Synthesis of a hydrotalcite-like compound from oil shale ash and its application in uranium removal

Oil shale ash (OSA) was utilized to synthesize a hydrotalcite-like compound (HTlc) via a facile acid-leaching and co-precipitation process. Chemical component, structural and morphological properties of HTlc were characterized by ICP-AES, FTIR, XRD, HRTEM, SEM, and XPS. The results showed that HTlc is Mg-Al based hydrotalcite with a lamellar morphology, incorporating other metal cations in its structure. Building on the synthetic HTlc, adsorption of uranium from aqueous solution was performed in a single component system with the variation of pH, adsorbent dosage, contact times, temperatures and initial concentrations of uranium. It is found that the adsorption process conforms to Langmuir isotherm model. Upon raising temperature from 298 to 318 K, the maximum adsorption capacity increases from 156 to 200 mg/g. The adsorption of uranium is revealed to follow the pseudo-second-order rate model by adsorption kinetics studies. Obtainable thermodynamic parameters showed that the uranium adsorption is endothermic and spontaneous in nature. Comparison with similar adsorbents demonstrates that HTlc is an effective and economic adsorbent to remove uranium from aqueous solution. And thus, the present work is expected to provide a new strategy for disposal of both wastewater of nuclear industry and waste product of oil shale industry.