UV-initiated synthesis of a novel chitosan-based flocculant with high flocculation efficiency for algal removal

In this study, maleyl chitosan- graft -polyacrylamide (MHCS-g-PAM), a novel chitosan-based flocculant , was prepared through UV irradiation, and maleyl chitosan (MHCS) was designed and prepared with maleic anhydride and acrylamide (AM) through maleyl acylation reaction. The effects of monomer concentration, MHCS-to-AM ratio, illumination time, initiator concentration, pH on viscosity, and grafting efficiency were investigated to optimize the synthesis of these substances. MHCS-g-PAM was characterized through Fourier transform infrared spectroscopy , nuclear magnetic resonance hydrogen spectroscopy, scanning electron microscopy, and thermal gravimetric analysis . Flocculation mechanisms in alga-containing wastewater at various pH levels and dosages were examined in detail on the basis of zeta potential measurements. Zeta potential experiments indicated that the adsorption-bridging and charge neutralization mechanisms played an important role in algal removal. Flocculation tests on algal removal demonstrated that the flocculation performance of MHCS-g-PAM was more effective than that of cationic polyacrylamide, polyferric sulfate, and polymeric aluminium. The optimal Chl- a and COD removal rate obtained by MHCS-g-PAM was 98.6% and 94.9% at pH   7 and 4   mg·L −   1 , respectively.