Recovery of Silver from Dilute Effluents via Electrodeposition and Redox Replacement

Abstract

In this study, the electrodeposition-redox replacement (EDRR) method was studied for the recovery of minor concentrations of silver from dilute solutions. The parameter optimization was carried out with synthetic solutions similar to silver oxide button battery recycling effluents, consisting of sulfuric acid and concentrated base metal (10 g•L −1 H 2 SO 4 , 60 g/L Zn 2+ ) with a minor amount of silver (100 ppm) and a varying amount of Fe 3+ ions. Results of these experiments were analyzed both electrochemically and by use of SEM-EDS. The role of dissolved Fe 3+ ions was studied by varying the concentration from 0 to 1000 ppm and the results showed that although the presence of Fe ions decreased silver recovery efficiency, final product purity was found to increase slightly. The EDRR process was also found to be more effective for Ag recovery and has less energy consumption when Fe 3+ concentrations are relatively low (≤ 100 ppm) when compared with conventional direct current electrowinning. In the final stage, silver was successfully recovered via EDRR, using the optimized conditions, from a real pregnant leaching solution (PLS) obtained from the leaching of silver oxide batteries.

Mechanism of selective gold extraction from multi-metal chloride solutions by electrodeposition-redox replacement

“…Indeed, the pure redox replacement action was reported for metal couples like platinum/lead, 81 platinum/nickel 82 or silver/zinc. 83 The common feature of these systems is that the sacrificial metal (either nickel, lead or zinc) can be present in the solution only in one oxidation state, i.e. "+2".…”

“…During the ED step of the EDRR process, iron(III) is reduced to iron(II), thus consuming some electric charge and decreasing the current efficiency. 83 In the RR step, the effect of iron is two-fold: ferric ions acting as an oxidant would enhance dissolution of the deposited copper and improve the purity of the gold deposit; 12 at the same time, ferrous ions may reduce dissolved gold in chloride media by a homogenous reaction, which increases overall recovery of gold from solution. 94…”

Formation of Formic Acid from Glucose with Simultaneous Conversion of Ag2O to Ag under Mild Hydrothermal Conditions

“… 35 Many researchers studied the methods to recycle silver by chemical reduction, chemical replacement, and ion exchange. 36 − 38 However, these methods were short of economy and environmental friendliness due to the use of expensive resins or high energy input. Herein, we propose a new method for selective conversion of glucose into FA with easily separated byproduct glycolic acid using Ag 2 O as a solid oxidant and simultaneous transformation of Ag 2 O into Ag under mild hydrothermal conditions.…”

Performance-Based Selection of the Cathode Material for the Electrodeposition-Redox Replacement Process of Gold Recovery from Chloride Solutions

“…THE recent innovation of electrodeposition-redox replacement (EDRR) [1][2][3][4][5][6] shows potential as a new method for the recovery of (precious) metals from hydrometallurgical solutions where their concentration is extremely low, i.e., at parts per billion to parts per million scale. All of the published articles, however, studied the phenomenon itself, mostly relying on ideal electrodes, such as platinum or glassy carbon, and topics such as true material selection of cathodes have not been discussed.…”