Degradation and toxicity evaluation of azo dye Direct red 83:1 by an advanced oxidation process driven by pulsed light

Abstract

Water contamination by dyes is an ecological problem that can be alleviated by advanced oxidation processes (AOPs). A common AOP uses hydroxyl radicals generated by splitting H2O2 using UV light. Pulsed light (PL) technology can be used as light source in AOPs having the advantage of producing fast effects. Direct red 83:1 (DR) is an azo dye that is being used to study the elimination of dyes from wastewaters but details about its degradation by a PL/H2O2 process are missed. In this work, the effect of H2O2 and dye concentrations, pH and salts on the decolourization of DR were determined by spectrophotometry. The PL/H2O2 process was able to degrade nearly 80 % of the dye after 45 light pulses. Absence of photolysis and inhibition by hydroxyl scavenging indicate that the degradation was due to oxidation hydroxyl radicals. The decolouration was higher at low dye concentration, high H2O2 concentration and alkaline conditions, and was inhibited by salts. These results are useful for the further use of DR as model dye to study the potential of PL as an alternative light source in AOPs for dye degradation. Further studies are recommended to estimate the treatment conditions required for enhancing toxicity abatement.