Synthesis of high-surface-area rod-like alumina materials with enhanced Cr(VI) removal efficiency

A facile synthesis of rod-like alumina materials was developed through systematical investigation, which enables the control of the specific surface area of ammonium aluminium carbonate hydroxide (AACH) using aluminum nitrate as a precursor and urea as a precipitant. Our studies indicated that the molar ratio of CO(NH₂)₂/Al influences crystallinity, morphology and the surface area of alumina materials. Amorphous alumina materials with nanorod morphology and high surface area (1029 m² g^-1) was obtained with 15:1 M ratio of CO(NH₂)₂ to Al. In addition, the results demonstrated that thermal behaviors of the as-prepared AACH affect their crystallinities. Furthermore, the amorphous Al₂O₃ prepared from AACH by calcination at 773 K was used as an adsorbent for Cr(VI) removal from water solution, and external factors were investigated, including contact time, adsorbent dosage, initial concentration of adsorbate and the pH of solution. It was found that the maximum adsorption capacity of prepared amorphous Al₂O₃ for Cr(VI) was 52.1 mg g⁻¹, which was higher than those of other reported Al₂O₃ samples.