Assessment of Biosorption Potential of Poplar Sawdust for Removal of Dyes from Wastewater under Single and Binary System

Abstract

In the present study, the performance of raw sawdust (RSD) as a biosorbent was assessed for the removal of model dyes (MB-Methylene blue and CR-Congo red) in single as well as binary systems under various wastewater conditions. Biosorption studies in single system under simulated wastewater conditions showed highest uptake of MB and CR taking place at pH 6 and 2, respectively. pH and FTIR studies revealed the binding to be electrostatic in nature, while a inter-particle diffusion mechanism was found to be operative. Irrespective of the nature of the dye, equilibrium was found to be achieved within 60 mins. Biosorption studies carried out in binary systems under similar experimental conditions in simulated wastewater showed no significant difference in the removal efficiency. This could be attributed to the fact that there is no competitive relationship between the cationic (MB) and anionic (CR) dyes when present simultaneously in the wastewater. On the other hand, the results as obtained under real wastewater binary system reveal lower removal capacity for the removal of the dyes which could be due to competitive adsorption of organic pollutants as verified by a 50 % reduction in COD in the real wastewater. Irrespective of the wastewater conditions, isotherm studies showed that at lower adsorbate concentrations, the Langmuir model was operative while the Freundlich model showed higher correlation at higher adsorbate concentrations. Experimental results thus verify the usefulness of RSD as an economic, cost effective and potential biosorbent for the removal of dyes from diverse wastewater conditions