The role of sulfonated chitosan-based flocculant in the treatment of hematite wastewater containing heavy metals.

• CS-g-P(AM-AMPS) possessed the multifarious functional groups. • Two synthesis pathways and two products were discovered in preparation via XPS. • CS-g-P(AM-AMPS) and PAFC played the different roles in hematite wastewater treatment. • Dissolved heavy metals were removed by chelation, adsorption and co-settlement. Hematite wastewater containing dissolved heavy metals is a potential threat to eco-environment and human health. Flocculation as an efficient and cost effective water treatment technology should be applied in its treatment. A sulfonated chitosan-based flocculant (CS-g-P(AM-AMPS)) was prepared via graft copolymerization. Two synthesis pathways and reaction products with different molecular structure were discovered in processes. CS-g-P(AM-AMPS) possessed the multifarious functional groups that contributed to its excellent performance in hematite wastewater treatment. Bridging, adsorption and entrapment in coagulation-flocculation were enhanced due to CS-g-P(AM-AMPS), and the impressive floc size and high removal efficiency were represented in the treatment as well. Dissolved heavy metals in the wastewater were removed by the chelation of sulfonate group in CS-g-P(AM-AMPS), the adsorption of other functional groups and the co-settlement with flocs. CS-g-P(AM-AMPS) will have the potential application in industrial wastewater treatment for its high flocculation performance, thermal stability and solubility. [ABSTRACT FROM AUTHOR]