Mineral Interactions Research Articles

ИССЛЕДОВАНИЕ СТОЙКОСТИ ХЛОРМАГНЕЗИАЛЬНЫХ КОМПОЗИТОВ К НАСЫЩЕННЫМ СУЛЬФАТАМИ СРЕДАМ

This article studies the resistance of composites based on dolomitic magnesian binders mixed with an aqueous solution of magnesium chloride to long-term exposure to liquid media saturated with sulfate ions. We evaluated the effect of the long-term saturation of samples in an aqueous solution of sodium sulfate on the change in their mass, linear dimensions, strength characteristics, and phase composition. Since magnesia binders belong to the group of air-hardening binders, two series of control samples were kept in air-dry conditions and in a state saturated with water. The duration of the experiment was six months. During this period, the change in the physical and mechanical characteristics and phase composition of the samples stored in water and an aqueous solution of sulfates are similar in nature and are caused by a low coefficient of water resistance of magnesia binders. No traces of chemical interaction of magnesium stone minerals with sulfate ions were found. Thus, chloromagnesium composites, provided that they have a high water-resistance coefficient, can be used in aggressive sulfate environments.

Investigation of Thermophysical and Physicochemical Characteristics of Al2O3-SiO2- CaO - Na3AlF6 Flux for SMAW Electrode Coating

This study investigated the thermophysical, physicochemical, and electrical characteristics of electrode coatings developed for application in the weld joint of nuclear power plants (NPPs). The extreme vertices design technique has been used in this work to develop the Al2O3-SiO2-CaO-Na3AlF6-based Shielded metal arc welding (SMAW) electrodes. Twenty-six electrode coating compositions were formulated, and flux coatings were milled into a fine powder for further characterization. X-ray diffraction (XRD) technique was utilized to investigate the structure and phases of the coating composition, and the Fourier transform infrared (FTIR) analysis technique was employed to determine the nature of bonds. The coating's thermal characteristics, including conductivity, diffusivity, and specific heat, were evaluated using hot disk equipment. Enthalpy change and thermal stability of flux coating were determined using the Differential thermal analysis(DTA)/ differential scanning calorimetry (DSC) technique.. The precision inductance (L), capacitance (C), and resistance (R) (LCR) instrument was used further to examine the electrical characteristics of the flux coatings. In addition, a regression model has been developed for each coating property using statistical analysis and investigated a correlation between the properties and mineral interactions. Results reveal that the individual elements and their binary and tertiary interaction significantly influence the physicochemical, thermophysical, and electrical properties of the flux coatings.

Critical mineral constraints in global renewable scenarios under 1.5 °C target

To avoid catastrophic climate change, the world is promoting a fast and unprecedented transition from fuels to renewables. However, the infrastructures of renewables, such as wind turbines and solar cells, rely heavily on critical minerals like rare earths, indium, etc. Such interactions between climate targets, energy transitions, and critical minerals were widely overlooked in the present climate scenario analysis. This study aims to fill this gap through an introduction of metal–energy–climate nexus framework with its application on global energy transition towards a carbon-neutral (or below 1.5 °C) target, in which six state-of-the-art integrated assessment models (IAMs) under different shared socioeconomic pathways were applied. Our analysis revealed that climate mitigation is expected to boost significantly the critical mineral demand by 2.6–267-fold, which varies greatly by IAM models. Solar power development may be constrained by tellurium (Te) and selenium (Se) shortage, while wind power will be jeopardized by the limited scalability of rare earth production. Moreover, a more sustainable pathway may come at higher demand for critical minerals along with higher renewable ratios. Consequently, a holistic investigation of the interaction of mineral, energy, and climate systems is highly recommended for future scenario designing.

Cu isotopes in groundwater for hydrogeochemical mineral exploration: A case study using the world-class Mount Isa Cu–Pb–Zn deposit (Australia)

Copper is the crux resource in the transition to renewable energy sources, with green technologies such as solar panels, wind turbines and batteries all relying on this critical metal for their componentry, and more importantly for connection to electrical grids. While demand intensifies, copper discovery rates continue to fall due to increased scarcity of deposits that are outcropping and/or detectable by conventional means. This has engendered novel methods of detecting Cu-bearing ore under cover, such as hydrogeochemical analyses to trace ore mineral interaction with natural waters. This notably includes the development of Cu isotope systematics in natural waters, wherein proximal to Cu-bearing ore bodies enrichment of water in the heavier Cu isotope occurs (e.g. from oxidative weathering), thus providing a fingerprint of water interaction with Cu-bearing sulfides. Here, Cu isotope compositions for eighteen groundwater samples overlying and distal to the world-class, sediment-hosted stratiform Mount Isa Cu–Zn–Pb deposit were analyzed to assess the utility of groundwater Cu isotope compositions as an exploration tool for Cu-bearing ore under cover. A further 12 chalcopyrite Cu isotope compositions were determined from two drill cores directly overlying the main Cu-bearing ore body, to establish a baseline Cu isotope composition for the Mt Isa deposit. Cu isotope data were synthesized together with field water parameters and placed within a geological context to construct a framework for interpretation. When accounting for industrially impacted sites and underlying geology, results show a clear trend towards heavy Cu isotope enrichment in groundwater proximal to known mineralization, with enrichments of ∼1 per mil (‰) or more relative to distal groundwater and primary deposit chalcopyrite. These results corroborate and expand upon similar work from surface and groundwater samples around porphyry, exotic and IOCG Cu-bearing deposits. Moreover, these results strongly indicate that groundwater Cu isotope systematics for exploration under cover has great potential as a vectoring tool, illustrating that thus far the technique is applicable across deposit types.

The Electrochemical Response of Chalcopyrite and Galena to Degrading Water Quality

Water is used as a liquid medium as well as a means of transportation during mining operations. Flotation, in particular, is a water intensive process where water makes up about 80–85% of the pulp phase. Process water contains organic and inorganic species which accumulate as they are recycled. To avoid the treatment costs of removing these contaminants, many mining operations allow the quality of their water to degrade over time. When this water is introduced into flotation circuits, the pulp chemistry is altered. Ionic species that accumulate in recycled process water have been shown by previous studies to be especially deleterious to flotation performance. Such ions include Ca2+, Cu2+, Mg2+, Pb2+, SO42− and S2O32−, amongst others. The flotation sub-process of collector adsorption which is responsible for inducing hydrophobicity on valuable mineral surfaces may be influenced by water chemistry. Accumulating ionic species have been shown to hinder collector adsorption which may reduce recovery of valuable minerals to the concentrate. Consequently, degrading water quality may threaten the economic viability of mining operations that make use of closed water circuits. Electrochemical techniques such as mineral rest potentials can be used to monitor the impact of changing water quality on collector–mineral interactions. Microflotation was used to determine whether mineral floatability was affected by changing water quality. This study therefore aimed to investigate whether electrochemical techniques such as rest potential measurements can be used to predict flotation performance under changing water quality. No definable relationship was found between the rest potential differences and the microflotation initial recoveries, however, rest potential measurements did identify the negative impact that thiosulphate ions may have on flotation processes.

Comparative study of the HP‐HTbehavior of a layered silicate apophyllite in water and paraffin oil

AbstractThe interaction of porous minerals with liquids, especially water, is involved in many technological and geochemical processes. Apophyllite (K,Na)Ca4[Si8O20](F,OH).8H2O, exhibiting mixed properties of layered and framework microporous silicates, is a promising object to model the interaction of a fluid with porous material. It was studied by the in situ Raman spectroscopy at simultaneously high pressure (HP) and high temperature (HT) up to 225°C and 9 GPa in order to clarify the effect of the composition of the pressure medium and the temperature on its HPbehavior. Penetrating (water) and nonpenetrating (paraffin oil) media were used. Independently of the compressing medium, at HT, the lattice vibrational modes of apophyllite demonstrate regular pressure shifts. Almost uniform shift rates imply little differentiation between the compression of silicate layers and interlayer ion‐molecular assemblage. Similar HPbehavior of apophyllite in penetrating and nonpenetrating media indicates no pressure‐induced overhydration within 1–9 GPa. Thereby, the significance of such structural factors, as a limited H2O mobility and relatively strong contacts between silicate layers, determining low structure tolerance towards the penetration of additional molecules, is emphasized. The elevated temperature does not affect the mobility of the interlayer H2O molecules to allow the pressure‐induced intercalation in apophyllite.

Understanding the rheology of kaolinite clay suspensions using Bayesian inference

Mud is a suspension of fine-grained particles (sand, silt, and clay) in water. The interaction of clay minerals in mud gives rise to complex rheological behaviors, such as yield stress, thixotropy, and viscoelasticity. Here, we experimentally examine the flow behaviors of kaolinite clay suspensions, a model mud, using steady shear rheometry. The flow curves exhibit both yield stress and rheological hysteresis behaviors for various kaolinite volume fractions (ϕk). Further understanding of these behaviors requires fitting to existing constitutive models, which is challenging due to numerous fitting parameters. To this end, we employ a Bayesian inference method, Markov chain Monte Carlo, to fit the experimental flow curves to a microstructural viscoelastic model. The method allows us to estimate the rheological properties of the clay suspensions, such as viscosity, yield stress, and relaxation time scales. The comparison of the inherent relaxation time scales suggests that kaolinite clay suspensions are strongly viscoelastic and weakly thixotropic at relatively low ϕk, while being almost inelastic and purely thixotropic at high ϕk. Overall, our results provide a framework for predictive model fitting to elucidate the rheological behaviors of natural materials and other structured fluids.

Mineral analysis of sandstone formation using chelating agents during sandstone matrix acidizing

For many years, the most common acid practice for sandstone acidizing is based on mud acid and dolomite formations using hydrochloric acid. During various stages of sandstone acidizing, different acids react with different minerals, and interactions of minerals with acids are an origin for precipitation reactions, which can be possibly deleterious as they may reduce reservoir permeability. During this research, the effects of chelates on pore size distribution, mineralogy, and grain size distribution have been investigated. Various chelates (GLDA, HEDTA, EDTA) were examined to react with different Berea Sandstone samples at a temperature of 180 °F and under 1000 psi confining pressure. Experimental techniques and analysis like Tescan Integrated Mineral Analysis (TIMA), were implemented in this research to understand the effect of chelates on Berea Sandstone. These results are related to elemental mass, element deportment, mineral mass, mineral locking, grain size distribution, and particle size distribution of the core samples reacted with different chelating agents. It has been found that all the chelating agents are effective in increasing the porosity and dissolving the cations from the Berea sandstone core sample. HEDTA proved to be more effective in dissolving quartz as compared to other chelates. GLDA proved to be more effective in the dissolution of rutile and zircon minerals. The significance of this research is the application of environment-friendly chelating agents to sandstone formation. Moreover, the detailed mineral analysis revealed that the most number of particles were dissolved by HEDTA.

Metagenomic Features Characterized with Microbial Iron Oxidoreduction and Mineral Interaction in Southwest Indian Ridge.

The Southwest Indian Ridge (SWIR) is one of the typical representatives of deep-sea ultraslow-spreading ridges, and has increasingly become a hot spot of studying subsurface geological activities and deep-sea mining management. However, the understanding of microbial activities is still limited on active hydrothermal vent chimneys in SWIR. In this study, samples from an active black smoker and a diffuse vent located in the Longqi hydrothermal region were collected for deep metagenomic sequencing, which yielded approximately 290 GB clean data and 295 mid-to-high-quality metagenome-assembled genomes (MAGs). Sulfur oxidation conducted by a variety of Gammaproteobacteria, Alphaproteobacteria, and Campylobacterota was presumed to be the major energy source for chemosynthesis in Longqi hydrothermal vents. Diverse iron-related microorganisms were recovered, including iron-oxidizing Zetaproteobacteria, iron-reducing Deferrisoma, and magnetotactic bacterium. Twenty-two bacterial MAGs from 12 uncultured phyla harbored iron oxidase Cyc2 homologs and enzymes for organic carbon degradation, indicated novel chemolithoheterotrophic iron-oxidizing bacteria that affected iron biogeochemistry in hydrothermal vents. Meanwhile, potential interactions between microbial communities and chimney minerals were emphasized as enriched metabolic potential of siderophore transportation, and extracellular electron transfer functioned by multi-heme proteins was discovered. Composition of chimney minerals probably affected microbial iron metabolic potential, as pyrrhotite might provide more available iron for microbial communities. Collectively, this study provides novel insights into microbial activities and potential mineral-microorganism interactions in hydrothermal vents. IMPORTANCE Microbial activities and interactions with minerals and venting fluid in active hydrothermal vents remain unclear in the ultraslow-spreading SWIR (Southwest Indian Ridge). Understanding about how minerals influence microbial metabolism is currently limited given the obstacles in cultivating microorganisms with sulfur or iron oxidoreduction functions. Here, comprehensive descriptions on microbial composition and metabolic profile on 2 hydrothermal vents in SWIR were obtained based on cultivation-free metagenome sequencing. In particular, autotrophic sulfur oxidation supported by minerals was presumed, emphasizing the role of chimney minerals in supporting chemosynthesis. Presence of novel heterotrophic iron-oxidizing bacteria was also indicated, suggesting overlooked biogeochemical pathways directed by microorganisms that connected sulfide mineral dissolution and organic carbon degradation in hydrothermal vents. Our findings offer novel insights into microbial function and biotic interactions on minerals in ultraslow-spreading ridges.

Improvement of fine muscovite flotation through nanobubble pretreatment and its mechanism

With the increasing demand for mineral resources, it is necessary to further recycle some fine muscovite which are not of high quality and discarded after the first development. This study was to improve the recovery of fine muscovite (−20 μm) by introducing of nanobubbles (NBs). A series of techniques including flotation test, mineral adsorption capacity measurement, Zeta potential measurement and the visualization of mineral and bubble interaction were used to investigate the flotation effect of NBs pretreatment on fine muscovite. The results showed that in the dodecylamine (DDA) flotation system, the flotation recovery of fine muscovite pretreated by NBs was higher than that without NBs pretreatment under any concentration of collector and flotation recovery was increased by about 7 %. Meanwhile, the dosage of reagent was reduced by 25 % at the same recovery. NBs pretreatment could reduce the adsorption capacity of DDA and electrostatic repulsion of the muscovite particles, which was beneficial to form particle agglomeration. In addition, the three-phase contact line of the muscovite pretreated with NBs could be formed faster (34 ms). Furthermore, the trajectory of muscovite particles pretreated by NBs were closer to bubbles, and easier to form obvious agglomeration. The introduction of NBs can enhance the flotation of fine muscovite, which provide a cost-effective approach for the fine particle flotation.

Mechanism insights into bacterial sporulation at natural sphalerite interface with and without light irradiation: The suppressing role in bacterial sporulation by photocatalysis.

Unveiling the mechanisms of bacterial sporulation at natural mineral interfaces is crucial to fully understand the interactions of mineral with microorganism in aquatic environment. In this study, the bacterial sporulation mechanisms of Bacillus subtilis (B. subtilis) at natural sphalerite (NS) interface with and without light irradiation were systematically investigated for the first time. Under dark condition, NS was found to inactivate vegetative cells of B. subtilis and promote their sporulation simultaneously. The released Zn2+ from NS was mainly responsible for the bacterial inactivation and sporulation. With light irradiation, the photocatalytic effect from NS could increase the bacterial inactivation efficiency, while the bacterial sporulation efficiency was decreased from 8.1% to 4.5%. The photo-generated H2O2 and O2- played the major roles in enhancing bacterial inactivation and suppressing bacterial sporulation process. The intracellular synthesis of dipicolinic acid (DPA) as biomarker for sporulation was promoted by NS in dark, which was suppressed by the photocatalytic effect of NS with light irradiation. The transformation process from vegetative cells to spores was monitored by both 3D-fluerecence EEM and SEM observations. Compared with the NS alone system, the NS/light combined system induced higher level of intracellular ROSs, up-regulated antioxidant enzyme activity and decreased cell metabolism activity, which eventually led to enhanced inactivation of vegetative cells and suppressed bacterial sporulation. These results not only provide in-depth understanding about bacterial sporulation as a new mode of sub-lethal stress response at NS interface, but also shed lights on putting forward suitable strategies for controlling spore-producing bacteria by suppressing their sporulation during water disinfection.

The Effects of Spent Mushroom Substrate on the Yield and Nutritional Value of Festulolium braunii (K. Richt.) A. Camus

The aim of the experiment was to assess the effects of mineral and mushroom substrate nitrogen on the yield and selected parameters of Festulolium braunii. To this end, a two-year field experiment was conducted between 2017 and 2018. Spent mushroom substrate was applied at three levels (10, 15 and 20 Mg·ha−1) and mineral nitrogen at four (30, 68, 105 and 180 kg·ha−1). Mineral phosphorus and potassium were used at one level only, with 60 and 150 kg·ha−1, respectively. The research also included the effects of the interaction between organic and mineral fertilizers and the determination of an optimal amount of nitrogen resulting in good-quality forage and a high yield. The plant used in the experiment was Festulolium braunii, an intergeneric hybrid of the Sulino variety. Treatment combinations significantly affected its yield, the content of total and digestible protein, as well as the energy values. For most forage parameters, the beneficial effects of mushroom substrate nitrogen and mineral nitrogen interaction were demonstrated, compared to the effects of mineral nitrogen applied on its own. The largest significant increase in the amount of biomass, was by 16% in comparison to plants treated with mineral fertilizers only (N4PK); a significant increase in energy level (by 17%), was recorded for grass treated with 15 Mg·ha−1 of mushroom substrate together with 68 kg·ha−1 of mineral nitrogen (SMS2 + N2PK). The highest dose of nitrogen contained in mushroom substrate applied together with the smallest amount of mineral nitrogen (SMS3 + N1PK) resulted in the highest increase in total and digestible protein concentrations in the grass, 18% and 21% more, respectively, than in plants treated with mineral fertilizers only. The interaction of mineral and mushroom substrate nitrogen did not significantly affect the digestibility of the forage and its concentration of net energy of lactation (NEL).

Comparison of cadmium adsorption by hydrochar and pyrochar derived from Napier grass

Biochar (e.g. pyrochar and hydrochar) is considered a promising adsorbent for Cd removal from aqueous solution. Considering the vastly different physicochemical properties between pyrochar and hydrochar, the Cd2+ sorption capacity and mechanisms of pyrochars and hydrochars should be comparatively determined to guide the production and application of biochar. In this study, the hydrochars and pyrochars were prepared from Napier grass by hydrothermal carbonization (200 and 240 °C) and pyrolysis (300 and 500 °C), respectively, and the physicochemical properties and Cd2+ sorption performances of biochars were systematically determined. The pyrochars had higher pH and ash content as well as better stability, while the hydrochars showed more oxygen-containing functional groups (OFGs) and greater energy density. The pseudo second order kinetic model best fitted the Cd2+ sorption kinetics data of biochars, and the isotherm data of pyrochar and hydrochar were well described by Langmuir and Freundlich models, respectively. In comparison with hydrochar, the pyrochar exhibited better Cd2+ sorption capacity (up to 71.47 mg/g). With increasing production temperature, the Cd2+ sorption capacity of pyrochar elevated, while the reduction was found for hydrochar. The mineral interaction, complexation with surface OFGs, and coordination with π electron were considered the main mechanisms of Cd2+ removal by biochars. The minerals interaction and the complexation with OFGs was the dominant mechanism of Cd2+ removal by pyrochars and hydrochars, respectively. Therefore, the preparation technique and temperature have significant impacts on the sorption capacity and mechanisms of biochar, and pyrochar has better potential for Cd2+ removal than the congenetic hydrochar.

Clay swelling inhibition mechanism based on inhibitor-water interaction: A COSMO-RS molecular simulation approach

• Four inhibition mechanisms employed by amino-acids for stabilizing clay-rich formations are proposed. • New data on the inhibition techniques employed by amino acids is introduced. • Natural amino acids mainly inhibit clay swelling via their interactions with the eater-based fluid and not the clay formation. The inclusion of clay stabilizers in water-based fluids (WBFs) during drilling, imparts WBFs with clay swelling-inhibitive properties. This protects the formation from damage due to the enhanced reduction of the swelling components (clay portions) of the formation by these chemicals during drilling. With the increasing demand for ‘green’ clay stabilizers for WBFs, knowledge of their inhibitive mechanisms is necessary for their effective selection and usage. Earlier, we proposed Amino acids (AAs) as effective “green and cheap’ clay stabilizers, However, the mechanisms through which AAs and other clay stabilizers perform shale stabilization have not been adequately described in open literature. This study is a follow-up work employed to evaluate and succinctly describe all the inhibition mechanisms utilized by AAs to prevent the swelling of the reservoir formations. Furthermore, we discovered a novel mechanism for describing the inhibitive potentials between clay stabilizers in WBFs. Herein, we employed five experimental techniques alongside a modelling tool - COSMO-RS, to evaluate and describe the inhibitive mechanisms of six AA clay stabilizers. This study confirmed that the interaction of AA and the water component of the WBF is a significant factor for AAs effective stabilizing potentials. This is an addition to literature which only highlights the interactions of clay stabilizers and clay minerals for the stability of the formation. This work evaluated all the possible interactions during a clay stabilization process and utilized statistical analyses to compare the percentage contributions of all the interactions among the clay stabilizers (AAs), clay minerals and WBFs. It was revealed that 38% of the swelling inhibition potentials of AAs depend on their interactions with the water component of the WBFs. Concurrently, 28% of the AAs inhibition potentials are based on their ability to modify the surface of reactive clays, while 15% is based on AAs ability to replace the exchangeable cations of swelling clays resulting in the strengthening of the clay's cleavage spacing. Lastly, 18% of AAs stabilizing potentials are based on their ability to neutralize the reactive moieties of swelling clays. The percentage distribution reveals that the effective interactions of AAs with the WBFs significantly contribute to their effectiveness in stabilizing shale formations. This study is essential as it provides researchers with a holistic methodology to characterize and evaluate clay stabilizers.

Particulate matter formation mechanism in pressurized fluidized bed combustion of various solid fuels

Pressurized fluidized bed combustion (PFBC) is an advanced clean coal technology, and co-combustion of coal and biomass can effectively reduce pollutant and greenhouse gas emission during power generation. However, studies concerning the particulate matter formation during coal and biomass co-firing in PFBC are very rare. In this work, experiments on combustion of different solid fuels (two lignites, one bituminous coal, rice husk) and co-combustion of coal and biomass were carried out at 10 kW pressurized fluidized bed with system pressure of 0.5 MPa. Despite the different fuel types, pressurized combustion produces PM1 with higher content of easily vaporized elements (Na, K, and S), while super-micron particles are mainly composed of refractory elements (Ca and Si). For the cases of cofiring coal with biomass, it was found that the mineral interaction can reduce the yield of submicron particles, such as PM0.4 formation in Zhundong lignite/rice husks and Xiaolongtan lignite/rice husks were reduced by 28% and 47%, while the reduction is 61% and 64% for PM1, and 80% and 75% for PM2.5. Overall, this work provides the insight on particulate matter formation during the combustion of various solid fuels in pressurized combustion conditions, which hopefully can help the development of PFBC technology.

Latitudinal changes in elemental composition of smectite in deep sea sediments and its implication for microbial activity along the transect of equatorial Pacific Ocean

In order to determine the sediment provenance and potential iron (Fe) source in abyssal environment, deep sea surface sediments from a transect of the equatorial Pacific Ocean (0–10°N along ~131°W) were investigated for clay mineral assemblages, the elemental composition of smectite, and biogeochemical characteristics, including total organic carbon (TOC), total nitrogen (TN), and adenosine triphosphate (ATP), all of which are closely related to the specific sediment source and cellular process. Not only the relative composition of clay minerals but also two types of smectite (Fe-rich and Al-rich) were detected along the latitudinal transect. The composition of smectite collected close to the equator (0–6°N) was more Fe-rich compared to that of smectite collected at 7–10°N, which was Al-rich. These two distinct compositional groups indicate the existence of at least two sources of smectite at the study sites: (1) Fe-rich smectite supplied from South America and (2) Al-rich smectite derived from Asia and North America. These results suggest that the elemental composition of smectite can be used alongside other conventional proxies to differentiate the provenances of abyssal sediments in the central Pacific Ocean based on the southernmost latitude with Asian and North American sources (7°N) as the present-day mean Intertropical Convergence Zone (ITCZ) position. Moreover, an increase in the Fe content of smectite (N0: 22.1 wt%, N6: 19.3 wt%, and N10: 16.5 wt%) is positively correlated with the latitudinal distribution of ATP concentrations in surface sediments. Therefore, Fe-rich smectite may be important as a Fe source associated with microbial activity in deep sea environments with potential consequences for microbe–mineral interactions.

A microbial driver of clay mineral weathering and bioavailable Fe source under low-temperature conditions.

Biotic and abiotic Fe(III) reduction of clay minerals (illite IMt-1) under low-temperature (0 and 4°C, pH 6) was studied to evaluate the effects of bioalteration on soil properties including clay structure and elemental composition. The extent of Fe reduction in bioreduced samples (∼3.8 % at 4°C and ∼3.1 % at 0°C) was lower than abiotic reduction (∼7.6 %) using dithionite as a strong reductant. However, variations in the illite crystallinity value of bioreduced samples (°Δ2θ = 0.580–0.625) were greater than those of abiotic reduced samples (°Δ2θ = 0.580–0.601), indicating that modification of crystal structure is unlikely to have occurred in abiotic reduction. Moreover, precipitation of secondary-phase minerals such as vivianite [Fe2+3(PO4)2⋅8H2O] and nano-sized biogenic silica were shown as evidence of reductive dissolution of Fe-bearing minerals that is observed only in a bioreduced setting. Our observation of a previously undescribed microbe–mineral interaction at low-temperature suggests a significant implication for the microbially mediated mineral alteration in Arctic permafrost, deep sea sediments, and glaciated systems resulting in the release of bioavailable Fe with an impact on low-temperature biogeochemical cycles.

The "Infernaccio" Gorges: Microbial Diversity of Black Deposits and Isolation of Manganese-Solubilizing Bacteria.

Simple Summary“Infernaccio” gorges are one of the Earth’s hidden habitats in Central Italy. Beyond the deep incisions and high slopes, these gorges are characterized by black deposits in gorge walls and covering rock surfaces. Several geological events have shaped these unique geological formations and their microbiota. This study investigated microbial contribution to black deposit formation and isolating Mn-oxide-solubilizing bacteria. Our results provided evidence of the putative role of Bacteria and Archaea in forming manganese oxide deposits. Findings also showed that these deposits are a source of valuable strains with manganese oxide bioleaching properties, essential for bioremediation and metal recovery.The present study explored the microbial diversity of black deposits found in the “Infernaccio” gorge. X-ray Powdered Diffraction (XRPD) was used to investigate the crystallinity of the samples and to identify the minerals. Scanning electron microscope and energy-dispersive X-ray spectroscopy (SEM-EDS) were used to detect the bacterial imprints, analyze microbe–mineral interactions, and highlight the chemical element distribution in the black deposits. 16S rRNA gene metabarcoding allowed the study of Archaea and Bacteria communities. Mn-oxide-solubilizing isolates were also obtained and characterized by culturable and molecular approaches. The multidisciplinary approach showed the occurrence of deposits composed of birnessite, diopside, halloysite, and leucite. Numerous bacterial imprints confirmed the role of microorganisms in forming these deposits. The Bacteria and Archaea communities associated with these deposits and runoff waters are dynamic and shaped by seasonal changes. The uncultured and unknown taxa are the most common and abundant. These amplicon sequence variants (ASVs) were mainly assigned to Proteobacteria and Bacteroidetes phyla. Six isolates showed interesting Mn solubilization abilities under microaerophilic conditions. Molecular characterization associated isolates to Brevibacterium, Bacillus, Neobacillus, and Rhodococcus genera. The findings enriched our knowledge of geomicrobiological aspects of one of the Earth’s hidden habitats. The study also unveiled the potential of this environment as an isolation source of biotechnologically relevant bacteria.

Interfacial characteristics and mechanical behaviors of geopolymer binder with steel slag aggregate: Insights from molecular dynamics

As a promising sustainable building material, geopolymer/steel-slag composite materials have been poorly known in the field of the interfacial characteristics of geopolymer/steel-slag interface, especially at the molecular level. Herein, in this work, molecular dynamics simulation was employed to reveal the interfacial characteristics and mechanical behaviors of geopolymer binder with steel slag aggregate. The molecular models of two geopolymer binders (C-A-S-H and N-A-S-H) and three main minerals of steel slag aggregate (Ca 2 SiO 4 , Ca 2 Fe 2 O 5 and CaCO 3 ) were constructed and carried out. Then the wetting characteristics of different mineral surfaces, interfacial characteristics, interaction mechanisms and mechanical behaviors of various geopolymer/steel-slag interfacial systems were elucidated and compared. It is found that the Ca 2 SiO 4 , Ca 2 Fe 2 O 5 and CaCO 3 of steel slag aggregate show strong hydrophilicity , attracting water molecules to accumulated on its mineral surface and promoting the diffusion of Ca 2+ and Na + at the interface. The interaction energy of geopolymer/steel-slag systems is mainly composed of electrostatic interaction energy. Thanks to the accumulation of water molecules on the mineral surface, the stronger hydrogen bond interaction occurs at the interface of the geopolymer/steel-slag system. The free metal cations from mineral surfaces and geopolymer binder respectively are coordinated with the accumulated water molecules to emerge hydrated ions , forming composite ionic clusters to stabilize the interfacial interaction . Mechanically, the interaction systems with C-A-S-H binder possess stronger interfacial tensile strength and shear strength. Steel slag with higher Ca 2 SiO 4 content can effectively form strong interfacial bonding , lowering the risk of interfacial tensile failure, whereas steel slag containing more Ca 2 Fe 2 O 5 can reduce occurrence possibility of shearing damage. CaCO 3 formed by carbonization of steel slag, is conductive to strengthening the interfacial interaction with geopolymer binder. • MD simulation can reveal the interfacial behaviors of geopolymer/steel-slag. • The interfacial interaction of geopolymer/steel-slag is mainly composed of electrostatic interaction. • The water molecules at the interface produce hydrogen bond interaction. • The water molecules, Ca 2+ and Na + migrate to the interface to form hydrated ions.

Constructed Wetlands for Treatment of Acid Mine Drainage: A Review

The coal mining industry is an industrial activity that impacts the environment. This activity will generate acid mine drainage due to the interaction of water, air and sulfide minerals. Acid mine drainage is wastewater with low pH and heavy metals content. These conditions will be given some negatives impact on the environment and human health. The low-cost, applicable and simple method to solve acid mine drainage in mining areas is constructed wetlands. Hence, this paper aims to describe the potential of wetlands as a low-cost and applicable method for acid mine drainage treatment. This paper also describes the holistic information about an overview of constructed wetlands, acid mine drainage (AMD) production and their negative impacts, recent trends in constructed wetlands, recommendation components of wetlands, potential application in rural areas and future considerations