Hexavalent Chromium Adsorption from Aqueous Solution by Agricultural Waste Materials

Abilities of agricultural waste materials （walnut shell-WS, rice husk-RH, and peanut hull-PH） were tested as adsorbents for the adsorption of Cr （Ⅵ） from aqueous solution. Batch adsorption experiments were carried out to study the adsorption kinetics mechanism of Cr（Ⅵ） effect of adsorbent dosage, pH, contact time, and temperature. The best results are obtained at 15 g/L adsorbent concentration, 60 rain contact time, 298 K temperature, and 50 mg/L adsorbate initial concentration at pH 2. The adsorption isotherms, using initial conceatratious of Cr（Ⅵ） between 10 and 500 mg/L for the Cr（Ⅵ） removal, show the maxidmum metal uptake capacities of adsorbent were 10.48, 6.71, and 8.54 mg/g for WS, RH, and PH, respectively. And the adsorption data fitted well to the Lanoomnir adsorption isotherm for WS, RH, and PH with correlation coefficients of 0.9862, 0.9723, and 0.971 4, respectively. Moreover, the FTIR analysis of WS, RH, and PH before and after adsorption of Cr（Ⅵ） suggested that Cr ions were combined to some functional groups of compounds contained in these materials.