Investigating the biosorption potentials of Arachis hypogaea shells for chromium ions from the aqueous media

Biosorption studies of chromium (VI) ions from aqueous solution were investigated for Arachis hypogaea (peanut) shell and modified peanut shells. The change of initial chromium ion concentration, contact time, pH and temperature were investigated. Different thermodynamic parameters for the adsorption of Cr (VI) were calculated using Freundlich, Langmuir and D-R models. Various kinetic models like pseudo 1^st order, pseudo 2^nd order and intra particle diffusion were also studied. The adsorption was followed by Langmuir isotherm model. The maximum Cr (VI) adsorption capacity q_max calculated from Langmuir adsorption isotherm was 166 mg/g. The thermodynamic factors ΔG°, ΔH° and ΔS° indicated that the adsorption process is spontaneous and exothermic. The kinetic data have indicated that the adsorption followed the pseudo second order kinetic model. This agricultural by-product, peanut shells, were successfully used as biosorbent for effective removal of Cr (VI) from aqueous solution. The adsorption data is better fitted by the Langmuir model and the adsorption capacity increases twice due to chemical treatment of peanut shells.