Feasibility study on decontamination of aged spent wash using activated carbon from Limonia acidissima shell

Need for eco-friendly and economical treatment of distillery spent wash has been inspiring researchers to investigate decontamination potential using natural materials. In this study, activated carbon was prepared from wood apple (Limonia acidicima) shells by thermo-chemical treatment with sulfuric acid at 200°C for 2 h in the absence of air. From the batch experiments with aged spent wash samples, maximum adsorption capacity (46.6 mg/g) was observed at a pH of 5.5, owing to the initial high uptake rate of polar compounds from spent wash. Based on the results from batch kinetic studies, two-site series and parallel interface models were found to be appropriate for representing the multi-phase transitions in the mass transfer rate. Comparison between different linear forms of Langmuir and Redlich-Peterson (R-P) isotherms revealed that prediction of adsorption capacity term is considerably affected by the axial setting in the logarithmic form. In order to overcome the difficulty of linear regression fit, chi-square test was identified as the suitable alternative to make comparison of all isotherms on the same abscissa and ordinate. Results of the present study showed that R-P isotherm and two-site interface kinetic models were invariably best suited for explaining the equilibrium and kinetic sorption of spent wash.