Adsorption of Cr(VI) from aqueous solution by prepared high surface area activated carbon from Fox nutshell by chemical activation with H3PO4

Adsorption studies of Cr(VI) onto activated carbon, FNAC-700-1.5 (BET surface area of 2636 m2/g and total pore volume of 1.53 cm3/g), prepared from Fox nutshell by chemical activation with H3PO4 at an impregnation ratio of 1.5 and activation temperature of 700 °C under N2 atmosphere were carried out in the present work. In batch adsorption experiments the effect of agitation speed, pH, temperature, adsorbent dosage, initial concentration of Cr(VI), and contact time were studied. Also adsorption kinetics, equilibrium, and thermodynamics of Cr(VI) adsorption were studied. The adsorption was found to follow the pseudo second order model. A maximum adsorption of 74.95 mg/g was obtained at the operating condition of 35 mg/L of initial concentration of Cr(VI) at pH of 2.0, temperature 45 °C and contact time of 3 h. Thermodynamic parameters such as ΔGo, ΔHo and ΔSo were calculated by using Vańt hoff equation. The adsorption process was endothermic and spontaneous one. In column experiments, the effects of the bed height of the packing material and flow rate of Cr(VI) solution on adsorption characteristics were studied. A maximum removal of 71.86% was achieved in the column study for 10 mg/L initial Cr(VI) concentration at 4 cm bed height, and 5 mL/min flow rate under ambient conditions at a temperature around 30 °C.