Preparation of a graft modified flocculant based on chitosan by ultrasonic initiation and its synergistic effect with kaolin for the improvement of acid blue 83 (AB 83) removal

Abstract

The chitosan (CTS) characterized with many functional amino and hydroxyl groups has been the research focus on flocculants preparation and synthesis because of the facile grafting and modification to enhance and enlarge its original functions. In this study, a new type of graft modified flocculant CTS-g-PAA and its combination with kaolin have been developed for the treatment of acid blue 83 (AB 83). The CTS-g-PAA prepared by ultrasonic initiation of acrylamide (AM), 3-Acrylamide propyltrimethylammonium chloride (AATPAC) and CTS. The factors affecting CTS-g-PAA molecular weight and CTS graft ratio were examined to have a better understanding and comprehending of the ultrasonic initiated polymerization. The structure and morphological characteristics of CTS-g-PAA were investigated and analyzed by infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H NMR), differential thermal/thermogravimetric (TG/DSC), scanning electron microscopy (SEM) and X-Ray Diffraction (XRD), respectively. The results indicated that the CTS cyclic structure was broken by ultrasonic initiation and the grafting occurred at amino group with C2 site of CTS. Meanwhile, the CTS-g-PAA coupled with kaolin exhibited superior flocculation performance better than the single removal effect, and the optimum removal rate for AB 83 could achieve 91.9%. The flocculation mechanism was discussed and summarized based on the conduction of zeta potential, FTIR of floc particles and the adsorption ability of the formed kaolin flocs. During the AB 83 flocculation, the CTS-g-PAA adsorption and flocculation contributed much to the AB 83 removal. The added kaolin particles played a crucial role in the enhancement of AB 83 adsorption and flocculation. The kaolin particles and the formed kaolin floc showed an adsorption effect for AB 83, and the kaolin particles also worked as the bridging between the CTS-g-PAA filled with AB 83 to strengthen the flocculation performance. As a result, the flocculation performance for AB 83 removal was greatly improved.