Selective Adsorption and Recovery of Silver from Acidic Solution Using Biomass-Derived Sulfur-Doped Porous Carbon

It is vital to recycle precious metals effectively suchas silverfrom waste sources because of limited natural reserves. Herein, passionfruit (Passiflora edulis Sims) shell-derived S-doped porous carbons (SPCs) were newly synthesizedby hydrothermal carbonization and following with activation by KOH/(NH4)(2)SO4, and the adsorption of Ag+ on SPC under acidic solutions was investigated. It was foundthat the activator of (NH4)(2)SO4 cannot only introduce the doping of S elements but also increase theproportion of mesopores in the as-prepared SPC. As the active site,the increasing S doping can improve the adsorption of Ag+ on SPC. The kinetic data of Ag+ adsorption by SPC wasconsistent with the pseudo-second-order kinetic model. The Langmuirisothermal model was used to well fit the Ag+ adsorptionisotherms of SPC, and the maximum adsorption capacity of the optimizedSPC-3 for Ag+ is up to 115 mg/g in 0.5 mol/L HNO3 solution. SPC-3 showed good selectivity toward Ag+ overdiverse competing cations, which is mainly attributed to the strongbonding between Ag+ ions and the sulfur-containing functionalgroups on the surface of SPC-3 resulting in the formation of Ag2S nanoparticles. The adsorbed Ag could be recovered as anelemental form by a simple calcination. This study provides a newinsight into the design of an environmentally friendly and efficientadsorbent for the selective recovery of silver from acidic aqueousmedia.

Automated summary

The synthesis of S-doped porous carbons derived from passionfruit shells was investigated for the effective recovery of silver from waste sources. The introduction of sulfur elements through ammonium sulfate activation not only increased the proportion of mesopores but also improved the adsorption capacity for silver ions. The study provides new insights into designing environmentally friendly and efficient adsorbents for the selective recovery of silver from acidic aqueous media.