Preparation of gamma alumina nanoparticles from kaolinitic sandstone and their application as a selective adsorbent for REEs from liquid waste

A process for synthesizing Gamma alumina from kaolinitic sandstone ore has been described in this paper. Fine kaolin was recovered from the sandstones after aggressive attrition scrubbing process followed by 2" and 1" hydro- cyclone classification. The produced −25 μm kaolin was transformed to active meta-kaolin via calcination at 750 °C for 5 h. Through metakaolin- H2SO4 interactions, and consequently precipitation in ethanol solution, aluminum sulfate was formed. After dryness and calcination at 900 °C for 2 h γ-alumina was prepared. The FT-IR, DLS, BET, XRD, SEM and EDX analyses confirmed the high purity of the nanosized γ-alumina product. In addition, the prepared γ-alumina was examined as the sorbent for rare earth species from waste materials. Adsorption and thermodynamic studies, in addition to the adsorption selectivity, desorption process, and reusability showed promising performance results. The maximum adsorption capacity of the prepared γ-alumina reached 142 mg/g.