Study on the Flocculation Performance of a Cationic Starch‐Based Flocculant on Humic Substances in Textile Dyeing Wastewater
Kexu Wang, Hongfei Liu, Yating Wang, Dishun Zhao, Jianhua Zhai
Abstract
Abstract Dissolved organic matter is one of the difficult problems in the treatment of textile dyeing wastewater, among which humic substances are the most harmful to the environment and human health. Herein, cationic starch‐based flocculants are prepared by free radical polymerization of corn starch (St) and methacryloyloxyethyl trimethyl ammonium chloride (DMC) in a redox‐initiated system of ammonium persulfate and sodium bisulfite. Corn starch‐graft‐poly(methacryloyloxyethyl trimethyl ammonium chloride) is denoted as St‐g‐PDMC. The St‐g‐PDMC is comprehensively characterized in terms of structural (element analysis, Fourier transform infrared, X‐ray diffraction, proton nuclear magnetic resonance spectroscopy), morphological (scanning electron microscopy), and thermal (differential scanning calorimetry) properties. Humic acid (HA) solution is selected to simulate negatively charged dissolved organic matter. The flocculation performance and mechanism of St‐g‐PDMC, cationic polyacrylamide (CPAM), and polymerized aluminum chloride (PAC) are systematically investigated. The experimental results show that St‐g‐PDMC functions mainly through the electric neutralization and bridging effect as the flocculation mechanism, CPAM using its own structure and the colloid formed by PAC through hydrolysis is more in line with the bonded bridging and net roll sweep trapping. The combined formulation of St‐g‐PDMC and PAC shows advantages over a single flocculant in the treatment of textile dyeing wastewater, and its cost is evaluated.