Papers by Keyword: Sulfide Mineral

Abstract: Reserves of high-grade gold ore worldwide are decreasing, and some industries have started processing refractory gold ore. Refractory gold ore contains sulfide minerals such as pyrite (FeS₂), chalcopyrite (CuFeS₂), galena (PbS), and sphalerite (ZnS). Gold in refractory ores occurs as fine-size gold-bearing sulfide minerals. In this study, the microwave-assisted roasting method has been investigated as a pretreatment for a refractory gold ore. This method can provide rapid heating radiation, cause micro-cracks, and trigger the decomposition of sulfide minerals. The presence of additive helps in the oxidation of sulfide minerals. The microwave-assisted roasting was carried out using variations in microwave power and time. Microwave power between 300 - 600 watts significantly affected the increase in roasting temperature and weight loss of refractory gold ore. The highest temperature reached 567°C in roasting at 800 watts for 30 minutes. The optimum condition for microwave roasting was achieved at 400 watts of power with a roasting time of 30 minutes. Metals extraction of Cu, Zn, Pb, and Fe reached 97.2%, 82.7%, 16.1%, and 2.1% in water leaching.

Abstract: This paper summarizes the result of experiment that was fourced on investigation of oxidation pretreatment on sulfide mineral for leaching of refractory gold concentrate by hydrogen peroxide in sulfuric acid. For a viable option, extraction rate of Fe, Cu was low, but extraction rate of arsenic reached nearly 100%. As the result of oxidation, elemental sulfur was not produced.

Abstract: Azo dyes have strong hydrophilic and good adhesion to solid surface. In this study, 23 kinds of typical azo compounds were tested as depressant of sulfide minerals. Absorption of azo compound on mineral surfaces was detected by UV. The result shows that some of them can be good depressants of single sulfide minerals. With the number of azo group increasing from 1 to 3, depression performances are improved. On the other hand, depression performances of azo dye are related to the type of group and the location of phenyls，the results of adsorption and the frontier molecular orbital energy calculation may be used to explain depression performances of azo dyes.

Abstract: Black rock strata with special engineering geological characteristics are distributed widely in different geological periods and areas. The scattered sulfide minerals in the rock strata are changed in a short time under the action of the oxygen-rich surface water and oxygen-rich groundwater. And the acidic water with strong erosiveness is formed. Then water--rock interaction between other minerals and the acidic water subsequently occurs with a series of chemical reactions. It can affect the stability of the black rocks themselves and other non-black rocks nearby directly, and cause engineering and environmental geological problems. Through the combination of engineering project and immersion test indoor, the mechanism of water-rock interaction of the black rock strata is researched. Engineering preventions and measures in the black strata region are proposed to avoid the damage to project and the ecological environment around.

Abstract: Selective separation of pyrite from galena and quartz was achieved through microbiologically induced flotation in presence of Bacillus subtilis. B. subtilis functions as a depressant for pyrite while it promotes the flotation of galena and quartz. Bacterial extracellular protein (EP) was isolated and the protein profile of bacterial cells grown in presence and absence of minerals established.

Abstract: Results of research on technological processes for treatment of refractory gold-arsenic ores using bioleaching of concentrates are presented. In October 2001 the first line of bioreactors on Mill-2 began operation with projected throughput of 3 million tons a year. In July 2007 Mill-3 began operation with projected throughput of 5 million tons a year. At present the closed joint stock company Gold Mining Company «Polyus» occupies a leading position in gold extraction from hard rocks in the Russian Federation. Processing of refractory gold-arsenic ores is conducted on Mill-2 and Mill-3 by a flotation-cyanide scheme using a unique biooxidation technology, BIONORD®, designed to process concentrates in the extreme climatic conditions of the North, . The achieved productivity of the Olympiada Mining Combine, from the processing of both oxidized and refractory ores of the Olympiada deposit, is 26.7 tons of gold a year. The gold is mostly present as finely dispersed and submicroscopic particles in close association with sulfide minerals, usually pyrite, pyrrhotite, arsenopyrite and antimonite. The average productivity of the lines is 1000 t/day. The process time is 100-150 h. The pulp density is 150-200 g/l. The working temperature is 39-40oC. The microbial association is represented by three species of chemolithotrophs: “Sulfobacillus olympiadicus”, Leptospirillum ferrooxidans, and Ferroplasma acidiphilum present in proportions 60-80%, 10-20%, and 10-17%, respectively. During the process 87% of sulfide minerals are oxidized. Thus, 98% of the pyrrhotite, 95.4% of the arsenopyrite, 70% of the antimony sulfides and 60% of the pyrite is oxidised. Biooxidation enables 97% of the gold to be released.

Abstract: Conventionally, physico-chemical methods are used in mineral processing for recovering value minerals from ores. The ageing of ore processing tailings and waste rocks, and mining tailings contamination by chemical reagents constitute a major threat to the environment. It is imperative to develop novel economically more efficient and environmentally benign methods of flotation and waste processing, exploiting the intriguing and exciting ability of bacteria to selectively modify the surface properties of solids. Microorganisms have not only facilitate hydrometallurgical leaching operations but have also show a great promise in mineral beneficiation processes such as flotation and flocculation. Several laboratory investigations revealed that microorganisms could function similar to traditional reagents. Microorganisms have a tremendous influence on their environment through the transfer of energy, charge, and materials across a complex biotic mineral-solution interface. The bio-modification of mineral surfaces involves the complex action of microorganism on the mineral surface. The manner, in which bacteria affect the surface reactivity and the mechanism of bacteria adsorption, is still unknown and accumulation of the primary data in this area is only starting. The bio-flotation and bio-flocculation processes concern the mineral response to the bacterium presence, which is essentially interplay between microorganism and the physicochemical properties of the mineral surface, such as the atomic and electronic structure, the net charge/potential, acid-base properties, and wettability of the surface. There is an urgent need for developing basic knowledge that would underpin biotechnological innovations in the natural resource (re)processing technologies that deliver competitive solutions.