Removal of Cr(III) from tanning effluent using adsorbent prepared from peanut shell

This article describes the development of an adsorbent from peanut shell (PNS) for removing Cr(III) from tannery effluents. Adsorbent was prepared by pyrolysis of peanut shell followed by activation with NaOH and was characterized by different analytical methods. Adsorption capacity and removal rate of Cr(III) were determined. The adsorption capacity of activated PNS was investigated through batch experiments with the effect of pH, adsorbent doses, contact time, initial concentration, and temperature. Adsorption capacity and rate of removal of Cr(III) were 74.79 mg/ g and 54.21%, respectively. The highest adsorption capacity (q(m)) calculated from Langmuir isotherm was 104.82 mg/g. Adsorption isotherm of Cr(III) on PNS was studied by Langmuir and Freundlich models which revealed that Langmuir model fitted the best with a R-2 value of 0.999. The adsorption kinetics of Cr(III) on PNS followed pseudo-second-order reaction model with a R-2 value of 0.9979. The experimental data of Cr(III) adsorption were also fitted well with the pseudo-secondorder kinetic model. Various physico-chemical parameters of chrome tanning effluent were also evaluated prior to and subsequent to adsorption.