Flocculation activity and evaluation of chitosan-based flocculant CMCTS-g-P(AM-CA) for heavy metal removal.

• Novel functionalized chitosan flocculants are successfully synthesized. • Flocculation conditions for reaching high removal efficiencies are optimized. • Characterization results provided empirical evidence for existence of chelating groups. • "3E" triangular model was used to evaluate its flocculation-chelation properties. • Flocculation-chelation capacity profile indicated multiple potential applications. In order to effectively remove the dissolved heavy metals and the heavy metals on the colloidal particles during the flocculation process, a novel dual-functional chitosan flocculant CMCTS-g-P(AM-CA) is prepared by ultraviolet light-initiated graft polymerization using CMCTS, AM, and ammonium dithiocarbamate. The main influencing factors of monomer concentration, monomer ratio, pH value, photoinitiator concentration, and illumination time are investigated on the basis of intrinsic viscosity, grafting rate, and grafting efficiency of CMCTS-g-P(AM-CA). Characterization results provided empirical evidence for existence of chelating groups. In addition, CMCTS-g-P(AM-CA) was applied to treat the simulated heavy metals and electroplating wastewater. The effect of CMCTS-g-P(AM-CA) dosage, pH value, and reaction G value on flocculation efficiency was also explored. After the two-stage flocculation, the residual concentration of Ni(II), COD, and turbidity of actual electroplating wastewater decreased to 0.96 mg/L, 93.00 mg/L, and 1.71 NTU after flocculation tests at optimal condition, respectively. Finally, the "3E" triangular evaluation model is established and applied to evaluate the flocculation performance of CMCTS-g-P(AM-CA) on the actual heavy metal wastewater further, thereby proving its excellent chelation flocculation performance. [ABSTRACT FROM AUTHOR]