Chitosan-carbamoylcarboxylic acid grafted polymers for removal of metal ions in wastewater

Water contamination by heavy metals is reported all over the world and requires strategic solutions to minimize its environmental impact. In this work, new materials based on chitosan (Q) were grafted with new mono carbamoylcarboxylic acids (mCCA) 1a and 1b were evaluated in the simultaneous removal of six metal ions by coagulation-flocculation process. The physicochemical properties and the interaction of carbamoylcarboxylic acid (CCA)-chitosans Q-1a and Q-1b, chitosan, 1a and 1b with metal ions were analyzed by zeta potential (zeta). CCA-chitosan Q-1a-5 shows significant removal of Cu2+ (99.8 %), Ni2+ (73.1 %) and Zn2+ (67.0 %) and optimal removal dose (ORD) of 20.0 mg/g of M2+, as well as Q-1b-10 performs the removal of Pb2+ (98.8 %), Cu2+ (99.1 %) and Ni2+ (81.1 %) with an ORD of 23.0 mg/g of M2+. The global metal ions removal is 81.2 % with Q-1a-5 and 79.3 % for Q-1b-10, highly superior than chitosan (42.3 % and ORD 34.3 mg/g of M2+). CCA-chitosan Q-1a5 and Q-1b-10 show an improved clarification kinetics (18.3 and 56.8 T%/h, respectively), sedimentation ratio (10.6 and 48.5 mm/h, respectively) and a Turbiscan Stability Index (TSI) value (40.2 and 80.2, respectively) and the metal ions removal is associate to a sedimentation, flocculation and coalescence phenomena, displaying the best characteristics for the wastewater treatment containing different metal ions.