Comparative study of adsorption of Ni (II) on RHA and carbon embedded silica obtained from RHA

In the present work an adsorbent called carbon embedded silica (CES) was developed by chemical modification of rice husk ash (RHA) and comparative study for Ni (II) removal was carried out. CES was characterized using techniques like EDAX, XRD, FTIR, XRF, and SEM. The specific surface area of CES was found out to be 100 m(2)/g and that of RHA as 44 m(2)/g. Batch experiments were performed to evaluate the influence of parameters like adsorbent dosage, initial pH, time, concentration of the adsorbate and temperature. It was observed that adsorption of Ni (II) followed pseudo second order kinetics in both the cases. Adsorption data fitted well with the Langmuir and Freundlich models. However. Langmuir isotherm displayed a better fitting. CES showed maximum 18 folds higher adsorption capacity over RHA. Thermodynamics parameters like heat of reaction, entropy of system and free energy were evaluated which confirms the feasibility of the process. (C) 2011 Elsevier B.V. All rights reserved.