Search Results (368)

Hydrogen sulfide (H₂S) prevalent in fuel gases such as natural gas and biogas necessitates removal prior to utilization or pipeline distribution. Biological desulfurization is considered a green purification technology employing sulfur-oxidizing bacteria (SOB) under ambient conditions to eliminate sulfur compounds, offering advantages including high efficiency, simplified equipment, and minimal chemical consumption. A highly efficient SOB TYWJ-2 was isolated in this study. Genomic analysis revealed that strain TYWJ-2 possesses a complete set of sulfur metabolism genes, enabling the metabolism of various inorganic sulfides, along with salt-tolerance genes that support adaptation to high osmolarity environments. The optimal conditions for desulfurization were determined through single-factor experiments and Box–Behnken response surface methodology. Long-term desulfurization performance demonstrated stable operational efficiency, with H₂S removal rates consistently reaching 99.72~99.87%. System performance remained robust under varying sulfur loads, elevated salinity, and intermittent operational shutdowns, with no significant decline in desulfurization efficiency observed. These findings indicate that strain TYWJ-2 holds considerable potential for the biological desulfurization of sulfur-containing biogas and natural gas. Full article

Octachlorinated metal phthalocyanines (MPcCl₈, M = Co, Zn, VO) represent an underexplored class of functional materials with promising potential for chemiresistive sensing applications. This work is the first to determine the structure of single crystals of CoPcCl₈, revealing a triclinic (P-1) packing motif with cofacial molecular stacks and an interplanar distance of 3.381 Å. Powder XRD, vibrational spectroscopy, and elemental analysis confirm phase purity and isostructurality between CoPcCl₈ and ZnPcCl₈, while VOPcCl₈ adopts a tetragonal arrangement similar to its tetrachlorinated analogue. Thin films were fabricated via physical vapor deposition (PVD) and spin-coating (SC), with SC yielding highly crystalline films and PVD resulting in poorly crystalline or amorphous layers. Electrical measurements demonstrate that SC films exhibit n-type semiconducting behavior with conductivities 2–3 orders of magnitude higher than PVD films. Density functional theory (DFT) calculations corroborate the experimental findings, predicting band gaps of 1.19 eV (Co), 1.11 eV (Zn), and 0.78 eV (VO), with Fermi levels positioned near the conduction band, which is consistent with n-type character. Chemiresistive sensing tests reveal that SC-deposited MPcCl₈ films respond reversibly and selectively to ammonia (NH₃) and hydrogen sulfide (H₂S) at room temperature. ZnPcCl₈ shows the highest NH₃ response (45.3% to 10 ppm), while CoPcCl₈ exhibits superior sensitivity to H₂S (LOD = 0.3 ppm). These results suggest that the films of octachlorinated phthalocyanines produced by the SC method are highly sensitive materials for gas sensors designed to detect toxic and corrosive gases. Full article

Activated carbons were synthesized from petroleum-based pitch and evaluated for the removal of trace siloxanes and hydrogen sulfide (H₂S) from gas streams. Oxidative stabilization followed by steam activation produced high specific surface area with enlarged mesoporosity (BET up to 1620.9 m² g⁻¹), as confirmed by N₂ sorption (BET/PSD), SEM, and elemental analysis. A GC/MS-based fixed-bed assay using 5 g of adsorbent, a 100 mL min⁻¹ challenge flow, and a 30 min readout was employed to quantify performance under consistent conditions. Under these tests, siloxanes were not detected at 30 min, and H₂S decreased to 0.38 ppm. Samples with greater mesopore volume while retaining high surface area showed higher 30 min removal. Surface-chemistry analysis indicated that oxygen functionalities introduced during stabilization facilitated pore development during subsequent steam activation without substantial loss of area. Taken together, the textural and adsorption results present a coherent picture in which a micro/mesopore architecture supports siloxane and H₂S control under the stated test conditions. The study records the key testing parameters and performance values to enable practical comparison of petroleum-pitch-derived activated carbons for gas purification. Full article

Anaerobic digestion of sugarcane vinasse is integral to enhancing ethanol distilleries’ environmental and energy performance by converting organic waste into biogas; however, the flammable and toxic nature of biogas has led to significant safety concerns, particularly in anaerobic bioreactors where biogas is produced and stored. This study provides a comparative risk assessment of different anaerobic reactor configurations—a covered lagoon biodigester (CLB), a continuous stirred-tank reactor (CSTR), an upflow anaerobic sludge blanket reactor (UASB), and an anaerobic structured-bed reactor (AnSTBR)—processing vinasse, focusing on fire, explosion, and hydrogen sulfide (H₂S) toxicity hazards. Jet fire scenarios posed the most severe threat, with fatal outcomes extending up to 66 m, while the fireball scenario exhibited no lethal range. The risks to human life from explosions were minimal (1.2%). H₂S toxicity was identified as the most critical consequence, with particularly severe impacts in CLB systems, where the hazardous zone was up to 20 times larger than in AnSTBR. Therefore, the design of anaerobic bioreactors for vinasse treatment must primarily address the risks associated with H₂S-rich biogas, as reactor configuration plays a key role in mitigating or amplifying these hazards—high-rate systems such as AnSTBR and UASB demonstrating safer profiles due to their compact design and lower gas storage volumes. Full article

Triazine solvent desulfurization is a highly efficient technology for removing hydrogen sulfide from natural gas. In this study, we used ASPEN HYSYS V11 with the Peng-Robinson (PR) equation to investigate the triazine consumption under different natural gas flow rates and hydrogen sulfide concentrations, as well as the sulfur capacity resulting from the reaction between triazine and H₂S at varying solution concentrations. Additionally, CFD simulations were employed to optimize the injection process of the triazine solvent by examining four key factors: gas flow velocity, injection volume, injection angle, and injection method. The results indicate that the required triazine dosage follows an exponential model, with a margin of error within 10%. A triazine mass fraction between 0.4 and 0.6 was found to be optimal. Among the factors studied, gas flow velocity has the most significant influence on desulfurization efficiency, while the injection rate plays a secondary role. An injection angle of 45° proved most effective, and the use of dual vertical symmetric nozzles achieved more uniform mixing between the natural gas and triazine solvent. Full article

The article evaluates the impact of blasting operations with explosives on hydrogen sulfide (H₂S) emissions from rock mass in a copper ore mine. The study showed that detonations of explosives cause increased release of H₂S and other gases from the rock mass interior into the mine workings space. Analysis of changes in H₂S concentration over a period of ±60 min relative to the moment of detonation, performed for data from 2014 and 2017, revealed significant differences in gas behavior. In 2014, the average H₂S concentration decreased after the blast, while in 2017, a marked increase was observed, although the absolute values were lower than in the previous period. The average time to reach the maximum concentration of H₂S after an explosion in 2014 was 24 min and 25 s, and in 2017, 29 min and 22 s. Stabilization of the mine atmosphere occurred in 2014 after 58 min and 15 s, and in 2017 after about 40 min and 57 s. In none of the analyzed periods did the concentration values exceed the threshold of 7 ppm, which means that the level of H₂S did not reach the values considered dangerous for the crew. The results indicate that blasting works significantly affect the dynamics of gas release from the rock mass, but do not pose a threat under the conditions studied. Full article

Natural gas is currently increasingly used in an energy transition framework and systematically requires upgrading processes in order to respect pipeline specifications. Carbon dioxide, and in some case hydrogen sulfide removal, is the major target of the purification step and can be achieved thanks to gas liquid absorption with chemical solvents or membrane separation. A systematic comparison of the cheap, currently used polymeric membranes and an expensive, high-performance zeolite material is reported on a natural gas upgrading case study (CH₄/CO₂ mixture), thanks to a dedicated process synthesis and optimization code (MIND). The zeolite membrane is shown to offer a simple, cost-effective one-stage process, while polymeric materials require more expensive classical two-stage processes. In a second step the impact of concentration polarization is more specifically investigated, through a process simulation study. The zeolite membrane remains the simplest, best cost-effective and most interesting process (one stage without compression, expander or vacuum pump). Full article

Recent scientific reports have highlighted the physiological role, toxicological effects, and pathophysiological aspects of gasotransmitters, particularly hydrogen sulfide (H₂S), which is recognized as a new member of this family. Endogenous generation of H₂S in the skin occurs through both enzymatic and non-enzymatic pathways. The main enzymes involved in its endogenous production are cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (3-MST) and cysteine aminotransferase. 3-MST and CSE are crucial for maintaining the epidermal barrier. H₂S may play a role in oncogenesis, acting as a gas signaling molecule that disrupts mitochondrial respiration and influences immune modulation, cell proliferation, apoptosis, tumor cell survival, and metastasis. Interestingly, H₂S exhibits dual effects in the biology of skin cancer, promoting tumor growth in some contexts and exerting antitumor activities in others. Data from the European Cancer Information System and Global Cancer Observatory show a significant global increase in skin cancer cases. The most common types of cutaneous malignancies, from both epidemiological and clinical perspectives, are basal cell carcinoma. squamous cell carcinoma, and melanoma. This review aims to evaluate the dysfunctional metabolism of H₂S and the specific profiles of the enzymes that synthesize H₂S in skin cancer. By comparing the roles of H₂S in normal cells with those in cancer cells, we can enhance current understanding of its implications in skin cancer biology. This research paves the way for new clinical strategies, including the development of H₂S-modulatory therapies tailored to the dynamics of tumor progression, which could help overcome therapeutic resistance. Full article

In this study, both experimental and simulation approaches were employed to investigate the removal efficiency of gaseous pollutants using two different types of packing materials—random and structured packings—under varying gas flow rates and column diameters. A synthetic gas mixture containing 2200 ppm H₂S and 26.75% CO₂ was used to evaluate the performance of the system. Simulation studies were conducted using Aspen Plus^TM V9, and the results were validated with experimental data. H₂S removal efficiencies were found to range between 79% and 98%, while CO₂ removal ranged from 6% to 20%. Comparative analyses revealed that an increase in gas flow rate and column diameter led to a decrease in pollutant removal efficiency for both types of packings. A previously unobserved packing-dependent scaling effect was revealed: increasing column diameter decreases removal efficiency for random packings but enhances it (up to a threshold) for structured packings, offering new scale-up guidelines. Most notably, a previously unobserved trend was identified: increasing column diameter exerts opposing effects on removal efficiency depending on packing type—a packing-dependent scaling behavior with significant implications for industrial column design. The findings provide valuable insights into the design and optimization of industrial-scale gas treatment systems, demonstrating that simulation data can effectively support the selection of appropriate column dimensions, gas flow rates, and packing types for varying pollutant concentrations. A mechanistic analysis revealed that the superior H₂S removal over CO₂ arises from its higher solubility, instantaneous reaction with OH⁻, and greater enhancement factor, with structured packings mitigating maldistribution effects at larger column diameters—offering new scale-up insights supported by the literature. Full article

Over 292 million tons of municipal solid waste (MSW) are generated annually in the United States, with more than half disposed of in landfills. Municipal solid waste landfills (MSWLFs) are stationary sources of air pollution and potential health risks for nearby communities. The Agency for Toxic Substances and Disease Registry (ATSDR) has completed over 300 public health assessments (PHAs) and related investigations at MSWLFs and open dumps since the 1980s. This paper reviews the ATSDR’s evaluations of air pathway concerns at 125 MSWLF sites assessed between 1988 and early 2025, with many being evaluated during the 1990s. Most sites were located in the Midwest and Northeast, and only 25% remained active. The ATSDR found no air-related public health hazard at 86% of sites. At sites where hazards were identified, common issues included elevated outdoor or indoor toxicants (e.g., hydrogen sulfide, benzene, trichloroethylene, and mercury) and unsafe methane accumulations. Contributing factors included older site designs, inadequate gas-collection, subsurface fires, and distance from nearby residences. Corrective actions effectively reduced exposures at the affected sites. Results suggest that well-located and maintained landfills minimize public health hazards, while aging or poorly managed sites pose risks. Continued monitoring and research are warranted as waste management shifts toward reducing, reusing, recycling, composting, and energy-recovery technologies to improve efficiency, advance technologies, and address systemic public health challenges. Full article

Low temperature combined with fluctuating irradiance frequently co-occurs and suppresses photosynthesis, with irreversible injury to photosystem I (PSI) recognized as a key constraint on growth and yield. To test whether exogenous hydrogen sulfide (H₂S) mitigates this “cold–fluctuating light” stress in mulberry, we established six treatment combinations (room temperature controls, sodium hydrosulfide, and hypotaurine, each with or without low temperature plus fluctuating light). We quantified PSI/PSII photochemical properties, gas exchange, reactive oxygen species (ROS), and antioxidant enzyme activities. Under cold with fluctuating light, PSI was strongly inhibited: Y_NA increased, whereas Y_I and ΔI/I_o decreased, and the P700 re-reduction half-time (t½) was prolonged (ANOVA, Tukey’s HSD, p < 0.05), indicating pronounced acceptor-side over-reduction and impaired electron transport. PSII performance also declined (lower F_v/F_m and PI_ABS, higher ΔV_J; p < 0.05). NaHS pretreatment significantly alleviated these effects relative to the stressed control: PSI/PSII metrics partly recovered, net photosynthetic rate (P_n) and water-use efficiency (WUE) increased, H₂O₂ and MDA decreased, and SOD/POD/CAT activities rose (p < 0.05). Notably, NPQ_high correlated negatively with Y_NA (Pearson r < 0, p < 0.001), consistent with the notion that enhanced energy dissipation relieves PSI acceptor-side limitation. We propose that exogenous H₂S stabilizes electron transport and supports carbon assimilation via a dual strategy—faster engagement of energy dissipation and activation of antioxidant defenses—highlighting its potential utility for managing stress in fruit crops under erratic early-season weather. Full article

Energy security is a growing societal and industrial concern that leads research and development toward more sustainable options. Biogas, a bio-alternative to conventional fuels, is a product generated from the anaerobic digestion of organic matter. This source of fuel production is more environmentally friendly compared to traditional fossil fuels, leading to a lower carbon footprint, higher air quality, and the promotion of a circular economy. Impurities of raw biogas, such as carbon dioxide, hydrogen sulfide, and other trace contaminants, make biogas conditioning necessary for most applications. In addition, biogas upgrading, technologies furthering biogas purity, is an important factor in the production of biomethane, a sustainable biofuel known more commonly as renewable natural gas (RNG). Diversifying fuel sources and providing energy sustainability while mitigating negative environmental effects makes RNG an attractive alternative to conventional natural gas. This document, Part I, provides an overview of current technologies related to biogas conditioning, such as sorption, oxidation, and biological treatments aimed at the removal of a wide variety of contaminants. Processes developed for biogas upgrading are also discussed, including physical/chemical absorption, pressure swing adsorption, and membrane separation. The focus of upgrading applies approaches in meeting a higher quality biofuel by further carbon dioxide exclusion to ease pipeline transport and increase combustion efficiency. These technologies present the core foundation of processes in the production of RNG; however, all face inherent challenges that deem further research and development a requirement for global adoption. The biggest challenges are either in the cost of reaching higher purities or the inability to do so without other operations. Thus, in conjunction with this document, emerging and developing technologies are provided in a separate analysis deemed Part II. Together, these documents offer a comprehensive understanding of current practices and growing technological developments. Full article

Hydrogen sulfide (H₂S), a highly toxic gas, is mainly sourced from petroleum refining, natural gas purification, and coal chemical processes. It poses significant risks to human health, causes environmental pollution, and accelerates equipment corrosion. Recent studies have demonstrated that electrochemical coupling systems offer an efficient, sustainable, and cost-effective strategy for removing sulfur-containing gaseous pollutants. These systems enable the conversion of H₂S into recoverable sulfur under mild conditions, while simultaneously harnessing the chemical energy of H₂S to drive the production of higher-value products (H₂, HCOOH, CH₄, CO, H₂O₂, etc.). Therefore, electrochemical systems for sulfur recovery have received increasing attention. This review highlights the significance of electrochemical recovery of sulfur from H₂S. It summarizes the reaction pathways and mechanisms involved in anodic sulfur oxidation, critically analyzes and discusses methods for detecting sulfur oxidation products, and summarizes the latest advances in sulfur oxidation reaction (SOR) anode materials and various electrochemical coupling systems. The aim is to enhance the fundamental understanding of electrochemical sulfur recovery and to provide insights for the design of novel SOR electrodes and integrated electrochemical coupling systems. Full article

Cucumis sativus L. is a globally important vegetable crop that occupies a significant position in protected agriculture due to its high nutritional value, short cultivation cycle, and considerable economic benefits. As a cold-sensitive plant, however, cucumber is highly susceptible to low-temperature stress. which can severely inhibit growth and development, hinder seed germination, and reduce photosynthetic efficiency. Under low-temperature stress, cucumber plants typically incur damage to cellular membrane structures, experience an accumulation of reactive oxygen species (ROS), exhibit a disruption in hormonal homeostasis, and suffer from the inhibition of pivotal metabolic pathways. In response, cucumber plants activate an array of resistance mechanisms, encompassing osmotic adjustment, reinforcement of the antioxidant system, and modulation of cold-responsive gene expression. This review summarizes the physiological and molecular mechanisms underlying cucumber’s response to low-temperature stress, aiming to provide effective strategies for improving abiotic stress resistance. The main findings are as follows: (1) Low-temperature stress damages cucumber cell membranes, suppresses photosynthesis and respiration, suppresses water and nutrient uptake/transport, and suppresses growth retardation. (2) Cucumber counters these adverse effects by orchestrating the accumulation of osmoregulators (e.g., soluble sugars, proline), activating activation defenses (e.g., SOD, CAT), and rebalancing its phytohormone network (e.g., ABA, GA, SA, ethylene). (3) At the molecular level, cucumber activates low-temperature-responsive genes (e.g., COR, GoIS) through transcription factors such as CBF, MYB, and WRKY, thereby enhancing cold tolerance. (4) Application of exogenous protectants (e.g., hydrogen sulfide, melatonin, oligosaccharides) significantly improves cucumber’s low-temperature tolerance by modulating the antioxidant system, promoting osmoregulatory substances accumulation, and regulating hormone signaling pathways. Future research should focus on elucidating the molecular regulatory network in cucumber under low-temperature stress and developing gene editing with multi-omics techniques to advance the development of cold-resistant cultivars and cultivation practices. This study offers a scientific foundation for research on cucumber cold tolerance and proposes potential solutions to agricultural challenges in the context of global climate change. Full article

Anaerobic digestion of manures, crop residues, food waste, and sludge frequently yields biogas with elevated hydrogen sulfide concentrations, which accelerate corrosion and reduce biogas quality. Microaeration, defined as the controlled addition of oxygen at 1 to 5% of the biogas production rate, has been investigated as a low-cost desulfurization strategy. This review synthesizes studies from 2015 to 2025 spanning laboratory, pilot, and full-scale anaerobic digester systems. Continuous sludge digesters supplied with ambient air at 0.28–14 m³ h⁻¹ routinely achieved 90 to 99% H₂S removal, while a full-scale dairy manure system reported a 68% reduction at 20 m³ air d⁻¹. Pure oxygen dosing at 0.2–0.25 m³ O₂ (standard conditions) per m³ reactor volume resulted in greater than 99% removal. Reported methane yield improvements ranged from 5 to 20%, depending on substrate characteristics, operating temperature, and aeration control. Excessive oxygen, however, reduced methane yields in some cases by inhibiting methanogens or diverting carbon to CO₂. Documented benefits of microaeration include accelerated hydrolysis of lignocellulosic substrates, mitigation of sulfide inhibition, and stimulation of sulfur-oxidizing bacteria that convert sulfide to elemental sulfur or sulfate. Optimal redox conditions were generally maintained between −300 and −150 mV, though monitoring was limited by low-resolution oxygen sensors. Recent extensions of the Anaerobic Digestion Model No. 1 (ADM1), a mathematical framework developed by the International Water Association, incorporate oxygen transfer and sulfur pathways, enhancing its ability to predict gas quality and process stability under microaeration. Economic analyses estimate microaeration costs at 0.0015–0.0045 USD m⁻³ biogas, substantially lower than chemical scrubbing. Future research should focus on refining oxygen transfer models, quantifying microbial shifts under long-term operation, assessing effects on digestate quality and nitrogen emissions, and developing adaptive control strategies that enable reliable application across diverse substrates and reactor configurations. Full article