Characterization and sorption properties of γ-AlOOH/α-Fe2O3 composite powders prepared via hydrothermal method

Properties of boehmite and hematite powders formed under hydrothermal conditions are well known. However, a synergistic effect is expected when the gamma-AlOOH/alpha-Fe2O3 composite powders are obtained under the same conditions. Hence, it should be possible to improve the properties (including adsorption) as compared to these of pure gamma-AlOOH and alpha-Fe2O3. The gamma-AlOOH/alpha-Fe2O3 composite powders were synthesized by hydrothermal method using metal nitrate solutions and urea as precursors. The influence of the [A13]:[Fe3+] ratio on the phase composition, textural properties, morphology, and thermal effects of composites was investigated. The gamma-AlOOH/alpha-Fe2O3 composite powders had a smaller particle size and showed higher specific surface area and sorption capacity as compared to these of pure gamma-AlOOH and alpha-Fe2O3. The sample prepared by using a solution with [Al3+]:[Fe3+] = 1 showed the highest specific surface area (98.1 m(2)/g) and adsorption capacity (4.17 mg/g) in the removal of Cr(VI) from aqueous solutions. Sorption experiments showed that the mean free adsorption energy is below 8 kJ/mol for all samples, indicating the adsorption process as the physical in nature and suggesting the possibility of Cr(VI) desorption and adsorbent regeneration. (C) 2016 Elsevier B.V. All rights reserved.