Development of natural pyrite-based adsorbents for efficient Ag plus removal from wastewater

Background: The presence of Ag+ in silver-containing wastewater necessitates recycling and treatment due to its significant economic value and potential environmental risks. Current adsorbents exhibit limitations, including high production costs, complex processing methods, and low adsorption efficiency. Consequently, there is an urgent demand for the development of novel and efficient adsorbents specifically designed for silver-containing wastewater. Methods: After crushing and milling, the surface of natural pyrite will reveal numerous S-active sites. It is anticipated that natural sulfide mineral-type Ag+ adsorbent materials could be developed, based on the affinity between Ag and S, to realize the efficient removal of Ag+ from silver-containing wastewater. Significant findings: The removal rate of silver from silver-containing wastewater by pyrite is more than 99 %. After 4 cycles of adsorption, pyrite still has a strong adsorption capacity for Ag+. Experimental characterization and Density functional theory (DFT) calculation show that Ag+ combines with S via chemisorption on the pyrite surface to produce Ag2S. The 4d orbitals of Ag+ overlap with the S 3p orbitals during adsorption, according to partial density of states analyses, which implies orbital hybridization. The electron density difference indicates that Ag+ interacts with sulfur (S) on the pyrite surface, accompanied by a transfer of charge.