Synthesis and decolorizing performance of modified flocculant for treating dyeing wastewater

To improve the decolorizing performance of epichlorohydrin and polyamine flocculants, the modified epichlorohydrin-dimethylamine decolorizing flocculant was prepared using diethylenetriamine as the cross-linking agent and epichlorohydrin and dimethylamine as raw materials. Its flocculating performance was studied through the flocculation experiment by using Reactive Brilliant Red X - 3 B as the simulated dyeing wastewater. Effects of material molar ratio, reaction temperature, water temperature, pH value, concentration of dyes and dosage of modified flocculant on the performance of the decolorant were studied. Mixed usage with polyacrylamide was also investigated. The optimized conditions to prepare the modified flocculant are that the molar ratio of epichlorohydrin to dimethylamine to diethylenetriamine is 1 :0. 95 :0. 05 and reaction temperature is 90 °C. The optimized conditions of flocculating decolorization are that water temperature is 20 °C, pH value is 4, concentration of dyes is 200 m g/L, and modified flocculant dosage is 125 mg/L. Under the optimized conditions of flocculating decolorization, the modified flocculant was used, achieving 91. 0 % color removal. The results indicate that the modified decolorizing flocculant shows a better performance than the unmodified decolorizing flocculant. The modifier improves the charge neutralization and bridging-netting function of the modified flocculant. Decolorization performance and salt tolerance of the modified flocculant are improved due to the mixed usage with polyacrylamide. © 2022 China Textile Engineering Society. All rights reserved.