Efficient removal of hexavalent chromium by high surface area Al2O3 rods

Abstract

Rod-like alumina materials were synthesized via a template-free hydrothermal method by using aluminum nitrate as precursor and urea as precipitating agent. The resulting alumina has a high specific surface area (up to 773 m² g⁻¹) and an abundance of hydroxyl groups, giving it a good Cr(VI) removal efficiency. External factors were investigated, including contact time, adsorbent dose, initial concentration of adsorbate and pH. The maximum adsorption capacity for Cr(VI) was 39.1 mg g⁻¹, which is superior to most of the reported alumina adsorbents. The Al₂O₃ samples before and after Cr(VI) adsorption were also characterized by FT-IR and XPS analysis. The results show that the adsorption can be mainly ascribed to the ion exchange between the abundant hydroxyl groups on the alumina surface and chromium anions. Together with an outstanding adsorption–regeneration performance, it is anticipated that the as-synthesized alumina materials are an attractive adsorbent for the removal of heavy metal ions from water.