Search Results (5,475)

Advanced nitrogen removal from secondary effluent of municipal wastewater treatment plants (WWTPs) faces substantial technical challenges. This study investigated the denitrification performance and underlying mechanisms of a pyrrhotite/sulfur-coupled autotrophic denitrifying biological filter (PS-CFBR) enhanced by Na₂S addition. This study investigated the denitrification performance of aPS-CFBR enhanced by Na₂S addition, operated at a controlled hydraulic retention time (HRT) of 6 h with varying alkalinity dosages (149–446 mg/L as CaCO₃) and influent sulfide-to-nitrogen (S/N) ratios (0.54–1.62). The results indicated that Na₂S addition shortened the PS-CFBR start-up period by 10 days. At an HRT of 6 h and an alkalinity dosage of 149 mg/L as CaCO₃, the TN removal efficiency in the Na₂S-supplemented reactor (R1) was 22.87% higher than that in the control (CK). The corresponding first-order rate constant (k) in R1 was 2.65-fold greater than in CK. Under low-alkalinity conditions (149 mg/L as CaCO₃), the effective influent S/N ratio was determined to be 0.54–1.08. The TN removal efficiency and rate constant (k) in R1 were 22.87% and 2.65-fold higher than those in CK at an S/N ratio of 0.54, respectively. The effluent pH remained stable at 7.30, SO₄²⁻ production was only 5.16 mg/L higher than that in CK, and alkalinity consumption per mg of N removed was 2.15 mg/L lower than that in CK. X-ray photoelectron spectroscopy (XPS) and microbial community analyses revealed that Na₂S promoted S_n²⁻ formation on the pyrrhotite surface and enriched denitrifying (Herbaspirillum, Flavobacterium, Sulfurimicrobium), iron-oxidizing (Pseudoxanthomonas), and iron-reducing (Clostridium) bacteria. RT-qPCR further indicated that Na₂S addition increased the abundances of denitrification functional genes (narG, nirS, nirK, norB, and nosZ). These findings provide valuable insights into the development of advanced denitrification technologies for secondary effluent from municipal wastewater treatment plants. Full article

Hydrogen sulfide (H₂S) has emerged as an important gaseous signaling molecule involved in numerous physiological and pathological processes, including redox regulation, inflammation, and cellular signaling. Accurate detection of H₂S in biological systems is therefore essential for understanding its roles in health and disease. Among various fluorescent platforms, the 1,8-naphthalimide scaffold has attracted considerable attention due to its unique photophysical properties, structural tunability, and high sensitivity to substituent modification. This review summarizes recent advances in the development of 1,8-naphthalimide-based fluorescent probes for H₂S detection. The fundamental photophysical mechanisms associated with the 1,8-naphthalimide fluorophore, including intramolecular charge transfer (ICT), photoinduced electron transfer (PET), and Förster resonance energy transfer (FRET), are discussed in relation to probe design. Emphasis is placed on reaction-based sensing strategies, highlighting organic reactions that enable selective recognition of H₂S, such as reduction, nucleophilic addition, nucleophilic substitution, and intramolecular cyclization. Representative probes are summarized and compared with respect to sensing mechanisms and photophysical behavior. In addition, the current challenges of 1,8-naphthalimide-based H₂S probes are discussed. We hope this review will provide useful perspectives for the development of efficient 1,8-naphthalimide-based fluorescent probes for H₂S detection. Full article

Odor management requires consideration of both compound concentrations and olfactory impacts determined by odor threshold concentrations. This study evaluated missing-data structures, interpolation performance, odor activity value (OAV)-based odor contributions, and seasonal compositional changes using 20 min monitoring data for 22 designated odor compounds collected from a livestock farm, a wastewater treatment facility, and an anonymized organic waste treatment facility in Eumseong, Republic of Korea (Site C), from 1 August 2022 to 30 June 2023. Because the dataset contained multi-week to multi-month block missing periods, compound-specific interpolation performance was assessed using block holdout validation with BiLSTM, BiGRU, TCN, Transformer, and HistGradientBoostingRegressor models. OAV, summed odor activity value (SOAV), and odor contribution (OC) were calculated primarily from observed concentrations, while fully interpolated series were additionally used for sensitivity comparison to evaluate interpolation-induced bias. Ammonia was excluded from OAV analysis owing to its low valid observation rate. Among the analyzable compounds, odor contribution was dominated by volatile fatty acids and trimethylamine rather than hydrogen sulfide. The livestock farm and wastewater treatment facility showed n-valeric-acid-dominated profiles, whereas Site C showed a mixed profile involving valeric acids and trimethylamine. Seasonal analysis indicated relatively consistent fatty-acid-dominated compositions at the livestock farm and wastewater treatment facility, while Site C showed a possible shift from fatty-acid dominance in warm seasons to trimethylamine dominance in cold seasons. These results provide an OAV-based framework for identifying odor management priorities in long-term continuous odor datasets with severe missingness. Full article

This article discusses the intelligent analysis of multisensory biogas data obtained from an experimental dataset generated by a Lab-on-Chip platform. The relevance of this work stems from the need for real-time monitoring of biogas quality and biomass condition under anaerobic digestion conditions, where changes in the concentrations of methane, carbon dioxide, hydrogen sulfide, oxygen, and temperature directly affect the stability of the technological process and the energy efficiency of the plant. This study utilizes a multisensor Lab-on-Chip/biosensor platform designed for rapid analysis of small samples of biogas, biomass, and biomix. The platform integrates gas, liquid, and optical sensor channels, as well as a module for transmitting data to the cloud. The experimental data obtained are processed using intelligent data analysis methods, including statistical analysis, correlation analysis, anomaly detection, and assessment of the relationships between monitored parameters. The scientific significance of this work lies in the application of an integrated approach to the analysis of multichannel experimental data obtained from the ESP32 microcontroller, which enables a more accurate and timely assessment of the state of the biogas process. The practical significance lies in the ability to use the proposed approach for remote monitoring, early detection of anomalies, and improving the efficiency of biogas plant management. Full article

Stress corrosion cracking (SCC) of prestressing steel threatens prestressed concrete structures with sudden, brittle failure and minimal visible warning. While mechanical stress, localized corrosion, and hydrogen uptake are recognized drivers, the mechanisms connecting sulfide exposure in cementitious materials to hydrogen uptake and crack initiation at the steel–concrete interface remain poorly understood. This review synthesizes the coupled electrochemical, mechanical, metallurgical, and environmental processes governing SCC, with particular emphasis on the interactions of sulfide species with chloride ingress, carbonation, pitting, and hydrogen-assisted cracking under sustained tensile stress. Evidence indicates that sulfides weaken passive-film protectiveness and facilitate hydrogen entry, while localized corrosion and acidification create favorable conditions for crack initiation and propagation. Because SCC susceptibility emerges from the combined effects of environmental exposure, steel microstructure, and mechanical loading, isolated environmental parameters cannot adequately predict risk. Accelerated laboratory tests offer comparative insight but have limited representativeness of the complex conditions of prestressed concrete. A critical gap persists: no quantitative relationship has yet been established between cement sulfide content, sulfide availability at the steel surface, hydrogen uptake, and actual SCC susceptibility. Bridging this gap requires service-representative experiments on stressed prestressing steel embedded in mortar or concrete to develop reliable durability criteria and move beyond precautionary regulatory limits. Full article

We report the synthesis of a modified benzothiazole sulfide. This compound contains a heterocyclic core, a Boc-protected hydroxylamine, and an appended alkyne. This benzothiazole was accessed through three total steps, including an amidation reaction and two nucleophilic aromatic substitutions. The identity of the title compound was confirmed through ¹H, ¹³C, ¹H–¹H COSY, HSQC, and HMBC NMR, in addition to IR, MALDI-MS, HRMS, and HPLC. Full article

Sulfide solid electrolytes (SSEs) are promising for all-solid-state lithium batteries (ASSLBs) due to their high ionic conductivity, mechanical deformability, and interfacial compatibility. However, SSE interfaces with anodes, cathodes, conductive additives, and current collectors are unstable, triggering safety failures like capacity degradation, internal resistance build-up, thermal runaway, and short circuits. This review summarizes recent progress on interface-induced safety failure mechanisms in sulfide-based ASSLBs, focusing on interface types, failure mechanisms, and thermal/mechanical degradation under multi-field coupling. We survey interface modification strategies and highlight advanced characterization techniques for probing interfacial phenomena. Key challenges and future research directions are discussed. Integrating recent findings, we identify interfacial instability as the primary bottleneck governing safety failures, providing a theoretical and technical framework for rational interface design, performance optimization, and safety enhancement. Throughout this review, we use SSE as the standard abbreviation for sulfide solid electrolytes. Full article

The selective separation of chalcopyrite from pyritic ores represents a major industrial challenge due to inadvertent copper activation. This study systematically investigates the batch flotation kinetics of a complex sulfide ore (Draa Sfar North, Morocco) using a first-order kinetic model ($R^2>0.916$). The impacts of pulp pH, chemical depressants, and specialized collectors were evaluated to optimize the copper/iron selectivity index ($S{I}_{Cu/Fe}$). The results reveal a high-alkalinity paradox: At pH 11.0, chalcopyrite kinetics experience a severe passivation bottleneck ($K_{i,Cu}=0.1330 {\min }^{-1}$). At pH 11.5, selectivity collapses ($SI=2.64$) due to persistent iron sulfide floatability ($K_{i,Fe}=0.2066 {\min }^{-1}$). Conversely, natural pH ($\approx 6.0$) provides a superior baseline ($SI=3.32$), where 40 g/t sodium cyanide (NaCN) yielded a peak index of $S{I}_{Cu/Fe}=10.25$. As an eco-friendly substitute, sodium lignosulfonate (LSNa) achieved outstanding performance ($S{I}_{Cu/Fe}=5.30$), reducing iron kinetics to their lowest level ($K_{i,Fe}=0.0356 {\min }^{-1}$) via ferric–anionic complexation. Furthermore, Danafloat 271 secured the highest collector-driven selectivity ($S{I}_{Cu/Fe}=5.03$) by suppressing the iron matrix ($K_{i,Fe}=0.0306 {\min }^{-1}$) following Hard–Soft Acid–Base principles. This study clarifies specific aspects of selective copper–iron flotation, demonstrating that natural pH circuits with green depressants or selective collectors offer a sustainable alternative. Full article

Pyrite is one of the most common sulfide minerals in polymetallic sulfide ores, and its flotation behavior directly affects the selective separation efficiency of valuable minerals. This study investigated the effects of collector type, pulp pH, pH regulator, and combined collector ratio on pyrite flotation using sodium butyl xanthate (SBX), diethyl dithiocarbamate (DDTC), ammonium dibutyl dithiophosphate (ADDP), and Aerophine 3418A (3418A), together with cyclic voltammetry (CV) and DFTB analyses. The results showed that DDTC and SBX exhibited stronger collecting ability than 3418A and ADDP at natural pH. Increasing pH significantly depressed pyrite flotation, with CaO exerting stronger inhibition than NaOH. Combined collectors displayed pronounced component dependence and ratio sensitivity. CV results indicated that collector adsorption on pyrite is an irreversible electrochemical process, and that calcium-bearing species in the CaO system passivate surface active sites, thereby inhibiting collector adsorption. DFTB calculations revealed that collecting performance is governed by the coordination stability of double-bonded S atoms with surface Fe sites and resistance to hydration. The research results can provide a theoretical basis for regulating pyrite flotation behavior and optimizing reagent regimes in the flotation separation process of complex sulfide ores. Full article

Nanoscale zero-valent iron (nZVI) exhibits great potential in the field of organic pollutant remediation due to its strong reducibility, high specific surface area and unique core–shell structure. However, pristine nZVI has inherent drawbacks including severe particle aggregation, surface passivation and poor electron selectivity, which greatly restrict its practical remediation performance. To improve the reactivity of nZVI, researchers have developed multiple modification approaches that significantly improve the dispersibility, stability and reactivity of nZVI. This review summarizes the main nZVI modification strategies, including metal modification, surface coating, carrier loading, sulfidation modification and biological integration. The advantages and limitations of each modification method are compared. Furthermore, the underlying removal mechanisms of modified nZVI toward typical organic pollutants are elaborated, covering direct reduction, advanced oxidation and synergistic degradation pathways. Key factors governing the degradation efficiency of modified nZVI are subsequently analyzed. Finally, existing bottlenecks for practical implementation and future research perspectives are proposed. Full article

Background: Volcanic gas emissions represent an important but frequently underestimated non-eruptive natural hazard capable of causing severe acute intoxication and sudden death, even in the absence of volcanic eruptions. Although numerous reviews have investigated the chronic health effects of volcanic emissions, evidence regarding acute exposure events remains fragmented. This systematic review aimed to synthesize the available evidence on acute intoxication events and fatalities associated with exposure to sulfur dioxide (SO₂), carbon dioxide (CO₂), and hydrogen sulfide (H₂S) of volcanic origin. Materials and Methods: A systematic literature search was conducted according to the PRISMA 2020 guidelines across six electronic databases (PubMed/MEDLINE, Scopus, Web of Science, Embase, Google Scholar, and WHO IRIS). Results: Six eligible studies describing fatal and non-fatal acute exposure events from five countries (Italy, France, the United States, Cameroon, and the Democratic Republic of Congo) were included. Carbon dioxide and hydrogen sulfide were the gases most frequently associated with fatal outcomes, predominantly occurring in confined spaces, geothermal areas, fumaroles, topographic depressions, or environments where adverse meteorological conditions promoted gas accumulation. The most common clinical manifestations included sudden loss of consciousness, pulmonary edema, respiratory failure, and asphyxial death. The largest documented event, the 1986 Lake Nyos disaster, resulted in more than 1700 fatalities following a massive limnic release of carbon dioxide. Conclusions: Across the included studies, recurring environmental determinants, exposure pathways, and toxicological mechanisms highlighted the critical role of environmental accumulation in shaping exposure risk. Despite the limited number of published cases, the available evidence demonstrates that acute volcanic gas exposure constitutes a significant yet underrecognized public health hazard. Strengthening environmental monitoring, risk communication, visitor safety measures, and interdisciplinary surveillance systems may substantially reduce preventable morbidity and mortality in volcanically active regions. Full article

Dimethyl sulfide (DMS) hydrolysis over protonated Y-type faujasite zeolite (H-FAU) was examined using a hybrid density functional theory/molecular mechanics approach. ONIOM2(M06/6-31+G(d,p):UFF) calculations identified stepwise and concerted pathways. In the stepwise route, initial demethylation produces methanethiol and a surface methoxide species; subsequent reaction of the methoxide with water yields methanol. The calculated activation barriers for the demethylation and hydrolysis steps are 36.6 and 25.0 kcal mol⁻¹, respectively. In contrast, the concerted pathway involves simultaneous demethylation and hydrolysis in a single elementary step without formation of a stable intermediate, with a significantly higher activation barrier of 63.8 kcal mol⁻¹. The results suggest that DMS hydrolysis preferentially proceeds via the stepwise mechanism, with the demethylation step being rate-determining. For the preferred stepwise pathway, the apparent activation barrier for the overall hydrolysis reaction, referenced to the initial state, is 23.2 kcal mol⁻¹. Full article

In deep-sea hydrothermal ecosystems, inorganic sulfur compounds serve as key energy sources for microbes through oxidation, reduction, or disproportionation reactions. However, to date, the bacteria that disproportionate sulfur remain poorly understood. Here, we characterized the physiological and metabolic characteristics of Sulfurovum sp. MH2-6, which was isolated from hydrothermal sediments of the South Mid-Atlantic Ridge. Based on the results of 16S rRNA gene sequence, average nucleotide identity, and DNA–DNA hybridization value, strain MH2-6 belonged to the same species as Sulfurovum mangrovi ST1-3^T. The isolate was able to grow chemolithoautotrophically using thiosulfate, sulfite, or sulfide as the sole energy source, and molecular oxygen as the sole electron acceptor. When using hydrogen as the sole energy source, this bacterium could utilize a wide range of electron acceptors, including oxygen, elemental sulfur, thiosulfate, nitrate, and sulfate. Various organic compounds also supported growth as carbon sources during hydrogen oxidation, suggesting a potential for chemolithomixotrophy. Notably, the isolate could grow via the disproportionation of thiosulfate and elemental sulfur in the presence of ferrihydrite. Further, genome analyses revealed that this bacterium contains a complete reductive citric acid cycle (rTCA) for carbon fixation, multiple hydrogenases, sulfur oxidation, reduction, and transfer enzymes, nitrogenase, and oxygen reductases. Transcriptomic comparisons between sulfur reduction and disproportionation conditions revealed that thiosulfate reductase, type IV sulfide: quinone oxidoreductase, and sulfite dehydrogenase were highly abundant in thiosulfate-disproportionating cultures, while rhodanese-like sulfurtransferases and sulfide dehydrogenase showed increased abundances when grown via elemental sulfur disproportionation. Together, these flexible energy- and carbon-utilizing strategies may enhance the persistence of MH2-6 in hydrothermal vent environments. Full article

The performance of the bacterium Acidithiobacillus ferrooxidans and sodium metabisulfite (MBS) as pyrite depressants in seawater flotation was compared. Microflotation experiments were conducted using pure pyrite, while batch flotation tests were performed using a sulfide ore sample containing pyrite. The results showed that A. ferrooxidans was more effective than MBS in depressing pure pyrite flotation. In the presence of the bacterium, pyrite recovery decreased from 95% to 64% at pH 8 and from 96% to 21% at pH 10. In contrast, MBS exhibited superior performance during flotation of the sulfide ore sample, reducing pyrite recovery from 81% to 57% at pH 8 and from 86% to 57% at pH 10. The results suggest that dissolved copper ions present during flotation of the sulfide ore promote the interaction between MBS and pyrite, thereby enhancing its depressant effect. Conversely, the performance of A. ferrooxidans appears to be reduced in complex ore systems because the bacteria may adhere to other mineral surfaces, decreasing their interaction with pyrite. This phenomenon was not observed during flotation of pure pyrite. SEM–EDS analyses confirmed the presence of copper-containing species on the pyrite surface after exposure to copper ions. These findings indicate that MBS is more suitable than A. ferrooxidans for pyrite depression in complex sulfide ores under seawater flotation conditions, particularly when copper-bearing minerals are present. Full article

Biochar is no longer considered merely a substitute for conventional fillers in asphalt materials; rather, it represents a multifunctional modifier that aligns with the goals of sustainable road design and urban mobility in smart cities. Its application now extends to the rheological modification of asphalt binders, mitigation of asphalt fume emissions, improvement in aging resistance and interfacial adhesion, and assessment of carbon sequestration potential. Biochar can improve the high-temperature stability, rutting and aging resistance, and asphalt–aggregate adhesion of asphalt materials in a suitable dosage, and at the same time reduce emissions of volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), hydrogen sulfide (H₂S), and other fumes. However, the above effects are highly dependent on the biochar feedstock, production process, physicochemical properties, particle size, dosage and degree of dispersion. An excess amount or uneven distribution will reduce the crack resistance and fatigue life at low temperatures; phase separation may also occur and VOC emissions will increase. Therefore, the main problem in this area has shifted from whether biochar is effective to when it can be applied for particular pavement performance goals, what pollutant control targets are aimed for, and over what life-cycle periods. This review integrates evidence obtained at the binder, mastic, and mixture scales and critically evaluates the influence of biochar on pavement performance, fume emissions, aging, interfacial adhesion, and environmental safety. It also argues that empirical dosage selection should be replaced by coordinated optimization of biochar structure, material performance, emission mitigation, and life-cycle impacts. Verification of the low-carbon benefits and environmental safety of biochar-modified asphalt will ultimately require standardized assessment frameworks and consistently defined system boundaries. Ultimately, this work provides a foundation for integrating biochar-modified asphalt into eco-friendly and resilient road infrastructures, aligning with the goals of smart urban mobility and sustainable transportation. Full article