Decolorization of anionic and cationic dyes by electro-adsorption process using activated carbon electrodes

Abstract

The performance of the Coconut shell (CS) and Bael shell (BS) activated carbon electrodes on removal of Methylene blue (MB) and Eosin-Y (EY) dyes have been carried out by electro-adsorption process. Modification of electrodes is done to enhance the decolourization performances. The colour removal capability of the electrodes are evaluated by varying the process parameters such as time (15-150 min), potential (5- 45 V) and initial dye concentration as (25-200 mg/L) in batch mode. The adsorption isotherm is determined by Langmuir, Freundlich and Jovanic-Isotherms models. The kinetic data are evaluated by using Pseudo-first and Pseudo-second order model and the rate of diffusion is determined by Intra-particle diffusion model. The electrochemical studies are carried out by cyclic voltammetry and Tafel plots. The experimental results depict that the adsorption isotherm follow the Langmuir isotherm model with the correlation co-efficient, R² = 0.99 for CS activated carbon electrode system, whereas the BS activated carbon electrode system strongly adhere to Freundlich Isotherm models. In addition, the rate kinetics follow Pseudo-first order kinetic model with R² = 0.99 for all the studies. The surface changes, elemental interaction, porosity, functional groups involved in electro-adsorption process and thermal stability are analysed for raw and modified form of electrodes using SEM, EDS, BET, FTIR and TGA respectively.