Pyrite Oxidation Research Articles

Eksistensi Lahan Pasang Surut Untuk Pertanian Di Desa Mulya Sari Kabupaten Banyuasin

Tidal land is land that is in a zone where it is still influenced by sea tides. This land is marginal and can still be developed while maintaining water availability and pyrite oxidation. In Sumatra, Kalimantan and Irian Jaya, tidal land has been opened through the transmigration program. This land was opened as agricultural land to meet the food needs of the community. One of the efforts in managing tidal land is water management. This research aims to determine the existence of tidal land as agricultural land in Mulya Sari village. The method used is field observation, data collection through direct interviews and related literature, and descriptive analysis. The results of the research show that for the existence of tidal land, the community in Mulya Sari village optimizes the channels built by orders and also those created by the community itself. The water conditioning in each plot of land and tertiary canals is maintained by the optimal operation of the automatic water gates. In addition, the water level must be above the ground water level to prevent oxidation of the pyrite layer. Under these conditions, the tidal land in Mulya Sari village continues to exist as agricultural land.
 
 Tidal land is land that is in a zone where it is still influenced by sea tides. This land is marginal and can still be developed while maintaining water availability and pyrite oxidation. In Sumatra, Kalimantan and Irian Jaya, tidal land has been opened through the transmigration program. This land was opened as agricultural land to meet the food needs of the community. One of the efforts in managing tidal land is water management. This research aims to determine the existence of tidal land as agricultural land in Mulya Sari village. The method used is field observation, data collection through direct interviews and related literature, and descriptive analysis. The results of the research show that for the existence of tidal land, the community in Mulya Sari village optimizes the channels built by orders and also those created by the community itself. The water conditioning in each plot of land and tertiary canals is maintained by the optimal operation of the automatic water gates. In addition, the water level must be above the ground water level to prevent oxidation of the pyrite layer. Under these conditions, the tidal land in Mulya Sari village continues to exist as agricultural land.

Composition and physico-chemical properties of aqueous extracts of lydites of the North Onega synclinorium in Karelia

Relevance. The need to obtain reliable information on chemical composition of aqueous extracts of lydites. There is lack of such information, but it is so important both for understanding dispersion of elements and their impact on natural waters of a region. It is necessary to study the composition of aqueous extracts as a result of water–rock interaction to determine possible sources of water pollution with toxic elements. Mineral composition of lydites of the North Onega synclinorium contains organic carbon and mist pyrite, which may contain increased concentrations of trace elements "harmful" for drinking water. To determine the ability of such elements to pass into a dissolved state, it is necessary to study aqueous extracts of lydites. Aim. To determine trace element composition and physico-chemical properties of aqueous extracts of lydites selected from two districts of the North Onega synclinorium to assess their environmental hazard. Objects. Geological section of the shungite-lidite-dolomite complex of the Zaonezhskaya formation of the Paleoproterozoic age of the North Onega synclinorium. Samples of lidites were taken at the Tetyugino (LT) and Shunga (LSh) sites of the Medvezhyegorsk district of the Republic of Karelia. Methods. Field studies, including investigation of stratigraphic position of lydites in geological sections of the Tetyugino and Shunga sites and sampling, laboratory experiment, aqueous extraction, scanning electron microscopy, Raman spectroscopy, X-ray fluorescence analysis, Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results. Mineralogical composition of the lydites of both sites is similar. Taking into account high content of SiO2 and negligible content of other petrogenic oxides in chemical composition of lydites, it is possible to consider them as a source for obtaining pure quartz raw materials. The structure of lydites is clot-cryptocrystalline and clot-globular. Lydite extracts environment acidity depends on the totality of the minerals extracted from it, either basic (dolomite) or acidic (pyrite oxidation products). This factor is decisive in formation of chemical composition of lydite extracts, regardless of the location of the samples within a given geological object. Many elements extracted by water from the lydite samples of two regions under consideration are characterized by varying degrees of their extraction from the massive and veined parts of the sample. The cure coefficients of chemical elements in the form of the ratio of element average concentrations in the extract and lydite solid phase show the predominant intake of Cd, Mn, Mo, Sr, Rb, Li, Ni, Co, Li from Tetyugino lydites into water. Mo, Sb and W are predominantly extracted into the solution from the Shunga lydites. Average concentrations of most elements of the extracts of the Shunga samples satisfy the requirements for drinking water and, unlike shungite, they are not sources of harmful components in water. Therefore, it is advisable to carry out work on the possibility of their use for water purification for drinking purposes.

Simultaneous nitrate and chromium removal mechanism in a pyrite-involved mixotrophic biofilter.

Microbially mediated NO3--N and Cr(VI) reduction is being recognized as an eco-friendly and cost-effective remediation strategy. Iron sulfide mineral, as a natural inorganic electron donor, has a strong influence on NO3--N and Cr(VI) transformation, respectively. However, little is known about the simultaneous nitrate and chromium removal performance and underlying mechanism in an iron sulfide mineral-involved mixotrophic biofilter. This study demonstrated that the NO3--N and Cr(VI) removal efficiencies were stable at 62 ± 8% and 56 ± 10%, and most of them were eliminated in the 0-100-mm region of the biofilter. Cr(VI) was reduced to insoluble Cr(III) via microbial and chemical pathways, which was confirmed by the SEM-EDS morphology and the XPS spectra of biofilm and pyrite particles. SO42- was as a main byproduct of pyrite oxidation; however, the bacterial SO42- reduction synchronously occurred, evidenced by the variations of TOC and SO42- concentrations. These results suggested that there were complicated and intertwined biochemical relations between NO3--N/Cr(VI)/SO42-/DO (electron acceptors) and pyrite/organics (electron donors). Further investigation indicated that both the maximal biomass and greatest denitrifiers' relative abundances in microbial sample S1 well explained why the pollutants were removed in the 0-100-mm region. A variety of denitrifiers such as Pseudoxanthomona, Acidovorax, and Simplicispira were enriched, which probably were responsible for both NO3--N and Cr(VI) removal. Our findings advance the understanding of simultaneous nitrate and chromium removal in pyrite-involved mixotrophic systems and facilitate the new strategy development for nitrate and chromium remediation.

Evaluate the Depression of High-Concentration Pyrite in Copper Flotation by High-Chromium Grinding Media

ABSTRACT The copper (Cu) concentrators have to process high-pyrite-content ores due to rapid depletion of high-grade ores and a high demand for Cu by clean energy technologies. However, depressing high-concentration pyrite in copper flotation is challenging presently. For the first time, this study evaluated 30 wt% Cr steel, a type of high-chromium (HiCr) steel grinding media, which can effectively produce a high Cu concentrate grade in processing low-concentration pyrite ores, in treating 25% pyrite in a Cu feed at 1.7% Cu in comparison with treating 5% pyrite in a Cu feed at the same Cu grade. Flotation tests showed decreased Cu grade and Cu recovery as pyrite feed grade increased from 5% to 25%, which was attributed to the changed galvanic interaction between grinding media and sulfide minerals, supported by ethylene diamine-tetra acetic acid disodium extraction, pulp chemistry measurements, and electrochemical studies. As pyrite feed grade increased from 5% to 25%, the anodic role of 30 wt% Cr steel did not change, but the anodic role of chalcopyrite and the cathodic role of pyrite were enhanced, promoting chalcopyrite oxidation while retarding pyrite oxidation, both of which facilitated copper activation on pyrite and subsequent pyrite flotation. This study also compared 30 wt% Cr steel and traditional forged steel in depressing 25% pyrite in the feed, and forged steel poorly depressed pyrite due to a strong anodic role of forged steel and a strong cathodic role of pyrite during the galvanic interaction leading to strong copper activation on pyrite. This study points to a direction how to depress high-concentration pyrite in copper flotation.

Experimental study of water-extractable sulphate in Opalinus Clay and implications for deriving porewater concentrations

In northern Switzerland, the Opalinus Clay, a Jurassic claystone formation, is foreseen as host rock for a deep geological repository for radioactive waste. Characterizing its porewater is of particular importance for assessing the mobility of radionuclides and the stability of the engineered barriers. Although the porewater composition of the Opalinus Clay is fairly well known, there is still controversy on the sources of sulphate obtained by different porewater characterization methods. A striking observation is that sulphate concentrations from aqueous extraction and recalculated to in-situ conditions are consistently much higher than sulphate concentrations measured in borehole waters, squeezed waters and advectively displaced waters (“excess sulphate”). Accordingly, the main objective of this study is to better investigate the processes affecting dissolved sulphate concentrations during aqueous extraction and, thus, to reduce uncertainties in predicting the concentrations of this compound in the Opalinus Clay porewater. To this end, a series of extraction experiments were conducted using variable solid/liquid ratios, extraction times and extract solutions. In order to suppress sulphide-mineral oxidation, all the experiments were performed in a glovebox under oxygen-free conditions (atmosphere and solutions). Measurements of the sulphur and oxygen isotope composition of the dissolved sulphate in aqueous extracts are aimed to further constrain the source of the “excess sulphate”. Finally, the plausibility of the SO4 data from extraction experiments in terms of their representativeness for in-situ conditions was evaluated by simple geochemical modelling. The modelling shows that SO4 concentrations from aqueous extracts recalculated to in-situ conditions imply dissolved and exchangeable cation concentrations which are not consistent with measured data, thus, attesting non-conservative behaviour for sulphate during aqueous extraction. However, the various extraction experiments showed that pyrite oxidation was successfully suppressed during the experiments and neither contributions from e.g. organic material, congruent calcite dissolution and/or sulphate mineral dissolution provide enough SO4 to explain the “excess sulphate”. Ultimately, the various extraction experiments failed to definitely identify the source of the “excess sulphate” in aqueous extracts. However, the good agreement found between the δ18O and δ34S values of dissolved SO4 in aqueous extracts and those of borehole waters suggest that the “excess sulphate” might be weakly bound to mineral surfaces.

Influence of natural cellulose on hydroxyl radical generation by abiotic oxidation of pyrite under acidic conditions

Natural cellulose is one of the most important substances coexisting on the surface of pyrite. Oxidation of pyrite produces hydroxyl radicals (•OH). In this study, a pyrite-cellulose binary system was constructed with natural cellulose to investigate the effect of cellulose on the mechanism of •OH generation via oxidation of pyrite, and the mechanism for abiotic oxidative •OH production by pyrite under the influence of cellulose was investigated with oxidation and quenching experiments and characterization techniques. It was demonstrated that cellulose was chemisorbed onto the pyrite surface and some of the Fe(II) on the pyrite surface was masked, thus inhibiting the reaction between pyrite and O2 and decreasing the •OH production level from 33.54 to 22.48 μM under oxic conditions. In addition, the cellulose caused SS bond breakage, resulting in defects on the pyrite surface, which oxidized H2O to produce •OH in anoxic conditions. Therefore, under anoxic conditions, cellulose promoted the production of •OH and increased the •OH content from 11.85 to 14.78 μM. In addition to •OH, pyrite oxidation also produced SO42−. The amount of SO42− produced by a single pyrite crystal was less than that produced in the pyrite-cellulose system in all cases, and the amount produced under oxic conditions was approximately 10 times greater than that produced under anoxic conditions. More sulfate production indicated more sulfur intermediates during the reaction, such as S2O32−, which may decompose to produce S0 or Sn2− adsorbed on pyrite and decrease the amount of •OH produced. During the oxidation of pyrite by H2O2, cellulose competed with pyrite to react with H2O2, which inhibited the reaction between pyrite and H2O2 and decreased •OH production. Therefore, natural cellulose influenced the abiotic oxidation of pyrite to produce •OH.

Source control on the acid mine drainage produced by the oxidation of pyrite and sulfur-containing uranium tailings based on the microbially induced carbonate precipitation technology

Large quantities of acid mine drainage (AMD) generated through the oxidation of sulfide-bearing minerals, particularly pyrite, pose a significant global environmental challenge. The implementation of efficient and fundamental governance methods is crucial as current conventional approaches fail to address the root cause of this problem. To investigate the technique of controlling AMD at its source, a 10-day static experiment was conducted in order to examine the inhibitory effect of Sporosarcina pasteurii (S. pasteurii) on oxidative acid production from pyrite under varying redox potentials (Eh) and Ca2+ concentrations. Additionally, a 180-day dynamic column experiment was carried out to assess the long-term stability of its inhibition and heavy metal fixation. The results of both short-term and long-term analysis indicate that the metabolic activity of S. pasteurii has beneficial effects on the control of AMD through sulfur oxidation, even in the presence of strong oxidants such as H2O2 and FeCl3. 1. It stabilizes pH within the neutral to alkaline range; 2. It maintains Eh at a low potential reducing environment; 3. It promotes an increase in SO42− concentration, followed by a decline and stabilization at lower concentrations; 4. It supplies carbonate for pyrite oxidation, maintaining a balance between acid production and consumption. Additionally, SEM, XRD, and XPS results demonstrated that the mineral surface appeared flat without prominent characteristic peaks of oxidation products, indicating effective inhibition of pyrite oxidation by S. pasteurii. The immobilization experiments for heavy metals showed that Cd exhibited the highest fixation effect with a rate of 94%; Mn, Cu, Zn, and Co had the second best fixation effect with ion concentrations decreasing by 82%, 83%, 87%, and 88% respectively; Ni and U(VI) decreased by rates of 75% and 69% respectively. These experimental findings suggest that S.pasteurii can effectively inhibit pyrite oxidation as well as sulfur-containing uranium waste rock oxidation while providing long-term stabilization for heavy metal immobilization.

A review: The formation, prevention, and remediation of acid mine drainage.

In abandoned open-pit coal mines, surface water and groundwater form acidic waters with high concentrations of metal ions due to chemical interactions with ores such as pyrite, and the formation of acid mine drainage (AMD) is one of the major sources of pollution of world concern. For this reason, this paper reviews the formation mechanisms and influencing factors of AMD. It also describes the prediction, prevention, and remediation techniques for AMD, identifying key research gaps. It also discusses the current challenges and shortcomings faced globally in the management of AMD. The formation of AMD is mainly caused by the oxidation of pyrite in mines, but it is mainly influenced by history, climate, topography, and hydrogeology, making the formation mechanism of AMD extremely complex. Currently, the remediation technologies for AMD mainly include active treatment and passive treatment, which can effectively neutralize acidic wastewater. However, the prediction technology for AMD is blank, and the source treatment technology such as passivation and microencapsulation only stays in the experimental stage. This leads to the high cost of treatment technologies at this stage and the inability to identify potential risks in mines. Overall, this review provides remediation tools for AMD from predicting root causes to treatment. Geophysical technology is an effective method for predicting the motion path and pollution surface of AMD in the future, and resource recovery for AMD is a key point that must be paid attention to in the future. Finally, integrated treatment technologies that deserve further exploration need to be emphasized.

Effect of damming on hydrogeochemical characteristics and potential environmental risks in a large reservoir: Insights from different vertical layer sampling

The water environment of large reservoirs is fragility due to effects from hydrological regulation of damming and anthropogenic inputs. As a critical path to quantify the natural chemical weathering and assess environmental risks, solute chemistry of river has been widely focused on. However, the complexed hydrological conditions of large reservoir affect the chemical compositions, and the significance of solute vertical geochemistry as an indicator of chemical weathering and water quality health remains explore. Therefore, the Three Gorges Reservoir (TGR) was selected as a typical study area, which is the world's largest hydropower project and subject to frequent water quality problems. Then, the chemical compositions in stratified water were determined. Ca2+ (52.8 ± 4.3 mg/L) and HCO3− (180.9 ± 8.9 mg/L) were the most abundant ions among cations and anions, respectively. Incremental mean concentration of total major ions followed with the increase of riverine depth and flow direction. An improved inversion model was used to quantify the source contribution, which weathering of dolomite (34%) and calcite (38%) contributed the most to total cations, and the influences of agriculture and sewage discharge were limited. Additional contributions of evaporite and pyrite oxidation were found in analysis of deeper water samples, which also results in 2%–67% difference in estimated CO2 release flux using data from different depth, indicating additional information about sulfuric acid driven weathering was contained. Finally, the water quality of the reservoir was assessed for irrigation and non-carcinogenic risks. Results showed the stratified water of TGR can be used as a good water source of irrigation. However, NO3− (5.1 ± 1.1 mg/L) may have a potential non-carcinogenic risk to children, especially in surface water. To sum up, this study provided an indispensable supplement to the water chemistry archives in the TGR basin, serving as theoretical references for environmental management of large reservoirs.

Degradation Characteristics and Mechanism of Black Sandy Dolostone Subjected to Wetting–Drying Cycles

The cyclic wetting–drying (W–D) effect as a typical form of weathering causes the engineering properties of rock degradation. Unlike previous research on soft sedimentary rocks, this study sought to investigate the influence of W–D cycles on the physical and mechanical properties of the black sandy dolostone. The results show that the surface hardness and uniaxial compressive strength decreased by 1.5% and 17.2%, respectively, after 12 W–D cycles. The behavior of water absorption of dolostone showed a logarithmic growth with W–D cycles. Analysis of the pH and electrical conductivity values of the soaking solution and microstructure of dolostone revealed that carbonate mineral and feldspar dissolution was the major reason to result in the increase in pore volume and micro-fissure. The oxidation of pyrite contained in the rock was deduced to accelerate the chemical reaction and rock degradation. The obtained results are expected to provide engineering values for rock mechanics studies when compared with in situ conditions.

Iron removal from kaolinitic coal gangue via magnetic separation after oxidizing calcination with the crystal structure of kaolinite protected

Iron is a harmful color-staining impurity that degrades the performance of coal gangue (CG) products, and pyrite is the predominant form of iron in kaolinitic coal gangue. In addition, iron extraction from CG as a supplemental iron ore resource is significant for increasing the added value of CG comprehensive utilization. Herein, calcination in a mild oxidizing atmosphere was implemented to enhance the magnetic properties of pyrite for subsequent magnetic separation. The sample was calcined at 300–1000 °C for 30–180 min, and the maximum magnetic susceptibility reached approximately 17 times that of the original ore. The iron recovery rates of the gangue calcined for 60–120 min were increased remarkably to 83.17–83.61%, while the iron recovery rate of the raw gangue was almost zero. After magnetic separation, the Fe2O3 content decreased from 5.58% for the raw gangue to 1.00% for the nonmagnetic products of gangues calcined for 60–120 min. Retention of the strongly magnetic magnetite, which was an intermediate product in the oxidation of pyrite to hematite, enabled the effective removal of iron from the gangue. Additionally, the kaolinite in the iron-removed coal gangue basically maintained its crystal structure.

The effect of biogeochemical redox oscillations on arsenic release from legacy mine tailings

Exposed and un-remediated metal(loid)-bearing mine tailings are susceptible to wind and water erosion that disperses toxic elements into the surrounding environment. Compost-assisted phytostabilization has been successfully applied to legacy tailings as an inexpensive, eco-friendly, and sustainable landscape rehabilitation that provides vegetative cover and subsurface scaffolding to inhibit offsite transport of contaminant laden particles. The possibility of augmented metal(loid) mobility from subsurface redox reactions driven by irrigation and organic amendments is known and arsenic (As) is of particular concern because of its high affinity for adsorption to reducible ferric (oxyhydr)oxide surface sites. However, the biogeochemical transformation of As in mine tailings during multiple redox oscillations has not yet been addressed. In the present study, a redox-stat reactor was used to control oscillations between 7 d oxic and 7 d anoxic half-cycles over a three-month period in mine tailings with and without amendment of compost-derived organic matter (OM) solution. Aqueous and solid phase analyses during and after redox oscillations by mass spectrometry and synchrotron X-ray absorption spectroscopy revealed that soluble OM addition stimulated pyrite oxidation, which resulted in accelerated acidification and increased aqueous sulfate activity. Soluble OM in the reactor solution significantly increased mobilization of As under anoxic half-cycles primarily through reductive dissolution of ferrihydrite. Microbially-mediated As reduction was also observed in compost treatments, which increased partitioning to the aqueous phase due to the lower affinity of As(III) for complexation on ferric surface sites, e.g. ferrihydrite. Oxic half-cycles showed As repartitioned to the solid phase concurrent with precipitation of ferrihydrite and jarosite. Multiple redox oscillations increased the crystallinity of Fe minerals in the Treatment reactors with compost solution due to the reductive dissolution of ferrihydrite and precipitation of jarosite. The release of As from tailings gradually decreased after repeated redox oscillations. The high sulfate, ferrous iron, and hydronium activity promoted the precipitation of jarosite, which sequestered arsenic. Our results indicated that redox oscillations under compost-assisted phytostabilization can promote As release that diminishes over time, which should inform remediation assessment and environmental risk assessment of mine site compost-assisted phytostabilization.

Uranium pre-concentration in sandstone-hosted U deposits: A case study from the Hailijin ore field, SW Songliao Basin, NE China

Economic U mineralization in sandstone was commonly attributed to oxygenated fluid infiltration in reduced sandstone, leading to U precipitation in redox front during late diagenetic stage. It was proposed that U can be pre-concentrated before this period based on trace amounts of U in altered products of Fe-Ti oxides, as revealed by electron microprobe analysis (EMPA). However, the obtained trace elements concentrations in altered Fe-Ti oxides (<1 wt%) is generally accompanied with relatively low analytical precision, leading to a skeptical explanation under this situation. In this work, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine trace elements concentrations in hematite from the uraniferous Lower Yaojia Formation (Hailijin ore field, SW Songliao Basin, NE China), aiming to fingerprint this proposed U pre-concentration in details. Some trace elements contents, such as Mo, Ge, Ca, P, Y, Pb, Th, Sn, and W, are positively correlated with U content in hematite. Given that uraniferous oxygenated groundwater with a near-neutral pH is unable to efficiently dissolve detrital phosphate (i.e., apatite and monazite) in the Lower Yaojia Formation, phosphorous must have been released from these P-rich phases before late diagenesis. Such a conclusion is supported by our observations that monazite from the reduced sandstone has a corrosive morphology, and exhibits a corresponding U enrichment in the corrosive rim. The dissolved P and U can be adsorbed by porous titania up to several thousand ppm during early diagenesis, providing a pre-concentrated metal source for remobilization during late diagenesis. It can not only account for a trace-element signature derived from monazite (i.e., Ca, P, Y, Pb, and Th) in hematite geochemistry, but also fingerprint Mo and Ge migrations resulted from oxidation of pyrite and organic matter, respectively. In addition to U, tungsten and Sn would be re-equilibrated with infiltrated oxidized fluid during the recrystallization of porous titania, and partially incorporated into simultaneously formed hematite grains due to high compatibility. The remobilization of pre-concentrated U induced by oxygenated fluid incursion led to U accumulation in a redox front during late diagenesis, forming uraninite nanoaggregates with relatively high concentrations of P, Y and Ti. Our work has verified that trace-element signature in hematite from sandstone is a reliable fingerprint to reveal ore-forming processes, and we propose for the first time that titania and phosphate play a crucial role for U pre-concentration in sandstone-hosted U deposits.

Impact of Seasonality on Copper Bioavailaility to Crabs (Ucides cordatus, Linnaeus, 1763) in Mangrove Soils of Todos os Santos Bay (Bahia, North Eastern Brazil)

Crab and soil samples were seasonally collected at four mangrove sites (Cacha Prego, CP; Ponta Grossa, PG; Ilha de Maré, IM; and Pitinga, PT) in Todos os Santos Bay, in NE Brazil. Total Cu levels in soils ranged from 2.5 to 89.4 mg kg−1, while in crab organs (muscles, hepatopancreas, and gills), Cu ranged from 20 to 1,320 mg kg−1, with the highest concentrations found in the Ilha de Maré population, where soils showed a clear Cu enrichment. Total Cu content did not explain the abnormally high Cu concentrations observed in crabs from Pitinga, where total content in soil was low. Geochemical partitioning indicated that most of the potentially bioavailable Cu was found in the oxidizable fractions, pyrite and organic matter. Pyrite oxidation during the dry season led to increased Cu bioavailability. This process was of relevance in soils of the Pitinga mangrove, where sulfide oxidation led to soil acidification and to an increase in Cu associated with the most labile fractions.

Tape Casting for Development of Thermal Batteries

Thermal (thermally activated) batteries are primary batteries which operate at temperatures ranging from 350°C to 650°C. Due to its long shelf life and high power density (up to 8kW kg-1)1, thermal batteries have been used reliably for military applications such as providing back up power for aircraft hydraulics, missiles and even the Galileo probe.2 Currently, thermal batteries are manufactured by a labour intensive pellet pressing method which limits the design and thickness of the batteries. To improve the power density of thermal batteries, tape casting has been examined. Tape casting is a common method of manufacturing commercial secondary lithium-ion batteries. Tape casting enables relatively thin films of battery components to be utilized which minimises the thickness of the battery components and gives the option to alter the design of the battery itself.Despite its many years in operation for important military applications, processing of thermal batteries into functional cast films has not been achieved so far due to the high operational temperatures of thermal batteries which negate the use of standard polymers. To counter this issue, high temperature polymers, inorganic binders and carbon nanotubes have been examined for their use as binders for thermal battery component inks. Their thermal stability was examined using STA and the oxidation of pyrite was analysed through EDS and PXRD. Successful processing of the constituent battery components is hoped to drastically improve the electrochemical performance of the cell and decrease the manufacturing cost of the batteries. R. A. Guidotti, G. L. Scharrer, E. Binasiewicz and F. W. Reinhardt, 1998.R. A. Guidotti and P. Masset, J. Power Sources, 2006, 161, 1443-1449.

Alkalinity generation from carbonate weathering in a silicate-dominated headwater catchment at Iskorasfjellet, northern Norway

Abstract. The weathering rate of carbonate minerals is several orders of magnitude higher than for silicate minerals. Therefore, small amounts of carbonate minerals have the potential to control the dissolved weathering loads in silicate-dominated catchments. Both weathering processes produce alkalinity under the consumption of CO2. Given that only alkalinity generation from silicate weathering is thought to be a long-term sink for CO2, a misattributed weathering source could lead to incorrect conclusions about long- and short-term CO2 fixation. In this study, we aimed to identify the weathering sources responsible for alkalinity generation and CO2 fixation across watershed scales in a degrading permafrost landscape in northern Norway, 68.7–70.5∘ N, and on a temporal scale, in a subarctic headwater catchment on the mountainside of Iskorasfjellet, characterized by sporadic permafrost and underlain mainly by silicates as the alkalinity-bearing lithology. By analyzing total alkalinity (AT) and dissolved inorganic carbon (DIC) concentrations, as well as the stable isotope signature of the latter (δ13C-DIC), in conjunction with dissolved cation and anion loads, we found that AT was almost entirely derived from weathering of the sparse carbonate minerals. We propose that in the headwater catchment the riparian zone is a hotspot area of AT generation and release due to its enhanced hydrological connectivity and that the weathering load contribution from the uphill catchment is limited by insufficient contact time of weathering agents and weatherable materials. By using stable water isotopes, it was possible to explain temporal variations in AT concentrations following a precipitation event due to surface runoff. In addition to carbonic acid, sulfuric acid, probably originating from oxidation of pyrite or reduced sulfur in wetlands or from acid deposition, is shown to be a potential corrosive reactant. An increased proportion of sulfuric acid as a potential weathering agent may have resulted in a decrease in AT. Therefore, carbonate weathering in the studied area should be considered not only as a short-term CO2 sink but also as a potential CO2 source. Finally, we found that AT increased with decreasing permafrost probability, and attributed this relation to an increased water storage capacity associated with increasing contact of weathering agent and rock surfaces and enhanced microbial activity. As both soil respiration and permafrost thaw are expected to increase with climate change, increasing the availability of weathering agents in the form of CO2 and water storage capacity, respectively, we suggest that future weathering rates and alkalinity generation will increase concomitantly in the study area.

Study on Electrochemical Behavior of Oxidized Pyrite in Alkaline Electrolyte

Nowadays, refractory gold ore production around the world accounts for about 30% of total gold production, and the low leaching rate of such gold concentrate seriously limits the efficient utilization of gold resources. The alkaline preoxidation process can improve the leaching rate of this kind of gold deposit and has good development and application prospects. Therefore, it is of great significance to study the oxidation and dissolution behavior of pyrite in an alkaline environment. In this paper, the oxidation process of gold-bearing pyrite in an alkaline electrolyte was studied using electrochemical techniques, and the oxidation products of a pyrite electrode in an alkaline solution were characterized using XPS, SEM, and other analytical methods. The results show that the optimum pH for pyrite electrochemical oxidative dissolution is about 12, and the oxidation potential of pyrite should be above 0.8 V. In the process of alkaline oxidative dissolution of pyrite, part of the S element enters the electrolyte in the forms of Sx2−, S2O32−, SO32−, and SO42−, and a small amount of the S element is adsorbed on the surface of the electrode in the form of S0 and becomes a part of the passive layer. The Fe element is adsorbed on the surface of the electrode in the forms of Fe(OH)2, Fe2O3, and Fe2(SO4)3, which become the main components of the passivation layer. This study provides a theoretical basis and reference data for the chemical preoxidation treatment of gold-bearing sulfide ores.

Utilization and Mechanisms of Tannic Acid as a Depressant for Chalcopyrite and Pyrite Separation.

Current flotation practices using lime or cyanide as depressants in chalcopyrite and pyrite separation have significant disadvantages, such as substantial reagent consumption, high slurry pH, and environmental hazards. This work aimed to explore the utilization and mechanisms of tannic acid (TA) as an eco-friendly alternative to lime or cyanide in chalcopyrite-pyrite separation. Flotation results showed that TA selectively depressed pyrite yet allowed chalcopyrite to float at neutral or alkaline pH. Adsorption density and zeta potential results indicated that TA adsorbed intensely on pyrite but minorly on chalcopyrite. Besides, potassium ethyl xanthate was still largely adsorbed on chalcopyrite but not on pyrite after TA adsorption. Surface analysis by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy further showed that the oxidation species of FeOOH and Fe2 (SO4)3, particularly FeOOH were the main active sites for TA chemical adsorption. Owing to the greater and faster oxidation of pyrite, more FeOOH and Fe2 (SO4)3 were generated on the pyrite surface, and the chemical adsorption of TA was more pronounced on the pyrite surface than on the chalcopyrite surface.

Soil organic matter stabilization during early stages of Technosol development from Ca, Mg and pyrite-rich parent material

The mechanisms underlying soil organic matter (SOM) accrual in Technosols are still poorly understood. Here we studied a 20-year chronosequence of three Technosols constructed with dolomitic limestone mining waste: two cultivated with sugarcane (for 3 and 7 years) and one under pasture (for ∼20 years). Through a combination of SOM physical fractionation and wet-chemical extractions, we aimed to unravel the processes driving SOM accumulation in these soils and developed a conceptual model for embryonic soils developed from Ca, Mg and pyrite-rich parent material. Our results revealed that the weathering of comminuted waste rocks (e.g., shale, siltstone) provided 2:1 minerals (especially smectite) to participate in mineral-organic associations. The weathering of primary minerals also promoted the formation of secondary minerals, which interacted with SOM and increased the amount of mineral associated organic matter (MAOM) up to 20 g SOC kg−1. Pyrite oxidation produced highly reactive secondary Fe phases, while the dolomite dissolution increased the concentrations of Ca2+ and Mg2+ and maintained near-neutral pH conditions, favoring the formation of cation-bridges. The progressive increase in the different operational Fe fractions (Fe in organomineral complex, poorly crystalline, and crystalline Fe oxides) along the Technosol chronosequence was strongly correlated with MAOM, highlighting the significant role of Fe in SOM accumulation. Furthermore, we observed substantial increase in particulate organic matter (POM), up to 22 g SOC kg−1, which was associated with increased aggregate formation and stability. These processes collectively contribute to the protection of SOM during early stages of soil development from in Ca, Mg, and pyrite-rich parent material, and thus indicate a high potential for carbon sequestration.

Perubahan pH, Fe-larut, dan P-tersedia di Tanah Sulfat Masam Aktual (Sulfaquept) yang Diberi Pupuk Kandang Sapi dan Genangan Air

Organic matter application and water management were frequently applied to prevent the oxidation of pyrite in acid sulfate soils. The purpose of this study was to determine the effect of cow manure application with varying height of inundation on soil pH, soluble-Fe, and available P of acid sulfate soils. This study employed factorial treatments and in a completely randomized design. The first factor was the dosage of cow manure: 0, 10, and 20 t ha-1, while the second factor was various water depths: 5, 10, and 15 cm. Results of study showed that the interaction of cow manure and water depth did not affect soil pH, but single factor of the treatments (cow manure and water depth) significantly affected soil pH. The interaction of cow manure and water depths did not significantly decrease the solubel-Fe in the fourth week. The interaction of cow manure and water depths significantly increased P-availability in the fourth week. Results of this study demonstrated that cow manure application and water depth improved soil pH and P-availability of acid sulfate soils.