An in-house UV-photolysis setup for the rapid degradation of both cationic and anionic dyes in dynamic mode through UV/H2O2-based advanced oxidation process

Abstract

ABSTRACT A simple in-house UV-photolysis setup was utilised in dynamic mode for the degradation of cationic (methylene blue, rhodamine B and crystal violet) and anionic (congo red, methyl orange and acid red 27) dyes using H2O2 as an oxidising reagent. The methodology was optimised by using methylene blue and acid red 27 as representatives of cationic and anionic dyes, respectively. The optimisation process involved the study of the following critical parameters: concentration of dye and H2O2 and sample flow rate for achieving complete and instantaneous degradation of dye. Using the experimental conditions established during optimisation, at a concentration of H2O2 (0.03% (v/v) dye concentration of 50 µg mL−1 and a sample flow rate of 6 mL min−1, it was possible for complete degradation (>99%) of dye compounds. TOC and COD values of treated samples were decreased to about 79% and 91%, respectively after second UV-photolysis/H2O2 treatment indicating the considerable degradation of dyes was occurred during UV-photolysis process. In addition, studies on the effect of various ions Na+, K+, Ca2+, Mg2+, Fe3+, Cl−, NO3 −, SO4 2-, PO4 3- and CO3 2- that are normally present in dye effluents were carried out and the results indicated that these ions had no significant effect on the degradation efficiency of dyes. The developed procedure was finally applied to real textile wastewater which was degraded very effectively (>99%) indicating that the developed UV-photolysis setup has high potential for commercial scale applications.