• Ecology and Resilient Infrastructure
• /
• v.3 no.4
• /
• pp.279-284
• /
• 2016

Mine tailings generated during mining activity often contain high concentrations of heavy metals, with pyrite-containing mine tailings in particular being a major cause of environmental problems in mining areas. Chemical cell technology, or fuel cell technology, can be applied to leach heavy metals in pyrite-containing mine tailings. As pyrite dissolves through spontaneous oxidation (i.e. galvanic oxidation) in the anode compartment of the cell, $Fe^{3+}$, sulfuric acid are generated. A decrease in pH due to the generation of sulfuric acid allows heavy metals to be leached from pyrite-containing mine tailings. In this study, pyrite was dissolved for 4 weeks at $23^{\circ}C$ in an acidic solution (pH 2) and in a galvanic reactor, which induces galvanic oxidation, and total Fe leached from pyrite and pH were compared in order to investigate if galvanic oxidation can facilitate pyrite oxidation. The change in the pyrite surface was analyzed using a scanning electron microscope (SEM). Comparing the total Fe leached from the pyrite, there were 2.9 times more dissolution of pyrite in the galvanic reactor than in the acidic solution, and thus pH was lower in the galvanic reactor than in the acidic solution. Through SEM analysis of the pyrite that reacted in the galvanic reactor, linear-shaped cracks were observed on the surface of the pyrite. The study results show that pyrite dissolution was facilitated through the galvanic oxidation in the galvanic reactor, and also implied that the galvanic oxidation can be one remediation option for pyrite-containing mine tailings.

• Journal of the Mineralogical Society of Korea
• /
• v.26 no.3
• /
• pp.139-150
• /
• 2013

In order to effectively leach Fe from pyrite, the application of microwave energy and ammonia solution has been conducted. Pyrite transforms into hematite and pyrrhotite when treated with microwave radiation for 60 minutes, and in this time the highest amount of Fe was leached by the ammonia solution. Up to 99% of the Fe was leached when the experimental conditions were: 325-400 mesh particle size for the pyrite and 60 min. was the microwave exposure time. The ammonia leaching conditions were 0.3 M sulfuric acid, 2.0 M ammonium sulfate and 0.1 M hydrogen peroxide concentration. The pyrite, hematite, and pyrrhotite were not detected using XRD analysis from the solid-residues treated by the ammonia solution except for quartz.

• Journal of the Mineralogical Society of Korea
• /
• v.28 no.3
• /
• pp.233-244
• /
• 2015

In order to study the phase transformation of pyrite and to determine the maximum Fe leaching factors, pyrite samples were an electric furnace and microwave oven and then ammonia leaching was carried out. The rim structure of hematite was observed in the sample exposed in an electric furnace, whereas a rim structure consisting of hematite and pyrrhotite were found in the microwave treated sample. Numerous interconnected cracks were only formed in the microwave treated sample due to the arcing effect, and these cracks were not found in the electric furnace treated sample. Under XRD analysis, pyrite and hematite were observed in the electric furnace treated sample, whereas pyrite, hematite and pyrrhotite were found in the microwave treated sample. The results of the pyrite sample leaching experiments showed that the Fe leaching was maximized with the particle size of -325 mesh, sulfuric acid of 2.0 M, ammonium sulfate of 1.0 M, and hydrogen peroxide of 1.0 M. The electric furnace and microwave treated samples were tested under the maximum leaching conditions, the Fe leaching rate was much greater in the microwave treated sample than in the electric furnace treated sample and the maximum Fe leaching time was also faster in the microwave treated sample than in the electric furnace treated sample. Accordingly, it is expected that the microwave heating can enhance (or improve) Fe leaching in industrial minerals as well as pyrite decomposition in gold ores.

• Proceedings of the KSEEG Conference
• /
• 2002.04a
• /
• pp.62-65
• /
• 2002

• Economic and Environmental Geology
• /
• v.36 no.6
• /
• pp.537-543
• /
• 2003

As pyrite is commonly associated with arsenopyrite, the use of pyrite including arsenopyrite for medicine requires close attention on arsenic toxicity. The toxicity was reduced by traditional processing operations include heating and quenching in vinegar. To verify the scientific effects of this process, pyrite containing many crystals of arsenopyrite was processed at temperatures from 45$0^{\circ}C$ to 85$0^{\circ}C$ and through as many as 5 processing cycles. Arsenopyrite completely disappeared when processed only once at $650^{\circ}C$ while it remained even after 5 processing cycles at 45$0^{\circ}C$. Arsenic was most abundant in medicinal mineral samples processed at 45$0^{\circ}C$ and sharply decreased when processed at $650^{\circ}C$ or 85$0^{\circ}C$ And arsenic extraction test in water was carried out from the processed pyrite medicine on the assumption that pyrite medicines with the lowest As metal content would be most desirable. Arsenic were most abundant in water extracted from medicinal mineral samples processed at 45$0^{\circ}C$ and sharply decreased when processed at $650^{\circ}C$ or 85$0^{\circ}C$. But the extracted As concentrations in water exceeded drinking water standards even when processed at 85$0^{\circ}C$. Increasing temperature promoted elimination of arsenopyrite and reduction of As in medicinal minerals and the extraction solutions. But the effects of processing cycles at the same processing temperature were not clear. Heating temperature is more important than number of processing cycles for the removal of arsenic, and it is necessary to heat pyrite to over $650^{\circ}C$ to remove it.

• Journal of the Mineralogical Society of Korea
• /
• v.24 no.3
• /
• pp.235-244
• /
• 2011

A batch experiment of pyrite oxidation was performed and the surfaces of the reacted pyrite were regularly observed with the scanning electron microscope (SEM) together with the chemical compositions of the solution to help understand the oxidation mechanisms of pyrite by Acidithiobacillus ferrooxidans (Af). The dissolved Fe concentrations clearly indicated that Af experiences the lag and then exponential growth phase. An Af cell was observed to be attached to the surface of pyrite during the lag, implying that a direct leaching by the microbe really happens for the period. It is not certain, however, whether the main mechanism of pyrite oxidation during that time was the direct leaching or not, because there were just a few cells confirmed to be attached and most of the dissolved Fe was Fe(III). The dissolved Fe concentration stayed almost constant from the mid-lag phase to just before the onset of the exponential phase, suggesting that AI needs an adaptation time to switch its oxidation mechanism from one to the other whichever it is during that stage of growth. The moment of Af's cell division was observed by SEM on the surface of pyrite during the lag phase. The corrosion outline around the dividing cell was quite similar to the shape of the cell itself, which implies that the rate of the microbial oxidation is very uneven and the rate when the cell metabolizes should be much faster than that calculated from the concentration variation of the dissolved Fe. The number of etch holes by Af is much higher on the inoculated surfaces, indicating the average rate of pyrite oxidation is also much faster than that of abiotic oxidation. The microbial etch holes on pyrite surface are small and deep, which may influence the transition of the growth phases of Af from lag to exponential.

• Journal of the Mineralogical Society of Korea
• /
• v.16 no.1
• /
• pp.1-17
• /
• 2003

The chemical composition of the arsenopyrite Ib adjoining“triple mutual contact”arsenopyrite + pyrite + hexagonal pyrrhotite may serve as a useful geothermometer in Stage II. In this study it corresponds to temperature T=33$0^{\circ}C$ and f( $S_2$)=10$^{-9.5}$ atm. And the pyrite-hexagonal pyrrhotite buffer curve indicates the probable range of the two variables; T= 315∼345$^{\circ}C$, and f( $S_2$)=10$^{-1}$0.5/∼10$^{-9}$ atm. The present antimony-bearing arsenopyrite (arsenopyrite Ic) is characterized by relatively high content of antimony, ranging from 4.95 to 8.91 percent Sb by weight and excess of iron and deficiency of anions are evident. Such a high antimonian arsenopyrite has never been known within single grain. But being the high content of antimony as in the arsenopyrite Ic, it does not serve as a geothermometer. The results of microprobe analyses for four pairs of asenopyrite and sphalerite in Stage III indicate the temperature range from 310 to 34$0^{\circ}C$, and sulphur fugacity range from 10$^{-10}$ ∼10$^{-9}$ atm. These values seem to correspond with those inferred from the Fe-As-S system.m..

• Journal of the Speleological Society of Korea
• /
• v.24 no.25
• /
• pp.69-80
• /
• 1991

광화시기가 같은 유화광물중에서 상접하는 황철석과 자류철석 내에 함유되어 있는 코발트와 니켈의 함량을 정량분석하여 이들 원소들의 Partition Coefficients로부터 Bezmen method를 이용하여 광물의 생성온도를 구하였다(217～395$^{\circ}$). 지질 연대가 같은 유화광물의 생성온도는 동시기에 생성된 인접한 석영내의 유체포유물의 filling temperature와 거의 일치한다(255～395$^{\circ}$). 따라서 이들 광산내의 광물의 생성온도는 지질온도계로 사용이 가능하며 광물의 생성환경을 규명하는데도 유용할 것이다.

• Economic and Environmental Geology
• /
• v.53 no.3
• /
• pp.221-234
• /
• 2020

We occur together with telluride minerals. Fluid inclusions in the euhedral quartz crystals are mainly aqueous liquid-rich inclusions, which have salinities about 0.18-2.24 wt% NaCl equivalent. Some quartz vein contains aqueous vapor-rich inclusions as well. Homogenization temperatures of the assemblages of the liquid-rich inclusions are about 141-384 ℃, and the temperatures are lower at the shallower vein samples. In the high Au-Ag grade depth intervals, relatively deeper fluids have relatively higher salinities and homogenization temperatures, while shallower fluids show somewhat wider ranges. These might indicate that the deep Au-Ag bearing hydrothermal fluids at the Moisan area experienced phase separation as well as mixing with meteoric water by decreasing pressure. Au-Ag precipitation in the Moisan deposit is not associated with pyrite, but pyrite include Au-Ag bearing phase as an inclusion, which might possibly be tellurides or electrum. Au/Ag ratios in the Au-Ag bearing phase do not change with different depth.

• The Korean Journal of Quaternary Research
• /
• v.3 no.1
• /
• pp.47-54
• /
• 1989

Pyrite ($FeS_2$) content in brackish and salt marsh sediments is relatively higher than the amount in freshwater marsh sediments. Different values of pyrite sulfur ($FeS_2$-S) content in sediments from the Hiroshima Delta indicate that poorly drained salt marsh had developed between 27.0m and 28.0m below mean sea-level and palaeo-sea-level was constant for several hundreds of years in the same depth during the early Holocene Epoch.