Application of green coagulants on paint industry effluent – a coagulation– flocculation kinetic study

ABSTRACT The behavior of green, eco-friendly coagulants, derived from Strychnos potatorum, Cactus opuntia, Moringa oleifera, Cyamopsis tetragonolobus and Portunus sanguinolentus was evaluated and optimized for the removal of color and turbidity from simulated paint industry effluent (SPE). A series of bench-scale flocculation experiments were conducted in jar test apparatus to examine the optimal dose of coagulant, at different initial pH and initial concentration of the effluent. The eluent type and concentration were varied, to extract the maximum amount of active coagulant compounds viz, proteins (from S. potatorum, M. oleifera), cellulose (from C. opuntia), chitosan (from P. sanguinolentus), polysaccharides (from C. tetragonolobus) and to attain the maximum removal efficiency. The obtained optimized conditions from the SPE were applied for the treatment of real paint industry effluent. All the five coagulants exhibited the maximum removal efficiency at the actual pH of the effluent itself. The coagulation kinetic study suggests the order of kinetics, and the model parameters were obtained from the linear equations. The time evolution pattern of formation of monomers, dimmers and trimmers was evaluated. The comparisons of the green coagulants with chemical coagulants have also been studied.