Study of algal biomass harvesting through cationic cassia gum, a natural plant based biopolymer

•Cationic cassia was synthesized and characterized.•Flocculation dosage was optimized for two different green algae.•Flocculation mechanism was hypothesized.•Cationic cassia was proved to be a better flocculant than cassia. Green unicellular microalgae have a capacity to entrap CO2 to increase their biomass through photosynthesis and are important for the value added product. The presence of COOH and NH2 groups are responsible for imparting negative zeta value. The present work emphasizes on the synthesis of cationic cassia (CCAS) by the insertion of quaternary amine groups onto the backbone of cassia (CAS) from N-3-Chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) which was further characterized via FTIR, SEM, elemental analysis and intrinsic viscosity. The optimal dosage of the synthesized cationic cassia is used to flocculate two different green fresh water algae viz. Chlamydomonas sp. CRP7 and Chlorella sp. CB4 were evaluated. 80 and 35mgL−1 was optimized dose for dewatering of above algae, respectively.