Synthesis and characterization of cationic tamarind seed polysaccharide: An effective flocculating agent.

A series of cationic tamarind seed polysaccharides (CTSPs) with different degrees of substitution were synthesized by etherification of tamarind seed polysaccharides (TSP) with 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHPTAC). By elemental analysis, zeta potential and FTIR, the successful linking of cationic groups on the chain of TSPs were confirmed, and the substitution degrees were determined as 0.143, 0.197 and 0.346, respectively. NMR data indicated that the quaternary ammonium groups were linked to C6 of T-Gal. Subsequently, the flocculation behaviors of CTSPs in kaolin solution were investigated, and the results showed that both the degree of substitution and pH affected their flocculation properties. Charge neutralization and positional blocking effects caused flocculation to show an increasing and then decreasing trend with increasing substitution of CTSPs, whereas the lower the pH, the less flocculant was required to achieve the same flocculation effect. The presence of positive charges allowed CTSPs to effectively remove negatively charged waste water such as kaolin suspensions. [Display omitted] • A novel cationic tamarind seed polysaccharide-based flocculant (CTSP) was designed and prepared. • The surface of CTSPs was more rough and uneven than that of TSP. • CTSP showed excellent flocculation ability in neutral and acidic range. • Charge neutralization plays a leading role in the process of flocculation. [ABSTRACT FROM AUTHOR]