Selective Adsorption and Recovery of Silver from Acidic Solution Using Biomass-Derived Sulfur-Doped Porous Carbon
Jinlong Fan, Li Duan, Xiangbo Zhang, Zhiming Li, Pengju Qiu, Yajiao He, Pei Shang
Abstract
It is vital to recycle precious metals effectively such as silver from waste sources because of limited natural reserves. Herein, passion fruit ( Passiflora edulis Sims ) shell-derived S-doped porous carbons (SPCs) were newly synthesized by hydrothermal carbonization and following with activation by KOH/(NH 4 ) 2 SO 4, and the adsorption of Ag + on SPC under acidic solutions was investigated. It was found that the activator of (NH 4 ) 2 SO 4 can not only introduce the doping of S elements but also increase the proportion 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 was consistent with the pseudo-second-order kinetic model. The Langmuir isothermal model was used to well fit the Ag + adsorption isotherms of SPC, and the maximum adsorption capacity of the optimized SPC-3 for Ag + is up to 115 mg/g in 0.5 mol/L HNO 3 solution. SPC-3 showed good selectivity toward Ag + over diverse competing cations, which is mainly attributed to the strong bonding between Ag + ions and the sulfur-containing functional groups on the surface of SPC-3 resulting in the formation of Ag 2 S nanoparticles. The adsorbed Ag could be recovered as an elemental form by a simple calcination. This study provides a new insight into the design of an environmentally friendly and efficient adsorbent for the selective recovery of silver from acidic aqueous media.