Application of kinetics and mathematical modelling for the study of colour removal from aqueous solution using natural organic polymer

The potential of using Moringa oleifera coagulant (MOC) as a coagulant in colour concentration reduction from Crystal Ponceau 6R dye using spectrophotometric method has been studied. The kinetics and mathematical modelling were employed to study the particle transfer rate during coagulation-flocculation process. The proximate composition, structure, and surface morphology of the coagulant were analysed using standard official methods, Fourier-Transform Infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM), respectively. The removal process was evaluated through time-dependent decrease in particle concentrations and consequently, flocs growth formations. Effects of the process parameters including pH, coagulant dosage, dye concentration, settling time, and temperature were tested and the best ranges were determined experimentally. The best operating conditions established were pH 2, 800 mg MOC/L coagulant dosage, 20 mg/L dye concentration, 420 min, and 303 K. The best colour removal was achieved at 93.8%. The values of rate constant, K and order of reaction, alpha obtained were 8.09E-04 L/mg min and 2, respectively. The coagulation time, of 87.72 min showed a rapid coagulation process. Coagulation-adsorption kinetics showed a high agreement of the process to pseudo-second order model implying that chemisorption is the rate controlling step. Adsorption of particles on the polymer surfaces occurred mostly as a mono-molecular layer according to chemisorption mechanism. Model equation was verified using experimental data and coagulation kinetics parameters in MATLAB environment. Cross validation test showed good prediction of the experimental data. The precursor extracts have potential for application as a coagulant while showing significant part of adsorptive phenomenon. Applying kinetics and modelling in wastewater treatment study is a requirement in separation processes that involves particle transfer.