Yingxia Ma,Miaoshi Li,Tianze Li,Haijun Yang,Ruilin Zhang,Xiaofei Ye,Wenli Meng,Xiaojun Chai,Cuixia Li
Industrial wastewater containing heavy metal Ag(I) causes irreversible harm to human health through food chain, necessitating effective removal methods. According to hard-soft acids-bases (HSAB) theory, nitrogen (N) and sulfur (S) functional groups form stable chelates with Ag(I). In this study, 2-amino-5-sulfanyl-1,3,4-thiadiazole (AST) with three N and two S groups served as organic ligand, and zinc nitrate hexahydrate provided metal center, novel amorphous metal-organic framework (Zn-AST) rich in N and S groups was synthesized via a one-pot solvothermal method. Batch experiments assessed the Zn-AST adsorption properties for Ag(I) in aqueous solutions. In addition, density-functional theory, frontier orbital theory, and molecular electrostatic surface potential analyses were used to elucidate the synthesis and adsorption mechanisms. The maximum adsorption capacity of Zn-AST for Ag(I) was 2932.91 mg/g. The Zn-AST exhibited good selectivity in the presence of Cu(II), Co(II), Ni(II), and Pb(II) ions, the removal rate for Ag(I) was 98.28 %, which was far higher than the values of other ions (all less than 10 %). The main adsorption mechanisms of Ag(I) by the Zn-AST involved electrostatic interactions, the formation of Ag–S bonds, and chelation between Ag and nitrogen functional groups. This study offers a viable strategy for developing unique adsorbents for Ag(I) removal from wastewater.
Yingxia Ma,Shuo Zhou,Tianze Li,Miaoshi Li,Wenhui Han
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
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