Removal of vanadium from aquatic environment using phosphoric acid modified rice straw

Vanadium (V) is a toxic metal, which dominantly exists as V5+ in an aquatic environment. Rice straw, which is an abundant agricultural by-product throughout China was used to treat V5+ containing wastewater as an adsorbent after phosphoric acid treatment. The effects of initial V5+ concentration, solution temperature, pH and reaction time on V removal by phosphoric acid modified rice straw (AcM) were systematically assessed. A pH range of 2.0-3.0 was favorable for V removal and the adsorption capacity of V by AcM increased with elevated solution temperature. The maximum adsorption capacity for water containing 500 mg V5+ L-1 was 24.70 mg V g(-1 )dry matter under the optimum operation (3.33 g L-1 AcM, pH = 2.0, 50 degrees C, and 200 rpm for 4 h). Adsorption experiment data fitted well to pseudo-second-order kinetic and Langmuir adsorption isotherm models. In the presence of coexisting ions, Na+, Cu2+, NO3- and Cl- had no significant (P > 0.05) effect on V removal. These results indicated that AcM derived from agricultural waste was effective to remove V5+ from aqueous solution.