Vanadium(V) removal and recovery by adsorption onto modified activated carbon derived from natural hydroxyapatite

Hydroxyapatite (camel bone, CB) was used for production of low cost activated carbon (CBC) and applied for vanadium removal from aqueous solution. Nitric acid, phosphoric acid and hydrogen peroxide were used as chemical catalysts to prepare the developed activated carbon. CB and CBC adsorbents were characterized using different available techniques such as SEM, FTIR, N-2 adsorption and desorption isotherms, as well as TGA-DTA thermal analysis. The efficiency of the prepared adsorbent was investigated using batch adsorption method. At optimum pH, CBC could adsorb 85% of vanadium after 30 min. Three isotherm models, namely Freundlich, Langmuir and Dubinin-Radushkevich, were used to analyze the sorption equilibrium data. The process was found to follow Langmuir adsorption isotherm model, indicating that vanadium ions adsorption process had physical character. The kinetic studies manifested that the adsorption process follows the pseudo-second-order reaction. The CBC adsorbent exhibited a feasible capacity (19.45 mg/g) for vanadium adsorption compared to the other works published in the literature. In addition, thermodynamic studies explained that adsorption process is spontaneous, exothermic and occurs preferably via physisorption mechanism. 0.5 M HCl solution was successfully used as eluting agent for vanadium desorption.