In Situ Reduction of Au(I) for Efficient Recovery of Gold from Thiosulfate Solution by the 3D MoS₂/Chitosan Aerogel

Abstract

A three-dimensional porous MoS2/chitosan (MoS2/CS) aerogel with excellent mechanical strength and stability was constructed in this work through anchoring MoS2 to the surface of the CS aerogel. It is found that the MoS2/CS aerogel can effectively recover gold from thiosulfate solution via direct in situ reduction of Au­(I) to Au0 under sunlight, thus realizing the one-step recovery of gold, which greatly benefits the development of thiosulfate leaching for gold extraction. Furthermore, according to the results of photocurrent, ultraviolet–visible absorption, and atomic absorption spectrophotometry, it has been found that the reduction of the MoS2/CS aerogel to Au­(I) is mainly consisted of photoreduction and chemical reduction, where photoreduction plays a dominant role, primarily because of the narrow band gap and higher conduction band edge of the MoS2/CS aerogel as well as the strong reducibility of photogenerated electrons.

Porous Aerogels and Adsorption of Pollutants from Water and Air: A Review

“…As an example, an aerogel with MoS 2 was successfully developed. This aerogel was used to enhance gold recovery, due to its ability to perform the previously required mineral reduction using light [ 94 ].…”

Efficient Recovery of Gold(I) from Thiosulfate Solutions through Photocatalytic Reduction with Mn(II)-Doped MoS2

“…The reduction of [Au(S 2 O 3 ) 2 ] 3− by MoS 2 mainly consisted of photoreduction and chemical reduction in which photoreduction played a dominant role. 21 What is more, MoS 2 could be reused from liquid through construction of threedimensional aerogels or combing with magnetic material such as Fe 3 O 4 . 22 From the perspective of catalysis using MoS 2 , the electronic conductivity of MoS 2 was unsatisfactory, 23−25 hinder further efficient recovery of [Au(S 2 O 3 ) 2 ] 3− .…”

“…Although adsorption won the most attention with its simplicity, high efficiency, and low cost, most adsorbents like activated carbon, modified activated carbon, and thiol- and amine-functionalized mesoporous silica did not exhibit good recovery. Lately, a photocatalytic reduction method combining adsorption and reduction procedures has been proposed for simplifying the recovery steps and enhancing the recovery. − …”

“…Based on the hard soft acid base principle and electrochemistry basic principle (conduction band (CB) of MoS 2 was lower in energy than the reduction potential of [Au­(S 2 O 3 ) 2 ] 3– to Au 0 ), sulfur-rich MoS 2 exhibited good adsorption and photocatalytic reduction ability of [Au­(S 2 O 3 ) 2 ] 3– . The reduction of [Au­(S 2 O 3 ) 2 ] 3– by MoS 2 mainly consisted of photoreduction and chemical reduction in which photoreduction played a dominant role . What is more, MoS 2 could be reused from liquid through construction of three-dimensional aerogels or combing with magnetic material such as Fe 3 O 4 …”

A Green and Sustainable Process for the Recovery of Gold from Low-Grade Sources Using Biogenic Cyanide Generated by Bacillus megaterium: A Comprehensive Study

“…5−7 Most noncyanide-based alternatives have been extensively studied; however, some drawbacks and problems such as recyclability, selectivity, and the influence on the downstream processes remain unsolved, meaning that there is a need for a viable substitute of chemical cyanide. 8,9 Considering all the challenges in gold processing, bioleaching/biocyanidation is recognized as a promising and feasible process to recover metals by producing a suitable amount of the extracting reagent in situ. 10−12 Therefore, gold could be solubilized effectively using this technology while minimizing the risk to the environment and leaving behind the least level of contamination.…”