The effectiveness of low-cost biosorbent: peanut hulls (Arachis hypogaea Linn.), was studied for Cr (VI) biosorption from aqueous solutions in a batch system. The FTIR study of acid treated biosorbent showed that the possibility of availability of function groups such as hydroxyl, carbonyl, carboxylic etc. The SEM represents a porous structure with large surface area. The effects of operational factors including solution pH, biosorbent dose, initial chromium (VI) concentration, contact time and temperature were studied. The optimum solution pH for chromium (VI) adsorption by biosorbent was 2.0 with the optimal removal 50.63 %. The adsorbent dose 5 mg/ml was enough for optimal removal of 60.70 %. The equilibrium was achieved after 150 minutes of contact. The equilibrium data were well described by typical Langmuir, Freundlich, Dubinin-Kaganer-Redushkevich (DKR) and Temkin adsorption isotherms. Sorption equilibrium exhibited better fit to Langmuir isotherm (R2 = 0.997) than Freundlich isotherm (R2 = 0.991), Temkin isotherm (R2 = 0.825) and Dubinin-Kaganer-Redushkevich (DKR) isotherm (R2 = 0.569). The maximum adsorption capacity determined from Langmuir isotherm was found to be 6.535 mg per g of biosorbent. Furthermore, to determine the adsorption mechanism, a detailed analysis has been conducted by testing kinetic models such as pseudo-first-order, pseudo-second-order, Elovich equation and Weber & Morris intra-particulate mixing equation. Results clearly indicates that the Weber & Morris intra-particulate mixing kinetic model was found to be correlate the experimental data strongest than other three kinetic models. Thermodynamic study revealed that the biosorption process was spontaneous, endothermic and increasing randomness of the solid solution interfaces. The peanut hulls (Arachis hypogaea Linn.) used successfully for biosorption studies of Cr (VI) from aqueous solutions, can be used very promisingly for industrial wastewater treatment.
