Enrichment Of Ag Research Articles

Enhanced CO2-to-CH4 conversion via grain boundary oxidation effect in CuAg systems

The authentic active sites of oxide-derived copper (OD-Cu), namely grain boundaries (GBs) and oxidized Cuδ+ species, is still debatable, and their role in governing CH4 conversion remains unclear. Herein, this study answers these questions using bimetallic catalysts by novel electro-shock strategy with controllable GBs for the oxidization of Cuδ+ species by modulating Ag loading. The Ag enrichment at the GBs facilitates the bonding of oxygen with the uncoordinated Cu atoms, resulting in GB oxidation effect. The obtained CH4 selectivity is twice that of GBs or nanoalloy effect. The enhanced performance is attributed to the stable Cuδ+ species and unique electron transfer mechanism from GB oxidation structure. Operando attenuated-total-reflection Fourier-transform-infrared-spectroscopy unveils the reaction pathway of CO2-to-CH4 and the sluggish reversible quenching processes of intermediates. Theoretical calculations indicate that the weak *CO adsorption on GB oxidation structure facilitates *CO hydrogenation, promoting CO2-to-CH4 conversion.

Assessment of Metal Pollution in Umm el-Surab Archaeological Layers, Northeast Jordan

This study aims to assess the extent of the anthropogenic pollution of Area A at the Umm el-Surab archaeological site, Jordan. It examines the concentrations of 21 metals from four Roman, Byzantine, and early and late Ayyubid-Mamluk layers. The site, located near Bosra and Umm el-Jimal, was continuously settled from the Roman till the Islamic periods. The chemical analysis and pollution indices (enrichment and contamination factors (EF, CF), and geo-accumulation index Igeo) show low enrichment in Zn, K, Sr, Na, Pb, Ba, Li, Mn, Mg, Mo, and Cu, and moderate enrichment in Cd, Ag, Ca, As, and Ni. Co is significantly enriched in one sample and moderately enriched in the other ones. The results show pollutant metals more enriched in the Byzantine layer than the rest of the layers. A likely primary source of the limited pollution is organic fuels and their firing product of ash, while a likely secondary source might be the pottery fragments spread in the layers. The results agree with the fact that the site was rural with limited industrial activities, especially metal production, like iron and copper, that would have increased the concentration of the analyzed metals.

The Silent VOICE—Searching for Geochemical Markers to Track the Impact of Late Jurassic Rift Tectonics

AbstractA causal mechanism for the Volgian Isotopic Carbon Excursion (VOICE) remains enigmatic. Elemental geochemical profiles of the Deer Bay Formation, Sverdrup Basin, Arctic Canada that record the VOICE and contemporaneous strata are herein examined to provide insight into depositional environments during Late Jurassic‐Early Cretaceous time. Silver (Ag) and Cadmium (Cd) are enriched across the VOICE at localities on Axel Heiberg Island, and in Tithonian (∼Volgian) strata of Ellef Ringnes Island. Other redox‐sensitive trace elements do not exhibit spatially or temporally consistent patterns and indicate oxic conditions. A lack of relationship across the VOICE between Ag and the quality, quantity, and isotopic composition of organic matter suggests that the negative isotope excursion and interval of Ag enrichment are not merely functions of changes in organic matter source or amount, while a lack of spatially consistent change in geochemical indices of weathering similarly excludes climate change and/or sediment provenance as a driver. Therefore, in a ventilated setting and without marked changes in organic matter content, Ag enrichment may be due to hydrothermal activity. Contemporaneous Ag enrichment in strata from Svalbard suggests that a source of hot fluid sufficient to produce Ag‐rich seawater may have been related to rifting in the adjacent proto‐Amerasia Basin. Hydrothermal activity may also have been a widespread source of isotopically depleted carbon. This work develops new geochemical fingerprints that may be used to trace the spatial extent of hydrothermal events that do not leave an extinction pattern but may nonetheless have a far‐reaching influence on biogeochemical systems.

The Carboniferous Wuzunbulake orogenic gold deposit in South Tianshan Orogen (NW China): Sericite Rb[sbnd]Sr geochronology, pyrite geochemistry, and metallogeny

The Kumishi area is located in the eastern part of the South Tianshan Orogen, which hosts several gold deposits and has substantial gold discovery potential. The timing of gold mineralization at Kumishi, however, has been poorly constrained owing to the absence of suitable dating minerals. Hydrothermal activity at Wuzunbulake is divided into the pre-ore stage 1 pyrite-quartz, syn-ore stage 2 quartz(-sulfide) and post-ore stage 3 quartz-calcite alteration/mineralization. Three types of pyrite have been recognized, i.e., Py1 (stage 1), Py2 (stage 2), and PyWR (from wallrock). Our in-situ RbSr dating on stage 2 sericite yielded an isochron age of 351.0 ± 17.4 Ma, indicating Early Carboniferous gold mineralization. Py1 and Py2 have δ34SΣS = 8.28–15.97 ‰ (avg. 12.88 ‰) and 6.92–8.70 ‰ (avg. 7.67 ‰), respectively, indicating that the sulfur in Py1 was metamorphic fluid sourced, while that of Py2 may have a mixed metamorphic fluid and wallrock source (0.84–3.27 ‰; avg. 2.31 ‰). For Py1, its contents of Au, As, Ag, Bi, Co, Cu, Mn, Ni, Pb, Sb, Tl are the lowest. Py2 has significantly higher Au-As-Ag, slightly higher Co-Cu-Ni-Sb-Tl, but lower Bi-Mn-Pb contents than those in PyWR. Considering also the sulfur isotope features, we considered that Py1 was primarily originated from the initial ore-forming fluid, and Py2 was derived from both the ore fluid and PyWR, with the former being more important and represents the source of gold. Based on that Py2 was formed by metasomatism on the PyWR margin and the element spatial coupling characteristics shown in EPMA geochemical maps, we inferred that the Au enrichment and precipitation are associated with fluid-rock reactions. The initial ore fluid is likely featured by the enrichments in Au, As, Ag, Co, Cu, Ni, Sb, Tl, and depletions in Bi, Mn, and Pb. The Wuzunbulake is best classified as an orogenic gold deposit based on its tectonic background, wallrock alteration style, and the ore-fluid source and characteristics.

Copper leaching behaviour during oxygen pressure leaching of zinc sulfide concentrate

ABSTRACT To optimise copper (Cu) leaching, this study investigated Cu behaviour during a two-stage oxygen pressure leaching process of zinc sulfide concentrate (ZnS). The results indicated that maintaining low temperature, low sulfuric acid (H2SO4) concentration, and low oxygen partial pressure during the first stage of leaching the reduction of ferric iron (Fe3+) by ZnS and the weak leaching of Cu. In the second stage, increasing the temperature, H2SO4 concentration, and oxygen partial pressure enabled efficient Cu leaching while converting iron (Fe) back to Fe3+ and returning it to the first stage. This two-stage process effectively mitigated Fe hydrolysis precipitation, resulting in a small residue yield and preventing Cu incorporation into jarosite. Cyclic validation experiments were conducted under optimum experimental conditions with a residue yield of 36.1%, the dissolution rates of Zn, Cu, and Fe impurity of 98.76%, 91.65%, and 81.05%, and the Zn, Cu, and silver (Ag) contents of leaching residue were 1.61%, 0.17%, and 0.524%, respectively. The primary phases in the leach residue included lead (Pb) sulfate, sulfur, and pyrite. This approach allowed for deep leaching of Zn and Cu as well as achieving efficient Pb and Ag enrichment.

Separation and Enrichment of Au and Ag from Lead Anode Slime by a Selective Oxidation–Vacuum Volatilization–Carbon Reduction Process

Huge amounts of Au and Ag are recovered from the hazardous waste lead anode slime. The conventional extraction of precious metals from lead anode slime is based on pyrometallurgical and electrolytic processes, which are seriously conditioned by the separation of harmful elements As and Sb. In this paper, an innovative and efficient oxidation–vacuum volatilization–carbon reduction process was proposed to separate and enrich Ag and Au from lead anode slime. Before vacuum volatilization, selective oxidation of the lead anode slime was performed. Then, vacuum volatilization and vacuum carbon reduction were used to obtain a gold- and silver-rich alloy. The feasibility of the process was verified experimentally and theoretically. The effects of temperature and time on vacuum volatilization separation and reduction enrichment were investigated. The experimental results showed that the Ag content in the resulting gold- and silver-rich alloy was as high as 67.58%, Au was as high as 4287 g/t, and the efficiencies for the recovery of Ag and Au from the lead anode slime were 99.25% and 99.91%, respectively. The gold- and silver-rich alloy can be directly used to produce Ag ingots. Moreover, no gas or wastewater was discharged in this process, so Ag and Au were recovered in a sustainable and cleaner manner.

Enrichment mechanism of selenium in Lujiaping formation in central South Qinling: Controls from mixed sources, sedimentary environment, primary productivity and paleo-climate during Ediacaran to early Cambrian period

The Ediacaran to lower Cambrian Lujiaping Formation in South Qinling exhibited extremely high level of Se enrichment, which has provoked extensive concerns since the critical role of Se in paleo-biological evolution and diversification as well as its bidirectional effects on current ecological environment and human health. Because of complex geological setting within South Qinling during the Ediacaran–early Cambrian interval, distribution pattern and mechanism of Se enrichment in Lujiaping Formation have not been fully understood. In this study, therefore, stratigraphic variations of Se concentration and enrichment level together with enrichment mechanism in Lujiaping Formation in the central part of South Qinling were systematically explored. The result showed that, in the whole Lujiaping Formation, Se concentrations varied from 0.19 to 129 μg/g, with an average of 13.28 μg/g. According to the enrichment factor, most of samples can be classified as strong enrichment and anomaly levels (EF = 10–1000) which mainly occurred in organic matter-enriched siliciclatic rocks including mudstone, shale and stone coal seams. Meanwhile, Se enrichment was accompanied with enrichment of Ag, Mo, As, Cd and V in Lujiaping Formation. Various geochemical proxies were collectively employed to identify potential mechanism of Se enrichment. The results indicated that Se was derived from both terrestrial detrital materials and deep hydrothermal fluids. Strong Se anomaly was intimately linked to authigenic enrichment of U and Mo, manifesting advantageous role of euxinic benthic condition to Se accumulation. Besides, weak watermass restriction, intermittent upwelling, high primary productivity and warm and humid climate were also beneficial to ultimate Se enrichment in Lujiaping Formation. This study complemented fundamental data of Se concentration and enrichment degree in strata of the Ediacaran–early Cambrian period in central South Qinling. Meanwhile, preliminary insight of correlation among Se enrichment, sedimentary environment, paleo-climate and biological blooming during the Ediacaran to early Cambrian interval was obtained, which laid the foundation for further researches.

Trace and minor elements in the ore minerals: An assessment of geochemical distribution in overprinting epithermal on porphyry mineralization at Chodarchay, NW Iran

The Chodarchay overprinting epithermal on porphyry mineralization occurs in the Tarom-Hashtjin subzone of the Alborz magmatic arc in northwestern Iran. Rock units include intrusions (phases I and II) and volcano-volcaniclastic rocks. The alteration types consist of potassic, phyllic, argillic, and propylitic. The porphyry type is mostly accompanied by potassic alteration. The Chodarchay Fault implies two extensional and compressional mechanisms. The porphyry type is associated with the extensional and the epithermal type with the compressional stage of the fault. Mineralization occurred mainly inside the Eocene volcanic and volcano-sedimentary rocks; some ores are associated with the Late Eocene quartz monzonite. The mineralization is divided into three zones from depth to surface: 1) Hypogene sulfide zone (deep); 2) Enriched supergene sulfide zone (near-surface); 3) Oxidized and leached zone (surface). The major sulfide minerals consist of chalcopyrite, pyrite, sphalerite, and galena. Based on the results of the new analyses, chalcopyrite hosts Ag as a solid-solution and contains Ag-rich Bi-sulfosalt micro-inclusions. Non-constant Cd/Zn ratio in the chalcopyrite can indicate varying physiochemical conditions during its crystallization. Low As contents in the pyrite caused relatively clean pyrite with very few elements. The Ni concentrations in the pyrite imply that it was sourced from mantle mafic–ultramafic rocks. Sphalerite is the only Au-host mineral among the sulfide minerals as a nano-mineral phase. Solid-solution Ag exists in the sphalerite. The sphalerite Fe/Zn ratios show that it was precipitated between 220 and 280 °C. Silver and Bi have the highest measured concentrations among all analyzed elements in the galena, mainly partitioning within the galena, but Hg and Cd are abundant in the sphalerite. Bornite is one of the major carriers of Ag and Bi. Silver and Bi exhibit considerable variations in the Cu-(Fe) sulfides. A new occurrence of sulfosalt minerals was identified at Chodarchay (N = 14). The discovered Bi-sulfosalts include cuprobismuthite group minerals (cuprobismuthite, hodrushite, and paderaite), aikinite-bismuthinite series (aikinite and friedrichite), emplectite, makovickyite, galenobismutite, gustavite, heyrovskyite, neyite, cupropavanite; and As-Sb-bearing Cu sulfosalts (watanabeite and colusite). This number of sulfosalts had not previously been reported from any of the Tarom or Alborz deposits or mines. The Au-Ag occurrence was reported from the neyite, emplectite, and gustavite. The Ag-rich minerals crystallize from fractionated fluids that cooled during rising. Silver-carrier sulfosalts may have been exsolution from pre-existing Ag-bearing chalcopyrite in the cooling system. Most of the Ag-bearing sulfosalt minerals formed at the margins and fractures of the chalcopyrite, indicating that the cooling started from these points. Thus, Ag at Chodarchay is hosted inside Cu-(Fe) sulfides, the significant part of them being chalcopyrite and Ag-rich sulfosalt micro-inclusions inside the chalcopyrite. The fluid temperature for the Ag and chalcopyrite precipitation is from 200 to 350 °C. Bismuth assemblages precipitated at > 350 °C. The cuprobismuthite group crystallizes at temperatures > 300 °C. The supergene process and rare secondary enrichment of Ag and Au took place in the oxidation zone; this enrichment is dependent on the presence of manganese. Based on the fire-assay results, the concentration of gold is greater at shallower depths.

Pyrite geochemical fingerprinting on skarn ore-forming processes: A case study from the Huangshaping W–Sn–Cu–Pb–Zn deposit in the Nanling Range, South China

Pyrite geochemistry has been extensively used to reveal ore-forming processes in diverse ore deposits, but its application in skarn systems is not well understood. The Huangshaping deposit in the Nanling Range (South China) uniquely develops W–Sn–Pb–Zn and Cu–Pb–Zn skarn mineralization systems, and both two systems have formed multi-types of pyrite, which provides a good window to reveal the mineralization histories of different skarn systems using pyrite trace element geochemistry. In the Cu–Pb–Zn system, texturally homogeneous Py1 mainly occurs in calcite veins within the host rock, whereas texturally homogeneous Py2 in the calcite-sulfide stage mainly occurs in skarn orebodies. Py3 in the siderite-sulfide stage replaces Py2 and commonly develops abundant pores or fractures, resembling the “bird's eye” texture. In the W–Sn–Pb–Zn system, Py4 in calcite veins can be divided into the oscillatory-zoned Py4a and irregular Py4b under BSE, and Py4b commonly replaces Py4a as veins or overgrowth. Texturally homogeneous Py5 in the calcite-sulfide stage occurs in skarn orebodies and is replaced by Py6 with a “bird's eye” texture in the siderite-sulfide stage.In the Cu–Pb–Zn system, Py1 may have formed by fluid cooling during its ascent along the hydraulic fractures indicated by its enrichment of Co, Ni, As, Sb, and Tl, whereas Py2 is likely formed under higher temperature and pH conditions caused by intense fluid-rock interactions evidenced by its depletion of Co, Ni, As, Sb, and Tl as well as its enrichment of Zn and Ag. In the W–Sn–Pb–Zn system, Py4b has higher contents of Co, Ni, As, Sb, and Tl than Py4a and similar contents of Ag, Zn, and Mo with Py4a, suggesting that decreasing temperature may have controlled the formation of Py4b. Py5 is featured by the depletion of As, Sb, Tl, and Mo as well as the enrichment of Zn and Ag, indicating that Py5 is likely formed under higher temperature and pH conditions resulting from the intense fluid-rock interactions. Marcasite replaces pyrrhotite and then is replaced by pyrite may be an important precipitation mechanism for pyrite with a “bird's eye” texture (Py3 and Py6) in both two skarn systems at Huangshaping. This study demonstrates that fluid-rock interaction is an important mechanism for sulfide precipitation at Huangshaping, which shows that pyrite geochemistry has good potential to reveal mineralization histories in skarn systems.

Unveiling remarkable hydrogen accumulation near ferrite crack tip: Role of unloading effect

We investigate the effect of stress state and hydrogen traps on hydrogen distribution proximity to ferrite crack tip. The results of hydrogen microprint and microstructure characterization indicate that diffusible hydrogen accumulates within crack wake, but the region of hydrogen enrichment ahead of crack tip is tiny according to Ag distribution. By comparing experimental data and numerical calculations, we conclude that the unloading-induced compressive stress region ahead of the crack tip leads to the formation of an overall diffusible H-depleted zone, thereby inhibiting the forward progression of the Ag enrichment zone ahead of the crack tip, whereas the extended size of Ag clustering area within crack plastic wake is primarily attributed to the level of crack plasticity generating dislocation and vacancy traps.

Metallogenetic process of Xunmei hydrothermal field (26°S), South Mid-Atlantic Ridge: Constraints from in-situ sulfur isotope and trace elements of sulfides

Seafloor hydrothermal sulfides at slow-spreading mid-ocean ridges (MORs) are of economic and scientific significance. The formation of newly discovered submarine hydrothermal sulfides on the South Mid-Atlantic Ridge (SMAR), particularly with respect to the fluid evolution, remains poorly understood. The Xunmei hydrothermal field is a typical volcanic dome-type hydrothermal field at 26°S on the SMAR. Based on the mineralogical zonation and assemblages, six distinct ore-forming stages were identified from low- to high-temperature stages with a seafloor weathering stage. The crystallinity of pyrite/marcasite and grain size of chalcopyrite increase gradually from the outer rim to the inner conduit of a sulfide chimney. The positive δ34SV-CDT values of pyrite/marcasite (2.1‰–8.2‰), chalcopyrite (2.5‰–5.6‰), and sphalerite (2.9‰–7.0‰) suggest 62%–91% of S was derived from the leaching of basement basalts, 9%–38% from reduction of seawater sulfate. In situ trace element data for sulfides show enrichments in Mn, Ag, Tl, and Pb in outer zones A and B, while enrichments in Se, In, and Sn in inner zones C and D, indicating an increase in precipitation temperature during chimney growth. Low pyrite Co contents, low Tl/Pb, low Sb/Pb, low Bi/Pb, high As, Ag, Cu, and Pb concentrations, suggesting that the pyrites precipitated from fluids that may have undergone supercritical phase separation during their ascent. High-temperature, Cl-depleted, vapor-rich hydrothermal fluids discharged into ambient cold seawater over multiple stages and probably evolved from low (<240 °C) to medium (∼ 263 °C) and high (∼ 317 °C) temperatures, reached a highest temperature of ∼335 °C, and then evolved to medium to low temperatures (∼ 270 °C to <240 °C) during the wanning of hydrothermal venting. The sulfur fugacity (fS2) likely evolved from a relatively low to high condition within the scope of intermediate sulfidation, and then decreased to low condition. The redox states (fO2) probably were strongly affected by seawater influx and evolved from relatively oxidized to original reduced conditions. The salinity decreased during chimney growth. Sulfide precipitation in the Xunmei hydrothermal field probably was the result of a combination of fluid-seawater mixing and phase separation. We propose a chimney growth and hydrothermal evolution models for the Xunmei hydrothermal field.

Distribution of Ag, Au, Bi, Cu, and Mo in surface soils. Case study: Mitrovica region, Republic of Kosovo

ABSTRACT This article presents the results of a geochemical investigation of an anthropogenic group of metals (Ag, Au, Bi, Cu, and Mo) in the surface of the Mitrovica region, Republic of Kosovo. In order to determine their content and to evaluate the contamination level, 156 topsoil samples were collected in an area of 301.5 km2. The content of elements was determined by inductively coupled plasma-mass spectrometry. The results showed that the average content of Cu (42 mg/kg), Bi (1.5 mg/kg), Ag (0.44 mg/kg), and Au (2.7 μg/kg) exceeded their average content in European and world soils by 3.4 and 1.4 times; 3.0 and 7.5 times; 1.62 and 8.8 times and 2.7 and 1.8 times, respectively. The average Mo content (0.68 mg/kg) exceeded the average content in European soils by 1.09 times, while the average content in world soil was not exceeded. Copper levels exceeded the Dutch target value of 36 mg/kg in 152 km2 and the Dutch action value of 190 mg/kg in 6.2 km2 of the study area. The enrichment factor and geo-accumulation index values for the analysed elements indicate that their higher content is of anthropogenic origin, mainly due to lead and zinc mining and metallurgical activities in the study area. The quality of soils in the Mitrovica region varies from highly contaminated with copper and bismuth, with extremely high enrichment of Cu, Bi and Ag in the soils of the central zone (Zone I) and the urban soils of the cities of Zveçan and Mitrovica. Therefore, the establishment of a monitoring and treatment programme for contaminated soils in this zone would be necessary to protect human health .

Mineralogy and genesis of the Pb-Zn-Sb-Ag vein H32A in the Příbram uranium and base-metal district, Bohemian Massif, Czech Republic

A detailed paragenetic, electron microprobe, fluid inclusion and S,C,O-isotope study was conducted on Pb-Zn-Sb-Ag mineralization of the vein H32A, Háje deposit, Příbram uranium and base-metal district, Czech Republic. The vein is hosted by folded Neo-Proterozoic sandstones and siltstones of the Teplá-Barrandian unit in exo-contact of the Central Bohemian Plutonic Complex of the Variscan age (354–335 Ma). The ore zone is close to a crustal-scale tectonic zone dividing two distinctly different basement blocks of the Bohemian Massif. A rich mineral assemblage consisting of 44 mineral phases formed during two major mineralization stages (siderite-sulphidic and calcite-sulphidic) widespread in the Příbram area. A complex history of the vein is evidenced from the presence of seven mineralization sub-stages and widespread repeated metasomatic replacement and dissolution of older vein during younger mineralizing events. The vein is dominated by carbonates (especially siderite-rhodochrosite, less frequently dolomite-ankerite-kutnohorite, rarely calcite), minor constituents are quartz, illite-muscovite, and chamosite (locally with up to 1.52 apfu Sb, 0.53 apfu Zn and 0.38 apfu Pb). Ore minerals are dominated by Ag-poor galena. The Fe-poor sphalerite, pyrrhotite, löllingite, arsenopyrite, Pb-Sb, Pb-Sb-Ag and Cu-Ag-Sb sulphosalts are subordinate phases and dyscrasite, native antimony and native arsenic are accessories. The fluid inclusion study revealed the wide ranges of homogenization temperatures (210–<100 °C) and salinities (0.0–30.5 wt% NaCl eq.) of exclusively aqueous fluid inclusions. General decrease of both parameters occurred during evolution of the vein. Sulphur isotope disequilibrium was found between co-existing galenas and sphalerites. The calculated fluid δ13C values range between −9.0 and −12.3 ‰ V-PDB, implying for a well-mixed source of carbon, or its significant re-cycling during processes of dissolution-reprecipitation of vein carbonates. The calculated fluid δ18O values are highly positive for early siderite (+7.2 to +9.6 ‰ V-SMOW), and near-zero for later dolomites and calcites (−2.9 to +3.2 ‰ V-SMOW). The siderite fluids likely represent deeply circulated waters, which underwent a significant isotope exchange with hot crustal rocks. Late low-salinity fluids were likely sourced from the Permian partly evaporated freshwater piedmont basins. The high-salinity Ca-Na-Cl brines rarely recorded in secondary fluid inclusions hosted by late calcite likely represent either local “shield brines” or basinal brines of marine provenance. The study site covers a metallogenetically significant portion of the Late Variscan fluid history within an active crust-scale tectonic zone hosted by basement of the Bohemian Massif. A pronounced Ag enrichment of this vein is mainly caused by widespread occurrence of inclusions of late-stage Ag minerals (dyscrasite) in the vein, which form rich concentrations in the shallower parts of the Háje deposit.

In situ trace element compositions of sulfides constraining the genesis of the worldclass Shuangjianzishan Ag-Pb-Zn deposit, NE China

The worldclass Shuangjianzishan Ag-Pb-Zn deposit, containing proven reserves of >21,665 t of silver @128.5 g/t, >3.3 Mt of lead @1.6 wt%, and >1.9 Mt of zinc @0.6 wt%, is the largest silver deposit in Asia. This giant Ag mineralization system has attracted extensive attention since its discovery. However, the incorporation mechanism of Ag in ore sulfides and the deposit genetic type are still greatly debated. We have conducted in situ LA-ICP-MS trace element analyses for sulfides in this deposit to address the above issues. Three paragenetic stages of mineralization were recognized at Shuangjianzishan, including pyrite + quartz + K-feldspar stage (I), galena + sphalerite + Ag-bearing sulfosalt + quartz + calcite + chlorite + sericite stage (II), and post-ore quartz stage (III). Most sulfides and silver minerals were deposited in stage II. In situ time-resolved depth profiles, principal component analysis (PCA), and correlation plots of trace element for sulfides indicate that trace elements are dominantly present in sulfides as solid solutions and nano-inclusions, and less as micro-inclusions. For silver, the most critical element in the studied deposit, its substitution mechanisms vary largely among sphalerite, pyrite, and galena. In sphalerite, Ag enters the crystal lattice associated with coupled substitution of Zn by Fe, Sn, Sb, and Ga. In pyrite, Ag enters the lattice through the coupled substitution of Fe by Cu, Zn, and Sn. In galena, Ag enters lattice by the coupled substitution of Pb by Sb and Zn. Based on the GGIMFis geothermometer calculations, the temperatures for ore stage II range from 290° to 333 ℃ (mean of 319 ℃), which are almost identical to the results of the sulfur isotope geothermometry and fluid inclusion thermometry from the previous studies. Furthermore, the trace element distributions in the Shuangjianzishan sulfides, e.g., the enrichment of Fe, Mn, Sn, Cu, Ag, Sb and Pb and the depletion of Ga, Ge, Co and In in sphalerite, as well as the geological and geochemical features, infer that the studied deposit is similar to the typical epithermal type deposit. We therefore propose that the worldclass Shuangjianzishan Ag-Pb-Zn deposit is an epithermal deposit, and this contribution indicates that in situ LA-ICP-MS trace element analysis of sulfides could help shed light on identifying the genetic type for the hydrothermal ore deposits.

Trace Element Analysis of Pyrite and Arsenopyrite Using the LA-ICPMS Technique in Pulai, Central Belt of Peninsular Malaysia

The Pulai gold deposit is one of the most promising gold prospects in the Central Belt of Peninsular Malaysia. It is found within the Permian-Triassic Gua Musang sequence of metasediments and metavolcanics and in a structurally controlled NE-SW major fault. Various ore minerals, including pyrite, arsenopyrite, chalcopyrite, sphalerite, pyrrhotite, and galena are typically associated with this deposit. Four types of pyrite (Pyrite 1, Pyrite 2, Pyrite 3, and Pyrite 4) and two types of arsenopyrite (Arsenopyrite 1 and Arsenopyrite 2) were characterised based on their morphological and textural differences. In this region, gold occurs as refractory gold in the nanoparticle form and in the state of Au+ within the structure of sulphides of variable concentrations. Through the detailed laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) trace element mapping analysis of pyrite and arsenopyrite, the main Au-bearing sulphides were found within vein-hosted Pyrite 4 and Arsenopyrite 2 during late phase mineralisation, while Pyrite 3 had the lowest Au concentration. Two phases of Au enrichment were recorded in Pyrite 4, mainly in the core (2 to 11.7 ppm; average 1.4 ppm) and margin of the grain (0.3 to 8.8 ppm; average 1.2 ppm), whereas the highest Au content was detected in the core of Arsenopyrite 2 (0.3 to 137.1 ppm; mean 31.9 ppm). The enrichment of Au is associated with As, forming a zoning elemental pattern distribution. Other trace elements, including Co, Ni, Sb, Pb, Bi, Cu, and Zn, show systematic variation in their composition between the various types of pyrite and arsenopyrite. For early-phase sulphides, the Au enrichment localised at the margin of Pyrite 2 and Arsenopyrite 1, together with Co–Ni, Pb–Bi–Sb, and Ag in the same oriented pattern, suggesting the remobilisation and redistribution of Au in sulfides. Meanwhile, the late crystallisation phase of vein-hosted sulphides formed a rich Au–As ore zoning pattern in the core of Arsenopyrite 2 and Pyrite 4. The second phase of Au enrichment continued at the margin of Pyrite 4 through the remobilisation and precipitation of Au together with Ni, Co, Sb, Pb, Bi, Ag, and Cu. Subsequent deformation then reactivated the late fluid system with the enrichment of Sr, Ba, Rb, Ag, and Zn along the fractures and outermost rim of Pyrite 4 and Rb–Sr–Ba–Pb–Bi along the rim of Arsenopyrite 2. The Pulai gold prospect is interpreted as an orogenic-style gold mineralisation where arsenic can be used as an indicator for proximity to ore mineralisation in exploration.

Distribution and sources of Ag, Au, Bi, Cu and Mo in surface soils. Case study: Mitrovica region, Republic of Kosovo

The objective of this study was to investigate the spatial distribution and content of a specificanthropogenic group of trace metals (Ag, Au, Bi, Cu and Mo) in surface soils (0 - 5 cm) of the Mitrovicaregion, Republic of Kosovo. The content of metals was determined by inductively coupled plasma - massspectrometry (ICP-MS). The average content of Cu (42 mg/kg), Bi (1.5 mg/kg), Ag (0.44 mg/kg) and Au(2.7 μg/kg) exceeded the average content of metals in European and world soils by 3.4 and 1.4 times, 3.0and 7.5 times, 1.62 and 8.8 times and 2.7 and 1.8 times, respectively. The average Mo content of 0.68 mg/kgexceeded the mean Mo content in European soil by 1.09 times, while the mean content in world soils wasnot exceeded. Copper levels were also found to exceed the Dutch target value of 36 mg/kg in 152 km2 andthe Dutch action value of 190 mg/kg on 6.2 km2 of the 301.5 km2of the study area. The values of theenrichment factor (EF) for the analyzed elements are all above 1.5, indicating that their higher content is ofanthropogenic origin, mainly due to lead and zinc mining and metallurgical activities in the study area. Thequality of the soils in the Mitrovica region varies from heavily contaminated with copper and bismuth, withextremely high enrichment of Cu, Bi and Ag in the soils of the central zone (Zone I) and the urban soils ofthe cities of Zveçan and Mitrovica.

An Ethyl-Thioglycolate-Functionalized Fe3O4@ZnS Magnetic Fluorescent Nanoprobe for the Detection of Ag+ and Its Applications in Real Water Solutions.

Ethyl-thioglycolate-modified Fe3O4@ZnS nanoparticles (Fe3O4@ZnS-SH) were successfully prepared using a simple chemical precipitation method. The introduction of ethyl thioglycolate better regulated the surface distribution of ZnS, which can act as a recognition group and can cause a considerable quenching of the fluorescence intensity of the magnetic fluorescent nanoprobe, Fe3O4@ZnS-SH. Benefiting from stable fluorescence emission, the magnetic fluorescent nanoprobe showed a highly selective fluorescent response to Ag+ in the range of 0-400 μM, with a low detection limit of 0.20 μM. The magnetic fluorescent nanoprobe was used to determine the content of Ag+ in real samples. A simple and environmentally friendly approach was proposed to simultaneously achieve the enrichment, detection, and separation of Ag+ and the magnetic fluorescent nanoprobe from an aqueous solution. These results may lead to a wider range of application prospects of Fe3O4 nanomaterials as base materials for fluorescence detection in the environment.

Synergistic tuning mixed matrix membranes by Ag+-doping in UiO-66-NH2/polymers of intrinsic microporosity for remarkable CO2/N2 separation

Novel mixed matrix membranes (MMMs) with superior CO2/N2 separation properties are of great importance for post-combustion CO2 capture from flue gas. Metal-organic frameworks (MOFs) as one of the most attractive porous fillers for MMMs fabrication, are considered to provide a solid molecular sieving mechanism for enhancing CO2/N2 selectivity. However, it causes the reduction in gas permeability and limits its further industrialization. Herein, we proposed a new strategy for filler functionalization by doping silver ions (Ag+) into UiO-66-NH2 nanoparticles through the double-solvent method and used for the preparation of advanced MMMs. The double-solvent method is benefits for the enrichment of Ag+ in the hydrophilic pores of UiO-66-NH2. As a result, the prepared novel MMMs called Ag+@UiO@PIM-1 with the polymers of intrinsic microporosity (PIMs) as polymer matrix, show outstanding CO2 permeability. According to the mixed gases (CO2/N2 = 10:90) permeation experiments under 25 °C and 2 bar, the membrane with 30%Ag+@10%UiO loading achieves more than 65% increase in CO2/N2 selectivity (∼30) and 120% in CO2 permeability (>15,000 Barrer) compared to the pristine PIM-1 membrane. By optimizing the Ag+ doping amount and Ag+@UiO loading content, the separation performance exceeds the 2019 CO2/N2 upper bound. To figure out the separation mechanism, the pore texture properties and CO2 affinity of the functional filler (Ag+@UiO) together with the membrane structure were characterized by XPS, PXRD, SEM, gas sorption, etc. The synergistic mechanisms by combing CO2 facilitated transport and molecular sieving from pore regulation were identified to enable advanced CO2/N2 membrane separation.

Adsorption and enrichment of Ag(I) from industrial wastewater using woody biomass-based biosorbent

In this study, a biosorbent prepared by sulphuric acid modified waste biomass was used to adsorb and enrich Ag+ from industrial wastewater. The Ag+ was converted into Ag(NH3)2+ according to the different chemical properties of the ions, as a way to improve the selective adsorption of Ag+ on the biosorbent. Response surface methodology was used to obtain the optimised modification conditions as follows: modification time was 4 h, modification temperature was 368.15 K and sulphuric acid concentration was 85 mass %. Porous structure and chemical functional groups of biosorbent were studied. The analysis of adsorption isotherms indicates that the adsorption process may be an irreversible heterogeneous chemical adsorption process, and the adsorption kinetics of biosorbent on Ag(NH3)2+ conform to the pseudo-second-order kinetic model. The redox mechanism of Ag(NH3)2+ adsorption was postulated based on characterisation analysis. The competitive adsorption experiments showed that the biosorbent had selective adsorption for Ag(NH3)2+ due to redox reaction, and the adsorption capacity of the biosorbent on Ag(NH3)2+ was 1285 mg g−1, which indicates that it has good prospects for application in recovery of Ag(I) from liquid waste resources in the future.

Improved strength and ductility of rapidly solidified 2195 alloy by pre-rolling combined with double aging and interrupted aging

Pre-rolling combined with double aging (DAT8) and interrupted aging (IAT8) were carried out to improve the mechanical properties of rapidly solidified 2195 Al–Cu–Li alloy. For the DAT8 treatment (4% pre-rolling + 120 °C/12 h + 165 °C/16 h), low aging temperature (120 °C) in the first stage forms abundant δ′ phase, which grows into well-dispersed T1 plates in the second stage (165 °C). The IAT8 treatment (165 °C/2 h + 4% pre-rolling + 65 °C/5 day + 165 °C/16 h) first produces some small GP zones, which are connected to dislocations generated by pre-rolling. Subsequent long-term low-temperature aging (65 °C/5d) results in the enrichment of Cu, Mg, Ag and Li atoms on dislocations, significantly enhancing the precipitation driving force of the T1 phase. The results show that DAT8 and IAT8 treatments simultaneously improve the strength and ductility of the alloy. The increased strength is mainly due to the dense precipitation of the T1 phase, generating higher precipitation strengthening, as well as the introduction of high dislocation density, yielding strain strengthening. The improved ductility is attributed to the fine and well-dispersed T1 phase, decreasing the incongruous deformation between precipitates and matrix, and suppressing the formation of precipitation free zone (PFZ), weakening local stress concentration at sub-grain boundaries.