Performance of polymer coagulants for colour removal from dye simulated medium: Polymer adsorption studies

Abstract

Evaluation of natural coagulants for colour removal from dye simulated wastewater has been studied. The proximate compositions and surface morphologies of the organic polymers are investigated. The effects of operational parameters including pH, coagulant dosage, dye concentration, settling time and temperature are tested and their optimum operating ranges determined. Acidic solution pH increased the colour removal efficiency. Accurate control of coagulant dosages is required for optimum destabilization of charged particles. Dye concentration is a driving force that shows the extent of particle transfer. Polymer performances on the flocculation process are measured through time-dependent decrease in particle concentrations and consequently, promoting flocs growth. Charge neutralization, polymer adsorption, inter-particle bridging and sweep-flocculation are the active mechanisms in the removal process. Adsorption of particles on the polymer surfaces occur mostly as a monomolecular layer and according to chemisorption mechanism. The agreement of pseudo-second order and Elovich model with high correlation (R²>0.926) confirms the coagulation-flocculation/adsorption kinetics behaving more as a second-order rate process.