Intensified degradation of reactive blue 222 (RB222) textile dye by a hybrid AOP system of hydrodynamic cavitation coupled with inline UV and PMS oxidant

Abstract

Treatment of textile wastewater poses a significant problem due to the recalcitrant nature of dyes. The present work aims to evaluate a hybrid advanced oxidation process (AOP) comprising hydrodynamic cavitation (HC), ultraviolet irradiation (UV) and different oxidants. Synthetic wastewater (SW) was prepared by dissolving 50 ppm of reactive blue 222 dye, salt, sodium carbonate and detergent. A venturi, a single-hole orifice plate and multiple-hole orifice plates were compared as cavitating devices for HC. Multiple-hole orifice plate 3 proved to be the most efficient cavitation device. Three different oxidants, namely Fenton, potassium peroxymonosulfate (PMS), and potassium persulfate (KPS), were compared in combination with HC + UV. PMS turned out to be the most effective oxidant at pH 6.5, and HC + UV + PMS was the most effective treatment process as compared to standalone methods. NaCl (salt) in wastewater promotes the degradation of RB222 dye, and sodium carbonate suppresses the degradation of RB222 by scavenging radicals. After 120 min, the TOC reduction for the HC-only, UV-only, HC + UV, UV + PMS (2 g/L), and HC + UV + PMS (2 g/L) process was 3.23 %, 4.17 %, 9.64 %, 32.48 %, 38.51 %, and 75.96 %, respectively. After 180 min of treatment with HC + UV + PMS (2 g/L), the maximum 85.66 % TOC reduction of SW was reached, and the complex intermediates formed are also reported.