Sodium Sulfide Research Articles

TSQ Incubation Enhances Autometallographic Zinc Detection in Cultured Astrocytes.

Zinc is a critical ion for a large number of cellular functions. In the central nervous system, zinc ions are involved in synaptic transmission. Therefore, zinc homeostasis is essential, and cells have developed a variety of mechanisms to control cellular zinc concentration, including the zincosome formation. Alterations of free zinc levels have been associated with brain dysfunction and are present in many illnesses and syndromes. Astrocytes are implicated in the maintenance of the neuronal milleu and brain homeostasis. In this work, we have analyzed the combination of direct (TSQ) and indirect (autometallography) zinc detection methods to increase sensitivity for studying zinc uptake by rat astrocytes in vitro. Zincosome formation was visualized with the zinc fluorochrome TSQ by light microscopy. Additionally, we improved both zinc precipitation and cellular fixation methods to preserve zinc ions and make them suitable for autometallography development. Our tests pinpointed paraformaldehyde and sodium sulfide as the more adequate methods for cellular fixation and zinc precipitation, respectively. TSQ incubation and pH of the fixative were shown to be crucial for autometallography. Using this improved method, we visualized the zinc content of zincosomes at the ultrastructural level both as silver autometallographic precipitates and as electrodense sulfide-osmium zinc precipitates.

Selenite Stable Isotope Fractionation during Abiotic Reduction by Sodium Sulfide.

Reduction of Se(IV) by sulfur reducing bacteria (SRB) can remove Se from groundwater either by direct respiration or the production of H2S(g) and subsequent abiotic reduction. This study examined abiotic Se(IV) reduction by H2S(g) to determine the associated Se isotope fractionation. The extent of fractionation was compared to the results with studies of Se(IV) reduction in systems containing microorganisms to assess whether these processes could be distinguished. A solution containing Na2S was added in increasing concentrations to solutions containing Se(IV) as SeO32- to reduce and precipitate Se. Precipitates with three distinct colors were observed. Powder X-ray diffraction (PXRD) results yielded three distinct spectra for each of the three colors of precipitate, which corresponded to SenS8-n (orange) or Se(0) (red) and S(0) (yellow). The δ82Se values of the residual dissolved Se increased as the aqueous Se concentration decreased. The S/Se in solution affected the isotopic fractionation, with an 82ε of 10.1 ± 0.6‰ observed for solutions with S/Se < 1.7, and of 7.9 ± 0.3‰ for solutions with S/Se > 1.7.

Remediation of Sulfides in Produced Waters of the Oil and Gas Industry Using Hydrogen Peroxide

Produced waters are often treated in open lagoons where hydrogen sulfide (H2S) can off gas, posing a risk to human health and the environment. The aim of this study was to optimize a treatment process using hydrogen peroxide (H2O2) to oxidize H2S while minimizing off gassing. Samples of produced water from West Texas and laboratory-prepared waters utilizing sodium sulfide (Na2S) or biogenic polysulfides were oxidized with H2O2 alone or in combination with copper or iron catalysts, sodium hydroxide (NaOH), or a commercial sulfide oxidizer, HydroPower Green™. Sulfur speciation was measured using Hach test kits for sulfide/sulfate/sulfite and Dräger tubes for headspace H2S. HydroPower Green™ (HPG) helped to reduce H2S in the headspace of water samples; some of this was pH related as NaOH also worked, but not as well as HPG. The dose of peroxide necessary to oxidize sulfides to sulfate is a function of the oxidation-reduction potential (Eh) of the water and total sulfide concentration as well as pH; approximately a 1–4:1 ratio of peroxide to sulfide concentration was needed to oxidize sulfidic waters of pH 7–10 with half-lives under 30 min. Both copper and iron catalysts reduce H2O2 demand and the half-life of H2S. Peracetic acid (PAA) and copper (II) sulfate pentahydrate (CuSO4, 5H2O) were explored as biocides for controlling sulfate-reducing bacteria (SRBs) that produce H2S. An AquaSnap (Hygenia) test kit was employed to monitor relative microbial activity in a wetland porewater containing H2S. Microbial regrowth occurred after a few days using the highest dose of PAA; these results showed that PAA was being used by bacteria as a carbon source even after the initial substantial reduction in the microbial activity. CuSO4, 5H2O at a dose of 1 ppm prevented microbial regrowth. The recommended treatment process from this research is determined by jar testing with H2O2, a base for pH control, a biocide, and possibly a metal catalyst or other co-oxidants in order to achieve oxidation of sulfides without H2S release or the precipitation of metal carbonates or oxides.

Mercury Concentrations in Dust from Dry Gas Cleaning of Sinter Plant and Technical Removal Options

Mercury (Hg) is a naturally occurring element and has been released through human activities over an extended period. The major source is the steel industry, especially sinter plants. During a sintering process, high amounts of dust and gaseous emission are produced. These gases contain high loads of SOx and NOX as well as toxic pollutants, such as heavy metals like Hg. These toxic pollutants are removed by adsorbing to solids, collected as by-products and deposited as hazardous waste. The by-products contain a high amount of salt, resulting in a high water solubility. In this study, to ultimately reduce the waste amount in landfills, leachates of the by-products have been produced. The dissolved Hg concentration and its distribution across different charges were determined. Hg concentrations between 3793 and 12,566 µg L−1 were measured in the leachates. The objective was to lower the Hg concentration in leachates by chemical precipitation with sodium sulfide (Na2S) or an organic sulfide followed by filtration. Both reagents precipitate Hg with removal rates of up to 99.6% for the organic sulfide and 99.9% for Na2S, respectively. The dose of the precipitator as well as the initial Hg concentration affected the removal rate. In addition to Hg, other relevant heavy metals have to be included in the calculation of the amount of precipitator as well. Between relevant heavy metals including Hg and sulfide, the ratio should be more than 1.5. The novelty of this study is the measurement and treatment of Hg in wastewater with a high ionic strength. The high salt concentrations did not influence the efficiency of the removal methods. An adjustment of the precipitator dose for each sample is necessary, because an overdose potentially leads to the re-dissolving of Hg. It could be shown that the emission limit of 0.005 mg L−1 could be reached especially by precipitation with Na2S.

Recovery of phosphorus from chemical-enhanced phosphorus removal sludge: Influence of sodium sulfide dosage on phosphorus fractionation, sludge dewaterability, and struvite product

Despite the potential of sodium sulfide (Na2S) for phosphorus (P) recovery from iron-phosphate waste, the underlying mechanism regarding its impact on P conversion and product quality has not been well addressed. In this study, the effects of Na2S addition on P release and recovery from a chemical-enhanced phosphorus removal (CEPR) sludge during anaerobic fermentation were systematically investigated. The results revealed that the effective mobilization of P bound to Fe (Fe–P) by Na2S dominated the massive P release from the CEPR sludge, while the organic P (OP) release was not significantly enhanced during anaerobic fermentation. Due to the rapid reaction of Na2S with Fe–P and the prevention of Fe(II)–P precipitation by excess S2−, the Fe–P was decreased by 9.7%, 15.2% and 24.9% at S:Fe molar ratios of 0.3, 0.5 and 1, respectively. After anaerobic fermentation, the released P mainly existed as soluble phosphate (SP), P bound to Ca (Ca–P) and P bound to Al (Al–P). The nitrogen and P contents in the fermentation supernatant significantly increased with higher S:Fe ratios, facilitating the efficient recovery of P as high-purity struvite. However, the increased Na2S dosage deteriorated the sludge dewaterability because of the dissolution of hydrophilic extracellular polymeric substances and the looser secondary structure of proteins. Comprehensively considering the P recovery, sludge dewaterability and economic cost, the optimal Na2S dosage was determined at the S:Fe ratio of 0.3. These findings provide novel insights into the role of Na2S in P recovery as struvite from CEPR sludge.

Transdermal Hydrogen Sulfide Delivery Enabled by Open-Metal-Site Metal-Organic Frameworks.

Hydrogen sulfide (H2S) is an endogenously produced gasotransmitter involved in many physiological processes that are integral to proper cellular functioning. Due to its profound anti-inflammatory and antioxidant properties, H2S plays important roles in preventing inflammatory skin disorders and improving wound healing. Transdermal H2S delivery is a therapeutically viable option for the management of such disorders. However, current small-molecule H2S donors are not optimally suited for transdermal delivery and typically generate electrophilic byproducts that may lead to undesired toxicity. Here, we demonstrate that H2S release from metal-organic frameworks (MOFs) bearing coordinatively unsaturated metal centers is a promising alternative for controlled transdermal delivery of H2S. Gas sorption measurements and powder X-ray diffraction (PXRD) studies of 11 MOFs support that the Mg-based framework Mg2(dobdc) (dobdc4- = 2,5-dioxidobenzene-1,4-dicarboxylate) is uniquely well-suited for transdermal H2S delivery due to its strong yet reversible binding of H2S, high capacity (14.7 mmol/g at 1 bar and 25 °C), and lack of toxicity. In addition, Rietveld refinement of synchrotron PXRD data from H2S-dosed Mg2(dobdc) supports that the high H2S capacity of this framework arises due to the presence of three distinct binding sites. Last, we demonstrate that transdermal delivery of H2S from Mg2(dobdc) is sustained over a 24 h period through porcine skin. Not only is this significantly longer than sodium sulfide but this represents the first example of controlled transdermal delivery of pure H2S gas. Overall, H2S-loaded Mg2(dobdc) is an easily accessible, solid-state source of H2S, enabling safe storage and transdermal delivery of this therapeutically relevant gas.

Economic production of eco-friendly dehairing keratinase and antioxidant feather hydrolyzate using Bacillus halotolerans

AbstractFeather is a high recalcitrance keratin-based biomass, and keratin-degrading microorganisms have been seen as beneficial tools for its biodegradation and production of valuable products with biomedical and industrial applications. In the current study, the isolated keratinolytic bacteria was identified on the base of its 16 S rDNA sequencing data as Bacillus halotolerans, and its efficiency in the hydrolysis of feather with the preservation of most of its amino acid constituent was estimated by high-performance liquid chromatography Pico-Tag (HPLC PICO-TAG) method. The produced hydrolysate possessed antioxidant activity of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity of 52.3 ± 5.6 mmole TE/g without possessing any cytotoxicity to human normal skin fibroplast cell line BJ-1 estimated by MTT assay. Moreover, the isolated strain was capable for producing keratinase under submerged fermentation of feather that was optimized by combining single-variable-at-a-time optimization with the application of statistical designs (Plackett-Burman and Box-Behnken). The optimum keratinase activity was 140.83 U/mL that was enhanced by 3.2-fold of the estimated initial activity, and the purified enzyme possessed optimum activity at pH 9.5 and 70 °C with a half-life of 69.3 min. Finally, the applicability of the purified enzyme in the dehairing of bovine hide was examined in comparison to sodium sulfide (Na2S) and lime (Ca(OH)2) conventional method. The results estimated the efficiency of the examined bio-treatment process, it achieved complete dehairing after 2 h with a good skin quality as manifested by scanning electron microscope (SEM). In addition, a significant reduction of the pollution load parameters was estimated.

Selective Recovery of Tin from Electronic Waste Materials Completed with Carbothermic Reduction of Tin (IV) Oxide with Sodium Sulfite

A new approach for the thermal reduction of tin dioxide (SnO2) in the carbon/sodium sulfite (Na2SO3) system is demonstrated. The process of tin smelting was experimentally optimized by adjusting the smelting temperature and amounts of the chemical components used for the thermal reduction of SnO2. The numbers obtained are consistent with the thermodynamic characteristics of the system and molar fractions of reactants derived from the proposed mechanism of the SnO2 thermal reduction process. They reveal that the maximum yield of tin is obtained if masses of C, Na2SO3 and SnO2 are approximately in the ratio 1:2:3 and the temperature is set to 1050 °C. The key role in the suggested mechanism is the thermal decomposition of Na2SO3. It was deduced from the available experimental data that the produced sulfur dioxide undergoes carbothermic reduction to carbonyl sulfide—an intermediate product involved in the bulk reduction of SnO2. Replacing sodium sulfite with sodium sulfate, sodium sulfide and even elemental sulfur practically terminated the production of metallic tin. The kinetic analysis was focused on the determination of the reaction orders for the two crucial reactants involved in the smelting process.

Therapeutic use of biologically produced sulfur nanoparticles from Allium fistulosum against antibiotic-resistant foodborne pathogens

Abstract. Saddiqua A, Ullah S, Khan MS, Rehman S, Abubakar AA, Safdar K, Ali S, Javaria S, Kanwal A, Batool SN, Bhatti F, Sucipto TH, Ansori ANM. 2024. Therapeutic use of biologically produced sulfur nanoparticles from Allium fistulosum against antibiotic-resistant foodborne pathogens. Biodiversitas 25: 2348-2354. Food spoilage is a significant issue since foodborne illnesses affect millionsworldwide. The main root cause of food spoilage is the presence of microbes, some of which show resistance to commercially available antibiotic drugs. Therefore, it is essential to search for fresh and effective antibacterial medications. Nanotechnology can give solutions to fight against foodborne pathogens. Sulfur nanoparticles show many beneficial and effective results as antimicrobial agents. The aim of this study was to evaluate the efficacy of biologically synthesized sulfur nanoparticles from Allium fistulosum to inhibit antibiotic-resistant foodborne pathogens. The green synthesis of sulfur nanoparticles was done by combining plant leaf extract with sodium sulfide. This study used the plant Allium fistulosum to make sulfur nanoparticles. The characterization of SNPs was done through a scanning electron microscope, UV spectrophotometer, fourier transform infrared spectrometer, and nanoparticle tracking analysis. Then, the antimicrobial properties of the bioengineered sulfur-based nanoparticles against foodborne pathogens were checked alone and in combination with market-available antibacterial agents. Aspergillus flavus and Salmonella typhi were among the foodborne pathogens against which SNPs' in-vitro antibacterial activity was tested. Sulfur nanoparticles from Allium fistulosum had 291 nm absorption spectra showing to be almost 100 nm in size and had a spherical shape. The strongest antibacterial efficacy against S. typhi was observed by SNPs (24 mm). Synergistic antibacterial action was seen when nanoparticles were combined with antibiotics of commercial importance. A noticeable antifungal effect against A. flavus was observed by combining SNPs with amphotericin B. The findings of in vitro studies prove that novely designed sulfur nanoparticle have profound impacts on microorganisms. It was also observed that the effect of antibiotics like ampicillin and amphotericin B was enhanced when coupled with nanoparticles.

AlxGa1–xAs(100) (x ∼ 0.3) surfaces treated with aqueous sodium sulfide solution: Chemistry and electronic structure

Chemical composition and electronic structure of the native-oxide-covered AlxGa1–xAs(100) (x ∼ 0.3) surfaces were investigated by x-ray photoelectron spectroscopy and photoluminescence before and after treatment at room temperature with a concentrated aqueous solution of sodium sulfide in order to get inside into mechanism of sulfide solution interaction with aluminum-containing III–V alloys. Even short treatment of the n-AlGaAs(100) surface leads to the removal of the most of the native oxide layer so that the surface is covered with a thin layer of residual aluminum and gallium oxides with a thickness of approximately 1 ML, which can be formed during air exposure after termination of the chemical treatment. Longer treatment of the n-AlGaAs(100) surface does not further reduce the amount of residual aluminum and gallium oxides. The etching of native oxide layer on the p-AlGaAs(100) surface proceeds slower and the lowest amount of residual aluminum and gallium oxides is achieved after etching for 12 min. At the same time sulfur is hardly adsorbed at the AlGaAs(100) surfaces after interaction with the solution. It is found that the lower the amount of residual aluminum and gallium oxides on n- and p-AlGaAs(100) surfaces, the higher is the photoluminescence intensity. The band bending on the native-oxide-covered n- and p-AlGaAs(100) surfaces is about 0.85 and 0.5 eV, respectively, while the ionization energy is nearly the same for both surfaces. Treatment of n- and p-AlGaAs(100) surfaces with an aqueous sodium sulfide solution causes simultaneous decrease in their ionization energy.

Shape-controlled electro-synthesis of pyrrhotite

Recently, iron sulfide nanomaterials have drawn increased interest, due to their novel properties and extensive applications depending on their structure. To date, various methods have been employed for the synthesis of iron sulfide nanostructures with different shapes and morphologies. The synthesis method of iron sulfide nanomaterial is a challenge, as a small variation in sulfur content can lead to formation of different phases of iron sulfide. In this study, iron sulfide nanostructures were synthesized using our fast, simple, efficient, economical and environmentally friendly method in an electrochemical cell containing two iron sheets as electrodes in an aqueous solution of sodium sulfide. This method, with many advantages such as low-toxicity, low cost and easy handling, helps to control the properties of the products through the synthesis by tuning the growth conditions. Here, the influence of applied voltage ranging from 5 V to 25 V and annealing temperatures of 200 °C and 800 °C on the structure and magnetic properties of the products were studied. The samples were analyzed by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). XRD patterns confirmed the formation of monoclinic and hexagonal pyrrhotite at 200 °C and 800 °C, respectively. Based on SEM images, pyrrhotite in different shapes, such as quasi-spherical, feathers, sheets and flower-like structures, are formed depending on the applied voltage and annealing temperature. According to VSM results, all samples annealed at 200 °C are magnetically soft with only a little hysteresis, but the magnetization increases from 2.3 emu/g to 10.1 emu/g when applied voltage varies from 5 V to 25 V. All samples annealed at 800 °C exhibit an antiferromagnetic behavior. With increasing the applied voltage, the value of remanence magnetization and coercivity increases up to ∼2000 Oe and ∼0.14 emu/g, respectively.

‘Off–On’ determination of lead (Pb2+) and fluoride (F−) ion in fish and wastewater samples using N, S co-doped carbon quantum dots (N, S-CQDs)

Lead is a global priority pollutant. Its presence in aquatic systems is harmful to the human health. Fluoride is essential to the human body, especially in dental health. However, excess fluoride in the body can lead to serious health concerns. Therefore, a simple approach to monitoring lead and fluoride in environmental samples is paramount. In this study, we synthesized N and S co-doped carbon quantum dots under the hydrothermal method by employing citric acid, glutamine, and sodium sulphide (Na2S) as precursors. Characterization of the developed nanosensor was carried out using Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) spectrophotometer, ultraviolet–visible spectroscopy (UV–Vis), and X-ray diffraction (XRD). The as-prepared nanosensor is spherical with an average particle diameter of 3.45 ± 0.86 nm and emits light in the green region of the spectrum. This material was employed as an ‘on–off’ and ‘off–on’ fluorescent sensor to determine Pb2+ and F− rapidly and selectively. The fluorescence was quenched (turned off) in the presence of Pb2+ because of the strong interaction between Pb2+ ions and the surface functional groups of the as-synthesized material. Subsequently, the quenched fluorescence of the N, S-CQDs + Pb2+ system was restored (turned on) upon the introduction of F− ions, owing to the formation of ionic bonds between Pb2+ and F−. The N S-CQDs were selective towards Pb2+. At the same time, the N, S-CQDs + Pb2+ system exhibited selectivity towards F− ions amidst other ions with low detection limits (LODs) of 13.35 nM and 43.17 nM for Pb2+ and F−, respectively. The dynamic quenching mechanism was suggested based on the absorption spectra and lifetime results. Satisfied recoveries of 89.30–116.40% for Pb2+ and 90.22–115.05% for F- (RSD < 5) were obtained in practical samples of wastewater and fish. We believe that the as-synthesized N S-CQDs can effectively serve as reliable, accurate, and swift nanosensor for detecting Pb2+ and F− in environmental samples.

Effect of porous media heterogeneity and FeS re-generation for multiple cycles on arsenic immobilization under in-situ conditions

Arsenic (As) contamination in groundwater is a well-established concern. Several studies have explored the possibility of immobilizing arsenite [As (III)] in-situ within the aquifer. Recent studies show a uniform distribution of ferrous sulfate (FeS) synthesized within homogenous porous media and demonstrated promising performance in immobilizing As(III). Upscaling from bench-scale to field-scale systems involves the integration of physical and chemical heterogeneities. Thus, the distribution of reducing agent (i.e., FeS), subsequent capturing of As(III) in the upscaled heterogeneous porous media system is a complex and uncertain phenomenon. Therefore, this study focuses on assessing the performance of FeS when synthesized for multiple cycles under constant flow and constant head conditions for immobilization of As(III) through a heterogeneous porous media system. A 3-D heterogenous porous media system is first simulated using a sequential indicator simulator model (SISIM). Then, the same heterogeneous media is prepared in the laboratory by packing three different-sized sand within a 3-D tank (0.67 m × 0.40 m × 0.40 m) which is subdivided into a total of 150 grids (0.096 m × 0.08 m × 0.08 m). FeS is synthesized in-situ by sequential injection of sodium sulfide (Na2S) and ferrous sulfate (FeSO4‧6H2O), as detailed in the previous study. The outcome of the study suggests that flow within the model subsurface porous media is non-uniform and follows an inter-connected preferential flow path. The progression of in-situ synthesized FeS is faster in the areas of higher hydraulic conductivity. The immobilization of As (88%) is promising by FeS synthesized within heterogeneous porous media. An overall reduction of porosity (7.7%) and hydraulic conductivity (68.3%) are observed, which is more predominant along the preferential flow path where deposition of FeS is significantly higher. To maintain constant flow rate, 60% increase in head difference is required. Whereas the flow rate decreases by 47.2% when constant head condition is adopted. Overall, the newly synthesized FeS shows promising performance in immobilizing As(III) within heterogeneous model subsurface porous media; however, there might be some possibility of pore-clogging and bypassing of flow due to deposition and subsequent retention of As, which may impact the As removal efficiency in the longer run.

Feasibility of stabilizing Cd, Pb, and Ni in MSWI fly ash using leachate as an alternative stabilizer

For the synergistic disposal of municipal solid waste incineration (MSWI) fly ash and leachate, MSWI fly ash was stabilized using leachate, sodium sulfide (Na2S), and sodium diethyldithiocarbamate (DDTC) separately or simultaneously. Results show that the leaching concentration of Cd, Ni, and Pb can be reduced when leachate is used alone but exceeds the landfill admission contents. The leaching concentration of heavy metals were lower than the threshold of the pollution control standard of Chinese garbage landfill (GB 16889-2008) after curing for 14d when DDTC was beyond 1.5%, and Na2S more than 10% except for Pb. The results of orthogonal experiment showed that the lowest leaching concentration was got at 5-fold dilution of leachate, 3% Na2S and 0.8% DDTC, and DDTC was the most influential factor. The leachate can be utilized as a partial stabilizer for stabilization of fly ash. After chemical stabilization, the crystal structure of fly ash changed little, and the surface was densified. The analysis of two-dimensional correlation spectroscopy results showed that the different order between the major function groups of fly ash and stabilizers was got, may be related to chelation, chemical reactions, and precipitation.

Sulfidation of Iron - Based Nanomaterial as Catalyst for Water Splitting Using Hydrothermal

Consumption of fossil fuels causes greenhouse effect and global warming, hence the need for renewable energy sources that are environmentally friendly. Hydrogen is one of the abundant elements on earth. Hydrogen refers to a clean and renewable energy source, hydrogen can be a good choice to reduce greenhouse gas emissions. One way to produce hydrogen is by electrochemical water splitting. This study aims to determine the characterization of iron-based nanomaterials (iron sulfide - iron hydroxide) as a water splitting catalyst in general. Iron sulfide synthesis was carried out using hydrothermal sulfidation method for 6 hours at 80 oC with nickel foam as substrate. Synthesis of iron sulfide varying the concentration of sodium sulfide nonahydrate (0.0125 M, 0.025 M, 0.05 M and 0.1 M) produced brownish yellow to blackish grey colored samples. Characterization results using XRD showed that iron sulfide peaks were detected at higher concentrations of sodium sulfide nonahydrate. Based on the results of analyzing iron hydroxide using SEM, it is known that the sample is in the form of nano walls and on iron sulfide, it is known that the sample is in the form of nanoscale particles. Based on electrochemical measurement results, iron hydroxide can be a good catalyst for hydrogen evolution reaction (HER) compared with commercial Pt/C. The overpotential of iron hydroxide is smaller than Pt/C, which is only 15 mV at a current density 10 mA/cm2 and iron sulfide can be a good catalyst for oxygen evolution reaction (OER) with electrocatalytic measurement results close to commercial RuO2. This is indicated by the small overpotential (260 mV at current densisty 10 mA/cm2 and small tafel slope (51 mV/dec).

Detection and evaluation of susceptibility to antibiotics in non-hydrogen sulfide-producing antibiotic-resistant soil microbe: Pseudomonas guariconensis.

Antimicrobial resistance in bacteria is a global threat that can make antibacterial treatments ineffective. One well-known method of antibiotic resistance and a common defensive mechanism in many harmful bacteria is the synthesis of endogenous hydrogen sulfide (H2S) in bacteria. In this study, soil bacteria were screened using the lead acetate agar test and the triple sugar iron test to determine that they were non-endogenous H2S producers. This was further validated by full genome analysis of the identified organism against the gene sequences of H2S-producing genes. Antibacterial resistance of the bacteria was phenotypically analyzed using the Kirby-Bauer disk diffusion method. Then, the effect of exogenous H2S on the antibiotic-resistant bacteria was checked in sodium sulfide, leading to antibiotic re-sensitization.

Fabricating of multi-interfacial charge transfer paths in the novel noble-metal-free Ni2P/ZnS/g-C3N4 ternary nanocomposite for enhanced charge separation and transfer for photocatalytic H2 generation

This work reports the development of a novel Ni₂P/ZnS/C₃N₄ ternary nanocomposite photocatalyst for efficient hydrogen (H₂) production. The nanocomposite was synthesized using a facile approach combining hydrothermal synthesis, ball milling, and wet impregnation methods then characterized using various techniques. Photocatalytic H₂ generation was evaluated under simulated solar irradiation with sodium sulfite (Na₂SO₃)/sodium sulfide (Na₂S) as sacrificial reagents. The optimized 3NP/ZnS-8CN (3% Ni2P/ZnS/8% C3N4) catalyst displayed an exceptional H₂ generation rate of 3991 µmol h⁻¹ g⁻¹, exceeding both pristine g-C3N4 (by 10.2 times) and 3% Ni2P/ZnS (by 1.2 times). This represents the highest reported rate of H₂ evolution for a graphitic carbon nitride (g-C3N4) based ternary nanocomposite under simulated solar radiation. Furthermore, the 3NP/ZnS-8CN photocatalyst exhibited good stability over four reaction cycles. This study provides valuable insights for designing efficient noble metal-free g-C3N4-based photocatalysts, which can significantly contribute to the transition to solar-driven hydrogen generation. The results of this study suggest that the synthesized composite materials hold significant promise for the advancement of new energy technologies.

Separation of V(Ⅴ) and Cr(Ⅵ) from vanadium-containing solutions based on E-pH diagrams of V-Cr-S-H2O system

The extremely similar physicochemical properties of vanadium and chromium lead to the difficulty in separating from each other. In this study, a novel hydrometallurgical process was devised to selectively precipitate chromium from vanadium-containing solutions, facilitating the efficient separation of V(V) and Cr(VI) while enabling the recovery of both vanadium and chromium species. The speciation of vanadium and chromium in solutions was investigated through the construction of E-pH diagrams for V-Cr-S-H2O system at 298 K, 363 K, and 453 K. The results revealed that under conditions of pH approximately 12 and temperature 363 K, the reduction potential of SO42-/S2- was found to lie between that of CrO42-/Cr(OH)3 and VO43-/V2O3. This suggests that selective reduction of Cr(VI) could be achieved using S2- as reducing agent. In order to validate the theoretical findings, single-factor experiments were conducted on a laboratory scale. The effects of various parameters including initial pH, sodium sulfide dosage, reaction time, temperature, and initial concentration of vanadium-containing solutions on the chromium precipitation ratio and vanadium loss ratio were investigated. The experimental outcomes showed that the chromium precipitation ratio reached 99.8 % while the vanadium loss rate was only 3.5 % when the experiment was conducted at the optimal conditions: the initial pH was set to 12, sodium sulfide dosage was 2.0 times of the theoretical dosage, reaction time was 60 min and the temperature was 363 K. Then, the chromium concentration in the solution decreased from 2407 mg/L to 3.3 mg/L. Ultimately, V2O5 with a purity of 99.0 % and Cr2O3 with a purity of 97.2 % were successfully obtained.

PRECIPITATION OF ARSENIC FROM THERMAL WATER

The presented scientific research reveals the results of experiments on the precipitation of arsenic in the form of sulfide (As2S3) from the Daridag thermal water using sodium sulfide as a reagent. The main factors impacting the precipitation of the As2S3 compound were determined: the amount of precipitant (Na2S), the ratio of solid and liquid phases (S:L), pH of the initial solution, precipitation time and temperature, also optimal parameters were obtained. According to the results obtained, the yield during precipitation of arsenic tri-sulfide from from thermal water under certain temperature conditions (t=30-450С, pH=1-2; S:L - 1:1000; = 30-50 min.) were 99.6 %. The properties of the samples were studied by physicochemical research methods (X-Ray, SEM/EDS). X-ray phase analysis showed that the sediment sample obtained under these conditions is X-ray amorphous. The composition and morphology of the obtained sample was confirmed by scanning electron microscopy and spectroscopy (SEM/EDS)

Sulfide mediated zero valent iron for enhanced nickel removal under neutral condition: Reaction kinetic, mechanism, and stability

The application of sodium sulfide (Na2S) as sulfidation reagent of zero valent iron (ZVI) has been well studied, however, the effect of Na2S existence on ZVI reactivity remains obscure. In this study, Ni(II) removal performance, mechanism, and stability by ZVI with Na2S were investigated at neutral condition. The results showed that Ni(II) removal sharply increased from < 5–100% by ZVI within 60 min with the increase of Na2S concentration, but the subsequent Ni(II) release occurred. In addition to the slight Ni(II) removal by Na2S in aqueous phase, Ni(II) was mainly removed by the adsorption and reduction by Na2S mediated ZVI system. Characterization analysis indicated that Na2S could lead to the severe Fe0 corrosion and the main corrosion product on ZVI was lepidocrocite, which played the dominant role for Ni(II) immobilization. Meanwhile, the formation of iron sulfides on ZVI surface would enhance Ni(II) reduction and partially transform the adsorbed Ni(II) to NiS. Moreover, the higher ionic strength could further enhance the initial Ni(II) removal rate but the stability became poor. Regardless of the additive methods, the Ni(II) removal significantly enhanced in the system of ZVI and Na2S combination. Overall, this work reveals the sulfide mediated Fe0 corrosion and provides a potential method for enhancing the reactivity of ZVI in the treatment of Ni(II) pollution.