금은광산 광석광물의 품위향상 및 유가금속 회수를 위한 용출특성

Abstract

This study aims to collect valuable metal through the biological, physicochemical leaching and electrolysis and also to confirm if a resource-recycling can be used to handle tailings in bulk, which are considered to be environmentally problematic.

The enhancing of Au-Ag-Te content in tellurium-bearing ore mineral by bio-oxidation-leaching

The purpose of this study is to enhance the content of valuable metals such as Au-Ag-Te in tellurium-bearing minerals by bio-oxidation-leaching. It was confirmed that pyrite, chalcopyrite, sphalerite and galena were produced together with tellurium-bearing minerals including hessite, sylvanite and tellurobismuthite from ore minerals and concentrates through microscopic observation and SEM/EDS analysis. In a bio-oxidation-leaching experiment, with regard to Au, Ag, Te, Cu and Fe, the changes in the amount of leaching and the content of leaching residues were compared and analyzed with each other depending on the adaptation of an indigenous microbe identified as Acidithiobacillus ferrooxidans. As a result of the experiment, the Au-Ag-Te content in tellurium-bearing ore mineral was enhanced in the order of physical oxidation leaching, physical/non-adaptive bio-oxidation-leaching and physical/adaptive biological leaching. It suggests that the bio-oxidation-leaching using microbes adapted in tellurium-bearing ore mineral can be used as a pre-treatment and a main process in a recovery process of valuable metals.

Reductive leaching of Mn from deep-sea manganese crust, and upgrading of Au-Ag-Te contents from invisible gold concentrate by biooxidation

In order to upgrade Au-Ag-Te content in gold concentrate and reductively leach Mn from deep-sea manganese crust, bioleaching experiments were carried out. Indigenous acidiphile bacteria were collected from local mine drainage and then cultured for 6 years and 4 months. The bacteria were confirmed, by PCR and 16S rRNA analysis, as an Acidithiobacillus ferrooxidans, which can oxidize Iron and elemental sulfur. In order to increase the bacteria's tolerance to heavy metals, this indigenous acidophilic bacteria was repeatedly subcultured in an adaptation-medium containing 382.98 mg/l Cu for 35 periods of 21 days. As a result of bioleaching experiments with the bacteria, soluble ions, such as Cu and Fe, were increased in experimental samples in the order of the control, the non-adapted bacteria sample, the adapted bacteria without manganese crust sample, and the adapted bacteria sample. Mn content was increased in the order of control, non-adapted bacteria, and adapted bacteria sample as reductively leached. In the solid-residue, the insoluble elemental Au, Ag and Te content was increased in the order of control, non-adapted bacteria, adapted bacteria without manganese crust, and adapted bacteria sample. Accordingly, it is expected that more Au, Ag and Te can be upgraded in the gold concentrate and more Mn, Ni, Co, Cr can be reductively leached from the manganese crust if the bacteria is adapted to heavy metal ions and an optimization of conditions is found in future bioleaching processes.

The Characteristic dissolution of valuable metals from mine-waste rock by heap bioleaching, and the recovery of metallic copper powder with Fe removal and electrowinning

In order to recover the metallic copper powder from the mine-waste rock, heap bioleaching, Fe removal and electrowinning experiments were carried out. The results of heap leaching with the mine-waste rock sample containing 0.034% Cu showed that, the leaching rate of Cu were 61% and 62% in the bacteria leaching and sulfuric acid leaching solution, respectively. Sodium hydroxide (NaOH), hydrogen peroxide (H2O2) and calcium hydroxide (Ca(OH)2) were applied to effectively remov Fe from the heap leaching solution, and then H2O2 was selected for the most effective removing Fe agent. In order to prepare the electrolytic solution, H2O2 were again treated in the heap leaching, and Fe removal rates were 99% and 60%, whereas Cu removal rates were 5% and 7% in the bacteria and sulfuric acid leaching solutions, respectively. After electrowinning was examined in these leaching solution, the recovery rates of Cu were obtained 98% in bacteria and obtained 76% in the sulfuric leaching solution. The dendritic form of metallic copper powder was recovered in both leaching solutions.

Enhancement of Au·Ag leaching by mechanochemical activation and thiourea-thiocyanate mixing solution

In order to enhance the Au·Ag leach rate, a mechanochemical activation process and a mixed thioureathiocyanate solution has been applied to Au concentrate. To achieve mechanochemical activation, the Au concentrate was mechanically ground using a dry and a wet process. The results of a particle size distribution analysis and an XRD analysis, average particle size and crystallite size were much smaller in the dry-sample than in the concentrate sample. As well the size was smaller in the wet-sample than in the dry-sample. In SEM and XRD analysis, the amorphization effect was observed in the wet-sample due to mechanochemical activation. Au·Ag leaching experiments were carried out with a thiourea solution, a thiocyanate solution and a mixed thiourea-thiocyanate solution. The Au · Ag leach rate was much greater in the dry-ground-sample than in the concentrate sample, and the leach rate was greater in the wet-ground-sample than in the dry-sample. The Au·Ag leach rate was much greater in the thiocyanate solution than in the thiourea solution, and the leaching rate was much greater in the mixed thiourea-thiocyanate solution than in the thiocyanate solution. Up to a 99% leach rate for Au · Ag were only achieved in the wet-sample using the mixed thiourea-thiocyanate leaching solution.

Selective phase transformation of arsenopyrite by microwave heating and their enhancement Au recovery by thiocyanate solution

In order to investigate selective phase transformations and to determine the maximum Au leaching factors from microwave treated Au-bearing complex sulfides, a microscope, SEM-EDS analysis, and thiocyanate leaching tests were performed. When the Au-bearing complex sulfides were exposed to microwave heating, increasing the microwave exposure time increased temperature and decreased weight. Arsenopyrite was first selectively transformed to hematite, which formed a concentric rim structure. In this hematite, oxygen and carbon was detected and always showed high iron content and low arsenic content due to arcing and oxidation from microwave heating. The results of the leaching test using microwave treated sample showed that the maximum Au leaching parameters was reached with 0.5 g concentration thiocyanate, 2.0 M hydrochloric acid, 0.3 M copper sulfate and leaching temperature at 60℃. Under the maximum Au leaching conditions, 59% to 96.69% of Au was leached from the microwave treated samples, whereas only 24.53% to 92% of the Au was leached from the untreated samples.

The characteristic of Te recovery in gold concentrate using electrolysis

In order to obtain pure metallic Te from gold concentrate, roasting treatment, hypochlorite leaching, Fe removal and electrolysis experiments were carried out. The contents of Au, Ag and Te from the concentrate sample and roasted sample were much more soluble in the hypochlorite solution than in aqua regia digestion, whereas the metals Pb, Zn, Fe and Cu were easier to leach with the aqua regia than the hypochlorite. With the addition of NaOH in the hypochlorite leaching solution prior to electrolysis, the Fe removal rate achieved was only 96% in the concentrate sample, while it reached 98% in the roasted sample. The results of electrolysis for 240 min, 98% of the metallic copper was recovered from the concentrate sample, while 99% was obtained from the roasted sample due to the removal of S by roasting. The amount of anode slime was also greater in the electrolytic solution with the roasted sample than with the concentrate sample. The results on the anode slime after the magnetic separation process showed the amount of metallic pure native tellurium recovered was greater in the roasted sample than in the concentrate sample.

Recycling of arsenic-rich mine tailings in controlled low-strength materials

This study investigated the engineering properties and leaching behavior of controlled low-strength materials (CLSM) containing arsenic-rich mine tailings and evaluates the feasibility of the tailings as source material for CLSM. The compressive strength of the CLSM mixtures was shown to satisfy that specified in American Concrete Institute (ACI) Committee 229R in which the content of cement was controlled to be 10-30% by the weight of the tailings. The leaching fraction of As from CLSM mixtures was found to be below 6% regardless of the mix proportion and grinding of samples. The leaching fraction from the mortar-type CLSM was lower than those of the slurry-type CLSM. Furthermore, the leaching fraction of the CLSM mixtures in the ground state by weathering and erosion was increased, whereas the absolute value remained below 2%, thus showing no significant influence.