Abstract:

Decolorization of printing & dyeing industry wastewater is a big challenge for wastewater treatment. In this study，ferrous hydroxy complex(FHC)was used to treat six types of simulation and industrial pollutant samples containing azo dye，and its reductive pretreatment mechanism and efficiency were studied. Influencing factors including morphology of ferrous iron，initial pH of wastewater，dosage of FHC，and molar ratio of Fe/OH^- on the reductive transformation were also studied to examine FHC reactivity towards various azo dyes. The results show that the FHC is of higher reductive reactivity. More than 90% of azo dyes could be removed when the dosage of FHC was 89.6 mg·L^-1. The structure morphology of FHC has great influence on its reductive decolorization. Although both FHC and green rust are of high reduction reactivity，dissolved ferrous iron can not practically react with azo dyes. These results indicated that the structure and morphology of ferrous iron play an important role in decolorization of azo dyes. The decolorization performance is much higher for FHC than that for green rust. The molar ratio of ferrous iron to hydroxyl in FHC can impact its reactivity. The pH value has great influence on reduction of azo dyes by FHC，however，there is 4—10 of pH wide range in which high efficiency of dyes removal can be reached. Experiments for treating textile industrial wastewater showed that the removal of COD_Cr was up to 49% and the BOD₅/COD_Cr ratio increased from 0.32 to 0.62，