Sulfide Ions Research Articles

Stabilizing lithium metal anodes with solid electrolyte interphase by embedding two-dimensional C3N4/Graphyne as protective layers

The diffusions of lithium ions and sulfide ions between lithium anodes and solid electrolyte interphase have been systematically investigated with both monolayer C3N4 and bilayer C3N4 embedded as protective layers. It is found that, pristine C3N4 would absorb lithium ions inside the C3N4 pores, and such Li-C3N4 could serve as feasible protective layers by providing suitable pathway for lithium ions with small energy barrier while preventing sulfur ions to diffuse with a much larger energy barrier. Heterostructures of C3N4/Graphyne are constructed to demonstrate that 2D materials with suitable pore size are effective to be protective layers for lithium metal anode.

Selective and sensitive colorimetric cyanide recognition in aqueous medium and food samples based on Ni(II) complex chemosensor

Since cyanide is highly toxic that can lead to respiratory arrest and death, it is important to develop practical diagnostic methods for the sensing of cyanide. In this study, the colorimetric sensing of cyanide was achieved by a nickel complex (NiC) sensor with thiourea binding sites. NiC was prepared and characterized by 1H NMR, single-crystal X-ray crystallography, FTIR, and Mass spectra. When the cyanide and sulfide ions were added to NiC sensor, the color changed from light yellow to canary yellow and pale yellow to golden yellow, respectively. NMR titration results confirmed that the colorimetric response toward cyanide resulted from the deprotonation and formation of a guest–host complex. A binding mechanism is proposed based on the mass spectra, 1H NMR titration, and stoichiometry studies. The binding constant and detection limit of the NiC sensor toward cyanide was also investigated. The detection limits of NiC toward cyanide and sulfide reached 35.4 nM and 28.7 nM, respectively, lower than the World Health Organization (WHO)-allowed cyanide concentration in drinking water. The NiC complex possesses high selectivity to cyanide and sulfide through deprotonation of the –NH- protons. The detection of trace amounts of cyanide ions in natural food samples, such as cassava flour and sprouting potatoes, was also achieved by the NiC sensor.

Heme protein identified from scaly-foot gastropod can synthesize pyrite (FeS2) nanoparticles.

The scaly-foot gastropod (Chrysomallon squamiferum), which lives in the deep-sea zone of oceans around thermal vents, has a black shell and scales on the foot. Both the black shell and scales contain iron sulfide minerals such as greigite (Fe3S4) and pyrite (FeS2). Although pyrite nanoparticles can be used as materials for solar panels, it is difficult to synthesize stable and spherical nanoparticles in vitro. In this study, we extracted organic molecules that interact with nano-pyrite from the shell of the scaly-foot gastropod to develop a low-cost, eco-friendly method for pyrite nanoparticles synthesis. Myoglobin (csMG), a heme protein, was identified in the iron sulfide layer of the shell. We purified recombinant csMG (r-csMG) and demonstrated that r-csMG helped in the conversion of ferric ions, sulfide ions and sulfur into spherical shaped pyrite nanoparticles at 80°C. To reduce the effort and cost of production, we showed that commercially available myoglobin from Equus caballus (ecMG) also induced the in vitro synthesis of pyrite nanoparticles. Using structure-function experiments with digested peptides, we highlighted that the amino acid sequence of r-csMG peptides controlled the spherical shape of the nanoparticle while the hemin molecules, which the peptides interacted with, maintained the size of nanoparticles. Synthesized pyrite nanoparticles exhibited strong photoluminescence in the visible wavelength region, suggesting its potential application as a photovoltaic solar cell material. These results suggest that materials for solar cells can be produced at low cost and energy under eco-friendly conditions. STATEMENT OF SIGNIFICANCE: Pyrite is a highly promising material for photovoltaic devices because of its excellent optical, electrical, magnetic, and transport properties and high optical absorption coefficient. Almost all current pyrite synthesis methods use organic solvents at high temperature and pressure under reducing conditions. Synthesized pyrite nanoparticles are unstable and are difficult to use in devices. The scaly-foot gastropod can synthesize pyrite nanoparticles in vivo, meaning that pyrite nanoparticles can be generated in an aqueous environment at low temperature. In this study, we demonstrated the synthesis of pyrite nanoparticles using a heme protein identified in the iron sulfide layer of the scaly-foot gastropod shell. These results exemplify how natural products in organisms can inspire the innovation of new technology.

1D Continuous Subnanofiltration with Ultrahigh Physical Selectivity for HS− Ion

In almost all cellular phenomena and life activities, transmembrane exchange of signals and metabolites is indispensable, and heavily dependent on high selectivity of membrane pores and channels. The involved principles of natural selectivity are widely inspired and adopted for future membrane design, but often limited by the geometry of those artificial channels. Herein, a smectic liquid crystal polymeric (SmP) membrane embedded with tubular cut‐through pillar[5]arene dimers (P5Ds) by self‐assembly is first constructed. The physical confinement effect of inner subnanosized P5D cavity enables SmP membrane to behave with 1D continuous hydrogen sulfide ion (HS−) flow and ultrahigh physical selectivity for HS−. The simulated calculations and corresponding energy analyses show that it is essentially attributed to the size of ion–water cluster, not its own size. It is anticipated to provide a highly precise platform for separation and detection of human endogenous hydrogen sulfide as representative biomarker.

A case study of flotation of chalcopyrite-molybdenite ore using a mixture of pyrogallic acid and o-isopropyl ethylthiocarbamate: Insights from ab initio calculations

To date, lime-free flotation processes are increasingly advocated due to many problems caused by the traditional process using lime (CaO) as a depressant and xanthate (BX) as a collector. In this work, we developed a combination of pyrogallic acid (PGA) and o-isopropyl ethylthiocarbamate (Z200) as an eco-friendly alternative to the lime-xanthate process for chalcopyrite-molybdenite (ccp-mlb) flotation. Roughing flotation experiments showed that this process yields ccp-mlb concentrate with similar recovery and grade of Cu and Mo as in the traditional lime-xanthate process. However, the huge advantage of the novel process is that it requires ten times lower dosages of sodium sulfide in the subsequent separation of ccp-mlb concentrate. The ab initio calculations explained this trend at the atomistic level, where hydrogen sulfide ions could desorb collector more easily from the Z200@ccp complex compared with BX@ccp. The same method could be applied for environmentally friendly separations of other resources with similar composition.

A BODIPY-based fluorescent chemosensor with 2, 6-substitution for visual and highly selective detection of S2–

BODIPY derivatives have often been employed as fluorescent sensors to probe toxic ions in environment and living systems, such as sulfide ion (S2−). Whilst many structure modifications have been exploited on groups at the 3, 5, 8-positions, there are quite few examples on tailoring the 2,6-substituents for chemosensor investigations. Herein, we design and synthesize a 2,6-substituted BODIPY molecule, LM-BDP, to use as a fluorescent probe for detecting S2− in aqueous media. The electronic and crystal structures of the probe are studied by density functional theory (DFT) calculations and single-crystal X-ray diffraction analysis. Spectroscopy investigations are performed in a variety of conditions, showing that LM-BDP exhibits a noticeable color change from pink to dark red and a fluorescence shift from yellow to pink channel with decreased intensity upon addition of S2−. The selectivity and sensitivity measurements show that LM-BDP can only response to S2− with a detection limit of 0.29 μM in less than 100 s. The remarkable contrast in fluorescence images in test-stripe and RAW 264.7 cell experiments indicates that the probe is a proper candidate for the application in detecting exogenous S2−.

Dual charge-accepting engineering modified AgIn5S8/CdS quantum dots for efficient photocatalytic hydrogen evolution overall H2S splitting

Low charge carrier separation and transfer efficiency continues to be the major obstacle to harvest solar energy to split hydrogen sulfide (H2S) as hydrogen source for H2 production with value-added utilization for waste by-products. Herein, we designed a Type-II core/shell AgIn5S8/CdS (AIS/CdS) quantum dots (QDs) photocatalyst capped with short-chain inorganic sulfide ion (S2−) ligand with dual charge-accepting engineering to promote charge carrier extraction and faster photogenerated electron transfer. Transient absorption spectroscopy analysis demonstrates that the excited electrons are fast injected into CdS shell from AIS core within 1.7 ps, instead of transferring to sub-bandgap states. Consequently, the highest photocatalytic hydrogen evolution rate of AIS/CdS QDs with S2- ligand is 12.74 mmol g−1 h−1 that is more than four times of pristine AIS core. This work offers insightful guidance on the rational design of charge-accepting engineering QDs-based photocatalysts, thereby stimulating solar to hydrogen generation and resource utilization of pollutants.

A new fluorescence detection method for sulfide ions based on Cu-containing metal–organic framework materials and dye-labeled DNA of arbitrary sequence

We developed a new quantitative detection method for trace sulfur ions (S2−) in water using a Cu-containing metal–organic framework material (CuBDC) and 6-carboxyfluorescein group (FAM)-labeled DNA of arbitrary sequence. Without S2− in the system, the FAM-labeled DNA can be adsorbed on the CuBDC surface through π–π stacking, hydrogen bonding, and van der Waals forces, and then the fluorescent dye FAM is near the Cu2+ on the CuBDC surface, and the fluorescence of FAM is quenched by a photoinduced electron transfer mechanism between Cu2+ and FAM. With S2− in the system, S2− reacts with Cu2+ in CuBDC to form the more structurally stable compound CuS, leading to CuBDC decomposition, and the FAM-labeled DNA detaches from the CuBDC surface and the fluorescence of FAM recovers. The quantitative detection of S2− is realized according to the change in FAM fluorescence intensity. Under optimized conditions, a good linear relationship holds between the fluorescence intensity (Fi) of FAM and the concentration (Ci) of S2− in the range of 2–120 nmol/L, and the detection limit is 1.5 nmol/L (3σ, n = 9). The method has good selectivity and accuracy, and it can be applied to rapidly and accurately analyze S2− in real water samples.

Corrosion Behavior of Stainless Steel in Seawater in the Presence of Sulfide

The effect of temperature (from 288 to 308 K) and concentration of sulfide ions (up to 40 ppm) on the corrosion behavior of AISI 304L and AISI 316L stainless steels in seawater was studied with measurements of open-circuit potential, linear and potentiodynamic polarization, and electrochemical impedance spectroscopy. An increase in temperature and pollutant concentration negatively affects the corrosion stability of stainless steels at the open circuit (the resistance, compactness, and thickness of the surface layer decrease and the corrosion current increases), in the passive region (the passivation current increases, the depassivation potential decreases, and the passive potential region narrows), and in the transpassive potential region (the rate of metal dissolution increases). The occurrence of pitting corrosion on the surface of the samples was confirmed with optical microscopy and a non-contact 3D profilometer. A few large pits (depth 80–100 μm and width 100 μm) were formed on the surface of AISI 304L steel, while several smaller pits (depth 40–50 μm and width 50 μm) were formed on the surface of AISI 316L steel. With increasing temperature and sulfide ion concentration, the width, depth, and density of the pits increased on both steel samples. In the studied temperature and concentration range of sulfide ions, the AISI 316L steels exhibited higher corrosion resistance. Overall, the influence of sulfide ions on steel corrosion was more pronounced than the influence of temperature.

Ratiometric fluorescence assay for sulfide ions with fluorescent MOF-based nanozyme

A novel ratiometric fluorescence strategy for sulfide ions (S2-) analysis has been developed using metal–organic framework (MOF)-based nanozyme. NH2-Cu-MOF displays blue fluorescence (λem = 435 nm) originating from 2-amino-1,4-benzenedicarboxylic acid ligand. Besides, it possesses oxidase-like activity due to Cu2+ node, which can trigger chromogenic reaction. o-Phenylenediamine (OPD), as a common enzyme substrate, can be oxidized by NH2-Cu-MOF to form luminescent products (oxOPD) (λem = 570 nm). Inner filter effect occurs between oxOPD and MOF. Upon exposure to S2-, oxidase-like activity of MOF is depressed significantly because of the generation of CuS. On one hand, the amount of free Cu2+ decreases, affecting the yielding of oxOPD. On the other hand, CuNPs with larger size are obtained during the oxidation–reduction reaction between Cu2+ and OPD, which show weaker autocatalytic ability for OPD oxidation. These result in the decrease and increase of intensities at 570 and 435 nm, respectively. This method exhibits sensitive and selective responses towards S2- with LOD of 0.1 μM. Furthermore, such ratiometric strategy has been applied to detect S2- in food samples.

Photo-induced Ag modulating carbon dots: Greatly improved fluorescent properties and derived sensing application

Carbon dots (CDs) have been attracted much attention and widely studied due to their excellent fluorescence (FL) properties, better biocompatibility and outstanding photo/chemical stability. However, the disadvantage of lower quantum yield (QY) still limits its wide application. Herein, we reported a novel and convenient strategy to prepare photo-induced Ag/CDs (p-Ag/CDs) by irradiating the mixed Ag+ and hydrophobic CDs (h-CDs) acetone solution with ultraviolet (UV) light. The obtained p-Ag/CDs exhibit a greatly enhanced FL emission together with a blue shift (460 nm) than h-CDs (520 nm). The QY of p-Ag/CDs is measured to be 51.1%, which is 10.4 times higher than that of h-CDs (4.9%), indicating that photo-induced Ag modulation can effectively improve the optical properties of CDs. The mechanisms for the FL enhancement and blue shift of h-CDs are studied in detail. The results prove that the greatly enhanced FL emission is from the generated Ag nanoparticles (AgNPs) by UV light irradiation based on metal-enhanced fluorescence (MEF), and the increased oxygen-contained groups in this process lead to the blue shift in CDs fluorescence. Interestingly, the p-Ag/CDs exhibit higher sensitivity and selectivity for sulfide ions (S2−) detection than that of h-CDs, which have a lower response to S2−. This work not only offers a novel strategy to improve the FL properties of materials but also endows them with new functions and broadens their application fields.

Chitosan-thymolsulfonephthalein-cobalt nanocomposites for colorimetric detection of sulfide anions in aqueous solution

BackgroundWater pollution by sulfide ions, arising from the exploration and exploitation of sulfide mineral ore, can cause many chronic and acute health challenges. However, owing to the cost of sophisticated equipment and technical expertise required to detect anionic sulfides in water has inspired the preparation of easy-to-use naked-eye colorimetric devices. MethodsIn this study, the functionalization of chitosan solution with thymolsulfonephthalein solution (CFTS) at moderate conditions was utilized for the chemical synthesis of cobalt nanocomposites (CFTS-CoNCs) based chemosensors. ResultsThe prepared material's scanning electron micrograph shows the high Co dispersion on the surface of CFTS with a thorn-shaped morphology in uniform spheres. In contrast, the transmission electron micrograph shows good dispersibility of the tiny rod-like particles distributed on a dendrite-like surface. The interaction of the orange-colored CFTS-CoNCs chemosensor solution with the colorless S2− ions was accompanied by an instant and stable black color change. Furthermore, the selective and sensitive chemosensor could detect ≥ 15 ppm aqueous S2− ions solution at lower pH. The mechanism of detection could be due to a nucleophilic attack of S2− on the cobalt-induced hydroxylmethylpropyl benzoxathiole amine cation giving rise to the strong UV–Vis absorption at 592 nm. ConclusionThe highly selective and sensitive CFTS-CoNCs chemosensor can be applied for real-time and quick on-site analysis. In addition, the colorimetric device will serve as a lifesaver in terms of reducing both time and cost, user-friendly, and hands-on tools for the rapid/accurate detection of sulfide ions in water.

H2S Emission and Microbial Community of Chicken Manure and Vegetable Waste in Anaerobic Digestion: A Comparative Study

In order to solve the problem of H2S corrosion in biogas utilization, it is necessary to understand the characteristics and mechanisms of H2S production in chicken manure anaerobic digestion (CMAD) and vegetable waste anaerobic digestion (VWAD). In this study, lab-scale batch tests of CMAD and VWAD were conducted for 67 days at 35 °C. The results showed that sulfide was found to be the major form of sulfur in CMAD (accounting for 90%) and VWAD (70%). The average concentration of H2S was 198 ± 79 ppm in CMAD and 738 ± 210 ppm in VWAD. Moreover, 81% of total H2S was produced at 20 days of methane production in CMAD, but 80% of total H2S was produced in the first day in VWAD because of the rapid production of biogas and fermentation acidification. The sulfide ion equilibrium model could universally and feasibly predict the H2S production in CMAD and VWAD. The abundance of Firmicutes, Bacteroidetes, Proteobacteria and Euryarchaeota accounted for about 95% of the total microbes in both CMAD and VWAD; the influence of the fermentation stage on the microbial community was greater than that of the difference between CM and VW; the abundance of SRB was 0.01~0.07%, while that concerning organosulfur compounds fermentation was 22.8~30.5%. This study indicated that the H2S concentration of CMAD biogas was more than five times that of VWAD because CM is alkalescent but VW is acidic.

Removal of Sulfide Ions from Kraft Washing Effluents by Photocatalysis with N and Fe Codoped Carbon Dots.

N and Fe codoped carbon dots (N,Fe-CDs) were fabricated from citric acid, L-glutamic acid and ferric chloride via a hydrothermal method for the photocatalytic removal of S2- from kraft washing effluents (KWE). The N,Fe-CDs were fluorescent nanoparticles (average size of 3.18 nm) and catalyzed the oxidation of S2- following a first-order kinetic model with an activation energy of 33.77 kJ/mol. The N,Fe-CDs tolerated elevated temperatures as high as 80 °C without catalyst deactivation. The N,Fe-CDs catalysts were reusable for at least four cycles, preserving over 90% of the activity. In the treatment of KWE from the kraft pulping of eucalyptus, the concentration of S2- was decreased by the N,Fe-CDs from 1.19 to 0.41 mmol/L in 6 h. Consequently, near complete remediation was obtained in 24 h. In addition, half of the chemical oxygen demand was removed after treatment with 500 mg/L of the N,Fe-CDs. In addition, the present photocatalyst was safe within a concentration of 200 mg/L, as indicated by the acetylcholinesterase inhibition test. Our findings may help develop a cleaner production process for kraft brownstock washing.

Cationic Polymer Functionalized Copper Nanocluster-Based Fluorescent Probe for the Selective and Sensitive Detection of S2– Ions

The sensitive and selective detection of sulfide (S2–) ions in water is of major interest due to its toxicity and physiological effects on organisms. Herein, we have designed a fluorescent probe, poly(allylamine) hydrochloride (PAH) functionalized copper nanocluster (Cu NC@PAH), for the detection of S2– ions. The synthesis of the probe is based on the electrostatic interaction between negatively charged Cu NCs and the positively charged polymer, PAH. The drastic enhancement of the photoluminescence (PL) intensity of Cu NCs and the quantum yield (QY) enhancement from 0.3 to 6% are evident after functionalizing with a cationic polymer matrix of PAH. The steady-state and time-resolved fluorescence studies support the aggregation-induced emission (AIE) phenomenon for PL QY enhancement. In addition, the Cu NCs@PAH exhibit excellent selectivity toward aqueous S2– ions. The probe displays a reasonable quenching response for S2– ions over a concentration range of 0–20 μM with a detection limit of 2.39 μM. We believe that this facile and economical synthesis methodology of Cu NCs@PAH with interesting AIE properties will extend the scope of previously available techniques for the detection of the S2– ion.

Native Gold of the Chudnoe Gold–Palladium Deposit (Subpolar Urals, Russia)

Abstract ––The Chudnoe gold–palladium deposit, located within the Central Ural uplift, is confined to the axial zone of an anticlinal structure complicated by faults. Veinlet mineralization is localized in fractured and brecciated Late Riphean–Vendian rhyolites. Native gold and palladium minerals are concentrated mainly in veinlets of Cr-containing muscovite (fuchsite) and, more seldom, at local sites of rhyolite metasomatism, almost free of sulfides. Using a representative material, we studied the composition and texture of native gold and the regularities of their spatial variations. Native gold has composition Au–Ag–Cu and contains Pd and Hg impurities. The proportion of elements varies significantly: The content of Au ranges from 65.8 to 92.7 wt.%, the content of Ag varies from 0.4 to 33.8 wt.%, the content of Cu reaches 12.7 wt.%, and the content of Pd is up to 2.9 wt.%. Gold formed as a homogeneous Au–Ag–Cu solid solution at temperatures above 220 °C. The presence of copper in native gold is probably due to the absence of sulfide ion from the ore-forming hydrothermal solution. With decreasing temperature, Au–Ag–Cu solid solution containing more than 1.1–2.5 wt.% Cu disintegrates into two or three phases, forming characteristic plate–lattice and tabular exsolution textures. In the case of two-phase exsolution, the final phases are Au3Cu and Au–Ag solid solution or AuCu and Au–Ag solid solution; and in the case of three-phase exsolution, these are Au3Cu, AuCu, and Au–Ag solid solution. In some cases, the exsolution was accompanied by the recrystallization of gold with the formation of grain intergrowths. The composition of native gold in the deposit varies significantly, showing a discrete character at different sites of the ore zones, which is consistent with the veinlet ore mineralization. At the final stages of mineral formation, native gold was partly replaced by secondary highfineness gold.

Corrosion and bacterial growth mitigation in the desalination plant by imidazolium based ionic liquid: Experimental, surface and molecular docking analysis

The desalination plants wieldy used CuNi alloys. However, it faces a fundamental corrosion problem in a 3.5% NaCl solution containing sulfide ions. In this research, we have examined ionic liquid's corrosion and bacterial inhibition activity, i.e., 1-Dodecyl-3-methylimidazolium iodide (IMD-IL). The obtained data from weight loss and electrochemical reveals the corrosion inhibitive performance of IMD-IL is 96.8% at 100 mg/L. The EIS suggests increasing the charge transfer resistance and film resistance with increasing IMD-IL amount, supporting the inhibitive action of IMD-IL molecules. The biological activity results reveal the deactivation of SRB action after the addition of IMD-IL molecules. The SEM and EDX studies support the IMD-IL adsorption onto the CuNi surface. The molecular docking results confirmed that IMD-IL could bind the cytochrome c, inhibiting its activity and thereby interrupting the electron transport pathway between bacteria and the CuNi.

Detection of cyanide and sulfide ions by different mechanisms using a fluorescent chemical sensor containing a fluorophore and a potential ligand for metal complexes.

Here, we present a fluorescent chemical sensor for the simultaneous detection of CN- and S2- ions, which are highly toxic to humans and the environment. When the BPMA-Flu-Cu2+ complex comprising BPMA-Flu, a fluorophore combined with Cu2+, was used, the fluorescence was turned off. However, the fluorescence was turned on again by the addition of CN- and S2- ions. BPMA-Flu is a unique compound containing both a fluorophore and a ligand coordinated to a metal ion. This strategy using the proposed BPMA-Flu-Cu2+-based fluorescent chemical sensor facilitated quantitative analysis of CN- and S2- ions with high selectivity and sensitivity, despite varying detection mechanisms. The detection limit was as low as 290 nM and 74 nM for CN- and S2- ions, respectively. The sensor was selective and excluded other anions at concentrations 10-fold higher than those of CN- and S2- ions. The recovery rates did not exceed 10% of the original values for the detection of CN- ions in rainwater and tap water. These results indicate acceptable accuracy and precision for practical applications.

Treatment of tannery effluent by adsorption onto fly ash released from thermal power stations: Characterisation, optimization, kinetics, and isotherms

Fly ash is a significant pollutant in thermal power stations. Although this waste harms the environment and humans, it is badly removed and managed, and only a few studies are interested in this waste. For that, this study aims to valorise fly ash into potential adsorbents to treat tannery effluents for the first time. The physicochemical characterisation showed that fly ash has a pHpzc of 9.78, a very porous structure, a high specific surface area of 3127.2 m2/g with a total pore volume of 3.27 cm3/g, and a high silica and aluminium percentage. SEM showed that the fly ash studied has a small particle size ranging between 32 nm and 100 μm. Batch adsorption experiments were done, and the effects of adsorption parameters were investigated. The kinetics and isotherms models indicate that the equilibriums were achieved in 30 min, where the maximum uptake capacity was 2496, 223.7 and 106.8 mg/g for Chemical Oxygen Demand (COD), chromium (VI) and sulfide ions, respectively. The kinetic data were well fitted to the pseudo-second-order model and showed that adsorption onto fly ash may be chemical and physical simultaneously. Freundlich’s model gave a better fit for the experimental adsorption equilibrium data and displayed multilayer adsorption. The thermodynamic isotherm showed that the adsorption onto fly ash is thermodynamically spontaneous (ΔG° < 0) and endothermic (ΔH° > 0). In conclusion, fly ash, which is a free material, has a more robust adsorption capacity than other expensive materials. Thus, it can be a promising, eco-friendly, attractive adsorbent for industrial wastewater treatment.

Geochemical transformations of sulfur in salt lakes (Transbaikalia)

The water column in brackish and saline lakes hosts various forms of sulfur including sulfide (hydrosulfide), elemental, thiosulfate, and sulfate sulfur. The unequal distribution of these reduced sulfur species indicates the presence of two opposing processes - sulfate reduction and oxidation of newly formed hydrogen sulfide. The scale of these processes varies among lakes, resulting in differing proportions of reduced sulfur forms. The bacterial reduction of sulfate ions is confirmed by a significant separation of sulfur isotopes into sulfide and sulfate ions, with the lighter isotope accumulating in the former and heavier isotope in the latter. In most soda, chloride, brackish, and salt lakes, sulfate reduction is the principal process responsible for relatively low sulfate ion content. Additionally, the presence of an oxidizing environment and sulfides in host rocks provide additional sources for sulfates, leading to the formation of sulfate-type lakes. The formation of specific types and subtypes of brackish and salt lakes is determined by processes such as water evaporation, dissolution of aluminosilicates, sulfate reduction, and oxidation of sulfides. The dominance of these processes contributes to the geochemical diversity of lakes.