Reductive removal of Cr(VI) by starch-stabilized Fe0 nanoparticles in aqueous solution

A comparative study of hexavalent chromium (Cr(VI)) removal from aqueous solution using Fe⁰ and Fe₃O₄ particles in nano and micro-scale was performed. Our results indicated that the Cr(VI) removal efficiency using starch-stabilized Fe⁰ nanoparticles, nonstabilized Fe⁰ nanoparticles, Fe₃O₄ nanoparticles, Fe⁰ and Fe₃O₄ microparticles was 99.25%, 60.4%, 9.13%, 6.92% and 6.17%, respectively. Results revealed that the Cr(VI) removal efficiency using Fe₃O₄ particles was highly dependent on pH with maximum removal efficiency at pH 3. The stabilized Fe⁰ nanoparticles efficiently remove Cr(VI) from aqueous solution in a wide pH range. In the present of Fe⁰ nanoparticles, increasing the initial Cr(VI) concentration from 10 to 50mg/L decreased removal efficiency and observed pseudo-first order rate constant (k_obs) from 100% to 56.4%, and 0.101 to 0.015min^-1, respectively. Increasing Fe⁰ nanoparticles dosage from 0.1 to 2g/L increased k_obs value from 0.028 to 0.110min^-1 and led to a 60% increase in the removal efficiency. The reaction rate constant decreased from 0.075 to 0.043min^-1 with increasing pH from 3 to 9, respectively. Our results suggest that stabilized Fe⁰ nanoparticles may serve as an effective agent for reductive removal of Cr(VI) from contaminated waters.