Application of different techniques for activation of H2O2/Fe3+ system: A comparative study

Abstract

In the present study, the efficacy of L-ascorbic acid (LAA), sodium sulphite (Na2SO3), sodium thiosulphate (Na2S2O3), and a mixed iron catalyst (Fe3+/Fe2+) to activate Fenton-like (H2O2/Fe3+) system was studied and compared. Aqueous solution of a model emerging contaminant (Diuron, DCMU) was used to assess the treatment efficacy of Fenton (H2O2/Fe2+) and activated/non-activated Fenton-like systems. The DCMU oxidation in Fenton and Fenton-like systems at a DCMU/H2O2/Fe m/m/m of 1/10/1 resulted in more than 99% (in 15 min) and 26% (in 2 h) target compound removal, respectively. The application of inorganic reducing agents (Na2SO3 and Na2S2O3) to activate the Fenton-like system proved ineffective with a negligible improvement in DCMU degradation as compared to the non-activated Fenton-like system. The application of organic reducing agent (LAA) to activate the Fenton-like system was more promising and demonstrated almost equal DCMU removal efficacy for both the Fenton system at a DCMU/H2O2/Fe2+ m/m/m of 1/10/1 and LAAactivated Fenton-like system at a DCMU/H2O2/Fe3+/LAA m/m/m/m of 1/10/1/1. The DCMU degradation in H2O2/(Fe3+/Fe2+) system was slower than in the Fenton system, but nevertheless, complete DCMU removal was observed after 2 h of oxidation at a DCMU/H2O2/Fe2+/Fe3+ m/m/m/m of 1/10/0.2/0.8. The highest mineralisation was observed in the classical Fenton system followed by the mixed catalyst-activated Fenton-like process. The activation of Fenton-like system by mixed iron catalyst (Fe3+/Fe2+) proved to be more feasible for the application in the water or wastewater treatment using un-regenerated ferric sludge catalysed Fenton process.