Highly selective recovery of silver ions from complex aqueous solutions using sulfhydryl-functionalized silica composites

The global shift toward green energy technologies has markedly increased the demand for silver, a critical metal with indispensable functional properties. However, the limited natural reserves of silver and its potential environmental risks highlight the urgent need for efficient recovery from secondary sources. In this work, a novel sulfhydryl-functionalized silica composite (DMTD/SiO 2 -P) was synthesized via a facile vacuum impregnation method for the highly efficient and selective adsorption of Ag(I) ions from complex aqueous matrices. The composite possessed a mesoporous structure, excellent thermal stability, and a high DMTD ligand loading of 31.74 wt%. In multi-cationic solutions containing nine competing ions, DMTD/SiO 2 -P exhibited outstanding selectivity toward Ag(I), achieving a separation factor (SF Ag/cations ) up to 5.62 × 10(Xiong et al., 2018 [ 4 ] ) . The adsorption reached equilibrium within 30 min at pH 1.0 and followed pseudo-second-order kinetics. The isotherm data fitted well to the Langmuir model, indicating a remarkable monolayer adsorption capacity of 371.29 mg·g −1 . The adsorbed Ag(I) was efficiently desorbed with 74 % elution efficiency using a 2 M thiourea (TU)–1 M HNO 3 solution. FT-IR and XPS analyses confirmed that the adsorption mechanism was governed by the synergistic coordination of Ag(I) with both nitrogen and sulfur atoms in the DMTD ligand. This study presents a promising and sustainable adsorbent, DMTD/SiO 2 -P, offering an effective approach for silver recovery and resource sustainability while mitigating environmental risks. • Sulfhydryl-functionalized silica composite fabricated via vacuum impregnation. • Exceptional Ag(I) selectivity with ultra-high separation factor at pH 1.0. • Efficient Ag(I) capture across acidity range from HNO 3 to pH 6.0. • High adsorption capacity and rapid kinetics under acidic conditions. • Cooperative S/N atom coordination mechanism revealed by spectroscopy.