40090-019-0188-1
.
Google Scholar
Crossref
Search ADS
 
Amor
C.
,
Rodríguez-Chueca
J.
,
Fernandes
J. L.
,
Domínguez
J. R.
,
Lucas
M. S.
 &
Peres
J. A.
2019
Winery wastewater treatment by sulfate radical based-advanced oxidation processes (SR-AOP): thermally vs UV-assisted persulfate activation
.
Process Safety and Environmental Protection
,
94
–
101
.
https://doi.org/10.1016/j.psep.2018.11.016
.
Google Scholar
 
Anipsitakis
G. P.
 &
Dionysiou
D. D.
2003
Degradation of organic contaminants in water with sulfate radicals generated by the conjunction of peroxymonosulfate with cobalt
.
Environmental Science and Technology
37
(
20
),
4790
–
4797
.
https://doi.org/10.1021/es0263792
.
Google Scholar
Crossref
Search ADS
PubMed
 
Arvaniti
O. S.
,
Bairamis
F.
,
Konstantinou
I.
,
Mantzavinos
D.
 &
Frontistis
Z.
2020
Degradation of antihypertensive drug valsartan in water matrices by heat and heat/ultrasound activated persulfate: kinetics, synergy effect and transformation products
.
Chemical Engineering Journal Advances
4
,
100062
.
https://doi.org/10.1016/j.ceja.2020.100062
.
Google Scholar
Crossref
Search ADS
 
Ayare
S. D.
 &
Gogate
P. R.
2019
Sonocatalytic treatment of phosphonate containing industrial wastewater intensified using combined oxidation approaches
.
Ultrasonics Sonochemistry
51
,
69
–
76
.
https://doi.org/10.1016/j.ultsonch.2018.10.018
.
Google Scholar
Crossref
Search ADS
PubMed
 
Barik
A. J.
 &
Gogate
P. R.
2017
Hybrid treatment strategies for 2,4,6-trichlorophenol degradation based on
.
Ultrasonics – Sonochemistry
.
https://doi.org/10.1016/j.ultsonch.2017.07.029
.
Google Scholar
 
Başaran Dindaş
G.
,
Çalişkan
Y.
,
Çelebi
E. E.
,
Tekbaş
M.
,
Bektaş
N.
 &
Yatmaz
H. C.
2020
Treatment of pharmaceutical wastewater by combination of electrocoagulation, electro-Fenton and photocatalytic oxidation processes
.
Journal of Environmental Chemical Engineering
8
(
3
).
https://doi.org/10.1016/j.jece.2020.103777
.
Google Scholar
 
Beckett
M. A.
 &
Hua
I.
2001
Impact of ultrasonic frequency on aqueous sonoluminescence and sonochemistry
.
Journal of Physical Chemistry A
105
(
15
),
3796
–
3802
.
https://doi.org/10.1021/jp003226x
.
Google Scholar
Crossref
Search ADS
 
Berkün Olgun
Ö.
,
Palas
B.
,
Atalay
S.
 &
Ersöz
G.
2021
Photocatalytic oxidation and catalytic wet air oxidation of real pharmaceutical wastewater in the presence of Fe and LaFeO3 doped activated carbon catalysts
.
Chemical Engineering Research and Design
171
,
421
–
432
.
https://doi.org/10.1016/j.cherd.2021.05.017
.
Google Scholar
Crossref
Search ADS
 
Chandak
S.
,
Ghosh
P. K.
 &
Gogate
P. R.
2020
Treatment of real pharmaceutical wastewater using different processes based on ultrasound in combination with oxidants
.
Process Safety and Environmental Protection
137
,
149
–
157
.
https://doi.org/10.1016/j.psep.2020.02.025
.
Google Scholar
Crossref
Search ADS
 
Changotra
R.
,
Rajput
H.
 &
Dhir
A.
2017
Natural soil mediated photo fenton-like processes in treatment of pharmaceuticals: batch and continuous approach
.
Chemosphere
188
,
345
–
353
.
https://doi.org/10.1016/j.chemosphere.2017.09.016
.
Google Scholar
Crossref
Search ADS
PubMed
 
Changotra
R.
,
Rajput
H.
 &
Dhir
A.
2019
Treatment of real pharmaceutical wastewater using combined approach of fenton applications and aerobic biological treatment
.
Journal of Photochemistry and Photobiology A: Chemistry
376
,
175
–
184
.
https://doi.org/10.1016/j.jphotochem.2019.02.029
.
Google Scholar
Crossref
Search ADS
 
Chen
X.
,
Sun-waterhouse
D.
,
Yao
W.
,
Li
X.
 &
Zhao
M.
2021
Free radical-mediated degradation of polysaccharides: mechanism of free radical formation and degradation, influence factors and product properties
.
Food Chemistry
365
,
130524
.
https://doi.org/10.1016/j.foodchem.2021.130524
.
Google Scholar
Crossref
Search ADS
PubMed
 
Cortez
S.
,
Teixeira
P.
,
Oliveira
R.
 &
Mota
M.
2010
Ozonation as polishing treatment of mature landfill leachate
.
Journal of Hazardous Materials
182
(
1–3
),
730
–
734
.
https://doi.org/10.1016/j.jhazmat.2010.06.095
.
Google Scholar
PubMed
 
Crini
G.
 &
Lichtfouse
E.
2019
Advantages and disadvantages of techniques used for wastewater treatment
.
Environmental Chemistry Letters
17
(
1
),
145
–
155
.
https://doi.org/10.1007/s10311-018-0785-9
.
Google Scholar
Crossref
Search ADS
 
Dong
Z.
,
Udepurkar
A. P.
 &
Kuhn
S.
2020
Synergistic effects of the alternating application of low and high frequency ultrasound for particle synthesis in microreactors
.
Ultrasonics Sonochemistry
60
,
104800
.
https://doi.org/10.1016/j.ultsonch.2019.104800
.
Google Scholar
Crossref
Search ADS
PubMed
 
Dopar
M.
,
Kusic
H.
 &
Koprivanac
N.
2011
Treatment of simulated industrial wastewater by photo-Fenton process. part I: the optimization of process parameters using design of experiments (DOE)
.
Chemical Engineering Journal
173
(
2
),
267
–
279
.
https://doi.org/10.1016/j.cej.2010.09.070
.
Google Scholar
Crossref
Search ADS
 
Dular
M.
,
Griessler-Bulc
T.
,
Gutierrez-Aguirre
I.
,
Heath
E.
,
Kosjek
T.
,
Krivograd Klemenčič
A.
,
Oder
M.
,
Petkovšek
M.
,
Rački
N.
,
Ravnikar
M.
,
Šarc
A.
,
Širok
B.
,
Zupanc
M.
,
Žitnik
M.
 &
Kompare
B.
2016
Use of hydrodynamic cavitation in (waste)water treatment
.
Ultrasonics Sonochemistry
29
,
577
–
588
.
https://doi.org/10.1016/j.ultsonch.2015.10.010
.
Google Scholar
Crossref
Search ADS
PubMed
 
Estrada-Flórez
S. E.
,
Serna-Galvis
E. A.
 &
Torres-Palma
R. A.
2020
Photocatalytic vs. sonochemical removal of antibiotics in water: structure-degradability relationship, mineralization, antimicrobial activity, and matrix effects
.
Journal of Environmental Chemical Engineering
8
(
5
),
104359
.
https://doi.org/10.1016/j.jece.2020.104359
.
Google Scholar
Crossref
Search ADS
 
Fedorov
K.
,
Plata-Gryl
M.
,
Khan
J. A.
 &
Boczkaj
G.
2020
Ultrasound-assisted heterogeneous activation of persulfate and peroxymonosulfate by asphaltenes for the degradation of BTEX in water
.
Journal of Hazardous Materials
397
,
122804
.
https://doi.org/10.1016/j.jhazmat.2020.122804
.
Google Scholar
Crossref
Search ADS
PubMed
 
Fedorov
K.
,
Dinesh
K.
,
Sun
X.
,
Darvishi Cheshmeh Soltani
R.
,
Wang
Z.
,
Sonawane
S.
 &
Boczkaj
G.
2022
Synergistic effects of hybrid advanced oxidation processes (AOPs) based on hydrodynamic cavitation phenomenon – A review
.
Chemical Engineering Journal
432
https://doi.org/10.1016/j.cej.2021.134191
.
Google Scholar
 
Feng
R.
,
Zhao
Y.
,
Zhu
C.
 &
Mason
T. J.
2002
Enhancement of ultrasonic cavitation yield by multi-frequency sonication
.
Ultrasonics Sonochemistry
9
(
5
),
231
–
236
.
https://doi.org/10.1016/S1350-4177(02)00083-4
.
Google Scholar
Crossref
Search ADS
PubMed
 
Ford
A. T.
 &
Fong
P. P.
2016
The effects of antidepressants appear to be rapid and at environmentally relevant concentrations
.
Environmental Toxicology and Chemistry
35
(
4
),
794
–
798
.
https://doi.org/10.1002/etc.3087
.
Google Scholar
Crossref
Search ADS
PubMed
 
Gadipelly
C.
,
Pérez-González
A.
,
Yadav
G. D.
,
Ortiz
I.
,
Ibáñez
R.
,
Rathod
V. K.
 &
Marathe
K. V.
2014
Pharmaceutical industry wastewater: review of the technologies for water treatment and reuse
.
Industrial and Engineering Chemistry Research
53
(
29
),
11571
–
11592
.
https://doi.org/10.1021/ie501210j
.
Google Scholar
Crossref
Search ADS
 
Gągol
M.
,
Przyjazny
A.
 &
Boczkaj
G.
2018
Wastewater treatment by means of advanced oxidation processes based on cavitation – A review
.
Chemical Engineering Journal
338
,
599
–
627
.
https://doi.org/10.1016/j.cej.2018.01.049
.
Google Scholar
Crossref
Search ADS
 
Ghafoori
S.
,
Mowla
A.
,
Jahani
R.
,
Mehrvar
M.
 &
Chan
P. K.
2015
Sonophotolytic degradation of synthetic pharmaceutical wastewater: statistical experimental design and modeling
.
Journal of Environmental Management
150
,
128
–
137
.
https://doi.org/10.1016/j.jenvman.2014.11.011
.
Google Scholar
Crossref
Search ADS
PubMed
 
Hu
X.
,
Wang
X.
,
Ban
Y.
 &
Ren
B.
2011
A comparative study of UV-Fenton, UV-H2O2 and Fenton reaction treatment of landfill leachate
.
Environmental Technology
32
(
9
),
945
–
951
.
https://doi.org/10.1080/09593330.2010.521953
.
Google Scholar
Crossref
Search ADS
PubMed
 
Huang
G. Y.
,
Liu
Y. S.
,
Chen
X. W.
,
Liang
Y. Q.
,
Liu
S. S.
,
Yang
Y. Y.
,
Hu
L. X.
,
Shi
W. J.
,
Tian
F.
,
Zhao
J. L.
,
Chen
J.
 &
Ying
G. G.
2016
Feminization and masculinization of western mosquitofish (Gambusia affinis) observed in rivers impacted by municipal wastewaters
.
Scientific Reports
6
,
1
–
11
.
https://doi.org/10.1038/srep20884
.
Google Scholar
PubMed
 
Ioannidi
A.
,
Arvaniti
O. S.
,
Nika
M. C.
,
Aalizadeh
R.
,
Thomaidis
N. S.
,
Mantzavinos
D.
 &
Frontistis
Z.
2022
Removal of drug losartan in environmental aquatic matrices by heat-activated persulfate: kinetics, transformation products and synergistic effects
.
Chemosphere
287
(
P1
),
131952
.
https://doi.org/10.1016/j.chemosphere.2021.131952
.
Google Scholar
PubMed
 
Jeworski
M.
 &
Heinzle
E.
2000
Combined chemical-biological treatment of wastewater containing refractory pollutants
.
Biotechnology Annual Review
6
,
163
–
196
.
https://doi.org/10.1016/S1387-2656(00)06022-1
.
Google Scholar
Crossref
Search ADS
PubMed
 
Jordens
J.
,
Appermont
T.
,
Gielen
B.
,
Van Gerven
T.
 &
Braeken
L.
2016
Sonofragmentation: effect of ultrasound frequency and power on particle breakage
.
Crystal Growth and Design
16
(
11
),
6167
–
6177
.
https://doi.org/10.1021/acs.cgd.6b00088
.
Google Scholar
Crossref
Search ADS
 
Kansal
A.
,
Siddiqui
N. A.
 &
Gautam
A.
2013
Assessment of heavy metals and their interrelationships with some physicochemical parameters in eco-efficient rivers of Himalayan region
.
Environmental Monitoring and Assessment
185
(
3
),
2553
–
2563
.
https://doi.org/10.1007/s10661-012-2730-x
.
Google Scholar
Crossref
Search ADS
PubMed
 
Keenan
C. R.
 &
Sedlak
D. L.
2008
Ligand-enhanced reactive oxidant generation by nanoparticulate zero-valent iron and oxygen
.
Environmental Science and Technology
42
(
18
),
6936
–
6941
.
https://doi.org/10.1021/es801438f
.
Google Scholar
Crossref
Search ADS
PubMed
 
Khorram
A. G.
 &
Fallah
N.
2018
Treatment of textile dyeing factory wastewater by electrocoagulation with low sludge settling time: optimization of operating parameters by RSM
.
Journal of Environmental Chemical Engineering
6
(
1
),
635
–
642
.
https://doi.org/10.1016/j.jece.2017.12.054
.
Google Scholar
Crossref
Search ADS
 
Leighton
T. G.
1995
Bubble population phenomena in acoustic cavitation
.
Ultrasonics – Sonochemistry
2
(
2
),
123
–
136
.
https://doi.org/10.1016/1350-4177(95)00021-W
.
Google Scholar
Crossref
Search ADS
 
Li
B.
 &
Zhu
J.
2016
Simultaneous degradation of 1,1,1-trichloroethane and solvent stabilizer 1,4-dioxane by a sono-activated persulfate process
.
Chemical Engineering Journal
284
,
750
–
763
.
https://doi.org/10.1016/j.cej.2015.08.153
.
Google Scholar
Crossref
Search ADS
 
Li
B.
,
Li
L.
,
Lin
K.
,
Zhang
W.
,
Lu
S.
 &
Luo
Q.
2013
Removal of 1,1,1-trichloroethane from aqueous solution by a sono-activated persulfate process
.
Ultrasonics Sonochemistry
20
(
3
),
855
–
863
.
https://doi.org/10.1016/j.ultsonch.2012.11.014
.
Google Scholar
Crossref
Search ADS
PubMed
 
Li
R.
,
Kong
J.
,
Liu
H.
,
Chen
P.
,
Liu
G.
,
Li
F.
 &
Lv
W.
2017
A sulfate radical based ferrous-peroxydisulfate oxidative system for indomethacin degradation in aqueous solutions
.
RSC Advances
7
(
37
),
22802
–
22809
.
https://doi.org/10.1039/c7ra03364h
.
Google Scholar
Crossref
Search ADS
 
Liang
H.
,
Sun
H.
,
Patel
A.
,
Shukla
P.
,
Zhu
Z. H.
 &
Wang
S.
2012
Excellent performance of mesoporous CO3O4/MnO2 nanoparticles in heterogeneous activation of peroxymonosulfate for phenol degradation in aqueous solutions
.
Applied Catalysis B: Environmental
127
,
330
–
335
.
https://doi.org/10.1016/j.apcatb.2012.09.001
.
Google Scholar
Crossref
Search ADS
 
Liu
H.
,
Bruton
T. A.
,
Li
W.
,
Van Buren
J.
,
Prasse
C.
,
Doyle
F. M.
 &
Sedlak
D. L.
2016
Oxidation of benzene by persulfate in the presence of Fe(III)- and Mn(IV)-containing oxides: stoichiometric efficiency and transformation products
.
Environmental Science and Technology
50
(
2
),
890
–
898
.
https://doi.org/10.1021/acs.est.5b04815
.
Google Scholar
Crossref
Search ADS
PubMed
 
Martínez
F.
,
Molina
R.
,
Rodríguez
I.
,
Pariente
M. I.
,
Segura
Y.
 &
Melero
J. A.
2018
Techno-economical assessment of coupling fenton/biological processes for the treatment of a pharmaceutical wastewater
.
Journal of Environmental Chemical Engineering
6
(
1
),
485
–
494
.
https://doi.org/10.1016/j.jece.2017.12.008
.
Google Scholar
Crossref
Search ADS
 
Milano
J.
,
Ong
H. C.
,
Masjuki
H. H.
,
Silitonga
A. S.
,
Chen
W. H.
,
Kusumo
F.
,
Dharma
S.
 &
Sebayang
A. H.
2018
Optimization of biodiesel production by microwave irradiation-assisted transesterification for waste cooking oil-Calophyllum inophyllum oil via response surface methodology
.
Energy Conversion and Management
158
,
400
–
415
.
https://doi.org/10.1016/j.enconman.2017.12.027
.
Google Scholar
Crossref
Search ADS
 
Mohapatra
D. P.
,
Brar
S. K.
,
Tyagi
R. D.
,
Picard
P.
 &
Surampalli
R. Y.
2014
Analysis and advanced oxidation treatment of a persistent pharmaceutical compound in wastewater and wastewater sludge-carbamazepine
.
Science of the Total Environment
470–471
,
58
–
75
.
https://doi.org/10.1016/j.scitotenv.2013.09.034
.
Google Scholar
PubMed
 
Monteagudo
J. M.
,
Durán
A.
,
González
R.
 &
Expósito
A. J.
2015
In situ chemical oxidation of carbamazepine solutions using persulfate simultaneously activated by heat energy, UV light, Fe2+ ions, and H2O2
.
Applied Catalysis B: Environmental
176–177
,
120
–
129
.
https://doi.org/10.1016/j.apcatb.2015.03.055
.
Google Scholar
 
Monteagudo
J. M.
,
El-taliawy
H.
,
Durán
A.
,
Caro
G.
 &
Bester
K.
2018
Sono-activated persulfate oxidation of diclofenac: degradation, kinetics, pathway and contribution of the different radicals involved
.
Journal of Hazardous Materials
357
,
457
–
465
.
https://doi.org/10.1016/j.jhazmat.2018.06.031
.
Google Scholar
Crossref
Search ADS
PubMed
 
Muthukumaran
C.
,
Praniesh
R.
,
Navamani
P.
,
Swathi
R.
,
Sharmila
G.
 &
Manoj Kumar
N.
2017
Process optimization and kinetic modeling of biodiesel production using non-edible Madhuca indica oil
.
Fuel
195
,
217
–
225
.
https://doi.org/10.1016/j.fuel.2017.01.060
.
Google Scholar
Crossref
Search ADS
 
Ng
K. K.
,
Shi
X.
,
Tang
M. K. Y.
 &
Ng
H. Y.
2014
A novel application of anaerobic bio-entrapped membrane reactor for the treatment of chemical synthesis-based pharmaceutical wastewater
.
Separation and Purification Technology
132
,
634
–
643
.
https://doi.org/10.1016/j.seppur.2014.06.021
.
Google Scholar
Crossref
Search ADS
 
Peyton
G. R.
1993
The free-radical chemistry of persulfate-based total organic carbon analyzers
.
Marine Chemistry
41
(
1–3
),
91
–
103
.
https://doi.org/10.1016/0304-4203(93)90108-Z
.
Google Scholar
 
Popat
A.
,
Nidheesh
P. V.
,
Anantha Singh
T. S.
 &
Suresh Kumar
M.
2019
Mixed industrial wastewater treatment by combined electrochemical advanced oxidation and biological processes
.
Chemosphere
237
,
124419
.
https://doi.org/10.1016/j.chemosphere.2019.124419
.
Google Scholar
Crossref
Search ADS
PubMed
 
Quang
H. H. P.
,
Dinh
N. T.
,
Thi
T. N. T.
,
Bao
L. T. N.
,
Yuvakkumar
R.
 &
Nguyen
V. H.
2022
Fe2 +, Fe3 +, Co2 +as highly efficient cocatalysts in the homogeneous electro-Fenton process for enhanced treatment of real pharmaceutical wastewater
.
Journal of Water Process Engineering
46
,
102635
.
https://doi.org/10.1016/j.jwpe.2022.102635
.
Google Scholar
Crossref
Search ADS
 
Rayaroth
M. P.
,
Aravind
U. K.
 &
Aravindakumar
C. T.
2016
Degradation of pharmaceuticals by ultrasound-based advanced oxidation process
.
Environmental Chemistry Letters
14
(
3
),
259
–
290
.
https://doi.org/10.1007/s10311-016-0568-0
.
Google Scholar
Crossref
Search ADS
 
Rayaroth
M. P.
,
Aravindakumar
C. T.
,
Shah
N. S.
 &
Boczkaj
G.
2022
Advanced oxidation processes (AOPs) based wastewater treatment – unexpected nitration side reactions – a serious environmental issue: a review
.
Chemical Engineering Journal
430
(
P4
),
133002
.
https://doi.org/10.1016/j.cej.2021.133002
.
Google Scholar
 
Rice
E. W.
,
Baird
R. B.
,
Eaton
A. D.
 &
Clesceri
L. A.
 (eds)
2012
Standard methods for the examination of water and wastewater, 22nd edn
.
American Public Health Association, Washington, DC, ISBN: 9780875530130
.
Google Scholar
 
Rokhina
E. V.
,
Sillanpää
M.
,
Nolte
M. C. M.
 &
Virkutyte
J.
2008
Optimization of pulp mill effluent treatment with catalytic adsorbent using orthogonal second-order (Box-Behnken) experimental design
.
Journal of Environmental Monitoring
10
(
11
),
1304
–
1312
.
https://doi.org/10.1039/b811556g
.
Google Scholar
Crossref
Search ADS
PubMed
 
Romero
A.
,
Santos
A.
,
Vicente
F.
 &
González
C.
2010
Diuron abatement using activated persulfate: effect of pH, Fe(II) and oxidant dosage
.
Chemical Engineering Journal
162
(
1
),
257
–
265
.
https://doi.org/10.1016/j.cej.2010.05.044
.
Google Scholar
Crossref
Search ADS
 
Sarath
K.
,
Gandhimathi
R.
,
Ramesh
S. T.
 &
Nidheesh
P. V.
2016
Removal of reactive magenta-MB from aqueous solution by persulfate-based advanced oxidation process
.
Desalination and Water Treatment
57
(
25
),
11872
–
11878
.
https://doi.org/10.1080/19443994.2015.1054886
.
Google Scholar
Crossref
Search ADS
 
Serna-Galvis
E. A.
,
Botero-Coy
A. M.
,
Martínez-Pachón
D.
,
Moncayo-Lasso
A.
,
Ibáñez
M.
,
Hernández
F.
 &
Torres-Palma
R. A.
2019
Degradation of seventeen contaminants of emerging concern in municipal wastewater effluents by sonochemical advanced oxidation processes
.
Water Research
154
,
349
–
360
.
https://doi.org/10.1016/j.watres.2019.01.045
.
Google Scholar
Crossref
Search ADS
PubMed
 
Singh
R.
 &
Prashant
R.
2017
A review on characterization and bioremediation of pharmaceutical industries ‘wastewater: an Indian perspective
.
Applied Water Science
,
1
–
12
.
https://doi.org/10.1007/s13201-014-0225-3
.
Google Scholar
 
Singh
S. K.
,
Tang
W. Z.
 &
Tachiev
G.
2013
Fenton treatment of landfill leachate under different COD loading factors
.
Waste Management
33
(
10
),
2116
–
2122
.
https://doi.org/10.1016/j.wasman.2013.06.019
.
Google Scholar
Crossref
Search ADS
PubMed
 
Soltani
R. D. C.
,
Mashayekhi
M.
,
Naderi
M.
,
Boczkaj
G.
,
Jorfi
S.
 &
Safari
M.
2019
Sonocatalytic degradation of tetracycline antibiotic using zinc oxide nanostructures loaded on nano-cellulose from waste straw as nanosonocatalyst
.
Ultrasonics Sonochemistry
55
,
117
–
124
.
https://doi.org/10.1016/j.ultsonch.2019.03.009
.
Google Scholar
Crossref
Search ADS
PubMed
 
Spina
F.
,
Anastasi
A.
,
Prigione
V.
,
Tigini
V.
 &
Varese
G. C.
2012
Biological treatment of industrial wastewaters: a fungal approach
.
Chemical Engineering Transactions
27
,
175
–
180
.
https://doi.org/10.3303/CET1227030
.
Google Scholar
 
Sunartio
D.
,
Ashokkumar
M.
 &
Grieser
F.
2007
Study of the coalescence of acoustic bubbles as a function of frequency, power, and water-soluble additives
.
Journal of the American Chemical Society
129
(
18
),
6031
–
6036
.
https://doi.org/10.1021/ja068980w
.
Google Scholar
Crossref
Search ADS
PubMed
 
Tak
B. Y.
,
Tak
B. S.
,
Kim
Y. J.
,
Park
Y. J.
,
Yoon
Y. H.
 &
Min
G. H.
2015
Optimization of color and COD removal from livestock wastewater by electrocoagulation process: application of Box-Behnken design (BBD)
.
Journal of Industrial and Engineering Chemistry
28
,
307
–
315
.
https://doi.org/10.1016/j.jiec.2015.03.008
.
Google Scholar
Crossref
Search ADS
 
Tan
C.
,
Gao
N.
,
Deng
Y.
,
An
N.
 &
Deng
J.
2012
Heat-activated persulfate oxidation of diuron in water
.
Chemical Engineering Journal
203
,
294
–
300
.
https://doi.org/10.1016/j.cej.2012.07.005
.
Google Scholar
Crossref
Search ADS
 
Thanekar
P.
 &
Gogate
P. R.
2019
Combined hydrodynamic cavitation based processes as an efficient treatment option for real industrial effluent
.
Ultrasonics Sonochemistry
53
,
202
–
213
.
https://doi.org/10.1016/j.ultsonch.2019.01.007
.
Google Scholar
Crossref
Search ADS
PubMed
 
Tiwari
B.
,
Drogui
P.
 &
Tyagi
R. D.
2020
Removal of emerging micro-pollutants from pharmaceutical industry wastewater
. In:
Current Developments in Biotechnology and Bioengineering
.
Elsevier B.V.
https://doi.org/10.1016/b978-0-12-819594-9.00018-8
.
Google Scholar
Crossref
Search ADS
 
Tran
N.
,
Drogui
P.
 &
Brar
S. K.
2015
Sonochemical techniques to degrade pharmaceutical organic pollutants
.
Environmental Chemistry Letters
13
(
3
),
251
–
268
.
https://doi.org/10.1007/s10311-015-0512-8
.
Google Scholar
Crossref
Search ADS
 
Vega
L. P.
 &
Peñuela
G. A.
2018
High frequency sonochemical degradation of benzophenone-3 in water
.
Journal of Environmental Engineering (United States)
144
(
8
),
1
–
7
.
https://doi.org/10.1061/(ASCE)EE.1943-7870.0001406
.
Google Scholar
 
Verma
A. K.
,
Dash
R. R.
 &
Bhunia
P.
2012
A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters
.
Journal of Environmental Management
93
(
1
),
154
–
168
.
https://doi.org/10.1016/j.jenvman.2011.09.012
.
Google Scholar
Crossref
Search ADS
PubMed
 
Vu
X. Y.
,
Bao
Z. C.
 &
Barker
J. R.
2004
Free radical reactions involving Cl•, Cl2-•, and SO4-• in the 248 nm photolysis of aqueous solutions containing S2O82- and Cl-
.
Journal of Physical Chemistry A
108
(
2
),
295
–
308
.
https://doi.org/10.1021/jp036211i
.
Google Scholar
 
Wacławek
S.
,
Lutze
H. V.
,
Grübel
K.
,
Padil
V. V. T.
,
Černík
M.
 &
Dionysiou
D. D.
2017
Chemistry of persulfates in water and wastewater treatment: a review
.
Chemical Engineering Journal
330
,
44
–
62
.
https://doi.org/10.1016/j.cej.2017.07.132
.
Google Scholar
Crossref
Search ADS
 
Wang
S.
 &
Zhou
N.
2016
Removal of carbamazepine from aqueous solution using sono-activated persulfate process
.
Ultrasonics Sonochemistry
29
,
156
–
162
.
https://doi.org/10.1016/j.ultsonch.2015.09.008
.
Google Scholar
Crossref
Search ADS
PubMed
 
Wang
S.
,
Zhou
N.
,
Wu
S.
,
Zhang
Q.
 &
Yang
Z.
2015
Modeling the oxidation kinetics of sono-activated persulfate's process on the degradation of humic acid
.
Ultrasonics Sonochemistry
23
,
128
–
134
.
https://doi.org/10.1016/j.ultsonch.2014.10.026
.
Google Scholar
Crossref
Search ADS
PubMed
 
Wei
Z.
,
Villamena
F. A.
 &
Weavers
L. K.
2017
Kinetics and mechanism of ultrasonic activation of persulfate: an in situ EPR spin trapping study
.
Environmental Science and Technology
51
(
6
),
3410
–
3417
.
https://doi.org/10.1021/acs.est.6b05392
.
Google Scholar
Crossref
Search ADS
PubMed
 
Wei
L.
,
Chen
W.
,
Li
Q.
,
Gu
Z.
 &
Zhang
A.
2018
Wastewater in heat-activated persulfate system
.
RSC Advances
8
,
20603
–
20611
.
https://doi.org/10.1039/c8ra01995a
.
Google Scholar
Crossref
Search ADS
PubMed
 
Xie
P.
,
Ma
J.
,
Liu
W.
,
Zou
J.
,
Yue
S.
,
Li
X.
,
Wiesner
M. R.
 &
Fang
J.
2015
Removal of 2-MIB and geosmin using UV/persulfate: contributions of hydroxyl and sulfate radicals
.
Water Research
69
,
223
–
233
.
https://doi.org/10.1016/j.watres.2014.11.029
.
Google Scholar
Crossref
Search ADS
PubMed
 
Yang
Q.
,
Zhong
Y.
,
Zhong
H.
,
Li
X.
,
Du
W.
,
Li
X.
,
Chen
R.
 &
Zeng
G.
2015
A novel pretreatment process of mature landfill leachate with ultrasonic activated persulfate: optimization using integrated Taguchi method and response surface methodology
.
Process Safety and Environmental Protection
98
,
268
–
275
.
https://doi.org/10.1016/j.psep.2015.08.009
.
Google Scholar
Crossref
Search ADS
 
Yang
L.
,
Xue
J.
,
He
L.
,
Wu
L.
,
Ma
Y.
,
Chen
H.
,
Li
H.
,
Peng
P.
 &
Zhang
Z.
2019
Review on ultrasound assisted persulfate degradation of organic contaminants in wastewater: influences, mechanisms and prospective
.
Chemical Engineering Journal
378
.
https://doi.org/10.1016/j.cej.2019.122146
.
Google Scholar
 
Yuan
R.
,
Jiang
Z.
,
Wang
Z.
,
Gao
S.
,
Liu
Z.
,
Li
M.
 &
Boczkaj
G.
2020
Hierarchical MnO2 nanoflowers blooming on 3D nickel foam: a novel micro-macro catalyst for peroxymonosulfate activation
.
Journal of Colloid and Interface Science
571
,
142
–
154
.
https://doi.org/10.1016/j.jcis.2020.03.041
.
Google Scholar
Crossref
Search ADS
PubMed
 
Zhang
M. F.
,
Qin
Y. H.
,
Ma
J. Y.
,
Yang
L.
,
Wu
Z. K.
,
Wang
T. L.
,
Wang
W. G.
 &
Wang
C. W.
2016
Depolymerization of microcrystalline cellulose by the combination of ultrasound and fenton reagent
.
Ultrasonics Sonochemistry
31
,
404
–
408
.
https://doi.org/10.1016/j.ultsonch.2016.01.027
.
Google Scholar
Crossref
Search ADS
PubMed
 
Zhou
C.
 &
Ma
H.
2006
Ultrasonic degradation of polysaccharide from a red algae (Porphyra yezoensis)
.
Journal of Agricultural and Food Chemistry
54
,
2223
–
2228
.
https://doi.org/10.1021/jf052763h
.
Google Scholar
Crossref
Search ADS
PubMed
 
Zou
X.
,
Zhou
T.
,
Mao
J.
 &
Wu
X.
2014
Synergistic degradation of antibiotic sulfadiazine in a heterogeneous ultrasound-enhanced Fe0/persulfate fenton-like system
.
Chemical Engineering Journal
257
,
36
–
44
.
https://doi.org/10.1016/j.cej.2014.07.048
.
Google Scholar
Crossref
Search ADS
 
© 2022 The Authors
This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/).