Removal and recovery of vanadium(V) by adsorption onto ZnCl2 activated carbon:: Kinetics and isotherms

Adsorption of vanadium(V) from aqueous solution onto ZnCl2 activated carbon developed from coconut coir pith was investigated to assess the possible use of this adsorbent. The influence of various parameters such as agitation time, vanadium concentration, adsorbent dose, pH and temperature has been studied. First, second order, Elovich and Bangham's models were used to study the adsorption kinetics. The adsorption system follows second order and Bangham's kinetic models. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherms have been employed to analyze the adsorption equilibrium data. Equilibrium adsorption data followed all the four isotherms-Langmuir, Freundlich, D-R and Temkin. The Langmuir adsorption capacity (Q(0)) was found to be 24.9 mg g(-1) of the adsorbent. The per cent adsorption was maximum in the pH range 4.0-9.0. The pH effect and desorption studies showed that ion exchange mechanism might be involved in the adsorption process. Thermodynamic parameters such as Delta G(0), Delta H-0 and Delta S-0 for the adsorption were evaluated. Effect of competitive anions in the aqueous solution such as PO43-, SO42-, ClO4-, MoO42-, SeO32-, NO3- and Cl- was examined. SEM and FTIR were used to study the surface of vanadium(V) loaded ZnCl2 activated carbon. Removal of vanadium(V) from synthetic ground water was also tested. Results show that ZnCl2 activated coir pith carbon is effective for the removal of vanadium(V) from water.