Efficiency of using peroxide-carbonate compounds in reagent complexes for leaching gold hard to recover from placer

The article deals with the data of theoretical and experimental studies of the processes of activation gold leaching using reactive peroxide carbonate compounds, obtained by electrophotochemical treatment of solutions of initial reagents of the corresponding composition, in the composition of reagent complexes. The obtained results of the experiments on the interaction of various carbonate and peroxide-carbonate compounds with sodium cyanide in the process of mixing activated and non-activated solutions with aqueous cyanide solutions in different order definitely prove that supramolecular percarbonate-cyanide compounds are being formed in them. It has been established that these activated solutions, prepared on the basis of the initial hydrocarbonate ones, contain metastable compounds that provide a higher rate of gold extraction from crude minerals than standard aqueous cyanic solutions of the same initial concentration.

Recovery of gold and base metals from waste printed circuits boards

This lab-scale experimental study presents a novel combined hydrometallurgical and electrochemical process for gold and non-precious metals (Cu, Ni, Pb and Zn) recovery, from waste printed circuit boards (PCB´s). First, a leaching of pins from PCB´s has been carried out and complete gold extraction was obtained using H2SO4 0.5 M (pH ≈ 1.5)/O2 (1 atm) in the temperature range from 288 to 343 K. The activation energies found showed values of 97.2 kJ∙mol-1, 86 kJ∙mol-1 and 93.6 kJ∙mol-1 for Cu, Ni and Zn respectively. Afterwards, leaching liquor was treated electrochemically in several conditions: selective Cu and Pb removal was performed at pH 1.5 and Ni and Zn removal was also obtained when pH increased to 5. All processes involved here are friendly, and even, final liquor could be reutilized.

On the possibility of flotation processing of technogenic gold-containing waste from enrichment plants

The aim of the work is the flotation processing of gold-containing tailings using composite flotation (CF) agents. According to the results of chemical analysis, the studied tailings sample contains 0.39 g/t gold. The main part of the initial tailings sample is represented by rock-forming minerals such as quartz, clinochlore, microcline, tremolite, albite, calcite, and muscovite. According to the results of the rational analysis, 39.50% of gold is in the hard-to-recover form with quartz; 28.87% is in the form of fine-grained gold; 31.63% is in intergrowths with sulfides and rocks. The optimum reagent scheme of flotation processing of tailings was chosen: degree of regrinding of 95% of grade -0,074 mm, consumption of sodium butyl xanthate of 100 g/t, consumption of foaming agent T-92 of 30 g/t. Under the chosen reagent scheme the gold-containing concentrate containing 6,4 g/t gold at the recovery of 49,68% was obtained. Preliminary regrinding of tailings allows to increase the gold recovery in the blanks concentrates by 27.96%. The reagent scheme of flotation of gold-containing tailings with the application of composite flotation (CF) agent was tested. A composition of sodium butyl xanthate and reaeflot was used as a composite flotation reagent for the improvement of gold extraction from flotation tailings. Application of composite flotation (CF) agent pre-treated on the dispersant increases gold recovery into gold-containing concentrate by 4.65%, in comparison with the basic collector sodium butyl xanthogenate. Consumption of flotation agent CF is reduced by 20%.

Designing of engineering solutions to enhance efficiency of high-copper gold-bearing ore processing

The modern metals industry is characterised by a downward trend in the quality of ores involved in processing, and conventional methods of extracting useful components are inefficient for raw materials with complex composition. To maintain the growing level of metal production it is required to introduce new efficient technologies for processing of low-grade and refractory ores as well as man-made deposits. The article describes processing methods of refractory raw materials with high cyanide content using copper-gold ores as an example, where gold is the primary commodity, and copper is the accompanying useful component. The most common method of processing copper-gold ores is preconcentration followed by selective leaching of copper and gold. In some cases, technologies involving copper by-products and cyanide recovery from the cyanide leaching solutions offer equally effective options for processing of the copper-gold ores and concentrates. Copper-gold ores are processed at gold mines using the cyanide procedures, supplemented if required by gravity and flotation concentration. In all variations of the cyanide treatment, most of copper minerals actively react with cyanides of alkali metals, binding the CN– ions into the copper complex of [Cu(CN3)]2–. This reaction results in an increased solvent consumption, as well as in number of challenges related to cleaning tailings and slurries from highly toxic cyanide compounds and dissolved copper. In addition to technological complications associated with the need to meet strict requirements for the maximum permissible concentrations, copper accumulated in the cycling solutions also causes a decrease in gold extraction from the processed ores.

Characterization of potential mercury contamination in the ASGM area of Mandailing Natal, North Sumatera

A large amount of Hg is used for gold extraction through the amalgamation process in the Mandailing Natal derived from artisanal and small-scale gold mining (ASGM) area located in the North Sumatera Province, Indonesia. The objective of this work was to characterize the potential contamination of total Hg in water, sediments, and soil in this ASGM area. Sampling was done in two locations in West Panyabungan and Huta Bargot Districts using grab sampling method. Results showed that accumulation of Hg in the studied soils and sediments was the highest, but Hg in aquatic solution was below the detection limit of the analytical method of the studied community wells and rivers. The highest concentration of Hg was found in the river sediments of the Saba Padang irrigation (1,63 mg/kg), and in the soil of the plantation area of Huta Bargot (1,62 mg/kg) respectively. These concentrations may pose a serious problem for aquatic and land life, related ecosystems, and human health. For further study, there is a need to study Hg availability in riverine biota to better understand the cycling of Hg in this ASGM area. Understanding the ecological impacts can assist in the prioritizing of impact mitigation efforts.

Characterization of gold ore from Babakan Loa Sub-District and leaching study in cyanide solution

Research on the characterization of gold ore from Babakan Loa sub-district and studies of leaching in cyanide solution has been carried out. This research was conducted to determine the characteristics of gold ore from Babakan Loa and the leaching behavior in cyanide solution. The preparations carried out were crushing and grinding to obtain several size fractions. The ore characterization was carried out through XRD, XRF, SEM-EDX, and wet chemical analysis. XRD analysis results show that the main mineral phases are quartz, hematite, goethite, kaolinite, montmorillonite, and berlinite. The main constituents of the ore were Si (60.96%), Fe (10.71%), K (5.47%), and Al (19.53%). The Au content was 7.8 ppm, and the results of SEM-EDX analysis show that the gold grain size is smaller than 10µm. The leaching process showed that the highest percent gold extraction data of 92.7% was obtained in experiments with 1000 ppm sodium cyanide concentration, 10% solids percent, and 104-149µm grain size. Increasing the percentage of solids and the reduction in grain size led to a decrease in the percentage of gold extraction. The clay content was suspected to be the cause of the ineffectiveness of the leaching process in this study.

Gold mining in Ecuador: Innovative recommendations for the management and remediation of mercury-contaminated waters

ASGM Mining processes have increased in recent years, becoming one of the main activities re-sponsible for serious impacts on ecosystems, affecting biodiversity and valuable resources such as soil and water. It is necessary to analyze the successful management developed by some countries in gold extraction, through innovative techniques and procedures, and recommend its replication in Ecuador. It is undeniable that mercury is one of the main contaminants in gold mining, it is important to establish the best techniques to protect natural resources. The first section of this paper analyzed the changes in Ecuadorian mining management with a focus on gold mining processes, followed by a description of ASGM mining and mercury use in Ecuador. Finally, the main sources of contamination were analyzed and recommendations were made to improve mining management and reduce contamination of water bodies. The methodology used was based on a bibliographic review of gray and scientific literature. The recommendations establish that mining management in Ecuador should focus its efforts on improving control and monitoring capacity, regularization of mining registries, and strengthening regulations with new policies. Finally, to reduce the impact of Hg on water bodies, it is necessary to educate ASGM miners about the risks of indiscriminate use of mercury and about techniques that can provide better socioeconomic benefits.