One-pot in situ construction of amido and hydroxyl co-modified layered double hydroxides for selective scandium adsorption

Abstract

Selective recovery of scandium has always been a research challenge and hotspot. Adsorption recovery is an effective method for selective separation and has aroused wide interest due to its environmental protection, energy saving, and high-efficiency recovery of low-concentration Sc³⁺. In this work, 3-amidopropyltriethoxysilane (KH550) was successfully introduced onto layered double hydroxides (LDHs) using a one-pot in situ hydrothermal method. Compared to traditional methods, the novel one-step in situ strategy leads to more groups being loaded onto the LDHs. The material has a high adsorption capacity and selectivity for scandium. The optimized KH550-LDHs (4K-LDHs) prepared with the optimal modified volume of 4 mL showed a high saturated adsorption capacity of 22.73 mg g⁻¹ and good scandium adsorption stability. This adsorbent not only selectively extracts Sc³⁺ from mixed rare earth ion systems but also effectively recovers Sc³⁺ from the Ca²⁺, Co²⁺, Mn²⁺, Zn²⁺ and Al³⁺ coexisting ion solutions. The synergy between amido and hydroxyl groups provides abundant active sites for selective adsorption. The research showed that the modified material was fitted with pseudo-second-order kinetics and the Langmuir model. This work provides a one-pot in situ construction strategy for preparing amido and hydroxyl co-modified layered double hydroxides for selective scandium adsorption.