Hydrothermal synthesis, characterization and sorption properties of Al/Fe oxide–oxyhydroxide composite powders

• Al/Fe oxide–oxyhydroxide composite powders were prepared by hydrothermal method.
• The composition, morphology, textural and thermal properties were investigated.
• A decrease in the Al/Fe ratio results in a nonmonotonic variation of surface area.
• Lamellar Fe2O3 and acicular FeOOH are formed in the presents of CTAB and Al3+.
• The γ-Al2O3/α-Fe2O3 composite powder exhibit a maximum adsorption capacity.

The Al/Fe oxide–oxyhydroxide composite powders were synthesized by hydrothermal method using metal salt solutions and urea as precursors. The effect of the [Al3+]:[Fe3+] ratio and CTAB on the phase composition, textural properties, morphology, and thermal effects of composites was investigated. The β-FeOOH/γ-AlOOH powders prepared by hydrothermal treatment of the solutions with [Al3+]:[Fe3+] = 6:1 showed highest surface area among the as-prepared samples. The morphology of the products was preserved after calcination at 700 °C, while the specific surface area significantly increased. The adsorption characteristics of Cr(VI) on the Al/Fe oxide–oxyhydroxide composite powders were investigated. It was shown that the adsorption equilibrium was attained within a short contact time (5–20 min). Adsorption isotherms of all samples were described by the Langmuir and Freundlich equations. Samples calcined at 700 °C showed higher adsorption capacity as compared to uncalcined samples. The α-Fe2O3/γ-Al2O3 composite powder has a greater sorption capacity as compared to these of pure γ-Al2O3 and α-Fe2O3.

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