Adsorptive Treatment of Textile Wastewater Using Activated Carbon Produced from Mucuna pruriens Seed Shells

Abstract

Mucuna pruriens seed shells (abundantly available agricultural waste) were processed, treated and activated using 60% orthophosphoric acid for removal of congo red and malachite green from an aqueous solution. Its physicochemical properties and its removal efficiencies on the textile dyes were determined. The effect of particle size, adsorbent dose, initial pH of solution, adsorbate concentration and contact time on the process of adsorption was investigated. The equilibrium, kinetic and thermodynamic properties of the dyes removal were also investigated. The experimental data were modeled using linear regression method of analysis. The correlation coefficient was used as a criterion for model adequacy and acceptance. Sum of squares error was used to validate the isotherm models. The pseudo second-order kinetic model was found to best correlate the experimental data. The intraparticle diffusion is not the only rate controlling step in the process. The experimental data were found to follow the Langmuir, Freundlich and Tempkin isotherm models. The negative free energy indicated that the adsorption processes were spontaneously feasible. The process of adsorption has been found to be endothermic in nature. The removal of malachite green was found to be more spontaneous and feasible than the removal of congo red on the adsorbent. From the study it was deduced that the Mucuna pruriens seed shells activated with phosphoric acid were found to be a good adsorbent for the treatment of textile wastewater containing congo red and malachite green.