Construction of dopamine supported Mg(Ca)Al layered double hydroxides with enhanced adsorption properties for uranium

A novel dopamine-supported Mg(Ca)Al layered double hydroxide composite was synthesized by co-precipitation method. The existence of Ca2+ and dopamine could promote the capture of uranium on the layered double hydrox- ides. In batch experiments, the composite exhibited good uranium removal performance, including high adsorption capacity (687.3 mg/g), strong anti-interference and good reusability (the removal percentage was still higher than 90 % after five cycles). At low initial uranium concentration, the uranium removal percentage on the composite exceeded 99.7 % and the residual concentration of uranium in the solution was <0.03 mg/L, reaching the limited stan- dard of the World Health Organization. The studies of adsorption kinetics and isotherm indicated that the uranium ad- sorption behavior on the composite conformed to the pseudo-second-order kinetic and Langmuir isotherm models, suggesting that the process was a monolayer adsorption dominated by chemical adsorption. Furthermore, the high-efficiency uranium adsorption on the Mg(Ca)Al layered double hydroxide was mainly attributed to the strong complexation between the active sites (-OH and-NH2) and uranium, the precipitation of interlayer inter- calation ions (CO32- and OH-) to uranium and the ion exchange of Ca2+ to uranium. Due to these advantages, the dopamine-supported Mg(Ca)Al layered double hydroxide composite is expected to be used as fine adsorbent to remove uranium from wastewater.