---

Background and purpose: In oil and petrochemical industries, organic aromatic compounds such as furfural are produced on a large scale. They are degradable or act as a deterrent for biological systems. In order to generate sulfate radical (SO4), persulfate (S2O8-2, PS) is often activated by heat, UV irradiation and intermediate metals like iron ions. The aim of this study was to investigate the efficiency of activated S2O8-2 by electrically produced iron using the iron electrode (modern process of electro/ persulfate) for furfural removal. Material and methods: In this study, a lab-scale batch reactor equipped to 4 electrodes and direct power source was used to remove furfural. The effects of key parameters such as pH, voltage, initial concentration of S2O8-2 and furfural on the process were studied. Furthermore, we investigated the changes in pH during the process and the effect of the optimized situation Results: The findings showed that initial pH, S2O8-2 initial concentration and voltage played an important role in furfural removal. Under acidic situations, an increase in the efficiency was seen, and by raising pH the amount of furfural removal decreased. We observed that 98% of furfural was removed in 60 min (pH=3, voltage=10 V, S2O8-2 concentration=8.4 mM). When the concentration of furfural was raised, the efficiency declined. At pH=5, 7, 9 and 11 after 60 min, the efficiencies were 66, 53, 48 and 12, respectively. By increasing voltage to 10 V, the highest rate of efficiency was seen. By applying S2O8-2 separately, after 60 min the efficiency was 39% while at these conditions, the efficiency of the electrochemical process was only 28%. By contrast, electro/persulfate could remove 98% of furfural. Conclusion: The use of S2O8-2 ion in electrochemical reactors equipped to iron electrode can increase the efficiency of the process. Thus, the application of this novel process could be of great benefit for industrial wastewater plants operators.

---

Background and purpose: In Electro/Fe2+/persulfate process, persulfate radicals are produced as powerful oxidizing agents which increase the efficiency of this process. The aim of this study was to investigate the efficiency removal of COD, TSS and dye from industrial effluent in Buali industrial area in Hamedan. Materials and methods: In this study, the batch experiment was performed using a reactor equipped with four iron electrodes. We studied the effects of some operating parameters including pH (3-11), divalent iron ion dose (0.1 to 0.5 g/L), concentration of persulfate anion (0.5-2 g/L) and direct current electric rate (1-5 A) in removal of COD, TSS and dye from wastewater. The COD, TSS and dye measurement was done according to the standard methods. Results: The results showed that under optimum conditions (pH: 3, Fe+2 dosage: 0.1 g/L and density: 5A) the removal efficiencies of process in COD, TSS and dye were 91.6, 73.5 and 93.1%, respectively. By making changes in the parameters, the efficiency of process also changed. The removal efficiency of single application of electrooxidation was 58.2%, 52.2% and 68% for COD, TSS and dye, respectively. Conclusion: The electro/Fe2+/persulfate process showed acceptable performance in removal of COD, TSS and dye. Therefore, this process could be used as a pretreatment unit to reduce the load of raw wastewater pollution before entering the conventional treatment units. Furthermore, the assessment of synergistic effects of persulfate revealed that single application of electrochemical degradation in optimum conditions had a much lower efficiency compared to electro/Fe+2/persulfate process.

---

Background and purpose: Phthalate esters (PEs) are a large family of industrial chemicals widely used as plasticizers. Phthalates can cause endocrine disruption and cancers. Nowadays, phthalate esters are commonly used in cosmetics, adhesives and toy industries and simply get into the surface water and groundwater. The aim of this study was to evaluate the performance of UV / Na₂S₂O₈ / Fe²⁺ in DEP removal from aqueous solution.

Materials and methods: In this study the effect of pH, concentration of persulfate, Fe²⁺ concentration and contact time on removal of diethyl phthalate were studied in laboratory scale using a cylindrical-shaped reactor containing a UV-C lamp (16 watts) by batch method. The residual concentrations of Diethyl phthalate )DEP( were determined by HPL. The effects of independent parameters on DEP removal were evaluated by Multi simplex and the response surface method (box Behnken method).

Results: In this study the optimum condition was obtained at pH = 11, persulfate concentration of 0.4 Mmol/L, 0.07 Mmol/L Fe²⁺ and 90 minutes contact time. The results showed that the DEP removal by UV / Na₂S₂O₈ / Fe²⁺ process followed a first-order reaction kinetic.

Conclusion: The results indicated high efficiency of UV / Na₂S₂O₈ / Fe²⁺ process (95% removal under optimal condition) in removal of DEP from aqueous solutions. This efficiency demonstrates that this method is acceptable in DEP removal on industrial scale.

---

Background and purpose: Metronidazole is a serious environmental pollutant due to high consumption and persistence in biological degradation. This study aimed at removal of metronidazole using ozone (O₃) activated persulfate (PS) in presence of ultrasound (US).

Materials and methods: A laboratory scale study was carried out in batch reactor using US irradiation and O₃ generator apparatuses. The effects of operating parameters such as pH of the solution, different initial concentrations of persulfate, initial metronidazole concentration, different ion strength, and radical scavenger were evaluated. Metronidazole concentration was determined using DR-5000 Spectrophotometer in 320 nm wavelength.

Results: The results showed that removal of metronidazole decreased by increasing the pH of solution from 3 to 11. The removal rate of metronidazole was dependent on initial PS dosages and the highest rate of removal was found in 500 mg/l (94.7%), but in higher concentrations the removal rate decreased. Also, the metronidazole removal rate decreased by increase in initial concentration of metronidazole. The COD removal rate in optimum condition was 56%.

Conclusion: Activation of PS by US/O₃ process could serve as a novel treatment for removal of metronidazole in aqueous solution.

---

Background and purpose: Using catalysts to enhance the efficiency of the ozonation process (known as catalytic ozonation process) has received much attention in recent years. This study aimed at examining the overall feasibility of using catalysts ozone as catalyst in ozonation process for decolorization and mineralization of a real textile wastewater in presence of persulfate.

Materials and methods: This experimental study was conducted on a laboratory scale reactor using a semi-batch mode. The effect of persulfate, ozone flow rate, reaction time and catalytic dose in dye and COD was investigated in an optimal state of textile wastewater. To obtain optimization test, the experiment was performed by fractional factorial method at three-level factorial (3k−p) with a high resolution (VI).

Results: In this study, 15 min contact time (P = 0.006) and 0.5g/L dose of catalyst (P=0.029) had the best effect on color removal. Moreover, the interaction of these parameters were found to be significant (P= 0.025). The optimum condition for color removal was achieved at 15 min reaction time, ozone flow rate of 2 L/min, 1.5 mM persulfate and catalyst dosage of 0.5 g/L. Optimum efficiency removal for color and COD in textile wastewater were 96% and 75%, respectively.

Conclusion: Application of nano-magnesium oxide with ozone in presence of persulfate showed synergistic effect and buffering property in decolorization and mineralization of textile wastewater. It also increases the efficacy of color removal and improves mineralization so, there would be no need for pH adjustment.

---

Background and purpose: Chlorophenol compounds are refractory and toxic contaminants that enter the environment as a result of industrial activities. They can contaminate water sources through leaking into the groundwater or being washed out from polluted soil. The aim of the present study was to evaluate the rate of 4-Chlorophenol (4-CP) degradation using the UV/NaPS process.

Materials and methods: In this investigation, the photochemical oxidation process was conducted in a batch type laboratory-scale photoreactor (1.5 L) equipped with a 50000  power. This study also investigated the effects of independent variables including sodium persulfate concentration (8.4-84 mmol/L), pH (3-10), 4-CP concentration (0.5.5 mmol/L), and reaction time (2-30 min) on the removal efficiency of 4-CP. The effluent concentration of 4-CP was measured by the UV-visible spectrophotometer at 280 nm wavelength. In addition, kinetic model was investigated.

Results: The optimum removal efficiency of 4-C by UV/NaPS process was 89.3% with sodium persulfate concentration of 8.4 mmol/L, pH of 5, initial 4-CP concentration of 1.5 mmol/L, and reaction time of 30 min. Moreover, 60.4% of the total organic carbon (TOC) was removed under similar condition. In addition, the data was found to follow the first-order kinetics.

Conclusion: Considering the growing use of UV radiation in water treatment processes and the considerable efficiency of UV/NaPS process in removing 4-CP, this method can be proposed for the elimination of 4-CP after performing cost-benefit analyses.

---

Background and purpose: Antibiotics are extensively used in treatment of diseases. Metronidazole is an antimicrobial agent and is a nitroimidazole derivative, which is widely used in treatment of infectious diseases caused by bacteria and protozoa. This compound is irrefrangible, toxic, carcinogenic, mutagenic, and has high solubility in water. Advanced oxidation process is an effective method for removal of metronidazole from aqueous solutions. The aim of this study was to evaluate the efficacy of advanced oxidation process based on persulfate (UV / Na₂S₂O₈) to remove metronidazole from aqueous solutions.
Materials and methods: In this research, the effect of some variables such as pH, persulfate concentration and contact time was studied by a UV-C lamp (16 watts). Also, the remaining concentration of metronidazole was measured by UV-Vis spectrophotometer Cecil model CE7400.
Results: The optimum conditions in this study were obtained at pH=9، persulfate concentration of 0.7 mmol/l, and contact time of 30 min. The removal of metronidazole by advanced oxidation process based on persulfate (UV / Na₂S₂O₈) followed the first-order kinetic model.
Conclusion: Persulfate-based advanced oxidation process (UV/Na₂S₂O₈) is an effective method for removal of metronidazole from aqueous solution. It is recommended as an effective and efficient process that could be used for purification of aqueous solutions.
 
 

---

Background and purpose: Pharmaceutical products, particularly antibiotics are emerging contaminants that cause major environmental challenges due to cumulative effects, different adverse effects, and leading to drug resistance. The aim of this experimental study was to evaluate the efficiency of advanced oxidation process by persulfate activated by UV in removal of ofloxacin from aqueous solutions.
Materials and methods: In order to investigate the removal efficiency of ofloxacin, major operating parameters including initial pH of solution (2-12), the concentration of persulfate (50-3500 mg/l), concentrations of ofloxacin (2-100 mg/l), reaction time (6-30 min), and UV radiation (8,15,30 Watt) were studied.
Results: Maximum removal efficiency of ofloxacin and COD in optimal conditions (pH =6, persulfate concentration = 350 mg/l, ofloxacin concentration = 40 mg/l, reaction time =20 min and UV radiation = 8 watt) were 94.35% and 79.17%, respectively. Advanced oxidation with activated persulfate by UV, deceased the concentrations of ofloxacin and COD to 2.26 and 37.21 mg/l, respectively.
Conclusion: The results showed that using UV activated persulfate is an efficient method in removal of ofloxacin from aqueous solutions.