Preparation of chitosan/DADMAC/lignin terpolymer and its application of dye wastewater flocculation

Natural polymer flocculants have received extensive attention for their wide source, non-toxicity and renewable raw materials. In this study, a terpolymer of chitosan/diallyl dimethyl ammonium chloride/lignin (CDL) was prepared by microwave-assisted copolymerization technology using chitosan, diallyl dimethyl ammonium chloride (DADMAC) and lignin as raw materials. The effects of monomer ratio, initiator dosage and microwave time on the flocculation efficiency were studied to optimize the synthesis process of CDL. The optimal synthesis parameter was optimized as the chitosan/DADMAC/lignin mass ratio of 2 g:2 g:2 g, the initiator content of 1.0 wt% and the reaction time of 18 min. The CDL showed excellent flocculation efficiencies for acid black 172 and reactive orange C-3R simulated wastewater (100 mg/L) with removal ratios of 99.8% and 97.7% at the CDL concentration of 250 mg/L, respectively. The terpolymer remained excellent flocculation efficiency at a wide range of CDL dosage, where the flocculation mechanism was mainly charge neutralization and bridging effect. Results also showed that the high temperature and acidic environment promoted the color removal process. The synthesized CDL terpolymer is a prospective flocculant due to the advantages of eco-friendliness, excellent flocculation performance, and wide effective temperature and pH ranges.