Photocatalytic Degradation of 4-Chlorophenol Using Zero Valent Iron Activated Persulfate and Zero Valent Iron Activated Hydrogen Peroxide Processes under UV Irradiation: A Taguchi Experimental Design

Abstract

4-chlorophenol (4-CP) is one of the seriously toxic chlorophenol compounds found in the effluent wastewater generated by oil refineries, pharmaceutical factories, and paper and leather producers which introduced into surface and ground water resources. This research aimed to study the feasibility of nZVI nanoparticles in activation of H₂O₂ and persulfate under UVA-LED irradiation based on Taguchi experimental design for 4-CP removal. This experimental study was conducted using a lab-scale batch reactor equipped with 18 ultraviolet light emitting diodes lamps with a wavelength of 390 nm. The effects of operating parameters such as pH of solution, contact time, dosage of nZVI, dosages of H₂O₂ and persulfate and different initial 4-CP concentration were evaluted by difiend factor of 4*4 using Taghuchi L-16 orthogonal array. Based on the results of the Taguchi method, the optimum conditions for removal of 4-CP in nZVI activated persulfate process included the initial 4-CP concentration of 25 mg/L, pH=3, reaction time of 60 min, nZVI and persulafte respective dosages of 2 and 2 mM. The highest removal efficiency and S/N values for this process were 51.83% and 34.29%, respectively. Also, optimum conditions for removal of 4-CP in nZVI activated H₂O₂ process were the initial 4-CP concentration of 25mg/L, pH=3, reaction time of 30 min, nZVI and H₂O₂ dosages of 0.75 and 1 mM. In this condition, the highest removal efficiency and S/N values were 81.76% and 38.25%, respectively. In both processes in this case, under acidic conditions, an increase in the active catalyst (Fe²⁺) activated more and more oxidants (radical hydroxide and radical sulfate) in both reactants, resulting in better efficiency of processes in these conditions. UVA-LED/H₂O₂/nZVI process could serve as a new and feasible approach for the degradation of 4-CP as well as other organic contaminants containing wastewater due to high efficiency, low contact time and need to the lowest oxidants agents. UVA-LED/H₂O₂/nZVI process could serve as a new and feasible approach for the degradation of 4-CP as well as other organic contaminants containing in wastewater due to high efficiency, low contact time and need to the lowest oxidants agents.