Preparation of magnetic Fe3O4@Zn-AST nanocomposites by in situ growth method for adsorption of Ag(I) from aqueous solution

A superparamagnetic Fe 3 O 4 @Zn-AST nanocomposite was constructed. • The Fe 3 O 4 @Zn-AST had abundant N, S-containing functional groups. • The Fe 3 O 4 @Zn-AST exhibits a saturation magnetization of 61.29 emu/g. • The maximum adsorption capacity of Fe 3 O 4 @Zn-AST for Ag(I) was 1410.68 mg/g. Silver as a precious metal, is extensively utilized in jewelry, electronics and some other fields due to its excellent conductivity and ductility. With the growing demand for silver, excessive exploitation of silver ore resources has generated large volumes of Ag(I)-containing wastewater. The direct release of untreated Ag(I)-containing wastewater contaminates ecosystems and poses risks to human health. Metal-Organic Frameworks (MOFs) exhibit a notably specific surface area, ample unsaturated metal sites, ease of functionalization, and tunable pore size and structure, which make them highly promising materials for effective adsorption of pollutants from wastewater. However, pure MOFs are typically in powder form, which are not easy to separate and recover after adsorption. In this work, using the zinc nitrate hexahydrate as the metal precursor along with 2-amino-5-sulfanyl-1,3,4-thiadiazole (AST) as the multi-dentate organic ligand, a superparamagnetic Fe 3 O 4 @Zn-AST nanocomposite was prepared via in-situ solvothermal method. The Fe 3 O 4 @Zn-AST exhibits a saturation magnetization of 61.29 emu/g, meeting the requirements for magnetic separation. The maximum Ag(I) adsorption capacity of Fe 3 O 4 @Zn-AST is 1410.68 mg/g, and adsorption process is mainly chemical adsorption, featured by endothermic, disordered, and spontaneous. Adsorption-desorption experiments prove that the removal efficiency can remain above 91% even after five cycles. From FT-IR and XPS, the Fe 3 O 4 @Zn-AST adsorbing Ag(I) was mainly through the synergistic effect of -SH, N-containing functional groups and electrostatic interactions. Given the magnetic separation advantage and superior Ag(I) adsorption, Fe 3 O 4 @Zn-AST could serve as a promising adsorbent. Download: Download high-res image (241KB) Download: Download full-size image