Kinetics and Energy Consumption for a Three-Stage Electrocoagulation Process for the Recovery of Au and Ag from Cyanide Leachates

Abstract

The most common processes used for the recovery of gold and silver from cyanide leachates are Merril-Crowe, activated carbon in pulp, and ion exchange resins; the process of electrocoagulation (EC) also is a promising new technique. EC is an electrochemical process whose mechanisms include oxidation, reduction, decomposition, deposition, coagulation, absorption, flotation, and precipitation. It has been used for the treatment of water and wastewater with different degrees of success. This study aimed to determine the kinetics of the reaction and the energy consumption at constant voltage, and at constant current using aluminum electrodes with two different distances between electrodes. EC was run in three stages for the removal of gold and silver from aqueous cyanide solutions from samples supplied by a Mexican mining company. Characterization of the sample showed initial concentrations of 49.48 and 383 mg/L of gold and silver, respectively. Results showed the effectiveness of the process by achieving removals up to 98.59% of gold and 99.43% of silver. Additionally, it was determined that the kinetics of the reaction is of zero order and that the lowest energy consumption can be achieved when working at constant voltage and with a separation of 0.8 cm between electrodes.

Recovery of resources from industrial wastewater employing electrochemical technologies: status, advancements and perspectives

“…Metals may also be collected as hydroxides through electrocoagulation methods. When balanced to conventional procedures, the electrocoagulation method benefits from its simplicity, ease of operation, shorter retention time, reduced or no added chemical, quick settling of the electrogenerated flocs, lower sludge formation, and eco-friendliness [ 12 , 80 , 81 ].…”

“…The initial Au and Ag values in the samples were 49.48 and 383 mg/L, respectively, according to the analysis. The elimination of up to 98.59% of Au and 99.43% of Ag demonstrated the process’s efficacy [ 15 , 80 ]. Potassium is obtained using redox transistor electrodialysis, and lithium is obtained through electrochemical sorption.…”

“…Nevertheless, the challenges of electrochemical coagulation technology in recovering valuable metals remain unchanged. Separating every metal component from a mixture of precipitates is always difficult [ 80 ]. As a result of the growing use of lithium consumption in cell phone electronics and electric vehicles, and the scarcity of lithium, the reclamation of wastewater from battery reusing plants has become more and more important and cost-effective.…”

“… Silver Electrically switched ion exchange technique, Non-electrode deposition method. 80 ,al. (2020) 2.…”

Electrocoagulation Process for Recovery of Precious Metals from Cyanide Leachates Using a Low Voltage

“…Several authors have used the electrocoagulation (EC) to remove heavy metals. − The EC has also been investigated as an alternative process for the recovery of precious metals, mainly for general gold and silver processes. − Gold and silver are generally recovered by electrowinning (EW) from cyanide solutions purified and concentrated by carbon adsorption. In addition, electrocoagulation is used for the treatment of high-grade gold solutions.…”