Abstract

Ni0.5Zn0.5Fe2O4 magnetic nanoparticles were synthesized to obtain a new efficient adsorbent for diclofenac sodium (DF) removal. Fourier Transform Infrared (FTIR), Energy Dispersive Spectrometer (EDS), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET) and vibrating sample magnetometer (VSM) were applied to characterize the prepared adsorbent. These analyses revealed that adsorbent was successfully prepared with average particle diameter of about 50 nm and a BET surface area of 168.09 m2/g. The saturation magnetization value of magnetic nanoparticles (MNPs) was found to be 24.90 emu/g, thus, adsorbent was efficiently separated from the solution by a facile and rapid magnetic separation process. The effect of adsorption time, amount of adsorbent, initial pH of the solution, initial diclofenac concentration and temperature on the removal of DF were evaluated. Also, the adsorption data were best fitted to the pseudo-first-order kinetic model and Langmuir isotherm model. The thermodynamics studies suggested spontaneous and exothermic adsorption. The maximum diclofenac adsorption amount of the synthesized nanoadsorbent was 52.91 mg/g, which is higher than many recently studied adsorbents.

HIGHLIGHTS

  • Facile and rapid separation of Ni0.5Zn0.5Fe2O4 magnetic nanoparticles from aquatic media using external magnetic field.

  • Diclofenac adsorption onto Ni0.5Zn0.5Fe2O4 MNPs was investigated in terms of isotherm, kinetic, and thermodynamics.

  • Effect of initial diclofenac concentration, contact time, adsorbent dosage, pH, and temperature were evaluated.

Graphical Abstract

Graphical Abstract
Graphical Abstract

INTRODUCTION

During the last several years, the existence of pharmaceutical compounds in aquatic media has been widely detected. These compounds are discharged into the aquatic systems through hospitals and drug factories (Calza et al. 2006; Ahmed & Hameed 2018). They have a risk of poisoning for human health and organisms. So, it is imperative to eliminate pharmaceuticals from water (Rivera-Utrilla et al. 2013; Lara-Martín et al. 2015).

Diclofenac (DCF) is one of the widely used pharmaceutical compounds for reduction of inflammation and pain relief (Soares et al. 2019; Shayesteh et al. 2020). Diclofenac consumption was found to be about 1,000 tons per year (Pylypchuk et al. 2018). Diclofenac is a non-degradable toxic substance and can be absorbed and enriched by organisms and human bodies (Xiong et al. 2019; Xu et al. 2021). Its long term exposure has adverse results such as thyroid disease, hemodynamic and renal effects (Hasan et al. 2016; Bickley et al. 2017). With these deleterious effects, the removal of diclofenac from effluents is extremely important.

Thus, various methods including flocculation, biodegradation, electrochemical degradation, chlorination, ozonation and adsorption, have been used to treat contaminated wastewaters (Finkbeiner et al. 2015; Shayesteh et al. 2016; Mohebali et al. 2018; dos Santos et al. 2019; Sharma et al. 2019; Nodehi et al. 2020). However, many of them suffer disadvantage of high investment and operating costs, disposal of resulting sludge and complexity (Carmalin Sophia et al. 2016). Among them, one of the most common and prominent methods is the adsorption process. This technique offers high adsorption capacity, simplicity of design and high efficiency (Bhadra et al. 2016; De Oliveira et al. 2017). Various adsorbents such as bentonite (Putra et al. 2009), montmorillonite (Parolo et al. 2008), natural zeolite (Ötker & Akmehmet-Balcioğlu 2005) and silica (Turku et al. 2007) have been employed for elimination of pharmaceutical pollutants from aquatic media.

Among a range of adsorbents, nano-sized adsorbents have recently attracted great interest as pharmaceutical adsorbents because of their high adsorption capacity based on their small size. In particular, magnetic nanoparticles (MNPs) attracted far more attention for use as magnetically separable nanoadsorbents. It had been proved that the magnetic property of nanoparticles allows them to be recovered rapidly and effectively by an external magnetic field from aquatic media in comparison to conventional approaches of centrifugation or filtration (Pashai Gatabi et al. 2016; Ashrafi et al. 2017; Fato et al. 2019; Thakur et al. 2020). The adsorption of pharmaceutical compounds on different magnetic nanoparticles like activated carbon modified with magnetite nanoparticles (Yegane Badi et al. 2018), MnFe2O4/rGO (Bao et al. 2018), NFO@SiO2@GPTS@Cys (Kollarahithlu & Balakrishnan 2019), and others have been studied.

This work is an effort to remove diclofenac pollutant using Ni0.5Zn0.5Fe2O4 MNPs from aqueous solution. For this purpose, Ni0.5Zn0.5Fe2O4 magnetic nanoparticles were prepared. Then, the characterization of adsorbents was conducted by some analytical techniques. After that, the adsorption process of this magnetic nanoadsorbent was carried out. Several parameters affecting the adsorption method, like contact time, initial diclofenac concentration, amount of nanoadsorbent, initial solution pH and temperature, were investigated. Also, equilibrium isotherm and kinetic model studies were done.

EXPERIMENTAL SECTION

Chemicals

Materials including iron chloride (FeCl3.6H2O), zinc acetate (ZnAc2.2H2O), nickel chloride (NiCl2.6H2O), sodium hydroxide (NaOH) and hydrogen chloride (HCl), of analytical grades, were employed. Sodium hydroxide (NaOH) and hydrogen chloride (HCl) were applied as pH-adjusting agents. Distilled water applied in all experiments.

Equipment

Fourier Transform Infrared (FTIR) of the synthesized sample was done through a potassium bromide (KBr) pellet with an FTIR spectrometer (Perkin Elmer Spectrum, Germany). The adsorbent surface area has been analyzed by Brunauer–Emmett–Teller (BET) method (NOVA® Station B, Quantachrome). To investigate the morphological features of magnetic nanoadsorbent, scanning electron microscope (SEM) images were obtained (VEGA\\TESCAN SEM). Qualitative composition analysis of MNPs was performed using an Energy Dispersive Spectrometer (EDS) attached to an SEM instrument. The magnetic features of the sample were determined from magnetization measurement using a vibrating sample magnetometer (VSM) (Lakeshore, USA). The diclofenac absorbance was determined using a UV–vis spectrometer (Shimadzu, Japan). An ultrasonic bath was used for the mixing of samples (DT31H, BANDELIN electronic, Germany).

Synthesis of Ni0.5Zn0.5Fe2O4 magnetic nanoparticles

The Ni0.5Zn0.5Fe2O4 MNPs were synthesized according to the procedure of Bajorek et al. (Bajorek et al. 2019). In the typical procedure, 18.81 g FeCl3.6H2O, 2.377 g NiCl2.6H2O and 2.195 g ZnAc2.2H2O were dissolved into the 250 ml of NaOH (1 mol/L) under continuous mechanical stirring (600 rpm) at 95 °C. Stirring continued until Ni0.5Zn0.5Fe2O4 MNPs formation (approximately 90 min). Then, a strong magnet was applied to collect synthesized MNPs from solution. Finally, the solid residue was washed repeatedly with distilled water and acetone, followed by drying at 50 °C for 12 h, to obtain nano-scale Ni0.5Zn0.5Fe2O4 powder.

Adsorption studies

The adsorption of diclofenac on Ni0.5Zn0.5Fe2O4 MNPs was investigated through batch technique. A stock solution (1,000 mg/L) was prepared by dissolving the appropriate amount of DF in distilled water, which was diluted to desired concentrations (15–150 mg/L). Various parameters affecting the adsorption process, namely contact time (15–90 min), adsorbent concentration (0.1–1.8 g/L), initial pH (3.2–10.3), initial diclofenac concentration (15–150 mg/L) and temperature (25–55 °C), were evaluated. The effect of each parameter was assessed by varying that parameter while the other parameters were kept constant. All batch experiments were performed in an ultrasonic bath, using 250 mL Erlenmeyer flasks including 50 mL diclofenac solution. For each experiment, 60 mg of MNPs was added to 50 mL of desired diclofenac solution, and 0.5 M HCl or 0.5 M NaOH was applied to adjust the solution pH. The resulting solution was mixed for a predetermined time. After adsorption, MNPs were separated magnetically. The remaining diclofenac concentration in solution was determined via UV–visible spectrometer.

The diclofenac removal efficiency was calculated using Equation (1) and the adsorption capacity of adsorbent was obtained by Equation (2) (Sarbisheh et al. 2017; Shayesteh et al. 2021):
formula
(1)
formula
(2)
where C0, Ce and C are the liquid-phase concentration of diclofenac in solution at the initial, equilibrium and final states, respectively (mg/L). V shows the liquid phase volume (L), and M stands for the mass of the adsorbent (g).

RESULTS AND DISCUSSION

Characterization results

The FTIR spectrum of Ni0.5Zn0.5Fe2O4 magnetic nanoparticles is shown in Figure 1. The bands at 489 cm−1 and 445 cm−1 are the characteristic bands of Ni-O and Zn-O, revealing the presence of Ni and Zn in the structure of synthesized Ni0.5Zn0.5Fe2O4 magnetic nanoparticles (Thakur et al. 2016; Sharma et al. 2020). The peak at 593 cm−1 can be assigned to the stretching frequencies of Fe-O in ferrite tetrameric sites. The peak observed at 1,624 cm−1 indicates the H-O-H bond. The absorption band at 3,421 cm−1 is due to hydroxyl groups (O-H stretching vibration bond) (Wu et al. 2006; Sharma et al. 2017).

Figure 1

FTIR spectrum of Ni0.5Zn0.5Fe2O4 magnetic nanoparticles.

Figure 1

FTIR spectrum of Ni0.5Zn0.5Fe2O4 magnetic nanoparticles.

The magnetic characteristic of the Ni0.5Zn0.5Fe2O4 magnetic nanoparticles was characterized by VSM analysis and the result is shown in Figure 2. The Ni0.5Zn0.5Fe2O4 MNP has a saturation magnetization of 24.90 emu/g. Within the external magnetic field, Ni0.5Zn0.5Fe2O4 magnetic nanoparticles indicated a good magnetic response and were separated in several seconds.

Figure 2

VSM magnetization curve of Ni0.5Zn0.5Fe2O4 nanoparticles.

Figure 2

VSM magnetization curve of Ni0.5Zn0.5Fe2O4 nanoparticles.

SEM was used to investigate the morphology of MNPs, as shown in Figure 3. Figure 3(a)–3(c) demonstrate the presence of nanosize particles, with an average diameter equal to 50 nm. As can be seen in Figure 3(a)–3(c), there are predominantly mostly regularly spherical-shaped particles. Also, small aggregates of MNPs are due to magnetic dipole-dipole interaction between nanoparticles. A similar observation was reported by Bennet and coworkers (Bennet et al. 2016). Also, the SEM image of Ni0.5Zn0.5Fe2O4 MNPs after the adsorption process (Figure 3(d)) shows that the adsorbent has a stable structure.

Figure 3

SEM-imaging of Ni0.5Zn0.5Fe2O4 magnetic nanoparticles (a-c) before adsorption (d) after adsorption.

Figure 3

SEM-imaging of Ni0.5Zn0.5Fe2O4 magnetic nanoparticles (a-c) before adsorption (d) after adsorption.

The result of elemental analysis of the Ni0.5Zn0.5Fe2O4 nanoparticles was provided from the energy dispersive spectrometry, presented in Figure 4. The existence of Ni and Zn peaks is consistent with the FTIR analysis. Also, the obtained MNPs revealed a BET surface area of 168.09 m2/g.

Figure 4

EDS spectrum of Ni0.5Zn0.5Fe2O4 magnetic nanoparticles.

Figure 4

EDS spectrum of Ni0.5Zn0.5Fe2O4 magnetic nanoparticles.

Effect of contact time on diclofenac adsorption

Determining equilibrium contact time is important to study the adsorption behaviour of diclofenac on Ni0.5Zn0.5Fe2O4 MNPs. To assess the impact of contact time, adsorption tests were done up to 90 min. As presented in Figure 5, an increase in diclofenac adsorption by increasing contact time can be seen. It is seen in this figure that after 60 min no considerable changes were observed and equilibrium time was attained. This fast equilibrium time might be due to high dispersion and high specific surface area of Ni0.5Zn0.5Fe2O4 MNPs. The results revealed that kinetic of adsorption of DF could be divided into two phases: an initial rapid phase where adsorption was fast, that can be attributed to a large number of vacant sites of adsorbent and high DF concentration gradient in the first few minutes, and a slower second phase where the adsorption rate was relatively small, that can be attributed to a lower number of vacant sites of adsorbent and the falling DF concentration in the solution after several minutes of adsorption process (Nassar 2012; Izanloo et al. 2019). A similar observation has been reported by Gaurav Sharma et al. (Sharma & Naushad 2020).

Figure 5

impact of contact time on diclofenac adsorption by Ni0.5Zn0.5Fe2O4 MNPs [C0 = 20 mg/L, pH = 6, adsorbent dose = 1.2 g/L, and T = 25 °C].

Figure 5

impact of contact time on diclofenac adsorption by Ni0.5Zn0.5Fe2O4 MNPs [C0 = 20 mg/L, pH = 6, adsorbent dose = 1.2 g/L, and T = 25 °C].

Effect of adsorbent dosage on diclofenac adsorption

Impact of adsorbent dosage on diclofenac removal is presented in Figure 6. The adsorbent quantity was varied within the range of 0.1 g/L to 1.8 g/L by keeping all other parameters constant. It is clear that increase in adsorbent dose results in an increase in removal efficiency from 18.83% to 57.15%, and leads to obtaining lower adsorption capacity from 37.66 mg/g to 7.01 mg/g. The increase in removal efficiency of diclofenac could be explained by the availability of more adsorbent for a certain amount of diclofenac. At higher adsorbent dose, more adsorption sites are available for DF. On the other hand, the reduction of adsorption capacity at high adsorbent dose may be due to excess binding sites of adsorbent. In other words, adsorption capacity relies on DF-to-binding sites ratio (Ashrafi et al. 2017; Huang et al. 2019).

Figure 6

impact of adsorbent dosage on diclofenac adsorption [C0 = 20 mg/L, pH = 6, contact time = 60 min, and T = 25 °C].

Figure 6

impact of adsorbent dosage on diclofenac adsorption [C0 = 20 mg/L, pH = 6, contact time = 60 min, and T = 25 °C].

Effect of initial pH on diclofenac adsorption

The pH of diclofenac media may be considered as an important parameter in diclofenac removal by Ni0.5Zn0.5Fe2O4 MNPs. In order to evaluate the effect of pH on diclofenac adsorption, the initial pH of the solution was regulated to 3.2, 6, 7.7 and 10.3 by either NaOH or HCl. The outcome of the experiments is shown in Figure 7. It is clear that the lowest adsorption capacity was observed at a pH of 10.3 (4.54 mg/g) and the maximum adsorption capacity was reached at pH 3.2 (9.81 mg/g). The higher adsorption capacity of diclofenac at low pH could be due to the positively charged adsorbent surface (Zha et al. 2013; Demiral & Güngör 2016).

Figure 7

impact of pH on diclofenac adsorption onto Ni0.5Zn0.5Fe2O4 MNPs [C0 = 20 mg/L, contact time = 60 min, adsorbent dose = 1.2 g/L, and T = 25 °C].

Figure 7

impact of pH on diclofenac adsorption onto Ni0.5Zn0.5Fe2O4 MNPs [C0 = 20 mg/L, contact time = 60 min, adsorbent dose = 1.2 g/L, and T = 25 °C].

Equilibrium study

The adsorption isotherm denotes equilibrium concentration of adsorbate between the adsorbent and solution. The three most common isotherm models are Langmuir, Freundlich and Temkin (Elabbas et al. 2016; Pathania et al. 2017; Farooghi et al. 2018).

The Langmuir isotherm suggests a homogenous adsorbent surface without interactions between adsorbed molecules. The linearized form of this isotherm is represented in Equation (3):
formula
(3)

Here in Equation (3), qe (mg/g) and Ce (mg/L) represent the concentration of drug on the adsorbent and in aqueous solution, respectively. qm (mg/g) represents the highest adsorption capacity on the adsorbent, and KL (L/mg) is Langmuir adsorption equilibrium constant. KL is referred to as adsorption energy. The values of and can be obtained through a plot of versus .

The Freundlich isotherm model is generally used for heterogeneous surface and multilayer adsorption. The linearized form of this isotherm is written as Equation (4):
formula
(4)
where KF and n are Freundlich parameters that show adsorption capacity of adsorbent and degree of adsorption. A plot of versus reveals a straight line of slope and an intercept of .
The Temkin isotherm model considers the interactions of adsorbates on the adsorbent. The linearized form the Temkin model is written as Equation (5):
formula
(5)
where bT (J/mol) is the Temkin constant, which represents the adsorption heat, AT (L/g) is called the Temkin isotherm binding constant, R (8.314 J/mol K) stands for the universal gas constant and T (K) denotes temperature. A linear plot of qe against ln Ce was applied to calculate bT and AT.

The variation in the adsorption amount with diclofenac initial concentration by Ni0.5Zn0.5Fe2O4 MNPs was investigated. The Ni0.5Zn0.5Fe2O4 MNPs adsorption capacity with different equilibrium concentrations of diclofenac is illustrated in Figure 8. According to this figure, the adsorption capacity of adsorbent, qe (mg/g), increased from 5.25 mg/g to 44.72 mg/g when equilibrium concentration increased, which is most likely due to enhanced driving force to overcome mass transfer resistance of the diclofenac between adsorbent and solution. A similar result was also reported by Hemmati et al. (Hemmati et al. 2016).

Figure 8

Isotherm plot of diclofenac adsorption onto Ni0.5Zn0.5Fe2O4 MNPs.

Figure 8

Isotherm plot of diclofenac adsorption onto Ni0.5Zn0.5Fe2O4 MNPs.

The adsorption isotherm is used to analyze the equilibrium data. For this purpose, adsorption equilibrium data for diclofenac removal onto Ni0.5Zn0.5Fe2O4 MNPs have been studied with the three most common adsorption isotherms, namely the Langmuir, Freundlich and Temkin. The isotherm parameters of models were obtained and tabulated in Table 1. According to Table 1, the values of correlation coefficient (R2) obtained from the Langmuir isotherm (0.9905) are higher than those from the Freundlich isotherm (0.9796) and Temkin isotherm (0.9328), indicating that the Langmuir model for experimental data could well describe the adsorption process, which reveals the monolayer coverage of diclofenac on the surface of the adsorbent. The maximum amount of adsorption capacity (qm) was 52.91 mg/g. A similar observation was reported by Sun et al. (Sun et al. 2017). Furthermore, the comparisons of maximum adsorption of DF onto different adsorbents are listed in Table 2. The result shows that the qm value obtained was higher than those reported from many recent studies.

Table 1

Isotherm constants of diclofenac adsorption on Ni0.5Zn0.5Fe2O4 MNPs

Isotherm model
Langmuir qm (mg/g) 52.91 
KL (L/mg) 0.0291 
R2 0.9905 
Freundlich KF 2.231 
1/n 0.6937 
R2 0.9796 
Temkin bT (J/mol) 184.73 
AT (L/g) 13.409 
R2 0.9328 
Isotherm model
Langmuir qm (mg/g) 52.91 
KL (L/mg) 0.0291 
R2 0.9905 
Freundlich KF 2.231 
1/n 0.6937 
R2 0.9796 
Temkin bT (J/mol) 184.73 
AT (L/g) 13.409 
R2 0.9328 
Table 2

Comparison of maximum adsorption of DF onto different adsorbents

Adsorbentsqm (mg/g)Reference
Bentonite organoclay Spectrogel 42.3 De Oliveira et al. (2017)  
CoFe2O4 18.4 Tran et al. (2020)  
GO@CoFe2O4 32.4 Tran et al. (2020)  
Clay mineral 15.9 Sun et al. (2017)  
Montmorillonite organoclay prepared with hexadecyltrimethylammonium 54.40 De Oliveira et al. (2017)  
Activated carbon from olive stones 11 Larous & Meniai (2016)  
Carbon nanotube 24.01 Hu & Cheng (2015)  
Hexadecyltrimethylammonium bromide-modified zeolite 45.87 Krajišnik et al. (2011)  
Reduced oxide graphene 59.67 Jauris et al. (2016)  
Activated carbon from cocoa shell 63.5 Saucier et al. (2015)  
Ni0.5Zn0.5Fe2O4 MNPs 52.91 This study 
Adsorbentsqm (mg/g)Reference
Bentonite organoclay Spectrogel 42.3 De Oliveira et al. (2017)  
CoFe2O4 18.4 Tran et al. (2020)  
GO@CoFe2O4 32.4 Tran et al. (2020)  
Clay mineral 15.9 Sun et al. (2017)  
Montmorillonite organoclay prepared with hexadecyltrimethylammonium 54.40 De Oliveira et al. (2017)  
Activated carbon from olive stones 11 Larous & Meniai (2016)  
Carbon nanotube 24.01 Hu & Cheng (2015)  
Hexadecyltrimethylammonium bromide-modified zeolite 45.87 Krajišnik et al. (2011)  
Reduced oxide graphene 59.67 Jauris et al. (2016)  
Activated carbon from cocoa shell 63.5 Saucier et al. (2015)  
Ni0.5Zn0.5Fe2O4 MNPs 52.91 This study 

Kinetic study

Adsorption kinetic models describe the rate of the adsorption process. To provide information about the adsorption mass transfer mechanism of the adsorbent, two well-known adsorption kinetic models were used. The experimental kinetic adsorption data were evaluated by pseudo-first-order and pseudo-second-order kinetic models (Chaudhry et al. 2016; Cholico-González et al. 2020).

The linearized mathematical form of the pseudo-first-order kinetic model is represented by Equation (6):
formula
(6)

Here in Equation (6), qe (mg/g) and qt (mg/g) represent the amount of MB diclofenac adsorbed at equilibrium and time t (min), respectively. K1 (min−1) is known as the pseudo-first-order adsorption rate constant. Values of qe and K1 may be calculated from the straight-line plot against t.

The linearized mathematical form of the pseudo-second-order kinetic model can be expressed as Equation (7):
formula
(7)

Here in Equation (7), K2 (g.mg−1 min−1) shows the rate constant of pseudo-second-order model. The qe and K2 were calculated from the straight-line plot versus t.

In this work, the pseudo-first- and second-order kinetic models have been applied to ascertain the adsorption mechanism. As outlined in Table 3, the R2 values calculated from pseudo-first-order and pseudo-second-order kinetic models were 0.9979 and 0.9971, respectively, indicating that the pseudo-first-order kinetic model provides the better fit.

Table 3

Kinetic model constants of diclofenac adsorption on Ni0.5Zn0.5Fe2O4 MNPs

Kinetic model
Experimental qe,exp (mg/g) 9.62 
Pseudo-first-order qe,calc (mg/g) 9.72 
k1 (min−10.0853 
R2 0.9979 
Pseudo-second-order qe,calc (mg/g) 11.32 
k2 (g.mg−1 min−10.0061 
R2 0.9971 
Kinetic model
Experimental qe,exp (mg/g) 9.62 
Pseudo-first-order qe,calc (mg/g) 9.72 
k1 (min−10.0853 
R2 0.9979 
Pseudo-second-order qe,calc (mg/g) 11.32 
k2 (g.mg−1 min−10.0061 
R2 0.9971 

Thermodynamic study

The influence of solution temperature on diclofenac removal by Ni0.5Zn0.5Fe2O4 MNPs was tested and results are shown in Figure 9. The adsorption capacity was reduced while increasing solution temperature from 298 to 328 K.

Figure 9

Effect of temperature on diclofenac adsorption onto Ni0.5Zn0.5Fe2O4 MNPs [C0 = 20 mg/L, contact time = 60 min, adsorbent dose = 1.2 g/L, and pH = 6].

Figure 9

Effect of temperature on diclofenac adsorption onto Ni0.5Zn0.5Fe2O4 MNPs [C0 = 20 mg/L, contact time = 60 min, adsorbent dose = 1.2 g/L, and pH = 6].

The thermodynamic parameters including Gibbs free energy variation (ΔG°), enthalpy variation (ΔH°) and entropy (ΔS°) can be obtained by the following expression (Bhatti et al. 2017):
formula
(8)
formula
(9)
formula
(10)

Enthalpy (ΔH°) and entropy (ΔS°) can be estimated from Equation (10). The obtained thermodynamic parameters are given in Table 4. The negative value of ΔH° reveals that the adsorption process is an exothermic process. The negative value of ΔS° can be ascribed to decreased the randomness of drug molecules while they adsorbed on the Ni0.5Zn0.5Fe2O4 MNPs. Also, the negative value of ΔG° indicates a spontaneous process.

Table 4

Thermodynamic parameters of diclofenac adsorption on Ni0.5Zn0.5Fe2O4 MNPs

Temp (K)ΔG° (J mol−1)ΔH° (kJ mol−1)ΔS° (J mol−1 K−1)
298 −435.8  − 4.4556  − 13.451 
303 −340.83 
318 −155.62 
328 −48.54 
Temp (K)ΔG° (J mol−1)ΔH° (kJ mol−1)ΔS° (J mol−1 K−1)
298 −435.8  − 4.4556  − 13.451 
303 −340.83 
318 −155.62 
328 −48.54 

CONCLUSION

This study reports the testing on synthesized Ni0.5Zn0.5Fe2O4 MNPs as an efficient adsorbent for diclofenac removal from an aquatic system. FTIR, EDS, SEM, BET and VSM were applied to characterize the prepared adsorbent. The magnetic property of the adsorbent allows for easy, efficient, and fast separation and recovery after use. The optimum parameters for the maximum adsorption were pH of 3.2, temperature of 298 K, and contact time 60 min. The adsorption time (60 min) indicates the adsorbent has a fast adsorption rate. The diclofenac adsorption data followed the Langmuir isotherm and pseudo-first-order kinetic model. The maximum Langmuir adsorption capacity of 52.91 mg/g was obtained for diclofenac removal from aquatic media. Calculated thermodynamic parameters revealed an exothermic and spontaneous process. Finally, it is concluded that Ni0.5Zn0.5Fe2O4 MNPs can be applied as a novel adsorbent in diclofenac removal applications.

NOVELTY STATEMENT

As far as we know, no attention has been paid to employ Ni0.5Zn0.5Fe2O4 magnetic nanoparticles in the role of an adsorbent for treating diclofenac-polluted water.

DATA AVAILABILITY STATEMENT

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

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