Pyrite Particle Size Research Articles

Stepwise oxidation of refractory pyrite using persulfate for efficient leaching of gold and silver by an eco-friendly copper(II)-glycine-thiosulfate system

Chemical oxidation is a promising pretreatment method for refractory pyrite enclosure to enhance Au/Ag extraction. Here, persulfate was employed for stepwise oxidation of a refractory pyrite concentrate with encapsulated Au/Ag: (i) pyrite oxidation began with heating-activation persulfate, where hydroxyl radical (•OH) acted as the primary oxidative species for fast-dissolving pyrite into Fe ions; (ii) pyrite self-dissolved Fe ions were in-suit used as a moderate activator of persulfate to generate •OH for sustainable oxidizing pyrite at room temperature. Mineralogical studies have confirmed that oxidation of the sulfide enclosure (FeS2) significantly reduced the particle size of pyrite, accompanied by pores creation and an increase in specific surface area. The variation of microstructure liberated Au and Ag particles to lixiviants for extraction, significantly improving leaching efficiency in an eco-friendly copper(II)-glycine-thiosulfate system to 92.2 % for Au and 88.6 % for Ag, respectively. This work provides a promising process for separating precious metals from refractory pyrite.

Effect of pyrite particle size on the denitrification performance of autotrophic or split-mixotrophic bioreactors supported by pyrite/polycaprolactone.

In this study, a pyrite-based autotrophic denitrification (PAD) system, a polycaprolactone (PCL)-supported heterotrophic denitrification (PHD) system, and a pyrite+PCL-based split-mixotrophic denitrification (PPMD) system were constructed. The pyrite particle size was controlled in 1-3, 3-5, or 5-8mm in both the PAD and PPMD systems to investigate the effect of pyrite particle size on the denitrification performance of autotrophic or split-mixotrophic bioreactors. It was found that the PAD system achieved the best denitrification efficiency with an average removal rate of 98.98% in the treatment of 1- to 3-mm particle size, whereas it was only 19.24% in the treatment of 5- to 8-mm particle size. At different phases of the whole experiment, the nitrate removal rates of both the PHD and PPMD systems remained stable at a high level (>94%). Compared with the PAD or PHD system, the PPMD system reduced the concentrations of sulfate and chemical oxygen demand in the final effluent efficiently. The interconnection network diagram explained the intrinsic metabolic pathways of nitrogen, sulfur, and carbon in the three denitrification systems at different phases. In addition, the microbial community analysis showed that the PPMD system was beneficial for the enrichment of Firmicutes. Finally, the impact mechanism of pyrite particle size on the performance of the PPMD system was proposed. PRACTITIONER POINTS: The reduction of pyrite particle size was beneficial for improving the efficiency of the PAD process. The change in particle size had an effect on NO2 --N accumulation in the PAD system. The accumulation of NH4 +-N in the PPMD system increased with the decrease in particle size. The reduction of pyrite particle size increased the production of SO4 2- in the PAD and PPMD systems. The correlations among the effluent indicators of the PAD and PPMD systems could be well explained.

Effect of oxidized pyrite activating persulfate on the degradation of aniline aerofloat: Mechanism and degradation pathway

Aniline aerofloat (dianilinodithiophosphoric acid, DDA) is a common flotation collector for sulfide minerals, but it is also toxic and difficult to be degraded. In this study, oxidized pyrite was used to degrade DDA through activating persulfate (PS). It was found that oxidized pyrite was far more effective than fresh pyrite at removing DDA from a PS system over a wide pH range. The effect of the pyrite oxidation time, initial pH, PS concentration, pyrite dosage and pyrite particle size on DDA degradation in the pyrite-PS system were studied and optimal conditions determined. Through analysis of the total Fe ions concentration, radical species identification and XPS analysis of the change of surface species Fe and S, the DDA degradation mechanism in the oxidized pyrite-PS system was determined. The degradation products were measured by gas chromatography-mass spectrometry (GC–MS) and a potential DDA degradation pathway was hypothesized. The results in this study suggest a template for the utilization of oxidized pyrite in gangue minerals to remove DDA from the wastewater in mineral processing plants.

Study of the Mechanism of Dearsenification of Arsenopyrite Enhanced by Mechanically Modified Pyrite and Bacteria

This study investigated the impact of mechanically modified pyrite on the dearsenification of arsenopyrite through bacterial oxidation. Pyrite was mechanically modified using a planetary high-energy ball mill, and the resulting changes in the crystal structure were characterized using particle size analysis, specific surface area measurements, scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD). Pearson correlation analysis was employed to examine the relationship between the crystal structure of modified pyrite and the bacterial oxidation of arsenopyrite. The study also investigated the mechanism of arsenic removal using pyrite with varying degrees of mechanical modification during arsenopyrite bio-oxidation. The key findings are as follows: (1) The maximum extent of arsenopyrite dearsenification by bacteria was achieved at a pyrite modification degree of 400 r·min−1 and reached 96.01%, which was 14.49% higher than that for unmodified pyrite and 24.13% higher than that in the absence of pyrite. At this degree, the modified pyrite exhibited a median diameter of 1.33 μm (minimum) and a specific surface area of 3123 m2·kg−1 (maximum). (2) Pearson correlation analysis revealed a significant negative correlation between the extent of arsenopyrite dearsenification and the particle size and grain size of pyrite, and a significant positive correlation with the specific surface area and the amorphous degree of pyrite. A smaller particle size and grain size, larger specific surface area, and a higher amorphous degree were associated with a higher extent of dearsenification. (3) The mechanism of enhanced arsenopyrite dearsenification using mechanically modified pyrite was attributed to autocatalytic dissolution. The galvanic effect directly enhanced dearsenification, while the mechanical modification facilitated the direct oxidation of pyrite by bacteria, releasing a significant amount of Fe3+ and indirectly enhancing the dearsenification of arsenopyrite.

Degradation of 1,2,3-trichloropropane by pyrite activating sodium percarbonate and the implications for groundwater remediation

1,2,3-trichloropropane (TCP) is a newly regulated groundwater contaminant, however, its remediation technology has not been fully investigated. In this research, pyrite (FeS2) was used as a novel activator of sodium percarbonate (SPC) for TCP degradation. TCP could be effectively removed by FeS2/SPC system with a much higher removal efficiency than the classic Fenton system. Free radical quenching test, hydroxyl radical probe reaction, EPR, XPS, XRD and SEM were used to elucidate the reaction mechanism. SPC was decomposed to produce H2O2, which was activated by Fe2+ dissolved from pyrite to produce HO· and O2-·. Both HO· and O2-· contributed to TCP degradation, but HO· played a more important role. The S elements of pyrite promoted the regeneration of Fe2+, thus enhancing the TCP degradation. The TCP removal efficiency significantly increased with increases in concentrations of pyrite and SPC and decreases in pyrite particle size and pH. Although HCO3-, Cl- and NOM inhibited TCP degradation by FeS2/SPC, the reaction system could still remove TCP in real groundwater. Overall, pyrite-activate SPC is a promising in-situ groundwater remediation technology.

Occurrence Characteristics of Fine-Grained Pyrite in Coal and Its Scaling Effect on Flotation Desulfurization.

To explore the occurrence and distribution characteristics of fine-grained pyrites in coal and the effect of pyrite particle size on flotation efficiency, coal samples from Guizhou province and Shanxi province, China, were selected for pyrite morphology observation and sulfur content test before and after flotation desulfurization experiments with different coal particle sizes. Experimental results showed that the fine-grained fine pyrites in coal have various occurrence forms and complex connections with the coal matrix. The fragmentation process can change the distribution of pyrite content in coal. Flotation desulfurization experiments showed that the sum of pyrite content in the cleaned coal and middlings gradually became significantly higher in coal particles with size 15-37 μm compared with particle sizes 37-44 and 44-75 μm. The complex occurrence morphology and crystal structure of fine-grained pyrite make it difficult to be removed from the coal matrix by ore grinding during flotation. Fine-grained pyrite mainly occurs in the form of framboïdal pyrite, disseminated pyrite, and monomer pyrite with a size of 0.69-33.94 μm in the middlings and cleaned coal. Therefore, 37 μm is considered as the critical dimension for ore grinding to improve the effective flotation desulphurization efficiency in this study, and some more effective methods should be used to increase the desulfurization efficiency of fine-grained pyrite.

The Kinetics of Pyrite Dissolution in Nitric Acid Solution.

Refractory sulphidic ore with gold captured in pyrite has motivated researchers to find efficient means to break down pyrite to make gold accessible and, ultimately, improve gold extraction. Thus, the dissolution of pyrite was investigated to understand the mechanism and find the corresponding kinetics in a nitric acid solution. To carry this out, the temperature (25 to 85 °C), nitric acid concentration (1 to 4 M), the particle size of pyrite from 53 to 212 µm, and different stirring speeds were examined to observe their effect on pyrite dissolution. An increase in temperature and nitric acid concentration were influential parameters to obtaining a substantial improvement in pyrite dissolution (95% Fe extraction achieved). The new shrinking core equation (1/3ln (1 − X) + [(1 − X)−1/3 − 1)]) = kt) fit the measured rates of dissolution well. Thus, the mixed–controlled kinetics model describing the interfacial transfer and diffusion governed the reaction kinetics of pyrite. The activation energies (Ea) were 145.2 kJ/mol at 25–45 °C and 44.3 kJ/mol at higher temperatures (55–85 °C). A semiempirical expression describing the reaction of pyrite dissolution under the conditions studied was proposed: 1/3ln(1 − X) + [(1 − X)−1/3 − 1)] = 88.3 [HNO3]2.6 r0−1.3 e−44280/RT t. The solid residue was analysed using SEM, XRD, and Raman spectrometry, which all identified sulphur formation as the pyrite dissolved. Interestingly, two sulphur species, i.e., S8 and S6, formed during the dissolution process, which were detected using XRD Rietveld refinement.

Interface adsorption mechanism of the improved flotation of fine pyrite by hydrophobic flocculation

• Fine pyrite (−26 μm) flotation was improved by combined use of two reagents. • Particle size of fine pyrite was flocculated to a value suitable for flotation. • Amidation of two reagents caused hydrophobic and flocculation of fine pyrite. • Reticulated polymeric hydrophobic product may generate on the surface. Hydrophobic flocculation is one of the effective method to solve the fine flotation. In this paper the hydrophobization and flotation performance of coco-alcyl-amine-acetate (C-1) on fine pyrite (−26 μm) was improved by ethylenediamine-N, N'-bis (2-hydroxyphenyl) acetic acid (C-2) and the corresponding interaction mechanism was discussed. Turbidity and microscope measurements show that fine pyrite can be better flocculated to an easily floated size using mixed C-1/C-2 (1:1) reagent scheme pH 8.5. Surface micropolarity results display that the flocculation of fine pyrite using mixed C-1/C-2 is mainly through the hydrophobization of it by reagent adsorption. C-2 and C-1 promoting the adsorption of each other could be implied by the significantly change in the surface roughness of pyrite. FTIR results show the amidation between the –NH– in pre-adsorbed C-1 with the –COO – of C-2. Hydrophobic and bridging flocculation are the primary and secondary factors of the bigger floc size. Considering the possibility of the amidation between –NH– in C-2 and -COS - in C-1 and thus the formation of reticulated polymer, the importance of the bridging flocculation may go up, which needs further study. The better flotation recovery of fine pyrite with mixed C-1/C-2 is consistent with the detection results and deductions.

Statistical analysis and significance of pyrite in the Wufeng-Lower Longmaxi Shale Formation in South China

Pyrite from outcrops of Late Ordovician–Early Silurian marine shales of the Sichuan Basin was studied in the laboratory setting. We characterized various occurrences of pyrite using optical microscopy, reflected light microscopy, X-ray analysis, scanning electron microscopy, and energy-dispersive analysis, and image analysis to aid visual estimates of pyrite in polished sections. We observed two classes and four subclasses of pyrite in this marine shale depositional environment. A total of 2964 pyrite framboids and 16,393 pyrite monocrystal particles were measured, with an average particle size value from 2.57 to 6.24 μm in framboidal pyrite and from 0.32 to 0.61 μm in component monocrystals. Over 88% of framboidal pyrite particle size ranges from 1.5 to 9 μm, and the diameter between 0.2 and 0.8 μm is greater than 89% of total pyrite monocrystal particles. The cubic form of pyrite has particle sizes that range from 2.56 to 101.93 μm, more than 83% ranging from 5 to 30 μm. Image analysis of pyrite particle reveals dimensions between 1.0 and 7.5 μm and shape factors from 0.9 to 1.0 (nearly round), indicating that the primary pyrite type in marine shale formation is framboidal pyrite. The framboidal pyrite has important geological significance for marine shale formations. Size analysis, organic matter content, and stratigraphic distribution of framboidal pyrite reveal that the average particle size of framboidal pyrite varies according to deposition in either a dysoxic or a euxinic sedimentary environment. The Fe and S atomic content in framboidal pyrite is relatively low and correlates with high C atomic content, which suggests a close relationship between framboidal pyrite and organic matter. We identified six pore types in this study. Pores are developed in organic matter that occurs between framboidal monocrystals, as well as in organic matter that surrounds framboidal pyrite. Despite their small size, organic porosity remains conducive to the natural gas adsorption, and porosity associated with pyrite may also contain methane in the subsurface.

Adsorption of Sb(Ⅴ) in Water by Natural Pyrite: Performance and Mechanism

The adsorption performance of three iron ores (pyrite, hematite, and magnetite) on Sb(Ⅴ) was compared and pyrite was shown to exhibit the highest adsorption performance. The effects of particle size, concentration, and pH on the adsorption performance were investigated with pyrite as the absorbent. The rejection of Sb(Ⅴ) was the highest (>80%) when pyrite (particle size <0.074 mm) was used as the absorbent with a concentration of 1 g ·L-1 and pH=7. The ion competition experiment indicated that PO43- can inhibit the adsorption of Sb(Ⅴ), while SO42- and CO32- have no significant effects on the adsorption of Sb(Ⅴ) because PO43- can compete with Sb(Ⅴ) for active adsorption sites on the surface of pyrite. The results also showed that the quasi-second-order kinetic model and Langmuir model can better simulate the adsorption process, which shows a single-layer adsorption behavior and chemisorption plays a main role in the rejection of Sb(Ⅴ). FTIR analysis suggested that the removal of Sb(Ⅴ) by pyrite was a coordinated ion exchange reaction. EDS and XPS results further confirmed that Sb(Ⅴ) was adsorbed on the surface of pyrite and was not reduced to Sb(Ⅲ), which is more toxic.

What does mediated electrochemistry reveal about regional differences in the redox properties of Boom Clay?

The Boom Clay is a potential host rock for geological storage of radioactive waste in the Netherlands and Belgium. The redox properties of the host rock are important in the context of safety assessment as they affect the speciation and thus the mobility of redox sensitive radionuclides. In this study, redox properties of the clay were assessed by mediated electrochemical analyses. The electron donating (EDC) and accepting (EAC) capacities and reduction potential of a suite of Boom Clay samples were determined. Boom Clay samples from various locations in the Netherlands and Belgium were investigated in unaltered form, and after size separation or chemical treatment to relate variations in redox properties to regional differences in diagenetic history or in the assemblage of allogenic minerals. In the investigated samples, the EDC can be attributed to the oxidation of pyrite, FeII in clay minerals and reduced natural organic matter (NOM) while the EAC can be ascribed to the reduction of FeIII in clay minerals and in Fe (oxyhydr)oxides. Combining Na-pyrophosphate extraction, to remove reactive NOM, with mediated electrochemical oxidation (MEO) allowed determining the individual EDC of NOM and FeII in clay minerals. Mediated electrochemical analysis showed systematic differences between samples from two locations in the Netherlands, Zeeland and Limburg. In samples from Zeeland, the reduction potential was higher, the EAC was larger, and the contribution of NOM to the EDC was smaller compared to samples from Limburg. These differences can be attributed to partial oxidation of Boom Clay in Zeeland during its diagenetic history but partial oxidation could also be a storage artefact. The electron yield obtained by pyrite oxidation in samples from Zeeland was larger compared to those from Limburg, which can be explained by a smaller particle size of pyrite in Zeeland. The size of pyrite particles, in turn, can be used as a proxy for the depositional conditions. The electrochemical activity of Fe in clay minerals did not vary systematically between the two locations in the Netherlands. In general, the fraction of electrochemically active Fe in clay minerals increased with the relative content of 2:1 clay minerals. In comparison with samples from the Netherlands, larger fractions of structural Fe in clay minerals were redox-active in samples from Belgium, which had a higher chlorite or glauconite content. This study demonstrates that mediated electrochemical analysis can reveal redox properties of Boom Clay, which might be of relevance for the migration of redox sensitive radionuclides or when assessing the impact of constructing and operating a repository for nuclear waste on the surrounding host rock.

Predicting sliding times of a particle over a bubble surface under various chemical conditions

In flotation separation, the sliding of particles over bubble surfaces may result in bubble–particle attachment interactions. This technical note investigates the influence of pulp pH, collector dosage and particle size of pyrite on the sliding interactions and proposes a model that can predict the sliding time under a wide range of conditions. The results showed that the increase in particle size resulted in higher sliding times probably due to longer time for the displacement of the liquid film on the surface of larger particles. A similar trend was also observed with an increase in pulp pH possibly due to the partial oxidation of pyrite surfaces at higher pulp pH. By contrast, the increase in collector dosage reduced the sliding times due to higher adsorption of collector molecules on pyrite surfaces. The sliding times were correlated with pulp pH, collector dosage and particle diameter. The proposed correlation was highly non-linear and can be used to successfully predict the sliding times under a wide range of conditions.

A Novel Method to Limit the Adverse Effect of Fine Serpentine on the Flotation of Pyrite

A novel method to limit the adverse effect of fine serpentine on the flotation of pyrite was investigated in this paper. The flotation results showed that coarser serpentine possessed a weaker depression effect on the pyrite flotation process, and the use of KAl(SO4)2·12H2O could efficiently limit the detrimental effect of fine serpentine on pyrite with a maximum increase of pyrite recovery from 14% to 86% at pH 9.0. The results of particle size measurements and rheological measurements exhibited that the addition of KAl(SO4)2·12H2O increased the particle size of serpentine buta hrdly affected the particle size of pyrite, then limited the formation of serpentine-pyrite aggregates. Adsorption test results showed that the adsorption density of potassium butyl xanthate (PBX) onto pyrite regained with the addition of KAl(SO4)2·12H2O, thereby achieving good flotation improvement. It can be concluded that KAl(SO4)2·12H2O is likely to be an effective pyrite flotation reagent, especially in the presence of fine serpentine.

Microwave fragmentation of a synthetic alundum-pyrite ore

ABSTRACT In the mining industry, the comminution process is very inefficient in terms of energy utilisation. Numerous research studies have investigated the use of microwave pre-treatment to fracture ore, prior to subsequent unit operations, such as grinding, flotation and leaching, therefore saving on energy consumption. The objective of the present work was to investigate the microwave fragmentation of a synthetic ore with controllable composition and particle size. The synthetic ore was composed of both a hyperactive material (pyrite) and an active material (alundum cement), which were compacted into a briquette. Heating behaviour, permittivity and thermogravimetric/differential thermal analysis (TGA/DTA) studies were conducted in order to understand the fundamental interactions of powdered samples with microwaves. The briquettes were processed in a microwave system followed by compression testing and image analysis to determine the effects of microwaving on the failure load and the fragmentation degree. It was found that the failure load of the briquettes decreased and the fragmentation degree increased with increasing pyrite particle size, pyrite content, and microwave energy absorption.

Paleo-environmental conditions of the Early Cambrian Niutitang Formation in the Fenggang area, the southwestern margin of the Yangtze Platform, southern China: Evidence from major elements, trace elements and other proxies

The Precambrian/Cambrian transition was a key time in Earth history, especially for marine biological evolution and oceanic chemistry. The redox-stratification with oxic shallow water and anoxic (even euxinic) deeper water in the Early Cambrian Yangtze Sea, which gradually became completely oxygenated, has been suggested as a possible trigger for the “Cambrian explosion” of biological diversity. However, for some areas in northern Guizhou where the exploration and research are lacking, identifying this pattern of redox-stratification by paleo-environmental analysis from borehole data is still in need. Here, we report a remarkable variation range in trace elements (Mo, V, U, Ni, Th, Co, Sc, Zn and Cu), molar Corg:P ratios and pyrite morphology from 27 core samples from one new drill hole (XY1, located in the Fenggang area, northern Guizhou) on the Yangtze Platform, South China.High levels of Ba (from 3242 ppm to 33,800 ppm) and total organic carbon (TOC; from 4% to 9.36%) in 15 core samples in the Lower Member (LM) of the Niutitang Formation indicated elevated primary productivity in the study area. Redox change was recorded based on enrichment factors (EFs) for RSTEs (Mo, U, and V), redox proxies (V/(V + Ni), Ni/Co, V/Sc and Th/U), Corg:P ratios and particle size of framboidal pyrite. These signatures demonstrate that the LM was deposited under anoxic conditions with sulfidic episodes, whereas the Upper Member (UM) of the Niutitang Formation was deposited under suboxic/oxic conditions with intermittently anoxic episodes. Mo/TOC ratios (from 3.72 to 39.86, mean 18.76) suggest weak-moderate water mass restriction. Mo-U covariation patterns (strong but variable enrichment of Mo and U; MoEF ranging from 31.45 to 257.97; UEF ranging from 4.68 to 39.07) in the LM show alternation of particulate shuttling and redox conditions occurred in the Early Cambrian Yangtze Sea, whereas Mo-U covariation patterns (moderate Mo enrichment but depletion or non-enrichment of U; mean MoEF: 7.29; mean UEF: 0.95) in the UM may indicate the combined influence of particulate shuttling and diagenetic diffusion of U via bioactivities, which result in low U values and an anoxic signature from frambiodal pyrite particle size (mean: 4.556 μm; median: 4.41 μm). Additionally, excess Ba (Baxs) concentration (33,800 ppm and 32,500 ppm) and association patterns of trace-metal enrichment in the LM indicate the existence of submarine hydrothermal events. In addition, during deposition of the UM, bioactivities indicated by Mo-U systematics and oxic conditions indicated by redox sensitive trace elements (RSTEs) and multiple-proxies, may be a cause of biological diversification recorded in the Early Cambrian. Finally, data in this record a progressive transition from anoxic bottom waters with euxinic episodes to overwhelming oxic conditions during Early Cambrian.

Effect of Pyrite Pretreatment, Particle Size, Dose, and Biomass Concentration on Particulate Pyrite Autotrophic Denitrification of Nitrified Domestic Wastewater

Abstract Nitrate (NO3−) loads from domestic and industrial wastewater contribute to surface and groundwater pollution and can have detrimental effects on human health and the environment. In this study, a particulate pyrite autotrophic denitrification (PPAD) process was compared with sulfur-oxidizing denitrification (SOD) in batch microcosms using a domestic wastewater seed. During a 65-day acclimation period, denitrification rates for PPAD reached 3.19 mg/(L·d), but were slower than the maximum rate for SOD (∼5 mg/[L·d]). Lower sulfate (SO42−) production (5.66 mg SO42−/mg NO3−-N) and alkalinity consumption (1.70 mg CaCO3/mg NO3−-N) were observed with PPAD than with SOD (7.54 mg SO42−/mg NO3−-N and 4.57 mg CaCO3/mg NO3−-N). Acetone pretreatment of pyrite particles initially resulted in a transient increase in the denitrification rate; however, the rate of denitrification was similar to untreated pyrite in subsequent cycles. Box–Behnken design and response surface methodology were used to optimize biomass ...

The effect of pyrite particle size on the electrochemical dissolution of gold during cyanidation

Pyrite is considered as the most common sulphide mineral that carries gold in refractory gold ores. In these ores, pyrite can be found in different particle sizes. Following flotation process, the flotation tailings is sent to the cyanidation circuit for gold extraction that may contain appreciable amounts of pyrite. Until now, the effect of pyrite on gold dissolution was reported to be either positive or negative in the open literature. This current research examines the effect of particle size and amount of pyrite on gold dissolution in a packed bed leach reactor (PBLR). Electrochemical characterization as a function of pyrite particle size on gold dissolution was tested. It was found that pyrite (4g) has positive galvanic effect on gold dissolution especially in the presence of fine particles, −106μm (i.e., 54% Au in the absence of pyrite vs. 95% with +20–53μm pyrite). On the other hand, gold dissolution showed a sharp decrease when particle size was coarser than +106μm. Highest gold extraction, 98%, was achieved when gold particles are in contact with +75–106μm pyrite particles. When the pyrite amount was doubled (8g of +75–106μm), gold dissolution was decreased to 35% due to the partial passivation of gold. If the pyrite amount were reduced by half (2g of +75–106μm), gold dissolution increased by 30% as compared to the case without pyrite. Different scenarios were also considered regarding to activation and passivation of gold. For instance, when gold was split and dispersed equally within the pyrite layer and within the adjacent quartz layer, gold dissolution was found to be around 35%, suggesting a negative effect of released species from pyrite. Cyclic voltammetry and potentiodynamic polarization findings are in line with the cyanide leaching results. The shift in open circuit potential in presence of pyrite is in support of observed leach kinetics. SEM-EDS results have confirmed the decrease in gold dissolution in the presence of coarse particles. These findings have revealed that pyrite particle size and its amount have significant impact on gold dissolution.

열전지용 황철석(FeS2) 입자크기 변화에 따른 전기화학반응 메커니즘

열전지용 황철석(FeS₂) 입자크기 변화에 따른 전기화학반응 메커니즘

湖南省老鸦巢铅锌矿床金属硫化物微区成分特征

文章对老鸦巢铅锌矿床的黄铁矿和闪锌矿进行了矿相学及电子探针分析，认为黄铁矿和闪锌矿主要以自形–半自形粒状分布，黄铁矿粒径0.5~3 mm，晶形多呈五角十二面体，少量为立方体、球状、草莓状、胶状；闪锌矿粒径0.5~1 mm，从早到晚其颜色逐渐变浅，自形程度变差，晚期闪锌矿沿裂隙、空洞充填，呈葡萄状的集合体与八面体方铅矿共生；区内黄铁矿弱亏硫不亏铁，Co/Ni变化大，平均值大于1，As含量较高，显示具有中低温热液成因特征；闪锌矿富硫亏锌，且w(Mn) < 0.15%、w(Fe) < 6%、Ga/In < 1、Zn/Cd在114~140之间，Cd与Zn/Cd呈明显负相关性，同时FeS分子投图对应温度为170˚C~220˚C，指示闪锌矿中低温岩浆热液成因的特征。 Objective: Through petrography and electron probe analysis on pyrite and sphalerite in Laoyachao Pb-Zn deposit, it can be known from the mineral microscopy observation that it is concluded that the pyrite and sphalerite in this area is mainly euhedral or Hypautomorphic granular distribution, pyrite particle size of 0.5 - 3 mm, crystal shape is pentagonal dodecahedron, with a small amount being cube, spherical, strawberry and gelatinous. Sphalerite particle size is of 0.5 - 1 mm, from early to late its color gradually becomes shallow, and the degree of self-shape becomes worse. The late sphalerite is filled with fissures and cavities, and the grape-like sphalerite aggregates are symbiosis with octahedral galena. The pyrite is slightly depleted with S in this area, the Co/Ni changes greatly, the average value is more than 1, and the content of As is higher, which shows the characteristics of medium and low temperature hydrothermal genesis. The sphalerite is rich Sulphur and loss of zinc, and w(Mn) < 0.15%, w(Fe) < 6%, Ga/In < 1, Zn/Cd between 114 and 140, Cd and Zn/Cd are negatively correlated. And the corresponding temperature of FeS molecule is 170˚C - 220˚C, which indicates the origin of low temperature magmatic hydrothermal in sphalerite.

Efficient pyrite activating persulfate process for degradation of p -chloroaniline in aqueous systems: A mechanistic study

Abstract In recent years, persulfate activation systems have received increasing attention due to their high oxidation reactivity when removing environmental pollutants. Pyrite, the most common metal sulfide on Earth’s surface, can supply abundant Fe2+ for persulfate activation. The role of the generated reactive oxygen species (ROS) in persulfate-pyrite systems however, is not fully understood. In this study, batch experiments were used to investigate p-chloroaniline (PCA) degradation by a pyrite-persulfate system. The effects of pyrite dosage, pH, temperature, air conditions (aerobic vs. anaerobic) and pyrite particle size on PCA degradation were examined. Radical detection was conducted using electron paramagnetic resonance (EPR) methods. Results from the EPR spectra indicated that PCA degradation was achieved by sulfate radical and hydroxyl radical oxidation. Aerobic conditions were more beneficial to PCA degradation than anaerobic conditions due to the generated superoxide radicals (O2 −) that activated the persulfate to produce more sulfate radicals (SO4 −). PCA degradation also increased with higher pyrite doses and under acidic conditions (pH 3.0 and 5.0). PCA was removed completely at pH 3.0 after 60 min. Temperature increase from 10 to 50 °C significantly promoted PCA degradation. These findings provide new understanding of the mechanism involved in pyrite activation of persulfate which can be used to improve PCA degradation by pyrite-persulfate systems.