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Contamination of industrial wastewater with dyes poses a significant threat to public health. Extensive efforts have been dedicated to mitigating the presence of dyes in aquatic ecosystems. This research focuses on the degradation of the azo-type NOVACRON® C-4B reactive red dye generated from the textile industry through ultraviolet (UV) radiation in conjunction with hydrogen peroxide (H2O2). This research investigated multiple variables, including dye concentration, pH levels, H2O2 concentration, UV exposure duration, and UV power, to evaluate their influence on the degradation process. The maximum dye degradation of 86 and 78% chemical oxygen demand (COD) reduction was achieved for 50 mg/L dye concentration at pH 4, 0.9 mL of H2O2, and 120 min of UV irradiation time. The degradation results were compared with other advanced oxidation processes to check the effectiveness of this system. It has been demonstrated that the UV/H2O2 system is effective and capable of degrading the azo dyes such as NOVACRON® C-4B reactive red dye effectively compared with other conventional biological and physiochemical treatment processes.

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  • Removal of NOVACRON® red C-4B reactive dye in wastewater was carried out.

  • Results proved that UV/H2O2 is an efficient technique for dye treatment in textile industry wastewater.

  • Degradation efficiency, initial concentration, treatment volume, and treatment time were compared with other AOPs.

  • Utilization of this process at an industrial scale for azo dye removal was recommended.

advanced oxidation process, dye removal, NOVACRON® C-4B reactive dye, textile industry wastewater, UV/H2O2
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Insufficient management of wastewater in recent years has exerted pressure on the limited freshwater resources globally, leading to pronounced water scarcity in numerous regions (Salehi 2022; Zhu et al. 2023). The global water demand is expected to rise 55% by 2050, while around 25% of the large cities globally have water stress levels (Schlamovitz & Becker 2021). In that situation, where 19% of global water is consumed for industrial production (Aquastat 2020), Europe accounts for 54% and Asia accounts for 10% of industrial water consumption, which poses a serious threat to present water quantity (Walling et al. 2022). In Pakistan, an estimated amount of 4.43 billion cubic meters of wastewater is generated annually, and industrial wastewater contributes about 1.37 billion cubic meters (Kahlown et al. 2006). Meanwhile, per-person water availability has fallen from 5,600 m3 to just 1,000 m3, leaving 80% of the population with no access to clean drinking water (masoomabatool 2021). In this situation, wastewater is a precious resource for reclaiming freshwater for human activities to prevent water shortage and human health risks due to toxic chemicals (Saleh et al. 2022). According to estimates, approximately 50,000 tons of wastewater are discharged annually from textile industries, containing untreated dye concentrations ranging from 10 to 30% (Oyetade et al. 2022).

Synthetic azo dye removal is ineffective through conventional biological and chemical treatment methods (Zhu et al. 2000; Neppolian et al. 2002; Saleem et al. 2022). They seem to possess several disadvantages, such as the production of many dangerous byproducts, garbage and sludge production, having several disposal problems and being too expensive (Iqbal et al. 2011). Therefore, it is crucial to develop effective and sustainable wastewater treatment technologies to treat such wastewater pollutants (Guo et al. 2022).

Advanced oxidation processes (AOPs) such as Fenton, photocatalysis, activated per sulfate, UV/O3, dielectric barrier discharge, and other AOP techniques have shown degradation of refractory organic pollutants such as persistent organic pollutants (POPs), antibiotics, iopamidol (Tian et al. 2020; Nawaz et al. 2021; Li et al. 2023), synthetic progesterones (Liang et al. 2022), sulfonamides (Wanga et al. 2021), and chlorfenvinphos (Zawadzki 2023). These techniques are gradually used to degrade micropollutants in wastewater (Peng et al. 2022). UV/H2O2 is also a promising and emerging technique that has attained growing attention in recent years; the degradation and removal of artificial sweetener saccharin (Ye et al. 2022), ibuprofen (Adityosulindro et al. 2022), small aromatic compounds (Ferreira et al. 2022), aniline (Benito et al. 2017), ofloxacin, and levofloxacin (Liu et al. 2020) gave satisfactory results. Decolorizing dye by UV catalysis in H2O2 is also effective by forming free radicals as active species (Castaño et al. 2022; Easton et al. 2023; Ma et al. 2023). The costs associated with it are less than other methods, and the process leads toward mineralization in most scenarios (Bezerra et al. 2021). Although the AOP is an effective treatment technology for the degradation of recalcitrant pollutants in wastewater, azo dyes are disreputably hard to degrade due to their persistence and complex chemical structure that does not degrade easily by conventional biological treatment and physiochemical processes (Kurbus et al. 2003; Liu et al. 2023). Furthermore, it has not been investigated for the removal of NOVACRON® C-4B reactive red dye. This study presents a new approach for the removal of NOVACRON® C-4B dye, employing UV/H2O2 as a standalone technology. The research aims to investigate the dye removal and COD reduction in synthetic wastewater considering various operational parameters to optimize the UV/H2O2 reactor.

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Reagents

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NOVACRON® C-4B reactive red dye was obtained from the local textile industry, hydrogen peroxide (H2O2, 30% w/v), sulfuric acid (H2SO4 98%), sodium hydroxide (NaOH, 1M Merck), and potassium dichromate (K2Cr2O7, analytical grade) were purchased from Sohail Chemicals, Rawalpindi. Each material was utilized under controlled conditions following established safety protocols.

Sample preparation

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A synthetic sample was prepared by adding the desired amount of NOVACRON® C-4B dye (50, 100, 150, and 200 mg/L) to 5.5 L distilled water; after complete mixing, 0.5 L sample was withdrawn for preliminary testing and initial COD along with the dye concentration was determined. The pH of the remaining 5 L sample was adjusted as desired by adding 98℅ sulfuric acid H2SO4 or sodium hydroxide (NaOH). After complete mixing, the sample was poured into the reactor, which was pre-illuminated with an 11 W or 6 W UV lamp for 15 min before sample addition to maintain its intensity (Hollman et al. 2020; Ye et al. 2022; Gan et al. 2023). A diaphragm pump was used for continuous mixing during the experiment with a flowrate of 1.7 L/min (Soleymani et al. 2019). Six batches of experiments were run according to the reactor operation plan shown in Table 1.

Table 1

Batches run design and conditions for different parameter

ParametersBatch 1Batch 2Batch 3Batch 4Batch 5Batch 6
H2O2 varyingpH varyingTime varyingDye conc. varyingUV power varyingOptimum conditions
H2O2 conc. (mg/L) 0.3
0.6
0.9
1.2 		0.9 0.9 0.9 0.9 0.9 
pH 4 2
4
6
8
10 		4 4 4 4 
Time (min) 120 120 30
60
90
120 		120 120 120 
Dye conc. (mg/L) 50 50 50 50
100
150
200 		50 50 
UV power (W) 11 11 11 11 6
11 		11 
ParametersBatch 1Batch 2Batch 3Batch 4Batch 5Batch 6
H2O2 varyingpH varyingTime varyingDye conc. varyingUV power varyingOptimum conditions
H2O2 conc. (mg/L) 0.3
0.6
0.9
1.2 		0.9 0.9 0.9 0.9 0.9 
pH 4 2
4
6
8
10 		4 4 4 4 
Time (min) 120 120 30
60
90
120 		120 120 120 
Dye conc. (mg/L) 50 50 50 50
100
150
200 		50 50 
UV power (W) 11 11 11 11 6
11 		11 
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Photochemical advanced oxidation reactor

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The experiments of NOVACRON® C-4B reactive red dye degradation by the UV/H2O2 system were performed in a custom-made photoreactor made of acrylic sheet with a 6-liter capacity and a working volume of 5 liters, as shown in Figure 1. Low-pressure mercury lamps (12 cm long, 6 W and 11 W, Philips) emitting 254 nm wavelength were used as a UV source (Wang et al. 2017). The UV light lamp was fixed within the center of the photoreactor at a vertical position contained in the quartz tube. The reactor was shielded with aluminum foil sheets to prevent the escape of light rays. A diaphragm pump with an optimum flow rate of 1.7 L/min (Saien et al. 2012) was used to recirculate the sample in the reactor for proper mixing.
Figure 1
Schematic of advanced oxidation reactor assisted with UV/H2O2.
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Schematic of advanced oxidation reactor assisted with UV/H2O2.

Figure 1
Schematic of advanced oxidation reactor assisted with UV/H2O2.
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Schematic of advanced oxidation reactor assisted with UV/H2O2.

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Theoretical design of advanced oxidation reactor

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The theoretical design contains components and dimensions of a reactor system, including a UV rod, a quartz sleeve, influent volume, and various calculations for the area and volume of the reactor. The reactor has a UV rod that is 10 inches long, a quartz sleeve that is 13 inches in length, and an influent volume of 5 liters (equivalent to 305 cubic inches). The area of the reactor is calculated by dividing the volume by the depth of the influent, resulting in an area of 25.4 square inches. The length and width of the reactor are assumed to be equal (1:1 ratio) therefore both are calculated as 5 inches. The total depth of the reactor, including a 3-inch freeboard at the top, is 15 inches. The total volume of the reactor is calculated to be 375 cubic inches or approximately 6.15 liters.

Analytical methods

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The pH of samples was measured using a pH meter (Milwaukee MW101 PRO, USA). The concentration and, ultimately, rate of degradation of NOVACRON® C-4B reactive red dye was calculated using a UV–Vis spectrophotometer (DR6000, Hach, Germany) at a wavelength of λmax = 290 nm. The calibration curve, as shown in Figure 2, was drawn initially by determining different mock dye concentrations.
Figure 2
Calibration curve for NOVACRON® C-4B dye.
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Calibration curve for NOVACRON® C-4B dye.

Figure 2
Calibration curve for NOVACRON® C-4B dye.
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Calibration curve for NOVACRON® C-4B dye.

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The percentage of dye degradation is calculated as follows:
(1)
where Co represents the initial dye concentration and Ct denotes the concentration at time t. Each measurement was conducted three times, and the average result was subsequently recorded.
Similarly, COD tests were performed before and after the experiments. In this test, the sample was oxidized by a strong chemical oxidizing agent, potassium dichromate (K₂Cr₂O₇), and sulfuric acid (H₂SO₄). The amount of dichromate consumed in the reaction was then titrated with a standardized solution of ferrous ammonium sulfate (FAS), and the COD was calculated based on the volume of the titrant used. Removal % of COD is calculated as follows:
(2)
where Ci is the COD of influent and Ce is the COD of effluent. Each measurement was made three times, and the average result was recorded to determine the percentage of removal.
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Effect of initial oxidant concentration

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Optimizing hydrogen peroxide concentration is crucial to minimize its usage while achieving maximum process efficiency. To optimize the UV/H2O2-assisted AOP for NOVACRON® C-4B degradation, the effect of oxidant dosage on dye removal was investigated. As expected, with the increase in oxidant concentration, dye removal efficiency also increased, along with increasing COD removal. The oxidant concentrations were checked at 0.6, 0.9, and 1.2 mL, as shown in Figure 3. At 0.9 mL concentration, the highest COD removal of 29% and dye removal of 47% were observed, which is mainly attributed to the generation of huge quantities of radicals at high oxidant dosages (Çobanoğlu & Değermenci 2022).
Figure 3
Effect of oxidant concentration on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.
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Effect of oxidant concentration on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.

Figure 3
Effect of oxidant concentration on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.
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Effect of oxidant concentration on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.

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Further increasing the oxidant concentration (1.2 mL) resulted in decreased COD removal to about 12% and decreased dye removal to about 27%, which is obvious that the excessive use of oxidants may cause the scavenging effect, which inhibits the degradation process (Chen et al. 2018; Zhu et al. 2019; Çobanoğlu & Değermenci 2022; Gan et al. 2023). A similar phenomenon was reported in previous studies as well, suggesting that in order to achieve the highest pollutant degradation, the oxidant concentration must be optimized. The reason for this phenomenon can be well explained by Reaction (R1), that excess H2O2 acts as a hydroxyl radical quencher, producing hydroperoxyl radicals and water (Afzal et al. 2012), and consequently, consuming the hydroxyl radicals present in the system which is the main cause of degradation. is a less reactive species that decomposes to non-radical products, often without reacting with organic pollutants (Bielski et al. 1985). Therefore, elevated levels of H2O2 could potentially scavenge hydroxyl radicals, reducing the efficacy of the oxidation process. As a result, the initial H2O2 concentration needs to be carefully controlled to optimize the removal process's efficiency.
(R1)

Effect of pH

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Process efficiency may vary depending on the contaminant present and the pH of the wastewater. Hence, the performance of the UV–H2O2-assisted process was investigated at different pH ranges from 2 to 10 with an interval of 2 (Çobanoğlu & Değermenci 2022; Kousar et al. 2022). Results showed that removal of dye and COD was maximum with efficiency of 57 and 38% under acidic conditions at pH 4. While a decline in removal efficiency was observed in the alkaline range. This could be because of the variability of the production and availability of reactive oxygen species (ROS) in the acidic and basic medium, the same phenomena have been witnessed by previous studies (Rehman et al. 2018; Miklos et al. 2019; Mansour et al. 2023; Tuncer & Sönmez 2023). These findings could be explained by the fact that hydroxyl radicals were abundantly available in acidic conditions for dye degradation (Zhang et al. 2020). Conversely, elevating the pH results in reduced production of hydroxyl species as H2O2 undergoes photodecomposition into H2O and O2 rather than forming hydroxyl radical (Muruganandham & Swaminathan 2004; Gu et al. 2012; Wang et al. 2019). Therefore, the efficiency of dye degradation and COD removal was decreased when pH was increased from neutral to alkaline range. Cheng ye et al. have also explained that in an alkaline medium H2O2 undergoes photodecomposition to form which is highly reactive towards and ⁠, eventually leading towards H2O and O2 formation (Ye et al. 2022). Therefore, lower pH was favorable in the degradation of dyes (Figure 4).
Figure 4
Effect of pH on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 2–10, UV power = 11 W, residence time = 60 min.
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Effect of pH on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 2–10, UV power = 11 W, residence time = 60 min.

Figure 4
Effect of pH on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 2–10, UV power = 11 W, residence time = 60 min.
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Effect of pH on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 2–10, UV power = 11 W, residence time = 60 min.

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Effect of time

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The time to degrade dye may vary depending on the complexity of its structure and experimental conditions (Figure 5). Hence, optimizing residence time ensures the length required to remove dye from wastewater considering the field requirements. Here, it was intended to eliminate dye and COD from wastewater by UV assisted with the H2O2 process and check its efficiency at different residence times while keeping H2O2 concentration and pH optimum. For this purpose, residence time was varied from 30 to 120 min at intervals of 30 min. The results discovered a clear connection between the residence time and the removal efficiency of dye and COD. A longer residence period resulted in higher removal efficiency, demonstrating that a longer exposure time responsible for a higher concentration of hydroxyl radical due to H2O2 photolysis (Luo et al. 2021) allows for more extensive interaction between the dye molecules and hydroxyl radicals, promoting degradation efficiency. At 120 min, maximum COD removal of about 78% and dye removal of about 86% was observed. The same phenomena have been noticed in previous UV/H2O2 systems (Cibati et al. 2022; Pai & Wang 2022; Asadollahfardi et al. 2023) as well as in several other AOP studies (de Souza et al. 2023; Easton et al. 2023; Jiang et al. 2023). It is because the longer the pollutant is exposed to hydroxyl radicals, the more time there is for the hydroxyl radicals (•OH) generated by the direct photolysis of H2O2 to react with the pollutants (Chen et al. 2023; de Souza et al. 2023). Therefore, higher residence time leads to a higher dye and COD removal efficiency, as more dye can be degraded into simpler, harmless compounds. However, the type of contaminants present in water may affect the optimum residence time depending on the complexity of the structure. Some dyes may be more resistant to degradation and require longer residence time in the UV/H2O2 process for effective removal (Tuncer & Sönmez 2023).
Figure 5
Effect of time on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 30–120 min.
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Effect of time on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 30–120 min.

Figure 5
Effect of time on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 30–120 min.
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Effect of time on COD and NOVACRON® C-4B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 30–120 min.

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Effect of initial dye concentration

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It is very important to know the dye concentration in the wastewater for an effective treatment. It poses a huge threat to the natural waterbodies if water is discharged with higher pollutant concentrations. Therefore, the effect of different initial dye concentrations on the performance of the UV–H2O2 system was accessed, and the elimination of higher dye concentrations was done (100, 150, and 200 mg/L). The dye removal efficiency for 50, 100, 150, and 200 mg/L of dye concentration was reported to be 86, 75, 54, and 43%, respectively. The highest initial dye concentrations resulted in a minimum degradation rate of about 43% as compared with removal efficiency for 50 mg/L dye concentration, indicating that the presence of a higher concentration (200 mg/L) of dye molecules might compete for hydroxyl radicals, leading to reduced dye removal efficiency (Asadollahfardi et al. 2023). This phenomenon is because higher dye concentrations result in a higher rate of hydroxyl radical hunting by the dye particles themselves, decelerating the degradation of each individual dye molecule (Yang et al. 2023). Another reason reported by Mansour et al. is that the process of photolysis of H2O2 slowed down due to less light reaching the dead zone, which diminishes the number of photons interacting with H2O2 and producing hydroxyl radicals (Mansour et al. 2023). COD removal efficiency decreased to 66, 46, and 34% for synthetic wastewater containing 100, 150, and 200 mg/L of dye concentrations, respectively. Hence, the dye concentration significantly impacts the efficiency and performance of the UV/H2O2 method for the removal of organic dyes as well as COD reduction (Figure 6).
Figure 6
Effect of dye concentration on COD and NOVACRON® red 4C-B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.
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Effect of dye concentration on COD and NOVACRON® red 4C-B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.

Figure 6
Effect of dye concentration on COD and NOVACRON® red 4C-B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.
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Effect of dye concentration on COD and NOVACRON® red 4C-B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.

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Effect of UV power

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The effect of 11 W and 6 W UV power was studied using two UV lamps while keeping other operational parameters optimum for removing 50 mg/L of NOVACRON® C-4B dye. For a UV–H2O2-assisted treatment, a higher intensity UV lamp (11 W) improved the rate of hydroxyl radical production (Zawadzki 2023), resulting in COD removal efficiency of about 38% while dye removal of 57%. Using a 6 W UV lamp resulted in a 36% reduction in COD removal efficiency and a 42% reduction in dye removal efficiency. This is because incident power influences the photolysis rate of H2O2 (Li et al. 2020; Mansour et al. 2023), subsequently increasing the NOVACRON® C-4B degradation rate (Figure 7).
Figure 7
Effect of UV power on COD and NOVACRON® red 4C-B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.
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Effect of UV power on COD and NOVACRON® red 4C-B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.

Figure 7
Effect of UV power on COD and NOVACRON® red 4C-B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.
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Effect of UV power on COD and NOVACRON® red 4C-B dye removal. Experimental conditions: dye = 50 mg/L, pH = 4, UV power = 11 W, residence time = 60 min.

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Mechanism of pollutant removal by the UV/H2O2 process

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AOPs offer compelling alternatives for treating water and wastewater contaminated with anthropogenic substances (Kim & Nithya 2023). High-energy hydroxyl radicals are produced by AOPs which possess a high oxidation potential of 2.8 V (Bach et al. 2010). These hydroxyl radicals engage with the contaminants until they undergo degradation (Nawaz et al. 2023). Notably, these reactive species can break down persistent and challenging-to-remove pollutants (Gaddale et al. 2023). In UV/H2O2, the creation of hydroxyl radicals arises from a precise combination of UV-C light rays with a wavelength of 200–300 nm (Oturan & Aaron 2014) and hydrogen peroxide (Manna & Sen 2023). Under the influence of UV radiations of specific wavelength, hydrogen peroxide undergoes dissociation via the Haber–Weiss mechanism, which is a consequence of O–O bond cleavage. The overall reaction happening in this process is shown below (Oppenländer 2003):
(R2)
Further hydroxyl radical generation is initiated by the following reactions:
(R3)
(R4)
Hydroxyl radicals may also form hydroperoxyl radical on reacting with H2O2, mostly in excess of H2O2. The generation of hydroperoxyl radical makes the contaminant degradation process slow due to its lower reactivity than hydroxyl radical (Audenaert et al. 2011). OH radicals react with the organic pollutants through a variety of mechanisms. The most common reaction pathway involves the abstraction of a hydrogen atom, which produces the organic radical R•·. R• then quickly reacts with dissolved oxygen to procedure the peroxide organic radical RO•2·. These organic radicals break down via bimolecular processes, producing various breakdown products of the pollutant as well as other less toxic byproducts such as formaldehyde, hydrogen peroxide, hydroperoxide radicals, and so forth (Cuerda-Correa et al. 2020). A detailed description of the pollutant removal mechanism by the UV/H2O2 process is illustrated in Figure 8.
Figure 8
Mechanism of the pollutant removal by the UV/H2O2 process.
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Mechanism of the pollutant removal by the UV/H2O2 process.

Figure 8
Mechanism of the pollutant removal by the UV/H2O2 process.
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Mechanism of the pollutant removal by the UV/H2O2 process.

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Analysis

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Capital and operational costs such as maintenance, equipment, chemicals, and cost of electricity are crucial to evaluate technology's total expense. However, the study takes into account only the treatment process with optimal operating conditions for the cost analysis (Miguel et al. 2024). Electrical consumption for the generation of UV radiation represents a major portion of operating costs in UV/H2O2. Furthermore, the expense of H2O2 consumption is inevitable. Therefore, the chemical and electricity consumption for each watt of UV lamp was considered. It was notable that the treatment cost for the UV/H2O2 system using an 11 W lamp and 6 W lamp was calculated as U$ 0.85 and U$ 0.56 per cubic meter, respectively. The results are shown in Table 2, indicating the cost for 1 m3 of wastewater treatment.

Table 2

Estimated expense for the treatment

TreatmentElectricity cost (U$/m3)aChemical cost (U$/m3)Total expenditure (U$)
UV (11 W) 0.64 – 0.64 
UV (6 W) 0.35 – 3.5 
UV/H2O2 (11 W) 0.64 0.21 0.85 
UV/H2O2 (6 W) 0.35 0.21 0.56 
TreatmentElectricity cost (U$/m3)aChemical cost (U$/m3)Total expenditure (U$)
UV (11 W) 0.64 – 0.64 
UV (6 W) 0.35 – 3.5 
UV/H2O2 (11 W) 0.64 0.21 0.85 
UV/H2O2 (6 W) 0.35 0.21 0.56 

aElectricity tariff in Taxila, Pakistan, 2024: U$ 0.15/kWh (IESCO 2024).

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Comparison of this research work and other studies

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Various factors influence the efficiency of reactions, including hydrogen peroxide concentration, power of UV radiation, temperature, pH, pollutant concentration, and recirculation rate (Fard et al. 2023). The removal efficiency achieved in this study was significant and comparable with most of the work conducted in the literature. Therefore, our study was compared with other AOPs based on the degradation efficiency, initial concentration, treatment volume, and treatment time, detailed in Table 3.

Table 3

Comparison of UV/H2O2 process with other advanced oxidation processes (AOPs)

TechniquesPollutantInitial conc.Treatment time (min)Treatment vol. (L)Degradation (percentage%)Ref.
UV/H2O2 NOVACRON® red C-4b 50 mg/L 120 5 86 This work 
UV/PS Saccharin 20 mg/L 45 0.5 85.39 Ye et al. (2022)  
UV/PS/Br− Bisphenol A 2 mg/L 5 – 76.3 Cai et al. (2022)  
UV/PS Oxytetracycline 10 mg/L 60 0.1 58.1 Türk et al. (2023)  
UV/O3 Chlorfenvinphos 1.0 mg/L 20 – 51 Zawadzki (2023)  
UV/O3/US Atrazine 5 mg/L 10 2 93.9 Wen et al. (2022)  
TiO2/UV Chlorfenvinphos 1.0 mg/L 20 – 57 Zawadzki (2023)  
H2O2/Fe3+/WMoOx Tetracycline 400 μM 60 0.1 86 Hu et al. (2019)  
O3/UV Azithromycin 0.6 mg/L 30 4 87 Liu et al. (2014)  
TechniquesPollutantInitial conc.Treatment time (min)Treatment vol. (L)Degradation (percentage%)Ref.
UV/H2O2 NOVACRON® red C-4b 50 mg/L 120 5 86 This work 
UV/PS Saccharin 20 mg/L 45 0.5 85.39 Ye et al. (2022)  
UV/PS/Br− Bisphenol A 2 mg/L 5 – 76.3 Cai et al. (2022)  
UV/PS Oxytetracycline 10 mg/L 60 0.1 58.1 Türk et al. (2023)  
UV/O3 Chlorfenvinphos 1.0 mg/L 20 – 51 Zawadzki (2023)  
UV/O3/US Atrazine 5 mg/L 10 2 93.9 Wen et al. (2022)  
TiO2/UV Chlorfenvinphos 1.0 mg/L 20 – 57 Zawadzki (2023)  
H2O2/Fe3+/WMoOx Tetracycline 400 μM 60 0.1 86 Hu et al. (2019)  
O3/UV Azithromycin 0.6 mg/L 30 4 87 Liu et al. (2014)  
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In this work, with an initial concentration of 50 mg/L and a treatment volume of 5 L in 120 min of treatment time of the UV/H2O2 system, 86% degradation efficiency was achieved, which is very efficient as compared with other AOPs, as mentioned in Table 3. Most of the studies in the literature showed that the degradation efficiency ranges from 51 to 93.9%. Wen et al. obtained the highest efficiency, 93.9%, while their treatment volume and initial concentration were very low, this is the most likely reason for their higher degradation efficiency. Therefore, it was obvious from the comparison that this work has a significant result for the degradation of NOVACRON® C-4B. This research work could be useful for better treating and managing industrial wastewater, thus reducing water pollution and putting less pressure on freshwater resources and aquatic bodies.

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The research investigated the removal of NOVACRON® red C-4B azo dye using a UV–H2O2 reactor under diverse experimental conditions. COD and dye removal efficiencies were examined under various operational parameters, including oxidant concentration, pH, treatment time, UV power, and dye concentration. Under optimum experimental conditions, a significant removal of NOVACRON® red C-4B dye by 86% and a corresponding reduction in COD by 78% were observed.

The results of this study, in comparison with other research, reveal that the UV/H₂O₂ process is an effective technology for removing azo dyes and COD from textile industry wastewater. Therefore, due to its low environmental impact, its application is recommended for treating azo dye-based effluents. It will be interesting to determine the gap between laboratory research and practical implementation for future work by investigating the practicality of deploying and integrating with other AOP systems to utilize at industrial levels. This would evaluate the economic viability of the treatment systems and provide a sustainable solution for the degradation of hazardous pollutants at the industrial level.

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We acknowledge the support from the local textile industry for providing the dye samples and the departmental staff for their cooperation during the whole experiment. Additionally, the authors would like to express sincere appreciation to the editor and anonymous reviewers for their helpful comments and suggestions.

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This work was not supported by any external funding.

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Conceptualization: M.I.N.; Methodology: T.J., F.N., L.C.; Formal analysis and investigation: T.J., S.F.; Writing – original draft preparation: T.J., F.N., L.C., M.I.N.; Writing – review and editing: M.U.S., S.P.; Resources: T.J., S.F., M.U.S.; Supervision: M.I.N., S.F.

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

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The authors declare there is no conflict.

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