Decoloration of three azo dyes in water by photocatalysis of Fe (III)–oxalate complexes/H2O2 in the presence of inorganic salts

Coloration of textiles is improved by inorganic salts, which increase pollution load on dyehouse effluent in general. In this paper, four inorganic salts including sodium chloride, sodium sulphate, sodium nitrate and potassium chloride were used for investigating their effects on photocatalytic decoloration of three azo dyes, Mordant Black PV, Reactive Blue MS and Direct Sky Blue 5B in water based on Fe (III)–oxalate complexes/H2O2 system in a specially designed photoreactor. Also the photocatalytic degradation and mineralization of the dyes were examined by UV–vis spectrum and TOC measurements. The results indicate that photocatalytic decoloration of the dyes is significantly limited in the presence of salts. Increasing concentration of inorganic salts in water can give rise to reduced decoloration efficiency and kinetic reaction constants of the dyes. Sodium chloride and potassium chloride exhibit stronger inhabiting power on photocatalytic decoloration and degradation than sodium sulphate and sodium nitrate under the same reaction condition.