Enhanced Performance of Natural Polymer Coagulants for Dye Removal from Wastewater: Coagulation Kinetics, and Mathematical Modelling Approach

This study explores the potentials of Brachystegia eurycoma coagulant (BEC) and Vigna subterranean coagulant (VSC) as natural organic polymers (NOPs) for the decolourisation of Crystal Ponceau 6R (AR 44) in wastewater. Materials characterisation studies were done on the precursors. A detailed kinetics study was employed. The decolourisation procedures were evaluated through time-dependent reduction in the concentration of particles, with the variation of the independent parameters. The proximate analysis showed protein contents of 19.77% and 18.15% for BEC and VSC, respectively. The functional test showed the presence of –OH, N–H, and C=H. The surface morphological study revealed some rough surfaces, different pores sizes, and compact-net structures. The order of removal efficiency was VSC > BEC with an optimum of 88.8% and 73.3%, respectively. The values of the coagulation rate constant (K) and coagulation order (α) obtained for BEC and VSC were 6.38 × 10− 4 L mg− 1 min− 1, 1.8 and 4.03 × 10− 3 L mg− 1 min− 1, 1.9, respectively. The coagulation time, Tag of 31.35 and 26.96 min for BEC and VSC, respectively, disclosed quick coagulation. The coagulation-flocculation kinetics demonstrated that the process conforms to the pseudo-second-order model with R2 >0.997, suggesting that the rate-controlling mechanism is governed by chemisorption. In the mass transfer study, experimental data were well predicted by the cross-validation test, with a percentage mean relative deviation modulus (M%) of 3.26 and 2.54 for BEC and VSC, respectively. These coagulants added meaningful progress in wastewater treatment by coagulation-flocculation while displaying significant adsorption features. Likewise, the usage of kinetics studies and particle behaviour modelling should be a prerequisite in water treatment processes.