Preparation, characterization and evaluation of chitosan biguanidine hydrochloride as a novel antiscalant during membrane desalination process

Scale deposition is considered as one of the most critical problems leading to permeate flux decline and deterioration of membrane surface in reverse osmosis (RO) desalination plants. This study aims to preparation of novel high effective scale inhibitor, chitosan biguanidine hydrochloride (CG), to inhibit the precipitation of calcium sulfate and carbonate onto the membrane surface. The modification of Chitosan by the guanidine group was to enhance its solubility in water, because chitosan as it is dissolves only in moderately acidic solutions. CG was synthesized and characterized by FTIR, C-13 NMR and H-1 NMR. The inhibition efficiency of our antiscalant was evaluated against CaSO4 and CaCO3 solutions at both static (induction time) and real application tests (cross-flow unit for 6 h). CG showed a good performance as scale inhibitor for CaSO4 and CaCO3 at about 10 and 15 mg.L-1 with flux decline of 2.6 and 5% in feed water, respectively. In addition, the induction time of precipitation of CaSO4 increased from 3 to 15 min with the addition of CG. SEM analysis at different magnifications for Cs and CG proved that CG strongly affects the morphology of the precipitated calcium sulfate and calcium carbonate leading to distortion of crystals. (C) 2018 Production and hosting by Elsevier B.V. on behalf of King Saud University.