Metal Precipitation Research Articles

Genesis of the Mamuniyeh copper deposit in the central Urumieh-Dokhtar Magmatic Arc, Iran: Constraints from geology, geochemistry, fluid inclusions, and H–O–S isotopes

The Mamuniyeh Cu deposit is located in the central part of the Urumieh-Dokhtar Magmatic Arc (UDMA), 10 km south of the city of Mamuniyeh, Iran. Mineralization is controlled by faults with a NW-SE trend and hosted within an Eocene volcanic sequence and Oligo-Miocene hypabyssal calc-alkaline monzonitic and gabbroic bodies. Quartz + chalcopyrite veins are most abundant and high-grade ore containing up to 5 wt% Cu, although quartz + pyrite veins have the most abundant sulphide content. In addition, quartz + chalcopyrite + specular hematite ± pyrite veins/veinlets are another common mineralized assemblage in the Mamuniyeh copper deposit, with pyrite, chalcopyrite, bornite, and oxide minerals (specular hematite, titanomagnetite, and magnetite) typical of the hypogene stage. Chalcocite, covellite, and dignite also formed at the margins of primary sulphides in the supergene (paleoweathering) stage. The mineralized veins exhibit colloform, crustiform, open space-fillings, replacements, and dissemination textural characteristics associated with mineralizing assemblages with silicification, argillization, chloritization, and sericitization assemblages. The salinity for L > V fluid inclusions is between 1.74 to 11.7 wt% NaCl and for (V > L) inclusions between 1.7 to 11.4 wt% NaCl. The average homogenization temperature and salinity for quartz + chalcopyrite + pyrite veins is 186 °C and 4.9 wt% NaCl. In the quartz + chalcopyrite assemblage an average of 185 °C and 4.5 wt% NaCl and for quartz + chalcopyrite + specularite ± pyrite (QCSP) an average of 195 °C and 5.59 wt% NaCl was determined. In these three vein types, the fluid density has almost identical values ranging from 0.8 to 1.0 g/cm3. The mineralizing system evolved in two-stages; the first metal precipitation occurred at less than 1 km of crustal depths and second metal deposition stage at shallower crustal levels (less than 500 m). Although it appears that the boiling process occurred within the fluids of the area, the primary factor contributing to Cu mineralization was influenced by fluidmixing processes. The δ18O and δD values of ore fluids computed vary from + 6.08 to −0.50 ‰ and −92 to −71 ‰, respectively, indicative of the blending of oxidizing and cooler meteoric waters with primary magmatic fluids. Calculated values of δ34S of H2S in equilibrium with chalcopyrite ranges from −7.6 to −1.9 ‰ and H2S in equilibrium with pyrite ranges from −7.1 to −3.8 ‰, respectively; this is consistent with monzodiorite to gabbro as the magmatic sulphur source for copper mineralizing fluids. Furthermore, the QCSP vein data align more closely with primary magmatic water compared to other veins, suggesting that precipitation occurred mainly from magmatic fluids, which experienced depletion in δ18O due to mixing with meteoric waters (shallow oxygenated ground waters), which caused sulphide deposition. The geochemical features for these magmas show that contamination with crustal materials occurred during the ascent of the parent magma, as well as the role of suprasubduction fluids released from the subducting plate in mantle metasomatism. Based on all evidence, Cu mineralization in the Mamuniyeh deposit has been categorized as a low-sulphidation epithermal-type system, which formed during active magmatism in the central part of UDMA.

Fabrication of Vanadium Oxide-encapsulated Hybrid Carbon Nanospheres for Enhanced Tribological Performance.

A new sulfur-containing carbon nanospheres encapsulated with vanadium oxide (V@SCN) is synthesized through a one-pot oxidation polymerization and then carbonization method. The prepared V@SCNs exhibit good dispersibility as a lubricant additive, which is owing to the inherited lipophilic organic functional groups in the sulfur-containing carbon shell derived from the carbonization of polythiophene. The agglomeration and precipitation of metals in the base oil are also avoided through the encapsulation of lipophilic carbon shells. The stress and thermal simulation results show that the vanadium oxide core bestows upon the carbon nanospheres enhanced load resistance and superior thermal conductivity, which contributes to their excellent tribological properties. Introducing 0.04M-V@SCN to the base oil leads to favorable tribological characteristics, such as a fourfold rise in extreme pressure capacity from 250 to 1050N, a reduction in friction coefficient from 0.2 to ≈0.1, and a substantial decrease in wear by 90.2%. The lubrication mechanism of V@SCNs as lubricant additive involves the formation of a robust protective film on the friction pair, which is formed via complex physical and chemical reactions with the friction pair during friction.

Heavy metal immobilisation with microbial-induced carbonate precipitation: a review

Microbial-induced carbonate precipitation (MICP) is a promising bioremediation technology for heavy metal immobilisation. This review explores the applications and efficacy of MICP in environmental challenges. It provides a comprehensive overview of the mechanism, primarily through ureolysis, detailing the process from urea hydrolysis to heavy metal precipitation as carbonate minerals. Alternative pathways like photosynthesis and nitrate reduction are also discussed, highlighting the broad applicability of MICP. The review covers the historical evolution and advancements of MICP as a sustainable solution for heavy metal contamination. Recent studies demonstrate the efficiency of MICP in achieving high removal rates in diverse environments. The sustainable operation, precise targeting of heavy metal species, and versatility of MICP are examined. Challenges such as high copper concentrations, acidic conditions, and cost considerations are addressed. The article provides future directions and solutions to these challenges, including leveraging machine learning for optimal performance and enhancing cost considerations through detailed analyses. This review improves understanding of MICP’s potential, provides a valuable resource for researchers in environmental engineering and the built environment, and encourages innovative approaches within these fields.

Bhargavaea beijingensis a promising tool for bio-cementation, soil improvement, and mercury removal

Microbially Induced Calcite Precipitation (MICP) has emerged as a promising technique for bio-cementation, soil improvement, and heavy metal remediation. This study explores the potential of Bhargavaea beijingensis, a urease-producing bacterium, for these applications. Six ureolytic bacteria were isolated from calcareous bricks mine soil and screened for urease and calcite production. B. beijingensis exhibited the highest urease activity and calcite precipitation. Urease activity, calcite precipitation, sand solidification, heavy metal removal efficiency, and compressive strength were evaluated. It showed significant heavy metal removal efficiency, particularly highest for HgCl2. Mortar blocks treated with B. beijingensis or its crude enzyme exhibited improved compressive strength, suggesting its potential for bio-cementation. Crack remediation tests demonstrated successful crack healing in mortar blocks using the bacterium or its enzyme. This study identifies B. beijingensis as a novel and promising MICP agent with potential applications in bio-cementation, soil improvement, and heavy metal remediation. Hence, B. beijingensis diversified abilities prove superior performance compared to commonly used strains like Bacillus subtilis and Shewanella putrefaciens in bio-cementation applications. Its high urease activity, calcite precipitation, and heavy metal removal abilities make it a valuable candidate for sustainable and eco-friendly solutions in various fields.

Mineralization processes in the Bainaimiao Cu-Au deposit in Inner Mongolia, China: Constraints from geology, geochronology, and mineralogy

The Central Asian Orogenic Belt underwent complex tectonic processes and is one of the most intensely accretionary areas globally. Porphyry copper deposits within the belt were likely subjected to deformation during tectonic processes. The Bainaimiao Cu-Au deposit is a typical example of a deformed porphyry deposit whose formation processes include a porphyry emplacement (Event I), a greenschist facies metamorphism (Event II), and a brittle deformation (Event III). Geochronology and trace element geochemistry of zircon, volatiles of magmatic apatite, along with the assemblages, textures, abundances, and compositions of phyllosilicates from these three events were investigated to unveil the physicochemical conditions under which the key geological events relevant to the deposit formation took place. LA-ICP-MS zircon U-Pb dating shows that the granodiorite porphyry in the northern and southern zones formed at 447.4 ± 1.6 to 445.8 ± 3.6 Ma and 436.1 ± 3.8 to 434.1 ± 3.3 Ma, respectively. The granodiorite porphyry in the northern zone has higher oxygen fugacity and Clmelt content but similar Smelt and Fmelt contents compared to the granodiorite porphyry in the southern zone. Microscopic and mineralogic observations point to Event I to be of high plagioclase (22–67 vol%) and quartz (6–40 vol%) content with a range of hydrothermal minerals related to potassic, phyllic, and propylitic alterations. Event II features high amphibole (38–83 vol%) or epidote-chlorite (up to 77 vol%) content with minerals precipitating along the schistosity planes. Event III is characterized by wide veins (3–80 cm) and the highest quartz (61–65 vol%) and calcite (12–19 vol%) content. Geothermometry results show the temperature of potassic and phyllic alterations of Event I to be ∼622 °C and ∼288 °C, respectively. Based on geothermometry and P-T pseudosections, the temperatures of metamorphism and metallic precipitation of Event II were ∼271–634 °C and 297–328 °C, respectively. Both mechanical and chemical mobilization of metallic elements results in Cu mineralization during Event II. The metallic precipitation temperatures of Event III spanned from 297 to 328 °C according to chlorite geothermometry. The ratios of Fe3+/Fetotal and Mg/(Mg + Fetotal) of biotite, chlorite Fe/(Fe + Mg), and white K-mica composition show the mineralizing fluid of Event III to be the most oxidized while that of Event II is the most reduced, F-rich and features the lowest water/rock ratio. This study suggests that deformation processes can increase the Cu mineralization grade of the deformed porphyry deposits through mobilization and re-precipitation of metallic elements.

Composite electrochemical coatings of Ni-CrB2 from sulfuric acid and sulfamate electrolytes: formation, structure and properties

Electrodeposited coatings are in demand in many industries: due to the high adhesive strength to the base metal, they can be applied to complex-shaped products, and the thickness of the deposited coating can be controlled. However, standard electrolytic coatings do not always meet the necessary operating requirements. In this case, the formation of composite electrolytic coatings, which consist in the modification of electrolytes by various dispersed particles, becomes an urgent task. These particles are introduced into the electrolyte and deposited together with the precipitate metals, which leads to changes in the coating properties. In this article, the structure, adhesive and corrosion properties of nickel-chromium diboride composite coatings obtained in the electrodeposition process are studied. Precipitation was carried out in sulfuric acid and sulfamate electrolytes with a concentration of dispersed chromium diboride particles of 10-40 g/l. The coatings consist of nickel and CrB2 phases. The adhesive strength of the coating with a steel base is satisfactory; chipping and peeling were not observed. The corrosion resistance of sulfamate electrolyte coatings is higher than that of the coatings obtained from sulfuric acid electrolyte due to the compactness of nickel precipitates. Chromium diboride in the coating provides 1.5-2 times greater corrosion resistance.

Environmental and socio-economic evaluation of a groundwater bioremediation technology using social Cost-Benefit Analysis: Application to an in-situ metal(loid) precipitation case study

Bioremediation can be an alternative or complementary approach to conventional soil and water treatment technologies. Determining the environmental and socio-economic impacts of bioremediation is important but rarely addressed. This work presents a comprehensive sustainability assessment for a specific groundwater bioremediation case study based on In-situ Metal(loid) Precipitation (ISMP) by conducting a social Cost-Benefit Analysis (CBA) using two different approaches: environmental Life Cycle Costing (eLCC) and Impact Pathway Approach (IPA). Externalities are calculated in two ways: i) using Environmental Prices (EP) to monetize Life Cycle Assessment (LCA) results and metal(loid)s removed at field scale, and ii) following the IPA steps to determine the social costs avoided by removing arsenic contamination at full scale. The results show that, in the baseline scenario, the project is not socio-economically viable in both cases as the Net Present Value (NPV) is −129,512.61 € and − 415,185,140 € respectively. Sensitivity and scenario analyses are performed to identify the key parameters and actions needed to reach a positive NPV. For instance, increasing the amount of water treated per year to 90 m3 and assuming a 20 % increase in operation costs and a 60 % increase in construction costs can make the project socio-economically viable at the field scale, while a reduction in the social discount rate from a 4 % to a 2 % can lead to a positive NPV at the full scale. The approaches proposed in this work may be useful for practitioners and policymakers when evaluating the environmental and socio-economic impacts of bioremediation technologies at different scales and regions, as well as human health impacts caused by contaminants at the current legal limits.

Acidophilic sulphate-reducing bacteria: Diversity, ecophysiology, and applications.

Acidophilic sulphate-reducing bacteria (aSRB) are widespread anaerobic microorganisms that perform dissimilatory sulphate reduction and have key adaptations to tolerate acidic environments (pH <5.0), such as proton impermeability and Donnan potential. This diverse prokaryotic group is of interest from physiological, ecological, and applicational viewpoints. In this review, we summarize the interactions between aSRB and other microbial guilds, such as syntrophy, and their roles in the biogeochemical cycling of sulphur, iron, carbon, and other elements. We discuss the biotechnological applications of aSRB in treating acid mine drainage (AMD, pH <3), focusing on their ability to produce biogenic sulphide and precipitate metals, particularly in the context of utilizing microbial consortia instead of pure isolates. Metal sulphide nanoparticles recovered after AMD treatment have multiple potential technological uses, including in electronics and biomedicine, contributing to a cost-effective circular economy. The products of aSRB metabolisms, such as biominerals and isotopes, could also serve as biosignatures to understand ancient and extant microbial life in the universe. Overall, aSRB are active components of the sulphur and carbon cycles under acidic conditions, with potential natural and technological implications for the world around us.

Exploring the catalytic potential of watermelon urease: Purification, biochemical characterization, and heavy metal precipitation

Bioactive urease from watermelon (Citrullus lanatus) seeds was purified using acetone fractionation, anion-exchange, and size-exclusion chromatography, achieving a 121-fold increase and specific activity of 3216 U/mg. The enzyme appeared as a single band on native and SDS-PAGE, with a molecular mass of 480 ± 10 kDa and subunit mass of 80 ± 10 kDa, indicating six identical subunits. Atomic absorption spectroscopy revealed 1.46 nickel ions per subunit. Watermelon urease exhibited serological similarities with jack bean and pigeon pea ureases, an optimal pH of 7.3, an activation energy of 3 kcal/mol, Vmax of 3571 μmol/min/mg, and Km of 0.16 mM. The enzyme displayed biphasic thermal and pH inactivation kinetics, a strong preference for urea, and a half-life of 70 days with 1 mM DTT. This study highlights watermelon urease's role in bioremediation by facilitating the precipitation of heavy metals as stable carbonates, promoting environmental sustainability.

Impact of mineral and non-mineral sources of iron and sulfur on the metalloproteome of Methanosarcina barkeri.

Methanogens often inhabit sulfidic environments that favor the precipitation of transition metals such as iron (Fe) as metal sulfides, including mackinawite (FeS) and pyrite (FeS2). These metal sulfides have historically been considered biologically unavailable. Nonetheless, methanogens are commonly cultivated with sulfide (HS-) as a sulfur source, a condition that would be expected to favor metal precipitation and thus limit metal availability. Recent studies have shown that methanogens can access Fe and sulfur (S) from FeS and FeS2 to sustain growth. As such, medium supplied with FeS2 should lead to higher availability of transition metals when compared to medium supplied with HS-. Here, we examined how transition metal availability under sulfidic (i.e., cells provided with HS- as sole S source) versus non-sulfidic (cells provided with FeS2 as sole S source) conditions impact the metalloproteome of Methanosarcina barkeri Fusaro. To achieve this, we employed size exclusion chromatography coupled with inductively coupled plasma mass spectrometry and shotgun proteomics. Significant changes were observed in the composition and abundance of iron, cobalt, nickel, zinc, and molybdenum proteins. Among the differences were alterations in the stoichiometry and abundance of multisubunit protein complexes involved in methanogenesis and electron transport chains. Our data suggest that M. barkeri utilizes the minimal iron-sulfur cluster complex and canonical cysteine biosynthesis proteins when grown on FeS2 but uses the canonical Suf pathway in conjunction with the tRNA-Sep cysteine pathway for iron-sulfur cluster and cysteine biosynthesis under sulfidic growth conditions.IMPORTANCEProteins that catalyze biochemical reactions often require transition metals that can have a high affinity for sulfur, another required element for life. Thus, the availability of metals and sulfur are intertwined and can have large impacts on an organismismal biochemistry. Methanogens often occupy anoxic, sulfide-rich (euxinic) environments that favor the precipitation of transition metals as metal sulfides, thereby creating presumed metal limitation. Recently, several methanogens have been shown to acquire iron and sulfur from pyrite, an abundant iron-sulfide mineral that was traditionally considered to be unavailable to biology. The work presented here provides new insights into the distribution of metalloproteins, and metal uptake of Methanosarcina barkeri Fusaro grown under euxinic or pyritic growth conditions. Thorough characterizations of this methanogen under different metal and sulfur conditions increase our understanding of the influence of metal availability on methanogens, and presumably other anaerobes, that inhabit euxinic environments.

Adsorption characteristics and mechanism analysis of heavy metal Zn2+by cement-soil and alkali activated slag-bentonite-soil

With the increasing emphasis on low-carbon environmental protection, alkali activated cementitious materials are gradually being used as a substitute for cement in vertical cutoff walls for polluted sites. The composition of barrier materials significantly impacts the adsorption of heavy metals, thereby affecting the service life of cutoff walls. However, the adsorption characteristics and mechanisms of traditional cement-soil (CS) and alkali activated slag-soil (AASS) for heavy metals are still unclear. This study investigates the adsorption characteristics of Zn2+ using different mix ratios of barrier materials. Various mix proportions were designed, and qualitative and quantitative analyses were conducted using X-ray diffraction and thermogravimetric tests, respectively. The research results indicate that the adsorption of Zn2+ by barrier materials prepared from CS and slag-bentonite-soil (AASBS) is mainly chemical adsorption. The adsorption rate of heavy metals can be enhanced by increasing the cement content in the CS mix ratio. This is primarily because an increase in OH- in the hydration products encourages the formation of heavy metal precipitation. The generation of C-S-H and ettringite in the hydration products and ion exchange of heavy metals improve the adsorption of heavy metals. Increasing slag and alkali activator dosage, along with decreasing alkali activator modulus, promotes C-A-S-H generation and increases OH-, enhancing heavy metal precipitation. Increasing the content of bentonite in the AASBS mixture promotes the generation of C-A-S-H, and the interlayer structure of bentonite promotes the ion exchange of heavy metals. The findings of the study may offer a theoretical foundation for the installation of AASBS vertical cutoff walls in contaminated areas.

Enhanced Nickel Recovery from Mixed Hydroxide Precipitate Through Selective Leaching with KMnO4 Oxidant

Mixed Hydroxide Precipitate (MHP), a metal precipitate with the dominant nickel and cobalt content in hydroxide compounds, can be leached as a lithium battery precursor. In this study, KMnO4 was used as an oxidant agent to increase the solubility of Ni and Co. The variation of the sulfuric acid concentration (0.5 - 1.5 M) as a leachate reagent, the concentration of KMnO4 (2.5 - 7.5 g/L), and the selective leaching temperature (60 - 80°C) were investigated. Solvent extraction using CYANEX 272 and D2EHPA was performed to separate the Ni, Co, and Mn. Atomic Absorption Spectrometry (AAS), Inductively coupled plasma mass (ICP-OES), and X-ray Fluorescence (XRF) were used to analyze the chemical compositions. At the same time, crystallographic analysis was observed with X-Ray Diffraction. It was observed that potassium permanganate increased the dissolution of Ni and Co to 91.3% and 85.4% but decreased the dissolution of Mn (37.53%) under the following conditions: 1.75 M sulfuric acid, 7.5 g/L potassium permanganate, and 60°C temperature. High purity of nickel crystal (99.64%) was observed with spontaneous nucleation due to the supersaturated nickel solution after solvent extraction with CYANEX 272. Thus, using permanganate ion as selective leaching of Ni and Co from Mn is promising.

Accelerated de-chelation of EDTA-metal complexes: A novel and versatile approach for wastewater and solid waste remediation

Industrial waste, including wastewater and solid waste, often contains toxic heavy metals that necessitate extraction and separation prior to safe disposal or reusing them. Sewage sludge incineration ash (SSIA), a non-incinerable waste, holds significant amounts of heavy metals such as iron, zinc, copper, nickel, chromium, and lead. Recovery and reuse of heavy metals from SSIA and further application of treated SSIA sludge remain challenging. Ethylenediaminetetraacetic acid (EDTA) is widely used for heavy metals chelation in different applications. While its chelation with heavy metals is rapid and easy to achieve, the de-chelation of the metal complexes is otherwise slow (∼3 days) and challenging due to their high stability constants. In this study, we investigate the recovery of heavy metals from SSIA through chelation using EDTA, and develop, for the first time, a method to rapidly de-chelate the EDTA-metal complexes through the facile chilling process (1 – 3 h) that accelerates the separation of EDTA and metal ions. A sequential precipitation of high-purity heavy metals from the EDTA-metal complexes was demonstrated with and without de-chelation. This novel and versatile method allows the separation of many valuable compounds from the treated SSIA, including regenerated EDTA, potassium hexafluorosilicate, iron phosphate, iron(III) hydroxide, iron silicate, titanium phosphate, calcium phosphate, copper(I) thiocyanate, nickel bis(dimethylglyoximate), lead(II) sulfate, and zinc sulfide. This approach opens doors for more sustainable waste management and the recovery of valuable resources from industrial waste.

Comparison and mechanism analysis of MgO, CaO, and Portland cement for immobilization of heavy metals in MSWI fly ash

The significant production of municipal solid waste incineration fly ash (MSWI FA) underscores the importance of developing efficient solidification materials. This study employed MgO and CaO for immobilizing MSWI FA (with a 70% fly ash incorporation), and the immobilization effect was compared with that of Portland cement (PC). Experimental findings revealed that MgO exhibited the most effective stabilization for heavy metals (Cd, Cu, Pb, and Zn) compared to CaO and PC. XRD, FTIR, TG, and SEM analysis indicated that the principal hydration products in MSWI FA binders solidified with MgO, CaO, and PC were Mg(OH)2, CaCO3, and C-S-H gel, respectively. Mg(OH)2 efficiently immobilized heavy metals through chemical complexation and surface adsorption mechanisms. The MgO-treated MSWI FA demonstrated the highest residual fractions and the lowest easily leachable fractions. Moreover, the leaching characteristics of heavy metals were significantly influenced by the pH level, so MgO-treated MSWI FA with a leachate pH of 9.18 achieved the precipitation and stabilization of most heavy metals. In summary, this study provided an effective material selection for MSWI FA immobilization and presented a novel strategy for MSWI FA management.

Fluid inclusion and He-Ar-Pb isotope studies of the Dabie-type Leimengou giant porphyry Mo deposit, Qinling Orogen

The Leimengou deposit is a Dabie-type porphyry Mo system in the Leimengou-Qiyugou orefield of Qinling Orogen. Orebodies host within the porphyry and the metasedimentary Taihua Supergroup. However, the characteristics and sources of ore-forming fluid, metal precipitation mechanism, and the sources of mineralizing substances remain unclear. In this contribution, by a comprehensive study comprising an investigation of deposit geology, fluid inclusion microthermometry, and He-Ar-Pb isotope, we discuss the source and evolution of ore-forming fluids and the molybdenum precipitation mechanism of the Leimengou deposit. The mineralizing process is divided into the Stage I quartz ± K-feldspar vein in potassic altered zone, Stage IIa molybdenite ± quartz vein, and Stage IIb molybdenite + quartz + pyrite ± purple fluorite vein in silicification-phyllic altered zone, Stage III quartz + pyrite + sphalerite + galena ± chalcopyrite ± green fluorite ± pink calcite in prophylitic altered zone and Stage IV quartz ± calcite vein in carbonatization zone based on cross-relationship. The Stage IIa and IIb veins characterize the main molybdenum mineralization stages. By microthermometry, CO2-bearing (C-), Water (WV- and WL-), and daughter minerals-bearing (S-) types of inclusions were recognized. The Stage I quartz contains C-type fluid inclusion assemblages (FIAs) with a salinity of 6.3 ± 1.4 wt% NaCl equiv., and a total homogenization temperature (Th, total) of 473 ± 3 °C. This suggests that the early fluids show characteristics of high temperature, CO2-rich, and moderate salinity, distinguishing them from those of Endako-type and Climax-type deposits. C-type and coexisting W-type FIAs from Stage IIa show similar salinity, ranging from 1.9 to 13.0 wt% NaCl equiv. and 1.9 to 14.1 wt% NaCl equiv., with Th, total of 349–376 °C and 327–392 °C, respectively. Moreover, C-type FIAs homogenize to distinct phases and also show similar homogenization temperatures, indicating fluid immiscibility. The FIAs in Stage IIb show an average salinity of 8.3 ± 7.4 wt% NaCl equiv. and a Th, total of 302 ± 14 °C. WL-type and WV-type FIAs coexist, with similar temperatures varying from 308 to 310 °C during this stage, indicating significant fluid boiling. These observations indicate that the decrease in temperature, fluid immiscibility, and decompression boiling collectively led to the precipitation of molybdenite. Trapping pressures are estimated to be 82–231 MPa for Stage IIa and 43–115 MPa for Stage IIb, corresponding to ore-forming depths of approximately 8.4 km and 4.3 km, respectively. Additionally, the He-Ar isotopes obtained from pyrite indicate a clear mixing trend of crustal fluids with mantle fluids at Stage IIb, with mantle-derived fluid components increasing during Stage III. This coincides with the tectonic shift from regional compression to extension, leading to the formation of many Dabie-type Mo deposits, alongside crustal thinning and the upwelling of asthenospheric mantle materials. Futhermore, Pb isotopes from the ore, ore-hosted gneiss, and ore-causative granitoids demonstrate that the Taihua Supergroup gneiss supplied ore-forming materials, suggesting a crustal origin for the Leimengou Mo deposit.

Backside metallization affects residual stress and bending strength of the recast layer in laser-diced Si

Thin Silicon dies separated by laser dicing form a thin layer via redeposition of ablated silicon known as recast layer. This work analyzed the influence of the recast layer microstructure and nanoscale residual stress gradients on the bending strength of bare and metalized silicon dies <100 μm. Scanning and transmission electron microscopy revealed an intricate microstructure of ablated silicon and elements of the wafer backside metallization within the recast layer. Refined silicon grains decorated by nanoscopic metallic precipitates at their grain boundaries were observed. Cross-sectional synchrotron X-ray nanodiffraction revealed that the altered microstructure increased the tensile residual stress from 200 to 295 MPa for bare and metalized dies, respectively. Additionally, the metalized die exhibited gradients in residual stress and grain size between the die front- and backside. Despite their similar frontside bending strengths of ∼340 MPa, observed in 3-point bending experiments, a considerable strengthening of the backside from 425 up to 957 MPa was measured for bare and metalized die, respectively. The origins of the tensile residual stress and the influence of the backside metallization on the die bending strength are discussed.

The Chain of Processes Forming Porphyry Copper Deposits—An Invited Paper

Abstract Porphyry-related mineral deposits are giant geochemical anomalies in the Earth’s crust with orders-of-magnitude differences in the content and proportion of the three main ore metals Cu, Au, and Mo. Deposit formation a few kilometers below surface is the product of a chain of geologic processes operating at different scales in space and time. This paper explores each process in this chain with regard to optimizing the chances of forming these rare anomalies. On the lithosphere scale, deposits with distinct metal ratios occur in provinces that formed during brief times of change in plate motions. Similar metal ratios of several deposits in such provinces compared with global rock reservoirs suggest preceding enrichment of Au or Mo in lithospheric regions giving rise to distinct ore provinces. The largest Cu-dominated deposits and provinces are traditionally explained by selective removal of Au during generation or subsequent evolution of mantle magmas, but the possibility of selective Cu pre-enrichment of lithosphere regions by long-term subduction cannot be dismissed, even though its mechanism remains speculative. Evolution of hydrous basaltic melts to fertile magmas forming porphyry Cu deposits requires fractionation toward more H2O-rich magmas in the lower crust, as shown by their adakite-like trace element composition. The prevailing interpretation that this fractionation leads to significant loss of chalcophile ore metals by saturation and removal of magmatic sulfide might be inverted to a metal enrichment step, if the saturating sulfides are physically entrained with the melt fraction of rapidly ascending magmas. Ascent of fertile magma delivers a large mass of H2O-rich ore fluid to the upper crust, along points of weakness in an overall compressive stress regime, within a limited duration as required by mass and heat balance constraints. Two mechanisms of rapid magma ascent are in debate: (1) wholesale emplacement of highly fractionated and volatile-rich granitic melt into a massive transcrustal channelway, from which fluids are exsolved by decompression starting in the lower crust, or (2) partly fractionated magmas filling a large upper crustal magma chamber, from which fluids are expelled by cooling and crystallization. Transfer of ore-forming components to a hydrothermal ore fluid is optimized if the first saturating fluid is dense and Cl rich. This can be achieved by fluid saturation at high pressure, or after a moderately H2O rich intermediate-composition melt further crystallizes in an upper crustal reservoir before reaching fluid saturation. In either case, metals and S (needed for later hydrothermal sulfide precipitation) are transferred to the fluid together, no matter whether ore components are extracted from the silicate melt or liberated to the ore fluid by decomposition of magmatic sulfides. Production and physical focusing of fluids in a crystallizing upper crustal magma chamber are controlled by the rate of heat loss to surrounding rocks. Fluid focusing, requiring large-scale lateral flow, spontaneously occurs in mushy magma because high water content and intermediate melt/crystal ratio support a network of interconnected tubes at the scale of mineral grains. Calculated cooling times of such fluid-producing magma reservoirs agree with the duration of hydrothermal ore formation measured by high-precision zircon geochronology, and both relate to the size of ore deposits. Ore mineral precipitation requires controlled flow of S- and metal-rich fluids through a vein network, as shown by fluid inclusion studies. The degree of hydrothermal metal enrichment is optimized by the balance between fluid advection and the efficiency of cooling of the magmatic fluid plume by heat loss to convecting meteoric water. The depth of fluid production below surface controls the pressure-temperature (P-T) evolution along the upflow path of magmatic fluids. Different evolution paths controlling density, salinity, and phase state of fluids contribute to selective metal precipitation: porphyry Au deposits can form at shallow subvolcanic levels from extremely saline brine or salt melt; high-grade Au-Cu coprecipitation from coexisting and possibly rehomogenizing brine and vapor is most efficient at a depth of a few kilometers; whereas fluids cooling at greater depth tend to precipitate Cu ± Mo but transport Au selectively to shallower epithermal levels. Exhumation and secondary oxidation and enrichment by groundwater finally determine the economics of a deposit, as well as the global potential of undiscovered metal resources available for future mining.

Efficient Leaching of Metal Ions from Spent Li-Ion Battery Combined Electrode Coatings Using Hydroxy Acid Mixtures and Regeneration of Lithium Nickel Manganese Cobalt Oxide

Extensive use of Li-ion batteries in electric vehicles, electronics, and other energy storage applications has resulted in a need to recycle valuable metals Li, Mn, Ni, and Co in these devices. In this work, an aqueous mixture of glycolic and lactic acid is shown as an excellent leaching agent to recover these critical metals from spent Li-ion laptop batteries combined with cathode and anode coatings without adding hydrogen peroxide or other reducing agents. An aqueous acid mixture of 0.15 M in glycolic and 0.35 M in lactic acid showed the highest leaching efficiencies of 100, 100, 100, and 89% for Li, Ni, Mn, and Co, respectively, in an experiment at 120 °C for 6 h. Subsequently, the chelate solution was evaporated to give a mixed metal-hydroxy acid chelate gel. Pyrolysis of the dried chelate gel at 800 °C for 15 h could be used to burn off hydroxy acids, regenerating lithium nickel manganese cobalt oxide, and the novel method presented to avoid the precipitation of metals as hydroxide or carbonates. The Li, Ni, Mn, and Co ratio of regenerated lithium nickel manganese cobalt oxide is comparable to this metal ratio in pyrolyzed electrode coating and showed similar powder X-ray diffractograms, suggesting the suitability of α-hydroxy carboxylic acid mixtures as leaching agents and ligands in regeneration of mixed metal oxide via pyrolysis of the dried chelate gel.

β-tricalcium phosphate enhanced biomineralization of Cd2+ and Pb2+ by Sporosarcina ureilytica HJ1 and Sporosarcina pasteurii HJ2

Microbiologically induced CaCO3 precipitation (MICP) has been proposed as a potential bioremediation method to immobilize contaminating metals. In this study, carbonate mineralizing bacteria HJ1 and HJ2, isolated from heavy metal contaminated soil, was employed for Cd2+ and Pb2+ immobilization with or without β-tricalcium phosphate addition. Compared with the only treatments amended with strains, the combined application of β-tricalcium phosphate and HJ1 improved the immobilization rates of Cd and Pb by 1.49 and 1.70 times at 24 h, and the combined application of β-tricalcium phosphate and HJ2 increased the immobilization rates of Cd and Pb by 1.25 and 1.79 times. The characterization of biomineralization products revealed that Cd2+ and Pb2+ primarily immobilized from the liquid phase as CdCO3 and PbCO3, and the addition of β-tricalcium phosphate facilitated the formation of Ca4.03Cd0.97(PO4)3(OH) and Pb3(PO4)2. Also, the calcium source was related to the speciation of carbonate precipitation and improved the Cd and Pb remediation efficiency. This research demonstrated the feasibility and effectiveness of MICP combined with β-tricalcium phosphate in immobilization of Cd and Pb, which will provide a fundamental basis for future applications of MICP to mitigate soil heavy metal pollutions.

Experimental Study on the Strength and Microstructure of Red Mud-Based Silty Sand Modified with Lime–Fly Ash

This study aimed to assess the viability of utilizing lime–fly ash (LF) and red mud (RM) in the modification of silty soil (LF-RMS) for subgrade filling. The primary objective of this research was to analyze the mechanical characteristics and examine the curing mechanisms associated with said modified materials. Different curing times were utilized in the analysis of mechanical properties (e.g., via unconfined compression testing), microstructure (via scanning electron microscopy, X-ray diffraction, and thermogravimetric-differential thermal analysis), and environmental indices (via assessment of corrosivity, heavy metal concentration, and radioactivity) with various dosages of red mud (DRM) and Lime–fly ash (DLF). Analyses of the curing mechanisms, failure modes, microstructures, and degrees of environmental impact associated with LF-RMS were also undertaken. The tests indicated that the unconfined compressive strength (UCS) exhibited an initial increase followed by a decrease as the DRM and DLF levels increased. Additionally, the strength of LF-RMS increased with an increase in curing time. It is worth noting that the specimen composed of 20% LF and 23% RM (D20%LF+23%RM) demonstrated a maximum UCS value of 4.72 MPa after 90 days of curing, which indicates that it has the strongest ability to resist deformation. The strength of the specimen cured for 90 days was 1.4 times higher than that of the specimen cured for 7 days (1.97 MPa). Furthermore, the toxic concentration and radionuclide index of LF-RMS were significantly reduced compared to those of pure RM. The overall concentration of heavy metals in the D20%LF+23%RM specimen decreased by more than 60% after curing for 28 days. The internal irradiation index and the external irradiation index decreased by 1.63 and 1.69, respectively. The hydration products in LF-RMS play a key role in the solidification of heavy metals, and the alkaline environment provided by RM also contributes to the precipitation and replacement of heavy metals. In this study, red mud, fly ash and lime were used to modify silty soil. The central tenets of sustainable development may be achieved through the reuse of RM as a road filler.