LAUSR

Abstract Properties of boehmite and hematite powders formed under hydrothermal conditions are well known. However, a synergistic effect is expected when the γ-AlOOH/α-Fe 2 O 3 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 γ-AlOOH and α-Fe 2 O 3 . The γ-AlOOH/α-Fe 2 O 3 composite powders were synthesized by hydrothermal method using metal nitrate solutions and urea as precursors. The influence of the [Al 3+ ]:[Fe 3+ ] ratio on the phase composition, textural properties, morphology, and thermal effects of composites was investigated. The γ-AlOOH/α-Fe 2 O 3 composite powders had a smaller particle size and showed higher specific surface area and sorption capacity as compared to these of pure γ-AlOOH and α-Fe 2 O 3 . The sample prepared by using a solution with [Al 3+ ]:[Fe 3+ ] = 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.