Direct red 89 dye degradation by advanced oxidation process using sulfite and zero valent under ultraviolet irradiation: Toxicity assessment and adaptive neuro-fuzzy inference systems modeling

Abstract

Sulfate-based advanced oxidation process mediated by zero-valent iron (ZVI) and ultraviolet radiation for the decomposition of sulfite salts resulted in the formation of strong oxidizing species (sulfate and hydroxide radi-cals) in aqueous solution is reported. Degradation of direct red 89 (DR89) dye via UV/ZVI/sulfite process was systematically investigated to evaluate the effect of pH, ZVI dose, sulfite, initial DR89 concentration, and re -action time on DR89 degradation. The synergy factor of UV/ZVI/sulfite process was found to be 2.23-times higher than the individual processes including ZVI, sulfite and UV. By increasing the ZVI dose from 100 mg/L to 300 mg/L, dye degradation was linearly enhanced from 67.12 & PLUSMN; 3.36 to 82.40 & PLUSMN; 4.12 by the UV/ZVI/ sulfite process due to enhanced ZVI corrosion and sulfite activation. The highest degradation efficiency of 99.61 & PLUSMN; 0.02 was observed at pH of 5.0, ZVI(0) = 300 mg/L, and sulfite(0) = 400 mg/L. Toxicity assessment by Lepidium sativum demonstrated that treated dye solution by UV/ZVI/sulfite was within the non-toxic range. The application of optimal adaptive neuro-fuzzy inference system (ANFIS) to predict DR89 degradation indicated high accuracy of ANFIS model (R-2 = 0.97 and RMSE = 0.051) via the UV/ZVI/sulfite process. It is suggested that UV/ZVI/sulfite process is suitable for industrial wastewater treatment.