One-step synthesis of periodic ion imprinted mesoporous silica particles for highly specific removal of Cd²⁺ from mine wastewater

Combining the advantages of MCM-41 mesoporous materials and molecularly imprinted polymers, we designed and synthesized periodic Cd²⁺ imprinted mesoporous silica (Cd-IMS) through a one-step hydrothermal process. Bifunctional ligand monomers [3-(γ-aminoethylamino)-propyltrimethoxysilane] and template ions (Cd²⁺) were immobilized in the hexagonal channel walls of MCM-41, prior to polymerization. The resultant Cd-IMS revealed a highly ordered hexagonal structure, nano-sized pore diameters and wall thicknesses, and a large surface area. In addition, this material revealed good binding properties, including a large adsorption capacity (saturation adsorption capacity of 40 mg/g), highly specific recognition ability (maximum imprinting factor of 3.0), and rapid adsorption kinetics (equilibration within 5 min). Selectivity coefficients [K_Cd-IMS (Cd²⁺)/K_Cd-IMS (Cu²⁺ or Pb²⁺)] of the Cd-IMS material demonstrated values of up to 2.29 and 3.08, respectively. Following six cycles of Cd²⁺ adsorption, the recovery of Cd-IMS remained stable at around 89.3 %, proving its recycling potential. Furthermore, Cd-IMS was successfully applied to selectively separate and remove Cd²⁺ from mineral wastewater samples, with high Cd²⁺ recovery rates. This suggests that the routine recovery of Cd²⁺ from wastewater may be realized in an economically viable manner.