Removal of U(VI) from aqueous solution by layered cobalt–magnesium double hydroxide composite

A novel layered cobalt–magnesium double hydroxide composite (L-CMs) was successfully prepared using a simple one-step co-precipitation method. Static adsorption experiments were conducted to examine the removal efficacy of U(VI) from aqueous solutions by the L-CMs and analyze the removal mechanism. L-CMs efficiently removed U(VI) from the aqueous solution under an adsorption time of 60 min, dosage of 0.4 g/L, and pH of 5.5 at room temperature, and the removal efficiency of U(VI) reached 94.59% with an initial U(VI) concentration of 10 mg/L. The adsorption process was fitted to the pseudo-second-order kinetic and Langmuir models, indicating that monolayer chemical adsorption occurred primarily. The maximum adsorption capacity fitted using the Langmuir model was 105.49 mg/g. Thermodynamic analysis revealed that U(VI) adsorption by L-CMs was endothermic. Structural characterization results showed that the primary mechanism involved the complexation of U(VI) by –OH, CO 3 2− and ion exchange by Mg 2+ and the presence of layered Co(OH) 2 in the L-CMs, which potentially facilitated ion exchange. The preparation of the composite materials was simple, and the synergistic effect between the materials enhanced the ion exchange of Mg 2+ in the materials and enriched the content of functional groups, making it a potential candidate for the treatment of uranium-containing wastewater.