Synthesis of an amphoteric chitosan-based flocculant and its flocculation performance in the treatment of dissolved organic matter from drinking water

The safety of drinking water arouses wide concern in countries. Dissolved organic matter (DOM) as a precursor of disinfection by-products is the potential threat to human health. An amphoteric chitosan-based flocculant, CS-g-P(AM-AMPS), was synthesized via graft copolymerization to improve DOM treatment in this study. Acrylamide as a trigger and bridge conduced to grafting sulfonate groups originating from 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) onto molecular chains of CS. Initiator dosage, reaction temperature and reaction time influenced the generation of free radicals and further impacted the characteristics and performance of CS-g-P(AM-AMPS). CS-g-P(AM-AMPS) possessing anionic sulfonate groups and cationic amido groups strengthened bridging and adsorption in drinking water treatment, enhanced the removal rate of DOM and the settling efficiency of flocs and weakened the inhibition of natural organic matter to coagulation. DOM was partly removed via co-settling with colloid particles and being trapped by flocs as well.