Metal Precipitation Research Articles

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.

Mineralized structures from the Alhué mining district, Chile: Using fluid inclusions and textures

The Alhué mining district (AMD) of the Coastal Range in Central Chile is situated approximately 70 km southwest of the city of Santiago and hosted in stratified Jurassic and Early Cretaceous sequences which are common in central Chile. More than 79 faults and veins are recognized in the AMD hosted in andesites and tuffs with clear structural control showing two distinct trends. Precious‐metal mineralization locally extends over strike lengths of up to 1000 m along these structures with grades averaging at 5 ppm gold and 23 ppm of silver. In this study, a University of Chile – YAMANA GOLD joint research project was created to better understand this particular deposit and explore the origin of gold anomalies found in the district using drill core, mine, and surface samples. Wide internal variations in homogenization temperature and electrolytes were observed at all scales: on the district scale, in mineralized structures intersected in drill core, and in hand specimens. This variability may reflect the diversity of ore-forming conditions in the mining district in addition to the different processes (including fault motion over time) and geochemical components within the district. Textural analyses and fluid inclusion assemblages (FIA) provide evidence for boiling and flashing mechanisms at several localities. Raman spectroscopy and LA-ICP-MS techniques allowed a better characterization of the fluid composition and mineral paragenesis. The presence of gold (∼3.8 ppm) and silver (∼1424 ppm) in both vapor-rich only FIAs (i.e. that contain 99 % vapor) hosted in quartz and liquid-rich FIA hosted in sphalerite implies that gold was transported as sulfide and chloride complexes. The AMD shows a transition from a high temperature environment (sometimes containing calc-silicate minerals) to a low temperature (epithermal) system. This mineralization depended on the type of vein system which tend to be mineralized in strike slip faults e.g. Maqui and Lorena structures. The consequence of flashing documented at dilational jogs, structural intersections and fault bends was likely an important outcome leading to the precipitation of metals at the AMD.Coexisting liquid-rich and vapor-rich fluid inclusions contained in a FIA were observed at the deepest levels in the Chilco vein and the proportion of samples showing boiling increases with depth, indicating that additional precious metal resources may be present below current exploration depths. In summary, our new results reveal that gold, silver and base metal veins found at the AMD in Chile are unique hydrothermal polymetallic ore deposits that are structurally controlled and related to an orogenic environment. A general model for the AMD is one where high temperature fluids from deep crustal mafic magmatic systems, probably as products of a devolatilization and far-from-equilibrium conditions, reach subsurface conditions along faults and are mineralized along these faults. Because having a truly unique ore deposit in the geologic record is very unlikely, the AMD forms an important case study that helps understand structurally controlled ore deposits. Thus our work can form a model for future exploration in the AMD and provide insight into exploration in other sites in Chile and along continental margin settings worldwide, in both poorly characterized known deposits and at greenfield sites.

Not so fast: Million-years of metal precipitation in Mississippi Valley type deposits inferred from in-situ petrochronology of hydrothermal carbonates

Mississippi Valley-type (MVT) deposits contain about 20% of global zinc resources and host critical raw materials crucial to the development of green technologies. Despite their economic and strategic importance, there is a lack of consensus on the duration of mineralizing fluid flow events in MVT systems. This study couples in-situ U-Pb dating with Sr-isotope and trace element analysis of syn- and post-ore gangue carbonates to establish: (1) timing and duration, (2) redox evolution, and (3) flow rates of mineralizing fluids in the world-class San Vicente Zn-(Pb) deposit (Peru). New radiometric ages bracket the crystallization of syn-mineralization dolomite, characterized by high Fe and Mn contents and Sr isotopic values overlapping with that of host carbonates, between 103.2 ± 4.1 Ma and 70.6 ± 5.6 Ma. This age interval reveals a direct genetic relationship between flow of mineralizing fluids and late Cretaceous Andean compressional tectonics. Basinal fluid expulsion coeval with known tectonic events continues in the district until Pliocene times, driving episodic crystallization of post-ore hydrothermal carbonates between 61.6 ± 9.3 and 2.7 ± 0.2 Ma. The low Mn and Fe content and high 87Sr/86Sr values characteristic of these post-ore, bedding-parallel and cross-cutting carbonate veins indicate a colder, oxidized environment. Our findings highlight the contribution of paired carbonate geochemistry and U-Pb geochronology in drawing links between tectonic events, fluid expulsion and the waxing and waning of mineralization potential in foreland basins. The results of this study challenge our understanding of timescales in MVT systems and imply that anomalous metal enrichment in basinal fluids over a short temporal interval is not a necessary precondition to form economic-sized, sediment-hosted Zn-Pb deposits. Rather, it is the coexistence of a focused fluid flow in an interconnected aquifer with suitable metal depositional mechanisms over a prolonged period of time (106–107 yr) that allows precipitation of economic amount of base metals at a specific site in the upper crust.

Multi-year time series of daily solute and isotope measurements from three Swiss pre-Alpine catchments

Time series analyses of solute concentrations in streamwater and precipitation are powerful tools for unraveling the interplay of hydrological and biogeochemical processes at the catchment scale. While such datasets are available for many sites around the world, they often lack the necessary temporal resolution or are limited in the number of solutes they encompass. Here we present a multi-year dataset encompassing daily records of major ions and a range of trace metals in both streamwater and precipitation in three catchments in the northern Swiss Pre-Alps. These time series capture the temporal variability observed in solute concentrations in response to storm events, snow melt, and dry summer conditions. This dataset additionally includes stable water isotope data as an extension of a publicly available isotope dataset collected concurrently at the same locations, and together these data can provide insights into a range of ecohydrological processes and enable a suite of analyses into hydrologic and biogeochemical catchment functioning.

Iron slag/activated carbon-electrokinetic system with anolyte recycling for single and mixture heavy metals remediation

The electrokinetic process has been proposed for in-situ soil remediation to minimize excavation work and exposure to hazardous materials. The precipitation of heavy metals in alkaline pH near the cathode is still challenging. Reactive filter media and enhancement agents have been used in electrokinetics to enhance the removal of heavy metals. This study investigated coupling industrial iron slag waste and iron slag-activated carbon reactive filter media with electrokinetic for a single and mixture of heavy metals treatment. Instead of using acid enhancement agents, the anolyte solution was recycled to neutralize the alkaline front at the cathode, reducing the operation cost and chemical use. Experiments were conducted for 2 and 3 weeks at 20 mA electric current. Copper removal increased from 3.11 % to 23 % when iron slag reactive filter media was coupled with electrokinetic. Copper removal increased to 70.14 % in the electrokinetic experiment with iron slag-activated carbon reactive filter media. The copper removal increased to 89.21 % when the anolyte solution was recycled to the cathode compartment. Copper removal reached 93.45 % when the reactive filter media-electrokinetic process with anolyte recirculation was extended to 3 weeks. The reactive filter media- an electrokinetic process with anolyte recycling was evaluated for removing copper, nickel, and zinc mixture, and results revealed 81.1 % copper removal, 89.04 % nickel removal, and 92.31 % zinc removal in a 3-week experiment. The greater nickel and zinc removal is attributed to their higher solubility than copper. The results demonstrated the cost-effectiveness and efficiency of the electrokinetic with iron slag-activated carbon reactive filter media with anolyte recirculation for soil remediation from heavy metals.

Multistage evolution of gold mineralization in the Kibali gold district: Insights from pyrite analyses

The Kibali gold district, located on the Congo Craton, comprises a Neoarchean gold resource exceeding 28.7 Moz. The district is located within a westerly-verging stacked fold-and-thrust belt associated with a compressional tectonic regime active from ca. 2.64–2.60 Ga. Deposits are hosted by a major fault zone that consists of a complex series of smaller thrust faults, shear zones, and folds, which extend over 60 km. Gold deposits are primarily hosted in BIF and clastic sedimentary rocks. The gold and associated sulfides are in veins and disseminated in NE-to NNE-trending ore shoots within the deformed and metamorphosed volcanosedimentary rocks. Pyrite is the dominant sulfide mineral and hosts both solid solution gold and free gold. Because of its strong association with the gold mineralization, our study focusses on unravelling the metallogeny of the area by considering pyrite textural analyses, in situ trace element analyses using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), and S isotopic composition (δ34S) analyses using Secondary Ion Mass Spectrometry (SIMS).Eight distinct pyrite types were identified, including microcrystalline sooty (py-0a), small grains (<40 μm) (py-0b), aggregate recrystallized (py-1), core-rich inclusion (py-2), vein-like (py-3), non-zoned (py-4a), oscillatory As-bands zoned (py-4b), and cubic euhedral (py-5) pyrite. The ore-forming processes occurred over a polyphase evolution. Syn-diagenetic pyrite py-0a in volcaniclastic layers of older basin sediments served as the primary repository of Au (15.6 ppm median) with a near-zero δ34S value. Late diagenetic or early metamorphic pyrite (py-0b) was found in younger basin sediments. Py-1 resulted from solid-state recrystallization of py-0a and py-0b. During the early ore stage, porous py-2 with high Au concentrations (3.1 ppm) and various trace element enrichments precipitated due to fluid-rock interaction. Metal precipitation occurred through sulfidation and carbonation of wall rock with a relatively reduced fluid undergoing 34S-depletion. However, py-3 displayed notable trace element depletion and a complex mineral association. In a second ore stage, py-4a and zoned py-4b deposition occurred, dominated by an over-pressured fluid fracturing brittle rock. Py-4b, rich in Au (5.5 ppm) concentrated in oscillatory zoned As-rich bands, resulted from interactions during pulsed fluid flow. This process involved fluid phase separation, non-equilibrium conditions, 32S-depletion, and precipitation of py-4b with a high δ34S value (6.4 ‰ mean). Subsequently, pyrite (0–4) generations underwent deformation during a later ductile deformation event, leading to the remobilization and concentration of invisible gold into adjacent gold grains within the high-grade shoot plunging NE. This process involved shearing, boudinaging, and folding ore minerals in tightly folded structures. Late-stage py-5 formed under gold-poor fluid conditions or inefficient gold depositional conditions. Brittle fracturing of these grains later provided local sites for remobilized gold. The study contributes insights into the origin and evolution of gold mineralization in the Kibali gold district, supporting a multistage ore-forming fluid system.

Biostimulation of sulfate reduction for in-situ metal(loid) precipitation at an industrial site in Flanders, Belgium

A 30-month pilot study was conducted to evaluate the potential of in-situ metal(loid) removal through biostimulation of sulfate-reducing processes. The study took place at an industrial site in Flanders, Belgium, known for metal(loid) contamination in soil and groundwater. Biostimulation involved two incorporations of an organic substrate (emulsified vegetable oil) as electron donor and potassium bicarbonate to raise the pH of the groundwater by 1–1.5 units. The study focused on the most impacted permeable fine sand aquifer (8–9 m below groundwater level) confined by layers of non-permeable clay. The fine sands exhibited initially oxic conditions (50–200 mV), an acidic pH of 4.5 and sulfate concentrations ranging from 600 to 800 mg/L. At the central monitoring well, anoxic conditions (−200 to −400 mV) and a pH of 5.9 established shortly after the second substrate and reagent injection. Over the course of 12 months, there was a significant decrease in the concentration of arsenic (from 2500 to 12 μg/L), nickel (from 360 to <2 μg/L), zinc (from 78,000 to <2 μg/L), and sulfate (from 930 to 450 mg/L). Low levels of metal(loid)s were still present after 34 months (end of study). Mineralogical analysis indicated that the precipitates formed were amorphous in nature. Evidence for biologically driven metal(loid) precipitation was provided by compound specific stable isotope analysis of sulfate. In addition, changes in microbial populations were assessed using next-generation sequencing, revealing stimulation of native sulfate-reducing bacteria. These results highlight the potential of biostimulation for long-term in situ metal(loid) plume treatment/containment.

First evidence of metallisation circle in a Chromium doped UO2 pellet submitted to a thermal gradient

In order to better understand the formation of metallic fission product precipitates at the centre of power ramped UO2 fuel, we performed a separate effects experiment. An annular pellet made of chromia doped UO2 with an initially uniform distribution of chromium oxide precipitates, was subjected to a temperature gradient. The chromia precipitates became metallic in the hottest part of the pellet but stayed in an oxide phase in the coldest part. The border between oxide and metallic precipitate, named metallisation circle, moved from the pellet inner surface towards mid-pellet as a function of heating time. After one hour of heating, stationary state under thermal gradient was reached. The position of the metallisation circle in stationary conditions allowed an assessment of the oxygen potential profile inside the pellet.

Magmatic–hydrothermal evolutionary processes in highly evolved granitic systems: Insights from zircons of the Baishitouquan pluton, NW China

Abstract As a robust accessory mineral in igneous rocks, the mineralogical and geochemical characteristics of zircon can record the lithological differentiation and magmatic–hydrothermal evolution of highly evolved granitic systems. The F-Rb–rich, highly evolved Baishitouquan pluton of NW China exhibits gradual lithological changes from leucogranite, amazonite-bearing granite, and amazonite granite in the lower levels of the pluton to topaz-bearing amazonite granite, topaz albite granite, and pegmatite in the upper levels. In this study, three types of zircon grains were identified in five lithological zones based on textural and chemical characteristics. Type I zircon, which mostly occurs in leucogranite and amazonite-bearing granite, exhibits oscillatory zoning in cathodoluminescence images and experienced low degrees of radiation damage (0.21–0.68 × 1015 α-decay events/mg), which is indicative of its magmatic origin. Type II zircon, which mostly occurs in amazonite granite and amazonite pegmatite, exhibits textures that are indicative of hydrothermal alteration (e.g., spongy texture, porosity, and microcracks), and has elevated concentrations of some cations, such as Ca and Al. Type II zircon contains a higher concentration of non-formula elements, including rare earth elements (REEs), and Hf, Th, and U, than Type I and III zircons. Additionally, Type II zircon exhibits a significant M-type lanthanide tetrad effect and experienced varying levels of radiation damage (3.75–11.72 × 1015 α-decay events/mg). These characteristics suggest that Type II zircon has a hydrothermally altered origin. Type III zircon, which is restricted to the topaz-albite granite, has the smallest crystal size among all types of zircon grains, shows a euhedral to anhedral mottled appearance, and is characterized by patchy, cloudy, or irregular zoning, with numerous fluid inclusions. This type of zircon contains higher concentrations of Ti (110–1030 μg/g) than other types of zircon grains. Additionally, this type of zircon experienced limited radiation damage (2.18–3.69 × 1015 α-decay events/mg), and has a smooth surface and homogeneous internal textures. These characteristics suggest that Type III zircon is the product of fluid interaction with hydrothermally altered Type II zircon. Accordingly, this type of zircon crystallized directly from a Zr-saturated hydrothermal fluid during the later stages of magmatic–hydrothermal evolution. These contrasting textural and compositional features of the three types of zircon grains are indicative of three stages of magmatic–hydrothermal evolution of the Baishitouquan pluton: magmatic, magmatic–hydrothermal transition, and hydrothermal. These magmatic and hydrothermal processes were involved in the enrichment, transport, and precipitation of rare metals, such as Rb. Accordingly, this contribution demonstrates that the textures and chemistry of zircon grains can serve as petrogenetic indicators for assessing magmatic–hydrothermal evolution and rare-metal mineralization in highly evolved granitic systems. Furthermore, this study presents a model of the magmatic–hydrothermal evolution of F-rich, highly evolved granitic systems through the lens of zircon.

Comprehensive bioremediation effect of phosphorus-mineralized bacterium Enterobacter sp. PMB-5 on cadmium contaminated soil-crop system

Phosphate-mineralizing bacteria (PMBs) have been widely studied by inducing phosphate heavy metal precipitation, but current researches neglect to study their effects on soil-microbe-crop systems on cadmium (Cd) contaminated. Based on this, a strain PMB, Enterobacter sp. PMB-5, was inoculated into Cd contaminated pots to detect soil characteristics, Cd occurrence forms, soil biological activities, plant physiological and biochemical indicators. The results showed that the inoculation of strain PMB-5 significantly increased the available phosphorus content (85.97%−138.64%), Cd-residual fraction (11.04%−29.73%), soil enzyme activities (31.94%−304.63%), plant biomass (6.10%−59.81%), while decreased the state of Cd-HOAc (11.50%−31.17%) and plant bioconcentration factor (23.76%−44.24%). These findings indicated that strain PMB-5 could perform the function of phosphorus solubilization to realize the immobilization of Cd in the complex soil environment. Moreover, SEM-EDS, FTIR, XPS, and XRD analysis revealed that strain PMB-5 does not significantly alter the soil morphology, structure, elemental distribution, and chemical composition, which suggested that remediation of Cd contamination using strain PMB-5 would not further burden the soil. This research implies that PMB-5 could be a safe and effective bioinoculant for remediating Cd-contaminated soils, contributing to the sustainable management of soil health in contaminated environments.

A Liquid Alloy Anode for the Electrolytic Reduction of Uranium Oxide in Molten Lithium Chloride

A cost-effective anode material for uranium oxide electrolytic reduction in lithium chloride is still in deficiency. In this work, the application of liquid lithium-bismuth alloy anode was investigated. In the LiCl electrolyte at 923 K, UO2 was reduced electrochemically in cathode, while Li-Bi alloy served as counter electrode. Partial reduction of UO2 was verified by X-ray powder diffraction when the cathode potential was intentionally controlled above the lithium reduction potential. In contrast, when the precipitation of lithium metal was intentionally controlled, the reduction of UO2 was significantly improved. The charge transfer coefficient of UO2/U reaction was also calculated. Regeneration of Li-Bi alloy in LiCl-Li2O through electrolysis was proposed. Carbon, gold, and platinum had been investigated as anode materials. According to the potential variation curve, lithium was not effectively reduced into bismuth as in pure LiCl when oxygen ion was present in the molten salt. These three materials failed to demonstrate advantage in the regeneration of Li-Bi alloy.

The impact of interfacial characteristics on the interfacial properties of 316 L/CuSn10 multi-material manufactured by laser powder bed fusion

Multi-material additive manufacturing (MMAM) enables the simultaneous creation of multi-material components in a single process, accomplishing customized different performances in specific regions of the same components. In particular, the copper-steel multi-material structure can provide considerable strength and high thermal conductivity, thus playing a crucial role in electronic components, heat exchangers and injection molds. However, few studies have explored the relationship between the microstructure and properties of the copper-steel fusion zone. Therefore, this study aims to reveal the heterogeneous evolution of the microstructure in the copper/steel fusion zone and its impact on the interfacial properties of 316 L/CuSn10 multi-material structure fabricated by laser powder bed fusion (L-PBF). We characterized the multi-layer specimens using laser confocal microscopy and SEM to obtain the macroscopic and microscopic microstructure, liquid metal embrittlement (LME) microcrack characteristics and precipitation evolution of the copper-steel fusion zone. The generation of liquid phase separation (LPS) was explored based on block specimens, and the textural characteristics of the fusion zone were analyzed using EBSD. As a result, because of multiple element precipitation and the high thermal conductivity of copper alloy, abrupt grain size changes occur in the fusion zone, affecting the fusion zone's corrosion resistance and nano-hardness. In tensile tests analyzing the anisotropy, the results show that LME microcracks have little impact on the interfacial bonding properties of the copper-steel bimetallic structure, among which the ultimate tensile strength of the specimens formed at 30° to the substrate reached a maximum of 562.9 MPa. These findings add substantially to our understanding of the relationship between the microstructure and properties of copper-steel bimetallic interface, and provide a theoretical reference for additive manufacturing copper-steel multi-material components.

Application of Gamma Irradiation in Groundwater Treatment Using Different Techniques

The different pollutants in the groundwater can be successfully excluded using potential gamma irradiation. Smart gamma irradiation coupled with ozonation can degrade most of the organic pollutants. Many pollutants’ parameters can be managed, such as total organic carbon (TOC), total dissolved solids (TDS), chemical oxygen demand (COD), biological oxygen demand (BOD), and turbidity. The disinfection of many bacterial cells has been successfully performed besides the deactivation of rotavirus. Based on this manner, the simulated triclosan (TC) can be completely degraded using two techniques of irradiation: reduction and oxidation status. The metals polluting the understudied groundwater can be nearly completely removed by using gamma irradiation under reduction conditions. The applied gamma irradiation can precipitate metal ions such as cadmium, mercury, and lead (in atomic form) in the simulated wastewater, and groundwater. Different patterns seriously influenced the metal ions removal, such as different hydroxyl scavenges and sample gassing with different gasses (hydrogen, nitrogen, and air). This technique results in metal ions decontamination yielding 99.4%, 97.8%, and 96.9%, for cadmium, mercury, and lead ions respectively at the optimum conditions.

Activity-Based Fluorescent Probes for Hydrogen Sulfide and Related Reactive Sulfur Species.

Hydrogen sulfide (H2S) is not only a well-established toxic gas but also an important small molecule bioregulator in all kingdoms of life. In contemporary biology, H2S is often classified as a "gasotransmitter," meaning that it is an endogenously produced membrane permeable gas that carries out essential cellular processes. Fluorescent probes for H2S and related reactive sulfur species (RSS) detection provide an important cornerstone for investigating the multifaceted roles of these important small molecules in complex biological systems. A now common approach to develop such tools is to develop "activity-based probes" that couple a specific H2S-mediated chemical reaction to a fluorescent output. This Review covers the different types of such probes and also highlights the chemical mechanisms by which each probe type is activated by specific RSS. Common examples include reduction of oxidized nitrogen motifs, disulfide exchange, electrophilic reactions, metal precipitation, and metal coordination. In addition, we also outline complementary activity-based probes for imaging reductant-labile and sulfane sulfur species, including persulfides and polysulfides. For probes highlighted in this Review, we focus on small molecule systems with demonstrated compatibility in cellular systems or related applications. Building from breadth of reported activity-based strategies and application, we also highlight key unmet challenges and future opportunities for advancing activity-based probes for H2S and related RSS.

Electrodialysis for efficient antisolvent recovery in precipitation of critical metals and lithium-ion battery recycling

It has proven effective to recover metal compounds from aqueous mixtures by use of antisolvents; organic compounds that induce selective precipitation. A challenge with antisolvents is that they are both costly to produce and recover on an industrial scale. In recycling of lithium-ion batteries and recovering critical metals, we find that electrodialysis can be a competitive method for purifying and recycling antisolvents. In this study we investigate the use of electrodialysis to separate salt and water from a ternary solution of water, KCl and ethanol. A coupled non-equilibrium electrochemical model is developed to understand how such systems may be operated, designed, and which characteristics that are required for the ion exchange membranes. We demonstrate how the water transference coefficients of the membranes should be tuned in the process optimisation and why membrane property design is crucial to the success of this concept. Residual mixtures from antisolvent precipitation, with ethanol (EtOH) solvent weight fractions around 0.6-0.7, can be demineralised and the EtOH fraction increased by 0.1-0.2 at an energy requirement of 60-200 kWh mEtOH−3 by use of electrodialysis. In an example application of the concept, aqueous KCl is precipitated by recycled ethanol in a cyclic process, requiring 0.161 kWh molKCl−1. This example case considers complete ethanol rejection by the membranes and abundant water co-transport, characterised by the transference coefficients: tw=15 and ta=0 for water and EtOH respectively. The findings pave the way for new applications with aqueous mixtures of critical metals.

Acid mine drainage treatment and metals recovery by means of selective precipitation using magnesium oxide (MgO): An experimental study

The treatment of acid mine drainage (AMD) by metals precipitation and neutralization releases a huge volume of highly polluted toxic sludge which can be valorized by the recovering of chemical species. In this study, the treatment of AMD and chemical species recovery by means of selective precipitation using magnesium oxide (MgO) was explored. One litre and half (1500 mL) of AMD from coal mine was used for the experiment. The pH of AMD water was gradually increased using an overhead stirrer and chemical species recovered at different pH gradients via a sequential precipitation technique. The results revealed that Fe(III) was recovered at pH 2.9–4 interval, Al at pH ≥ 4, Cu at pH ≥ 6.5, gypsum at pH 2.9–9.5 interval, Fe(II) at pH ≥ 7.5, Mn, Ni and Zn pH ≥ 8. The results further revealed significant removal of inorganic pollutants in the following order: Cu (100%) = Ni (100%) ≥ Fe (99.9%) ≥ Al (99%) ≥ Mn (98.6%) ≥ Zn (97.2%) ≥ SO42─ (76%). Reduction of electrical conductivity (EC) and total dissolved solid (TDS) were also observed in the order of 82% and 85% respectively. Characterization studies were used to underpin and succinct the fate of chemical species of pure MgO and sludge recovered at different pH gradients. The product water obtained at pH 9.5 conformed to the prescribed standard for effluent discharge as prescribed by regulatory bodies.

Precipitation of Ag-Pb-Zn ores of the Poshan vein deposit in the Qinling orogen (central China) by dilution of magmatic hydrothermal fluids

Abstract Constraints on the source, nature, and evolution of ore-forming fluids are crucial for better understanding the ore genesis and mechanisms that lead to metal precipitation. Here, we present results of in situ analysis for quartz oxygen isotopes and sulfide sulfur isotopes, combined with apatite U-Pb age and fluid inclusion data, to provide insights into the source and evolution of ore fluids of the Poshan Ag-Pb-Zn vein deposit in the Qinling orogen, central China. Quartz-carbonate-sulfide veins at Poshan are hosted in lower Paleozoic metavolcanic-sedimentary rocks and structurally controlled by fracture zones associated with the Heqianzhuang anticline. The Ag-Pb-Zn mineralization consists of three stages, which are represented by quartz-pyrite-arsenopyrite (stage I), quartz-carbonate-sulfide-silver minerals (stage II), and quartz-calcite ± native silver (stage III). Apatite texturally associated with galena from stage II has a U-Pb age of 125 ± 14 Ma (2σ; mean square of weighted deviates [MSWD] = 0.9), which suggests that the Poshan deposit formed in the Early Cretaceous and thus significantly postdated the Paleozoic and early Mesozoic orogenic deformation of the Qinling orogen. Aqueous-carbonic fluid inclusions from stages I and II have similar total homogenization temperatures of 263–347 °C and calculated salinities of 1.2–5.1 wt% NaCl equivalent, whereas the values for liquid-dominated aqueous inclusions from stage III are 211–245 °C and 0.5–3.0 wt% NaCl equivalent. Five quartz generations are recognized from the three paragenetic stages, including Qz-1 and Qz-2 from stage I, Qz-3 and Qz-4 from stage II, and Qz-5 from stage III. Based on in situ secondary ion mass spectrometry oxygen isotopic analysis of the five quartz generations (Qz-1 to Qz-5), the calculated δ18Ofluid values for the ore fluids are 7.8‰ to 9.2‰ (mean 8.3‰), −3.2‰ to 8.7‰ (mean 5.6‰), −3.5‰ to 7.4‰ (mean 4.6‰), −4.5‰ to 7.6‰ (mean −0.2‰), and −6.4‰ to 1.4‰ (mean −3.8‰). The oxygen isotopic data and trend among the five quartz generations are best interpreted to represent magmatically derived ore fluid being diluted by modified meteoric water to cause mineralization. Fluid mixing is considered to be the principal mechanism that led to Ag-Pb-Zn precipitation at Poshan. Sulfides coexisting with the quartz generations have δ34SV-CDT values of −1.7‰ to 4.4‰, with no systematic variations among different paragenetic stages. These data, combined with apatite U-Pb age and geologic relations, provide additional evidence for a magmatic origin of the Poshan Ag-Pb-Zn deposit, as inferred from the oxygen isotopes. This study highlights the role of fluid dilution in triggering Ag-Pb-Zn deposition, and sheds light on the origin of silver-polymetallic deposits in orogenic belts.

Efficient degradation of phenol in water by ball-milling modulated nitrogen-doped structured biochar

Presently, most kinds of biochar rely on the addition of transition metals to improve their electron transport capacity, thereby boosting the activation of oxidants. However, challenges such as the precipitation of transition metals and the chemical inertness of biochar are commonly encountered. Biochar with nitrogen-containing functional groups has emerged as a promising solution as oxidant activators. The nitrogen doping of biochar through ball milling is a straightforward, cost-effective, and efficient preparation method. To optimize the activation properties, a multi-step process involving roasting, ball milling, and tempering was employed to produce biochar. Sesame dregs was chosen as the precursor for this biochar. By optimizing the roasting temperature to 900 °C and using urea as the nitrogen source, biochar derived from sesame residue was successfully prepared. This biochar featured pyridine nitrogen as the primary functional group, exhibiting improved crystallinity and aromaticity. The activation of sodium persulfate (3.0 mM) with biochar eliminated phenol from wastewater with an initial concentration of 50 mg/L in just 15 minutes, achieving a remarkable mineralization rate of 96.77%. Even after undergoing six cycles of repeated use, the system consistently removed 97.73% of phenol within the same timeframe, maintaining a high mineralization rate of 86.77%. Notably, it was found that N-CN, N-6, and N-q were instrumental in stimulating reactive oxygen species (ROS), while ·OH, SO4·-, and 1O2 served as the primary ROS responsible for degrading phenol. The research also revealed a linear relationship between active oxygen sites and oxidized substances, offering insights into the mechanism of phenol degradation.

Advances in Understanding of Unit Operations in Non-Ferrous Extractive Metallurgy in 2023

Advances in Understanding of Unit Operations in Non-Ferrous Extractive Metallurgy in 2023