Degradation of Reactive Red 120 using hydrogen peroxide in subcritical water

Abstract

Reactive azo dyes, such as Reactive Red 120, are commonly used to dye cellulosic fibres. Reactive dyes have a low utilization degree compared to other types of dyestuff, since the functional group also bonds to water, creating hydrolysis. This results in only 60% fixation to fabrics, therefore creating considerable amounts of wastewater. In this work, we propose a simplified method that uses hydrogen peroxide and manipulates the properties of the aqueous environment of the wastewater to degrade the dye. No pumping systems or rotational parts are required, just a closed vessel and a source of heat. Hydrogen peroxide is used as an environmentally-friendly oxidant, as it leaves no residues after treatment. Complete degradation of RR 120 was achieved at all temperatures, dye and oxidant concentrations in no more than 70 min. The TOC removal ranged between 20–64% at all conditions. This method is a safe and environmentally-friendly process that has great potential for treating a wide range of textile wastewaters.