Sulfuric Treatment Research Articles

Enhanced production of Fe(II) and Fe(0) by elemental sulfur modification on iron oxide to boost peroxymonosulfate activation for pollutants removal

Sulfidation treatment has been evidenced as an effective strategy in enhancing the catalytic ability of iron-based oxides. However, the proportion of highly reactive Fe(II) species remains to be low due to the use of weak reductive sulfur source. In this regard, this research found that the strongly reductive elemental sulfur treatment not only dramatically improved the content of Fe(II) in magnetic Fe3O4 (40.1–60.3 %), but also induced the generation of zero valent iron Fe(0) (16.95 %). Correspondingly, the SFe-2 exhibited the excellent performance in degrading biphenol A (BPA) with a removal rate of 98 % within 30 min via peroxymonosulfate activation, far outperforming the other iron oxides-activating PMS system modified by Na2S, Na2SO3, and Na2SO4. This enhanced catalytic behavior was attributed to the generation of FeSO4 and FeS2 after sulfuration. The catalytic cycle of Fe(0) → Fe(II) ⇄ Fe(III) contributed to PMS activation, while FeS2 as a semiconductor enhanced the electron transfer, as a result quickening the reduction of Fe(III) to Fe(II). Both SO4−, OH, O2−, 1O2, and FeIVO2+ were involved. In addition, the validity of K2Cr2O7 in evaluating electron-transfer regime, the applicability of methyl phenyl sulfoxide (PMSO) in assessing the Fe(IV)-oxo complex with 1O2-engaged system, and the homogeneous/heterogeneous catalysis were both investigated. This research highlights the feasibility of improving Fe(II) proportion and catalytic capacity of iron-based oxides via simple sulfur-vapor modification strategy.

An investigation of methods to enhance adhesion of conductive layer and dielectric substrate for additive manufacturing of electronics

Additive manufacturing of conductive layers on a dielectric substrate has garnered significant interest due to its promise to produce printed electronics efficiently and its capability to print on curved substrates. A considerable challenge encountered is the conductive layer’s potential peeling due to inadequate adhesion with the dielectric substrate, which compromises the durability and functionality of the electronics. This study strives to facilitate the binding force through dielectric substrate surface modification using concentrated sulfuric acid and ultraviolet (UV) laser treatment. First, polyetheretherketone (PEEK) and nanoparticle silver ink were employed as the studied material. Second, the surface treatment of PEEK substrates was conducted across six levels of sulfuric acid exposure time and eight levels of UV laser scanning velocity. Then, responses such as surface morphology, roughness, elemental composition, chemical bonding characteristics, water contact angle, and surface free energy (SFE) were assessed to understand the effects of these treatments. Finally, the nanoparticle silver ink layer was deposited on the PEEK surface, and the adhesion force measured using a pull-off adhesion tester. Results unveiled a binding force of 0.37 MPa on unmodified surface, which escalated to 1.99 MPa with sulfuric acid treatment and 2.21 MPa with UV laser treatment. Additionally, cross-approach treatment investigations revealed that application sequence significantly impacts results, increasing binding force to 2.77 MPa. The analysis further delves into the influence mechanism of the surface modification on the binding force, elucidating that UV laser and sulfuric acid surface treatment methods hold substantial promise for enhancing the binding force between heterogeneous materials in the additive manufacturing of electronics.

Effect of surface treatment and resin cement type on the bond strength of polyetheretherketone to lithium disilicate ceramic

BackgroundThis study aims to evaluate the effect of surface treatment and resin cement on the shear bond strength (SBS) and mode of failure of polyetheretherketone (PEEK) to lithium disilicate ceramic (LDC). This is suggested to study alternative veneering of PEEK frameworks with a ceramic material.Methodseighty discs were prepared from PEEK blank and from lithium disilicate ceramic. Samples were divided into four groups according to surface treatment: Group (A) air abraded with 110 μm Al2O3, Group (AP) air abrasion and primer application, Group (S) 98% sulfuric acid etching for 60 s, Group (SP) Sulfuric acid and primer. Each group was subdivided into two subgroups based on resin cement type used for bonding LDC:1) subgroup (L) self- adhesive resin cement and 2) subgroup (B) conventional resin cement (n = 10). Thermocycling was done for all samples. The bond strength was assessed using the shear bond strength test (SBS). Failure mode analysis was done at 50X magnification with a stereomicroscope. Samples were chosen from each group for scanning electron microscope (SEM). The three-way nested ANOVA followed by Tukey’s post hoc test were used for statistical analysis of results. Comparisons of effects were done utilizing one way ANOVA and (p < 0.05).ResultsThe highest mean of shear bond strength values was demonstrated in Group of air abrasion with primer application using conventional resin cement (APB) (12.21 ± 2.14 MPa). Sulfuric acid groups showed lower shear bond strength values and the majority failed in thermocycling especially when no primer was applied. The failure mode analysis showed that the predominant failure type was adhesive failure between cement and PEEK, while the remaining was mixed failure between cement and PEEK.ConclusionThe air abrasion followed by primer application and conventional resin cement used for bonding Lithium Disilicate to PEEK achieved the best bond strength. Primer application did not have an effect when self-adhesive resin cement was used in air-abraded groups. Priming step is mandatory whenever sulfuric acid etching surface treatment is utilized for PEEK.

Sulfur migration mechanism of pig manure in supercritical water: A combined experimental and DFT study

Pig manure (PM) is a high concentration organic waste rich in sulfur, and its biofuel contains various sulfur-containing pollutants, which reduces the safety of the products. Supercritical water (SCW) can dissolve most organic matter, which is a technology worthy of further study. In order to reduce sulfur pollution in the process of PM resource utilization and better control the conversion path of sulfur, it is necessary to explore the migration mechanism of sulfur in the whole PM-SCW gasification process. The experimental results indicated that H2S was the only gaseous product. Only inorganic compounds (S2-, S2O32- and SO42-) were detected in the liquid. Sulfur in the solid mainly included thiol/thioether, thiophene and sulfone. The influence of different reaction conditions (temperature, residence time, PM concentration and catalysts) on sulfur migration was studied in a batch reactor. It was worth noting that the catalysts had a significant effect on H2S absorption. The lowest H2S yield was 3.2 * 10−4 mol/kg and more than 70% of the sulfur was distributed in the liquid under the condition of addition of K2CO3. While, the RTH2110 fixed most of the sulfur of PM (the maximum value reached 50.94%) in the solid. Thus, adding the catalysts flexibly can choose composition of the products. Furthermore, six possible pathways of sulfur migration in the solid were designed and the kinetic parameters were calculated by density functional theory (DFT). The results provided a basis for controlling sulfur in PM. Subsequently, the sulfur migration pathways during PM-SCW gasification process were comprehensively summarized through the combination of experiment and DFT. It provided a method for sulfur treatment in PM, which had guiding significance for the realization of pollution-free treatment of PM.

Nanoneedles like FeP engineered on Ni-Foam as an effective catalyst towards overall alkaline freshwater, urea, and seawater splitting

The slow kinetics of electrochemical urea and water oxidation processes at electrode surfaces, which can be recognised as promising resources for pollution-free hydrogen energy production, motivate the scientific community to design and fabricate low-cost, high-efficiency electrocatalysts. Because the performance of electrocatalysts is dependent on their structural, morphological, and electronic properties, herein, the tuning of these properties of Fe3O4@Ni-Foam via phosphorylation and sulfurization, yielding iron phosphide (FeP@Ni-Foam) and iron sulphide (FeS@Ni-Foam), with nanoneedles (along with microstructures) and nanoflower-like morphologies, respectively, is investigated. Among all the prepared samples, FeP is found to be the most effective electrocatalyst for the oxygen evolution process (OER), the urea oxidation reaction (UOR), and seawater electrolysis. The overpotentials observed for OER, UOR, and seawater splitting are significantly reduced when using FeP as compared to other materials, with values of 207 mV, 133 mV, and 287.1 mV, respectively, at a current density of 10 mA/cm2. The enhanced catalytic activity of FeP over FeS and Fe3O4 is attributed to morphological changes, improved electronic conductivity, and exceptional endurance. The theoretical studies reveal that FeP has a better density of states over the fermi level than FeS and Fe3O4, lowering the energy barriers for the OER and UOR processes and demonstrating significant catalytic activity towards these processes. This work demonstrates that phosphorylation and sulfurization treatments can alter morphologies and electrical characteristics, hence improving the catalytic activity of the materials.

Classification and Identification of Pinecone Mulching in Blueberry Cultivation Based on Crop Leaf Characteristics and Hyperspectral Data

While crushed pinecone mulch holds promise as a beneficial material for blueberry cultivation, research on its effectiveness remains limited. Crop leaf characteristics can serve as parameters for assessing mulching effects, although there are several limitations, including the need to analyze various distinct characteristics separately. The combination of hyperspectral data and machine learning techniques is expected to enable the selection of only the most important features among these characteristics. In this study, we investigated the impact of various mulching treatments utilizing pine tree byproducts, including crushed pinecones. Mulching variations included non-mulching (NM), crushed pinecones (PCs), a mixture of crushed pinecones and sulfur (PCS), pine needles (PNs), and sulfur treatment (S). Conventional methods were employed to measure leaf growth (length and width) and physiological characteristics (chlorophyll content, chlorophyll fluorescence, and stomatal conductance). Hyperspectral reflectance was also measured, and classification models using Partial Least Squares Discriminant Analysis (PLS-DA) and eXtreme Gradient Boosting (XGBoost) were developed for crop characteristics, vegetation indices (VIs), visible and near-infrared (VNIR), and short-wave infrared (SWIR). The results showed that using crushed pinecones as the sole mulching material for blueberries, without sulfur treatment, had a positive impact on blueberry growth. The PC treatment exhibited a dual effect on plant growth by lowering the soil pH to 5.89 and maintaining soil moisture within the range of 26.33–35.20%. We observed distinct differences in soil inorganic nutrient content, with higher concentrations of organic matter, total nitrogen, and available P2O5 and K+, which positively influenced blueberry growth. Mulching treatments demonstrated superior physiological characteristics, with two classification models identifying stomatal conductance (gs) as a key parameter influencing treatment classification (VIP scores &gt; 1 rank: 3, variable score rank: 1). The photochemical reflectance index (PRI) emerged as a major parameter among VIs, showing potential for measuring water stress (VIP scores &gt; 1 rank: 2, variable score rank: 1). In the SWIR PLS-DA model, wavelength peaks were mainly observed in the O-H overtone (1410 nm, 1450 nm, 1930 nm, 1940 nm, and 2100 nm). Overall, crushed pinecones were found to positively impact the initial growth of blueberries by enhancing water status (plant respiration).

Wettable sulphur application for Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) management: laboratory and semi-field experiments.

The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is a significant threat to crop production. Alternatives to synthetic pesticides are needed for its management. Here we investigated the effect of sulphur on H. halys. Experiments were performed to evaluate both mortality and deterrence/repellence of H. halys following sulphur treatments in laboratory and semi-field conditions. Brown marmorated stink bug mortality was not influenced by sulphur applications. However, in two-choice experiments in insect cages and olfactometer, more H. halys adults moved toward the untreated control rather than the sulphur-treated food sources, with a high effect as the concentration increased. A semi-field experiment using potted apple plants confirmed the results observed in the laboratory, showing a deterrent and/or repellent effect of sulphur-based products on H. halys. Sulphur applications were associated with a deterrent/repellent effect on the brown marmorated stink bug. The use of sulphur-based products could represent a promising tool for Integrated Pest Management strategies against H. halys in fruit crops. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Surface constructing FeOOH-decorated hollow cubic NixSy electrocatalyst for efficient oxygen evolution reaction

The development of low-cost, earth-abundant electrocatalysts for oxygen evolution reactions (OER) is of vital significance to alleviate the energy shortage, but it still faces challenges due to the sluggish kinetics of the four-electron transfer process. We synthesized and characterized a series of FeOOH-decorated hollow-cubic NixSy electrocatalysts (NixSy/FeOOH) with the morphology maintained after the sulfuration treatment and Fe dip-coating. The stoichiometric ratios, heating temperatures, and Fe inputs can affect the morphology and catalytic activity. The as-prepared optimum NixSy/FeOOH electrocatalyst exhibited the lowest OER overpotential (250 mV) at 20 mA cm−2 and Tafel slope (53.07 mV dec−1) in 1.0 M KOH and maintained long-term stability and good durability. The outstanding OER performance is likely attributed to the synergistic interaction and electron transfer between FeOOH and NixSy species. Therefore, the present work provides a promising route for the design and synthesis of stable and efficient OER electrocatalysts.

Short-Chain Sulfur Confined into Nitrogen-Doped Hollow Carbon Nanospheres for High-Capacity Potassium Storage.

Carbon-based materials are one of the ideal negative electrode materials for potassium ion batteries. However, the limited active sites and sluggish diffusion ion kinetics still hinder its commercialization process. To address these problems, we design a novel carbon composite anode, by confining highly reactive short-chain sulfur molecules into nitrogen-doped hollow carbon nanospheres (termed SHC-450). The formation process involves the controlled synthesis of hollow polyaniline (PANI) nanospheres as precursors via an Ostwald ripening mechanism and subsequent sulfuration treatment. The high content of constrained short-chain sulfur molecules (20.94 wt%) and considerable N (7.15 wt%) ensure sufficient active sites for K+ storage in SHC-450. Accordingly, the SHC-450 electrode exhibits a high reversible capacity of 472.05 mAh g-1 at 0.1 A g-1 and good rate capability (172 mAh g-1 at 2 A g-1). Thermogravimetric analysis shows that SHC-450 has impressive thermal stability to withstand a high temperature of up to 640 °C. Ex situ spectroscopic characterizations reveal that the short-chain sulfur provides high capacity through reversible formation of K2S. Moreover, its special hollow structure not only provides ample space for highly active short-chain sulfur reactants but also effectively mitigates volume expansion during the sulfur conversion process. This work offers new perspectives on enhanced K+ storage performance from an interesting anode design and the space-limited domain principle.

The Effect of Acid Treatment Time, Particle Size, and Synthesis Method on the Physical and Mechanical Properties of Dental Materials Produced from Flue Gas Desulfurization (FGD) Gypsum

FGD gypsum, a byproduct of coal-fired power plants, is readily available and relatively inexpensive, which makes it an ideal material for a variety of applications. This study considered the use of FGD gypsum as a substitute for natural gypsum in dental materials. The goal of this research was to investigate how acid treatment time, particle size, and the synthesis method impact the physical and mechanical properties of dental materials to be used in a dental study model for training in dental sciences, and for casting a gypsum model after the removal of the impression material from the patient's mouth. The study used various sulfuric acid treatment times (15, 30, and 60 min), particle sizes (less than 0.1 mm, 0.1-0.35 mm, and 0.4-0.45 mm), and synthesis methods (Method A for dental plaster and Method B for dental stone). From the results, an acid treatment time of 15 min was sufficient for removing impurities from the FGD gypsum while enhancing the compressive strength. The smaller particles provided higher compressive strength than the larger particles. FGD gypsum became lighter in color when treated with sulfuric acid, and the crystal structure had a rough and porous surface. The synthesis methods had a significant influence on the physical properties of dental gypsum. The increased alpha calcium sulfate hemihydrate (α-HH) phase content resulted in improved compressive strength. The gypsum synthesized using Method B exhibited the highest compressive strength due to the presence of the α-HH phase of 65.9%. While gypsum synthesized using Method A contained a α-HH phase of 58.9%. For further study, once the suitable conditions for synthesizing gypsum that meet the compressive strength requirements of the ISO standard for dental materials are achieved, there will be ongoing research and development to improve various properties. Additionally, practical applications will be considered, such as using it in conjunction with modern techniques such as 3D printing instead of traditional die-casting methods.

Schottky contacts on sulfurized silicon carbide (4H-SiC) surface

In this Letter, the effect of a sulfurization treatment carried out at 800 °C on silicon carbide (4H-SiC) surface was studied by detailed chemical, morphological, and electrical analyses. In particular, x-ray photoelectron spectroscopy confirmed sulfur (S) incorporation in the 4H-SiC surface at 800 °C, while atomic force microscopy showed that 4H-SiC surface topography is not affected by this process. Notably, an increase in the 4H-SiC electron affinity was revealed by Kelvin Probe Force Microscopy in the sulfurized sample with respect to the untreated surface. The electrical characterization of Ni/4H-SiC Schottky contacts fabricated on sulfurized 4H-SiC surfaces revealed a significant reduction (∼0.3 eV) and a narrower distribution of the average Schottky barrier height with respect to the reference untreated sample. This effect was explained in terms of a Fermi level pinning effect induced by surface S incorporation.

Obtaining of silicon dioxide from abrasive wastes

In the production of abrasive materials from metallurgical slags, fine waste with a size of less than 40 microns is produced, which contains valuable components. Unlike slag, this waste does not need to be pulverized for processing, which greatly simplifies the process. However, without silica extraction, it is impractical to carry out waste treatment. The authors of the work considered the possibility of obtaining silicon dioxide from abrasive wastes of Rezh, Orsk and Kyshtym, containing up to 20,7 % of silicon, up to 31,7 % of iron and up to 0,7 % of the sum of nickel and copper. Sulfuric acid treatment of waste produced a solution containing magnesium and iron (II) sulfates and silicic acid. It was found that during processing of Orsk wastes the degree of components extraction is significantly lower in comparison with Rezh and Kyshtym wastes 24,5, 67,8 and 59,3, respectively. The obtained solution is used to produce silica powders by dehydrating it. The dried mixture is subjected to aqueous washing of metal sulfates. As a result, samples with high specific surface area in the range of 387,6 to 841,5 m2/g were obtained. The average pore size is 2,3–3 nm, which allows us to attribute these silicas to mesoporous silica. SiO2 content in the samples reaches up to 98 %. Samples of silicon dioxide from abrasive materials were compared with that obtained from metallurgical slag of Pechenganickel Combine and have similar parameters. The obtained insoluble leaching residue contains concentrate of non-ferrous metals and according to X-ray data it consists of calcium sulfate, so after separation of non-ferrous metals it can be used in construction industry.

Effect of Sulfuric Acid Corrosion on Flotation Performance of Calcite by Changing Surface Roughness.

Surface roughness is a crucial factor that affects the flotation performance of minerals. In this study, the effect of sulfuric acid corrosion on the surface roughness of calcite flotation was investigated through microflotation tests, scanning electron microscopy (SEM-EDS), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and contact angle analysis. Microflotation test results show that sulfuric acid treatment has a serious negative effect on the floatability of calcite. When the sulfuric acid dosage was 4 mL (3 mol/L), the flotation recovery of calcite was reduced to less than 19%. SEM-EDS and AFM results verified that the sulfuric acid treatment significantly changed the surface morphology of calcite, reduced the average surface roughness and surface area, and reduced the amount of active Ca2+ sites on the calcite surface. As characterized by FT-IR and contact angle analyses, the sulfuric acid treatment enhanced the hydrophilicity of the calcite surface and reduced the amount of sodium oleate adsorbed on the calcite surface. Consequently, sulfuric acid corrosion can reduce the average surface roughness of calcite and have a serious negative effect on the flotation performance of calcite.

Synthesis of WS2 Ultrathin Films by Magnetron Sputtering Followed by Sulfurization in a Confined Space

In the quest for advanced materials suitable for next-generation electronic and optoelectronic applications, tungsten disulfide (WS2) ultrathin films have emerged as promising candidates due to their unique properties. However, obtaining WS2 directly on the desired substrate, eliminating the need for transfer, which produces additional defects, poses many challenges. This paper aims to explore the synthesis of WS2 ultrathin films via physical vapor deposition (PVD) followed by sulfurization in a confined space, addressing the challenge of film formation for practical applications. Precursor layers of tungsten and WS2 were deposited by RF magnetron sputtering. Subsequent sulfurization treatments were conducted in a small, closed, graphite box to produce WS2 films. The physical and chemical properties of these precursor and sulfurized layers were thoroughly characterized using techniques such as X-ray reflectometry (XRR), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The findings reveal notable distinctions in film thickness, structural orientation, and chemical composition, attributable to the different precursor used. Particularly, the sulfurized layers from the tungsten precursor exhibited a preferred orientation of WS2 crystallites with their (00L) planes parallel to the substrate surface, along with a deviation from parallelism in a small angular range. This study highlights the necessity of precise control over deposition and sulfurization parameters to tailor the properties of WS2 films for specific technological applications.

Effect of Nitrogen and Sulphur Levels on Growth Attributes and Yield of Indian Mustard [Brassica juncea (L.) Czern &amp; Coss] in Vindhya Plateau Region of Madhya Pradesh, India

In the Rabi season of 2022, a field experiment was conducted in the Vindhya plateau region of Madhya Pradesh at the agricultural field of SAGE University Bhopal. The objective was to investigate the impact of nitrogen and sulfur nutrition on the growth and yield of Indian mustard (Brassica juncea L.). The experimental soil, characterized as sandy loam with a slightly alkaline pH, exhibited good drainage. Despite having a moderate amount of available phosphorus and potassium, the soil had low levels of organic carbon and nitrogen, with a low electrical conductivity of 1.65 dS/m (1:2, soil: water).&#x0D; The experiment comprised 27 nitrogen and sulfur treatment combinations in a split-plot design with three replications. The treatments included three nitrogen levels (100, 120, and 140 kg ha-1) and three sulfur levels (20, 40, and 60 kg ha-1). The mustard variety Giriraj was cultivated, and the study focused on evaluating the effects of these treatments on growth, yield, and nutrient uptake.&#x0D; Results indicated that various mustard crop attributes, such as plant height, number of green leaves-1, branches plant-1, siliqua plant-1, seeds siliqua-1, and 1000 seed weight, as well as yields (biological, seed, and oil yield), exhibited significant increases with rising nitrogen levels from 100 kg N ha-1 to 140 kg N ha-1. Similarly, applying 60 kg S ha-1 resulted in maximum plant height, number of green leaves, dry matter production, oil yield, and the highest net returns among sulfur levels.&#x0D; The combination of 140 kg N ha-1 and 60 kg S ha-1 proved to be cost-effective, leading to increased yields, net returns, and a higher B:C ratio compared to other nitrogen and sulfur levels. Therefore, this study recommends the application of 60 kg S ha-1 and 140 kg N ha-1 for enhancing mustard crop yields, net returns, and the benefit-cost ratio.

Comparative study of fresh phosphogypsum treatment by sulfuric acid and neutralization with NaOH and CO2

AbstractThe newly formed, fresh phosphogypsum (PG) at the filter cake of the Dinh Vu Diamoni photphate DAP fertilizer factory was studied and treated with dilute sulfuric acid. The impurities were removed by sulfuric acid treatment and the carbonatation by NaOH and CO2 to create calcium carbonate. The results showed that fresh PG at filter cake contained the P2O5 total of 1.38%, and the phosphorus pentoxides effectively were removed at 69.32%. The acid‐treated PG was neutralized by NaOH and CO2 aeration, creating CaCO3 in situ nano‐microparticles identified by scanning electron microscopy (SEM) images and CaCO3 intensity by X‐ray diffraction (XRD). In this study, the cement mortar test, which used treated PG from both sulfuric treatment and NaOH neutralization within CO2 aeration, has better compressive strength properties and hydration supported by SEM images, XRD results, and thermogravimetric analysis.

Atmospheric leaching of Ni, Co, Cu, and Zn from sulfide tailings using various oxidants

The growing demand for nickel and cobalt increases the interest in extracting metals from secondary sources, such as flotation tailings. A preferential strategy for the processing of the complex and/or low-grade secondary sources may be material integration into existing primary processes. In this research, a robust sulfuric acid leaching treatment was studied for metal extraction from sulfidic flotation tailings (Ni 0.45 %, Co 0.80 %, Cu 0.20 %, Zn 0.58 %). The impact of leaching parameters on metals extraction was studied; oxygen gas (1–2 L/min), ferric ions (0.05–0.3 M), and hydrogen peroxide (0.5–0.8 M), temperature (30–90 °C), sulfuric acid concentration (0.2–2 M), and solid–liquid ratio (50–100 g/L). It was found that after 30-minutes 20.0 % of nickel, 5.6 % of cobalt, and 33.0 % of the main impurity iron were extracted using oxygen as oxidant. Increasing temperature and sulfuric acid concentration were shown to have a positive effect on extraction. Also, with the further addition of ferric ions, cobalt extraction could be slightly increased (from 6.2 % to 8.3 %) whereas both nickel and cobalt could be increased with hydrogen peroxide (nickel 22.9 %, cobalt 14.2 %). However, the use of H2O2 can be challenging due to its high environmental footprint as well as partial decomposition by ferric ions, increasing H2O2 consumption further. The results suggest that the mineralogy of the investigated tailings limited feasible metals extraction using atmospheric conditions up to ≈ 20 % for nickel and ≈ 10 % for cobalt, with nickel distributing stronger into non-refractory minerals while cobalt reported more to pyrite. For other base metals, zinc extraction from sphalerite was shown to be efficient (up to ≈ 90 %) whereas copper extraction was limited (up to ≈ 30 %). In future, such atmospheric sulfuric acid leaching may provide a robust recovery route for non-refractory minerals present in the tailings, while full valorization of sulfide tailings matrix will require higher intensity processing with technologies such as pressure oxidation (POX), concentrated chloride leaching, bioleaching, roasting-leaching or very fine milling of the raw material prior to atmospheric leaching.

Enhanced Adsorption Capacity of Methylene Blue Dye onto Kaolin through Acid Treatment: Batch Adsorption and Machine Learning Studies

Algerian kaolinite, sourced from Djebel Debbagh nuance 3 (DD3), was used as a low-cost adsorbent to remove methylene blue (MB) dye from water. Its adsorption capacity was enhanced through sulfuric acid treatment (treated-DD3). In response to the urgent demand for clean water, various technologies have been developed to address dye removal from wastewater. This study, specifically delving into the treatment of textile wastewater, examined the efficacy of treated-DD3 through adsorption processes. The acid treatment increased the surface area and pore volume of DD3. X-ray diffraction showed crystalline phases in both, with treated-DD3 having higher crystallinity. Fourier-transform infrared spectroscopy found no significant differences post-acid treatment. Scanning electron microscopy revealed DD3 had large, stacked particles with low surface area, while treated-DD3 had increased porosity and a smoother surface. Various parameters affecting MB adsorption were studied. The Langmuir and Freundlich models were used for isotherm parameters. Treated-DD3 exhibited a higher MB adsorption capacity (64.58 mg/g according to the Langmuir model) than DD3 (44.48 mg/g). Thermodynamic analysis indicated spontaneous and endothermic MB adsorption onto both DD3-BM and treated-DD3-BM systems under different pH conditions. Treated-DD3 effectively reduced chemical oxygen demand (from 304.056 mg/L to 34.44 mg/L) and biological oxygen demand (from 80 mg/L to 20 mg/L) in real textile wastewater. The adsorbent exhibited rapid removal and decolorization, surpassing 93% within the first 7 min of the experiment. The Gaussian process regression and particle swarm optimization (GPR–PSO) predicted MB adsorption capacity effectively (R = 0.9989, R2 = 0.9978, adj-R2 = 0.9978, RMSE = 1.1390, and MAE = 0.3926).

Nano‐Au‐decorated hierarchical porous cobalt sulfide derived from ZIF‐67 toward optimized oxygen evolution catalysis: Important roles of microstructures and electronic modulation

AbstractEnhancing both the number of active sites available and the intrinsic activity of Co‐based electrocatalysts simultaneously is a desirable goal. Herein, a ZIF‐67‐derived hierarchical porous cobalt sulfide decorated by Au nanoparticles (NPs) (denoted as HP‐Au@CoxSy@ZIF‐67) hybrid is synthesized by low‐temperature sulfuration treatment. The well‐defined macroporous–mesoporous–microporous structure is obtained based on the combination of polystyrene spheres, as‐formed CoxSy nanosheets, and ZIF‐67 frameworks. This novel three‐dimensional hierarchical structure significantly enlarges the three‐phase interfaces, accelerating the mass transfer and exposing the active centers for oxygen evolution reaction. The electronic structure of Co is modulated by Au through charge transfer, and a series of experiments, together with theoretical analysis, is performed to ascertain the electronic modulation of Co by Au. Meanwhile, HP‐Au@CoxSy@ZIF‐67 catalysts with different amounts of Au were synthesized, wherein Au and NaBH4 reductant result in an interesting “competition effect” to regulate the relative ratio of Co2+/Co3+, and moderate Au assists the electrochemical performance to reach the highest value. Consequently, the optimized HP‐Au@CoxSy@ZIF‐67 exhibits a low overpotential of 340 mV at 10 mA cm–2 and a Tafel slope of 42 mV dec–1 for OER in 0.1 M aqueous KOH, enabling efficient water splitting and Zn–air battery performance. The work here highlights the pivotal roles of both microstructural and electronic modulation in enhancing electrocatalytic activity and presents a feasible strategy for designing and optimizing advanced electrocatalysts.

Utilizing sulfuration of supercritical fluid treatment to improve sensitivity and humidity resistance of chip-type gas sensors

This research investigates a novel supercritical-fluid sulfuration (SCF-S) treatment used to enhance the sensitivity of SnO2-based chip-typed gas sensors and enable them to resist the influence of moisture during the alcohol detection. The fluid of supercritical state possesses helpful features, such as high permeability of gas and high solubility of water. The SCF-S process introduces the sulfuration penetrating the whole tin oxide membrane with sulfur bonding and thin film transformation. The surface morphology and the lattice structure have been confirmed by Scanning Electron Microscope (SEM) and X-ray diffraction analysis (XRD), respectively. To further verify the composition content after the novel SCF-S treatment, the qualitative and quantitative analyses are conducted, and both show the sulfur doping results. Moreover, different electronic properties are gained in the experiments where the concentration of alcohol and environment humidity vary. In order to understand the sensing reaction model after SCF treatment, response performance at different temperatures and the reliability of the reaction model are further investigated. From the present results, it is demonstrated that SCF-S process has a good potential in terms of the sensitive and selective detection of alcohol.