Acidic Environment Research Articles

Intrinsic Activity: A Critical Challenge of Alkaline Hydrogen Oxidation Reaction

AbstractAnion exchange membrane fuel cells (AEMFCs) are advantageous for reducing or even eliminating the dependency on platinum resources, as the alkaline environment allows the use of non‐precious metal catalysts for oxygen reduction reaction at the cathode. However, the intrinsic activity of hydrogen oxidation reaction (HOR) catalysts in alkaline environments is 2 to 4 orders of magnitude lower than in acidic environments, which becomes the major challenge for AEMFCs. This review examines the current developments in the intrinsic activity of alkaline HOR catalysts and systematically summarizes the hydrogen activation mechanism with a focus on potential influencing factors and enhancement strategies. Furthermore, it offers insights into the prospects for developing more efficient alkaline HOR catalysts.

ASIC1a regulates airway epithelial cell pyroptosis in acute lung injury by NLRP3-Caspase1-GSDMD pathway.

Acidosis is the most common complication that seriously affects the prognosis of acute respiratory distress syndrome (ARDS). Acid-sensitive ion channel 1a (ASIC1a) is activated in acidic environments to regulate inflammatory process. However, the role of ASIC1a in ARDS is unclear. In this study, we examined the expression of ASIC1a in airway epithelial cells in an acidic environment. We then investigated whether blocking ASIC1a could inhibit pyroptosis of airway epithelial cells and the molecular mechanism. In the mouse acute lung injury (ALI) model, we observed the changes of lung histopathology, arterial blood gas and pyroptosis related indexes after ASIC1a inhibition. Bronchoalveolar lavage fluid (BALF) from patients with ARDS were collected to explore the expression level of ASIC1a in ARDS patients. Inhibiting ASIC1a can reduce the airway epithelial cell pyroptosis induced by an extracellular acidic environment. ASIC1a can bind to PRKACA, and silencing ASIC1a and PRKACA can inhibit the occurrence of pyroptosis in airway epithelial cells. Compared with control group, arterial blood pH and PaO2 in ALI group were significantly reduced. The inflammation in the lungs is more intense, and the mRNA and protein of NLRP3, Caspase1 and GSDMD were increased, while ASIC1a specific blocker psalmotoxin-1 alleviated this phenomenon. The expression of ASIC1a in BALF of ARDS patients was significantly increased, especially in non-survival group. Acidic micro-environment can induce the increased expression of ASIC1a, and inhibition of ASIC1a can alleviate the inflammation and airway epithelial cell pyroptosis in ARDS. ASIC1a may be a new target for the treatment of ARDS.

Revitalizing sumatriptan: transforming expired medication into a potent solution for corrosion control in acidic environments

The concerns regarding pharmaceutical waste, particularly expired drugs have prompted the exploration of their alternative applications. This research highlights the potential of repurposing expired pharmaceuticals as eco-friendly corrosion inhibitors for their industrial applications. An expired drug sumatriptan was investigated for its anticorrosive properties on MS in 1 M HCl medium. Electrochemical techniques, including potentiodynamic polarization and electrochemical impedance spectroscopy, were employed to evaluate the inhibition efficiency and complemented by surface characterization studies (SEM, EDAX, CA and AFM). The results demonstrated that sumatriptan acts as an effective mixed-type inhibitor, achieving maximum inhibition efficiencies of 94.51% and 93.85% from PDP and EIS studies respectively for 500 ppm at 318 K. The adsorption of sumatriptan on the metal surface followed the Langmuir isotherm having an R2 value of ∼1, suggesting a physical adsorption behaviour with Δ G° values ranging from −16.286 to −21.518 kJ mol−1. The results demonstrate the effectiveness of sumatriptan as a corrosion inhibitor and the potential of repurposing expired pharmaceuticals as eco-friendly and sustainable alternatives.

Biocompatible nanocomposite hydroxyapatite-based granules with increased specific surface area and bioresorbability for bone regenerative medicine applications.

Hydroxyapatite (HA) granules are frequently used in orthopedics and maxillofacial surgeries to fill bone defects and stimulate the regeneration process. Optimal HA granules should have high biocompatibility, high microporosity and/or mesoporosity, and high specific surface area (SSA), which are essential for their bioabsorbability, high bioactivity (ability to form apatite layer on their surfaces) and good osseointegration with the host tissue. Commercially available HA granules that are sintered at high temperatures (≥ 900°C) are biocompatible but show low porosity and SSA (2-5 m2/g), reduced bioactivity, poor solubility and thereby, low bioabsorbability. HA granules of high microporosity and SSA can be produced by applying low sintering temperatures (below 900°C). Nevertheless, although HA sintered at low temperatures shows significantly higher SSA (10-60 m2/g) and improved bioabsorbability, it also exhibits high ion reactivity and cytotoxicity under in vitro conditions. The latter is due to the presence of reaction by-products. Thus, the aim of this study was to fabricate novel biomaterials in the form of granules, composed of hydroxyapatite nanopowder sintered at a high temperature (1100°C) and a biopolymer matrix: chitosan/agarose or chitosan/β-1,3-glucan (curdlan). It was hypothesized that appropriately selected ingredients would ensure high biocompatibility and microstructural properties comparable to HA sintered at low temperatures. Synthesized granules were subjected to the evaluation of their biological, microstructural, physicochemical, and mechanical properties. The obtained results showed that the developed nanocomposite granules were characterized by a lack of cytotoxicity towards both mouse preosteoblasts and normal human fetal osteoblasts, and supported cell adhesion to their surface. Moreover, produced biomaterials had the ability to induce precipitation of apatite crystals after immersion in simulated body fluid, which, combined with high biocompatibility, should ensure good osseointegration after implantation. Additionally, nanocomposite granules possessed microstructural parameters similar to HA sintered at a low temperature (porosity approx. 50%, SSA approx. 30m²/g), Young's modulus (5-8 GPa) comparable to cancellous bone, and high fluid absorption capacity. Moreover, the nanocomposites were prone to biodegradation under the influence of enzymatic solution and in an acidic environment. Additionally, it was noted that the hydroxyapatite nanoparticles remaining after the physicochemical dissolution of the biomaterial were easily phagocytosed by mouse macrophages, mouse preosteoblasts, and normal human fetal osteoblasts (in vitro studies). The obtained materials show great potential as bone tissue implantation biomaterials with improved bioresorbability. The obtained materials show great potential as bone tissue implantation biomaterials with improved bioresorbability.

SARCINA VENTRICULI-RELATED GASTRITIS: A RARE CASE OF GASTRIC INFECTION IN A PATIENT WITH DELAYED GASTRIC EMPTYING

Sarcina ventriculi (SV), which is also called Clostridium ventriculi, is a rare, non-motile, aerobic, Gram-positive coccus that breaks down carbohydrates through fermentation. It thrives in acidic environments, making the human stomach a suitable habitat, particularly in conditions associated with gastric stasis. SV belongs to the Clostridiaceae family. Recent studies have implicated Sarcina ventriculi in severe gastrointestinal conditions, including emphysematous gastritis, pyloric stenosis, gastroparesis, gastric outlet obstruction, gastric perforation, and gastric adenocarcinoma. Increased awareness of this organism and further studies are essential to understanding its role in human disease.

The effect of three urease inhibitors on H. pylori viability, urease activity and urease gene expression

BackgroundTreatment of Helicobacter pylori (H. pylori) infections is challenged by antibiotic resistance. The urease enzyme contributes to H. pylori colonization in the gastric acidic environment by producing a neutral microenvironment. We hypothesized that urease inhibition could affect H. pylori viability. This work aimed to assess the effects of acetohydroxamic acid (AHA), ebselen and baicalin on urease activity, bacterial viability and urease genes expression in H. pylori isolates.MethodsForty-nine H. pylori clinical isolates were collected. Urease activity was assessed using the phenol red method. The urease inhibition assay assessed inhibitors' effects on urease activity. Flow cytometry assessed the effect of inhibitors on bacterial viability. Real time PCR was used to compare urease genes expression levels following urease inhibition.ResultsUrease activity levels differed between isolates. Acetohydroxamic acid inhibited urease activity at a concentration of 2.5 mM. Although baicalin inhibited urease activity at lower concentrations, major effects were seen at 8 mM. Ebselen's major inhibition was demonstrated at 0.06 mM. Baicalin (8 mM) significantly reduced ATP production compared to untreated isolates. Baicalin, ebselen and acetohydroxamic acid significantly reduced H. pylori viability. Increased urease genes expression was detected after exposure to all urease inhibitors.DiscussionIn conclusion, higher concentrations of baicalin were needed to inhibit urease activity, compared to acetohydroxamic acid and ebselen. Baicalin, ebselen and acetohydroxamic acid reduced H. pylori viability. Therefore, these inhibitors should be further investigated as alternative treatments for H. pylori infection.

A Photoelectric Synergistic Flexible Solid Slippery Surface for All-Day Anti-Icing/Frosting.

The accumulation of ice on surface has caused great harm to lots of fields such as transportation or aerospace. Nowadays, various equipment or tools used in low-temperature environments, which face the risk of interface icing, usually have irregular shapes. Traditional rigid anti-icing materials are difficult to meet practical application requirements. Thus, it is crucial to develop flexible anti-icing materials that can be applied to various shape surfaces (curved surfaces, flat surfaces). In this paper, a photoelectric synergistic flexible solid slippery surface (FSSS) is prepared by using flexible basalt fiberglass cloth, flexible copper foil, flexible polyurethane/carbon nanotubes mixture, and flexible solid lubricant (the mixture of coconut wax and coconut oil). Even under harsh conditions of the temperature as low as -80 °C, the FSSS exhibits excellent all-day anti/de-icing performance whether on flat or curved surface. Moreover, the FSSS shows long-term stability both on flat and curved surface: situated in air for 60 days, submerged in water for 60 days, kept in acid environment (pH 1) and base environment (pH 13) for 30 days. Besides, the FSSS can also achieve self-healing function under -80 °C. This flexible surface provides a novel approach for de-icing/frosting of multi-shaped objects in the future.

Revealing mitochondrial microenvironmental changes triggered by ferroptosis regulation.

Ferroptosis is a unique form of iron-dependent cell death characterized by dramatic ultrastructural changes in mitochondria. Since mitochondria are intracellular energy factories and binding sites for producing reactive oxygen species, there is increasing evidence that mitochondria are closely related to ferroptosis and play a crucial role in the regulation and execution of ferroptosis. The pH of the mitochondrial microenvironment is an important parameter for cellular physiological activities. Its abnormal fluctuations are commonly thought to be associated with cancers and other diseases. Herein, a surface-enhanced Raman scattering (SERS)-based pH nanosensor with high sensitivity and targeting function was utilized to quantify and monitor mitochondrial pH value. This nanosensor was constructed by gold nanorods (AuNRs) functionalized with pH-responsive molecules (4-mercaptopyridine, MPy) and mitochondrion-targeting peptides (AMMT) that can precisely deliver AuNRs to mitochondria. Super-resolution fluorescence imaging was employed to evidence the mitochondrial targeting feature of this nanosensor. Ferroptosis regulation induces intracellular accumulation of lipid peroxide (LPO) and reactive oxygen species (ROS), which cause changes in the mitochondrial pH. This method reveals that ferroptosis leads to the gradual acidification of the mitochondrial internal environment. The conclusion deduced by this study will be helpful for the evaluation and diagnosis of diseases according to intracellular abnormal microenvironments.

Metal-organic framework-based dual function nanosystems for aluminum detoxification and plant growth in acidic soil.

Plants encounter various abiotic stresses throughout growth and development, with aluminum stress emerging as a major global agricultural challenge that hinders plant growth and limits crop yields in acidic soils. In this study, nanomaterials with dual functions, controlled release and adsorption, were constructed to alleviate aluminum toxicity. Specifically, two metal-organic frameworks, UiO-66 and ZIF-8, were used to load naphthylacetic acid and tryptophan, respectively. These two controlled-release systems were then combined with a chitosan-based matrix (NT@CS@UZ) to enable the regulated release of both compounds at distinct rates. Concurrently, the porous structure of these materials facilitates the adsorption of soluble aluminum in the plant rhizosphere. Results show that the acidic environment accelerates ZIF-8 degradation, triggering an early release of tryptophan under aluminum stress conditions. This early release promotes plant growth and alleviates stress damage. Naphthylacetic acid is subsequently released at a slower, sustained rate to stimulate root growth and further mitigate aluminum toxicity in roots. Additionally, NT@CS@UZ effectively adsorbs aluminum ions, limiting Al3+ uptake by plants and creating a low-aluminum barrier to protect roots. These dual function nanomaterials significantly boost crop yield and enhance stress resilience, presenting new avenues for food security and sustainable agricultural practices.

Evaluation of cactus mucilage as a green corrosion inhibitor for copper in sulfuric acid environment

This study investigates the corrosion inhibition performance of cactus mucilage for copper in 0.5 M H2SO4 solution. The cactus mucilage was extracted using a pure water extraction method and characterized using FTIR and GC-MS analyses. The inhibition efficiency was evaluated using potentiodynamic polarization and EIS techniques, while surface morphology was analyzed using SEM and AFM. The potentiodynamic polarization results revealed that cactus mucilage acts as a mixed-type inhibitor, with inhibition efficiency increasing from 78.6% at 100 mg L-1 to 94.5% at 600 mg L-1. The EIS measurements showed a significant increase in charge transfer resistance from 0.56 k? cm-2 in the uninhibited solution to 8.26 k? cm-2 with 600 mg L-1 cactus mucilage. The adsorption of cactus mucilage on the copper surface followed the Langmuir isotherm model, with a strong adsorption equilibrium constant of 23.6 × 103 M. Compared to other green inhibitors, cactus mucilage exhibited superior inhibition efficiency and sustainability advantages, making it a promising eco-friendly alternative for copper corrosion protection.

Gene expression profiling reveals host defense strategies for restricting Candida albicans invasion and gastritis to the limiting ridge of the murine stomach.

Candida albicans is a fungal constituent of the human gastrointestinal microbiota that can tolerate acidic environments like the stomach, where it can be associated with ulcers and chronic gastritis. In mice, C. albicans induces gastritis without concurrent intestinal inflammation, suggesting that the stomach is particularly prone to fungal infection. We previously showed that C. albicans invasion in the limiting ridge does not extend to or elicit an inflammatory response in the adjacent glandular region, indicating regionalized gastritis in the murine stomach. However, the molecular pathways involved in the host response to C. albicans specifically in the limiting ridge have not been investigated. Here, we found that gastric dysbiosis was associated with C. albicans limiting ridge colonization and gastritis. We isolated the limiting ridge and evaluated the expression of over 90 genes involved in mucosal responses. C. albicans infection triggered a type 3 immune response marked by elevated Il17a, Il17f, Il1b, Tnf, and Il36g, as well as an upregulation of Il12a, Il4, Il10, and l13. Chemokine gene induction (including Ccl2, Ccl3, Ccl4, Ccl1l, Cxcl1, Cxcl2, Cxcl9, and Cxcl10) coincided with an influx of neutrophils, monocytes/macrophages, and eosinophils. Hyphal invasion caused tissue damage, epithelial remodeling, and upregulation of genes linked to epithelium signaling and antimicrobial responses in the limiting ridge. Our findings support a need for continued exploration into the interactions between the immunological milieu, the host microbiota, and clinical interventions such as the use of antibiotics and immunotherapeutic agents and their collective impact on invasive candidiasis risk.

Development of Alginate Hydrogels Incorporating Essential Oils Loaded in Chitosan Nanoparticles for Biomedical Applications

A hybrid alginate hydrogel–chitosan nanoparticle system suitable for biomedical applications was prepared. Chitosan (CS) was used as a matrix for the encapsulation of lavender (Lavandula angustifolia) essential oil (LEO) and Mentha (Mentha arvensis) essential oil (MEO). An aqueous solution of an acidic Natural Deep Eutectic Solvent (NADES), namely choline chloride/ascorbic acid in a 2:1 molar ratio, was used to achieve the acidic environment for the dissolution of chitosan and also played the role of the ionic gelator for the preparation of the chitosan nanoparticles (CS-NPs). The hydrodynamic diameter of the CS-MEO NPs was 130.7 nm, and the size of the CS-LEO NPs was 143.4 nm (as determined using Nanoparticle Tracking Analysis). The CS-NPs were incorporated into alginate hydrogels crosslinked with CaCl2. The hydrogels showed significant water retention capacity (>80%) even after the swollen sample was kept in the aqueous HCl solution (pH 1.2) for 4 h, indicating a good stability of the network. The hydrogels were tested (a) for their ability to absorb dietary lipids and (b) for their antimicrobial activity against Gram-positive and Gram-negative foodborne pathogens. The antimicrobial activity of the hybrid hydrogels was comparable to that of the widely used food preservative sodium benzoate 5% w/v.

CuS-NiTe2 embedded phosphorus-doped graphene oxide catalyst for evaluating hydrogen evolution reaction.

The hydrogen evolution reaction (HER), a crucial half-reaction in the water-splitting process, is hindered by slow kinetics, necessitating efficient electrocatalysts to lower overpotential and enhance energy conversion efficiency. Transition-metal electrode materials, renowned for their robustness and effectiveness, have risen to prominence as primary contenders in the field of energy conversion and storage research. In this investigation, we delve into the capabilities of transition metals when employed as catalysts for the HER. Furthermore, we turn our attention to carbon nanomaterials like graphene, which have exhibited tremendous potential as top-performing electrocatalysts. Nevertheless, advancements are indispensable to expand their utility and versatility. One such enhancement involves the integration of phosphorus-doped graphene. Our research focuses on the synthesis of CuS-NiTe2/PrGO, a nanocomposite with a crystalline structure, through a straightforward method. This nanocomposite exhibits enhanced catalytic activity for the HER, boasting a Tafel slope of 57 mV dec-1 in an acidic environment. Consequently, our findings present a straightforward and efficient approach to developing high-performance electrocatalysts for HER.

TMIC-24. BICARBONATE RECEPTOR SLC4A4 SENSITIZES INFILTRATING GLIOBLASTOMA CELLS TO CHANGES IN EXTRACELLULAR PH

Abstract BACKGROUND Glioblastoma progression involves changes in extracellular pH (pHe) related to rapid cell turnover and growth. There exist differences in pH between contrast-enhancing solid tumor and non-enhancing infiltrating tumor. SLC4A4 is a two-way bicarbonate transporter used in cortical astrocytes to buffer intracellular pH. METHODS In patients undergoing surgery for newly diagnosed IDH wild-type glioblastoma, we obtained tissue from solid tumor and infiltrating tumor. Single-nucleus RNA sequencing (n=15), immunohistochemistry (n=20) were carried out to identify SLC4A4 in infiltrating tumor beyond the contrast enhancing edge. SLC4A4 knock-down models were used to evaluate functional biology of this bicarbonate receptor using our tumor – cortical organoid model of infiltrating glioma and gliomaspheres. pH measurements were recorded using pH sensitive microelectrodes to evaluate changes on pH buffering ability of tumor cells during acid titration assays. RESULTS Single-nucleus RNA sequencing (n=15) and spatial RNA sequencing (n=3) showed SLC4A4 to be the highest expressed transmembrane receptor on infiltrating glioblastoma cells but not solid tumor. IHC (n=20) confirmed higher protein expression in infiltrating tumor (p=0.0390). Infiltrating cells were specifically sensitive to decreasing pHe (p=0.0105). In the infiltrating glioma cortical-organoid model, the slc4a4- had increased proliferation (GFP+ cell quantitation; n=10, p=0.0410). There was also increased proliferation in wild-type cells treated with SLC4A4 inhibitor DIDS (n=10, p=0.0016). Immunostaining of these models showed that downmodulation of SLC4A4 was associated with increased Ki67 and decreased caspase staining. CONCLUSIONS SLC4A4 plays a role in pH buffering in glioblastoma. We hypothesize that loss of SLC4A4 in solid tumor allows for desensitization of these cells to an acidic extracellular environment and allows for increased tumor growth and density while infiltrating tumor remains sensitivity to changes in pHe. An understand of pH regulation may lead to therapeutic efficacy through pH modulation of tumor.

Localized Transformation of 2D Perovskite by Protonated Metformin for Efficient Carbon‐Based Perovskite Photovoltaic and Photo‐Charging Applications

AbstractDimensional engineering is promising for achieving a high power conversion efficiency (PCE) and long‐term stability of perovskite solar cells (PSCs). However, insulated organic spacers in 2D perovskites often severely hinder carrier transport between the internal layers of devices. Herein, the “protonation‐induced localized transformation of 2D perovskites” is proposed to overcome the low carrier transport and conductivity of 2D/3D perovskite heterojunctions. Metformin, with its multiple amine groups and a substantial difference between its pKa value and perovskites, is protonated in an acidic environment or directly converted into the hydrochloride salt for the surface passivation of methylammonium lead iodide. This leads to the transformation of disorderedly oriented layered 2D perovskite into vertically oriented ones at grain boundaries. Consequently, the PCE of a carbon‐based PSC treated by protonated metformin increased considerably, reaching an optimal level of 14.13%. Additionally, applying this passivation strategy to a planar device (ITO/4PADCP/perovskite/PCBM/BCP/Ag) increased PCE from 20.82% to 22.09%, confirming the applicability of the strategy. To demonstrate the practical stability, an integrated PSC–supercapacitor device is assembled, which shows good cycling stability. This article introduces a novel method to improve carrier transport in 2D/3D perovskite heterojunctions, promoting the extensive utilization of dimensional engineering.

Poly(vinyl alcohol) potentiating an inert D-amino acid-based drug for boron neutron capture therapy.

Since the discovery of D-amino acids, they have been considered inactive and have not been used as potent drugs. Here, we report that simple mixing with poly(vinyl alcohol) (PVA) unleashed latent potentials of D-amino acids in boron neutron capture therapy (BNCT). PVA formed boronate esters with seemingly useless boronated D-amino acids and induced tumor-associated amino acid transporter-superselective internalization and prolonged intracellular retention, accomplishing complete cure of tumors. The superselective internalization was achieved by switching the internalization pathway from ineffective pass through the transporter to the transporter-mediated endocytosis. The acidic environment in the endo-/lysosome dissociated the boronate esters and elicited the stealthiness of the drugs, preventing their externalization and prolonging intracellular retention time. In a subcutaneous tumor model, this system accomplished surprisingly high tumor-selective accumulation that could not be achieved by conventional approaches and induced drastic BNCT effects. PVA may be a unique material to unlock potentials of seemingly inert molecules.

Zinc Oxide-Enhanced Copper Sulfide Nanozymes Promote the Healing of Infected Wounds by Activating Immune and Inflammatory Responses.

Bacterial infection and an excessive inflammatory response are two major factors that affect the healing of infected wounds. The zinc oxide/copper sulfide (ZnO-CuS) microspheres (MSs) developed in this work can kill bacteria and resist inflammation. ZnO-CuS exhibits different enzyme-like activities depending on pH. In acidic environments, ZnO-CuS exhibits peroxidase-like (POD-like) activity and can convert hydrogen peroxide (H2O2) into hydroxyl radicals (•OH) for sterilization. Under neutral conditions, ZnO-CuS removes reactive oxygen species (ROS) and can convert excess ROS into water and oxygen. The in vitro results of the antibacterial test demonstrate the pronounced disruption effect of ZnO-CuS on the bacterial biofilm and cell membrane. The transcriptome sequencing results of wounded animal tissue reveal that ZnO-CuS MSs increase the expression of proteins produced by immune cells, and reduce the expression levels of inflammatory factors at the wound site. Therefore, antimicrobial activity and rapid wound healing can be achieved by regulating the immune response and reducing the inflammatory response. The results from hemolysis, routine blood and blood biochemistry analyses demonstrate the excellent biosecurity of the ZnO-CuS MSs.

Electronic Structure Modulating of W18O49 Nanospheres by Niobium Doping for Efficient Hydrogen Evolution Reaction.

Hydrogen, known for its high energy density and environmental benefits, serves as a prime substitute for fossil fuels. Nonetheless, the hydrogen evolution reaction (HER), essential in electrolysis, encounters challenges with slow kinetics and significant overpotential, which elevate costs and reduce efficiency. Thus, developing efficient electrocatalysts to reduce HER overpotential is vital to enhance hydrogen production efficiency and minimize energy consumption. Adjusting the electronic structure of transition metal oxides via elemental doping is a potent strategy to improve the effectiveness of electrocatalysts for hydrogen evolution. In this work, we synthesized a set of niobium-doped tungsten oxides (Nbx-W18O49) under anoxic conditions using a straightforward "one-pot" solvothermal approach. After doping Nb, the oxygen vacancy content inside W18O49 was increased, which induced a synergistic effect with the active sites of tungsten. In acidic environments, the hydrogen evolution activity of the Nb0.6-W18O49 electrocatalyst is second only by 20 wt % Pt/C. It attains a current density of -10 mA cm-2 at an overpotential of 102 mV. By comparison with W18O49, Nb0.4-W18O49 and Nb0.5-W18O49, Nb0.6-W18O49 demonstrates a reduced charge transfer resistance, which significantly enhances its conductivity and the speed of electron movement across interfaces. Coupled with this feature are notably faster HER kinetics. Additionally, it exhibits excellent stability, meaning it maintains its performance and structural integrity over prolonged periods and under various operational conditions. This article provides a new perspective for discovering inexpensive and efficient hydrogen evolution electrocatalyst materials.

Extraction of gold from gravity-flotation concentrates via surfactant and oxidation reagents

The focus of this work is to establish a hydrometallurgical technique for efficiently extracting gold from the aggregated gold-rich concentrate produced by a mining facility in one of Kazakhstan's deposits. The leaching techniques applied to gravity-flotation concentrates include hydrometallurgical gold recovery processes using the surfactant sulfanol and the oxidizing reagent trichloroisocyanuric acid (TCCA). The findings indicate the effectiveness of leaching gravity-flotation concentrates with oxidizing (accelerating) reagents. Gold extraction through cyanidation of the blended concentrate, ground to 89–90% passing 10 µm with TCCA, averaged 84.0%, compared to 65.76–67.8% with conventional direct cyanidation. The advantage of employing chlorine-based oxidants, such as TCCA, in hydrometallurgical processing lies in their applicability in both acidic and alkaline environments, whereas other oxidants are constrained by specific technological conditions. Technical trichloroisocyanuric acid (TCCA), a chlorine-containing oxidizer with the formula C3O3N3Cl3, containing 25–30% calcium hypochlorite as an impurity, proved to be the most effective in enhancing gold leaching techniques. Apart from improving the efficiency of the leaching process, the use of TCCA is economically viable. The wholesale cost of technical TCCA is ~ $700 per ton, significantly lower than many other oxidants commonly used in gold hydrometallurgical production. With its higher active chlorine content, TCCA consumption per ton of gold-bearing raw material is nearly half that of hypochlorite or peroxide. Additionally, TCCA use minimizes the formation of unwanted impurities in both the pulp and the productive solution.

Insights Into the Adsorption Behavior of Polyethylene Microplastics Towards Lead(II) Ions

ABSTRACTMicroplastics and metals represent widespread contaminants which can cause significant damage to aquatic ecosystems and organisms. However, the complex interactions between microplastics and various metals in water environments remains to be understood. This study aims to investigate the interaction dynamics between lead(II) ions and polyethylene in freshwater environments. Adsorption trials were conducted systematically by adjusting operational parameters such as initial Pb(II) concentration, equilibrium pH value, and residence times. An in‐depth characterization study using scanning electron microscopy (SEM), x‐ray diffraction and Fourier transform infrared (FTIR) analysis was conducted to explain the adsorption mechanism of polyethylene microplastics (PEM). The data indicated the porous surface of PEM, highlighting the presence of diverse functional groups. According to the Langmuir model, the PEM exhibited maximum Pb(II) uptake of 3.69 mg/g at pH 4.5. The pseudo‐first‐order model demonstrated superior fitting to Pb(II)‐PEM kinetics. Desorption trials were performed to assess the release of Pb(II) from Pb(II)‐bounded PEM using various chemical agents. It was observed that 0.01 M HNO₃ desorbed Pb(II) ions optimally, achieving a desorption efficiency exceeding 99.9%. Consequently, desorption trials provided evidence that Pb(II)‐bounded PEM may release Pb(II) ions in acidic environments, facilitating the transfer of Pb(II) to the digestive tracts of aquatic organisms.