Effect of chelating agents on Reactive Green 19 decolorization through Fe⁰-activated persulfate oxidation process

The effect of chelating agents on the decolorization of Reactive Green 19 (RG19) through Fe⁰ activated persulfate (PS/Fe⁰) process was investigated. Though other previous studies reported that chelating agent can enhance the degradation of organic contaminant in Fenton-like system, our finding showed that the presence of chelating agents would chelate free Fe²⁺ and minimize free Fe²⁺ concentration, which resulted in the retardation of RG19 decolorization. RG19 decolorization decreased to 7%, 21%, and 15% in the presence of sodium citrate, sodium EDTA, and sodium oxalate, compared with control test (without chelating agent, 99%) within 10 min. The degradation efficiencies decreased with increasing chelating agent concentrations because of complex formation with Fe²⁺. Higher PS concentration, Fe⁰ dosage, and temperature had an obvious enhancement for RG19 decolorization efficiency. Elucidation of RG19 containing sodium EDTA degradation pathways indicated that PS/Fe⁰ process could degrade RG19 to carboxylic acids and inorganic salts efficiently. The presence of sodium EDTA had no influence on by-products, and EDTA just played a chelating agent function for chelating Fe ions.