Fluorine-containing sludge (FCS) generated by the semiconductor and photovoltaic industries is hazardous waste, and its treatment and resource utilization are both urgent and critically important. To address the issues of lengthy process flows and low efficiency in the current resource recovery of CaF₂ in FCS, a novel method for converting CaF₂ through low-temperature calcination using Mg(NO₃)₂·6H₂O was proposed. The effect of roasting parameters on the conversion efficiency of CaF₂ was explored and optimized, and the reaction kinetics were clarified. Under the optimal conditions, 98.12% of CaF₂ in FCS was converted to MgF₂. The roasting of CaF₂ follows a chemical diffusion-controlled mechanism with an activation energy of 23.28 kJ/mol. Ultimately, a MgF₂ product with a purity of 98.30% was obtained. Density functional theory calculations showed that Mg(NO₃)₂·6H₂O remained molten at low temperatures, reducing the chemical energy barrier for breaking the Ca-F bond and promoting the reaction. This method offers a straightforward, quick, and effective way to treat FCS and recover fluorine resources, laying a foundation for producing other fluorides and opening a new path for future FCS treatment strategies.

The role of organic carbon source as electron donor in incomplete denitrification, particularly in nitrite (NO₂⁻) accumulation, remains crucial yet poorly understood. A detailed understanding of carbon and nitrogen metabolic interactions is essential for advancing technologies that integrate partial denitrification (PD) with anammox. In this study, the carbon transformation and gradient utilization of various volatile fatty acids (VFAs) were explored to elucidate their impacts on nitrate (NO₃⁻) and NO₂⁻ reduction during PD. Long-term experiments revealed that composite VFAs (a mixture of acetate, propionate and butyrate) achieved the highest nitrate-to-nitrite transformation ratio (NTR) of 79.1%, outperforming single VFA (69.5% with acetate and 69.4% with propionate). The NO₂⁻ accumulation during PD was strongly influenced by the utilization of exogenous, endogenous and extracellular carbon, which varied significantly with VFAs type and dosage. Polyhydroxybutyrate (PHB) served as the primary endogenous electron donor in acetate-driven PD, promoting modest NO₂⁻ accumulation, while polyhydroxyvalerate (PHV) along with glycogen (Gly) was the key contributor in propionate-driven PD, supporting complete NO₃⁻ reduction. In contrast to single VFA-driven PD, the lower levels and delayed utilization of PHB and PHV in composite VFAs-driven PD enabled more stable and efficient NO₂⁻ accumulation. Furthermore, metagenomic analysis illuminated that the transition from single VFA to composite VFAs strengthened the potential for both electron production and their transport to NO₃⁻ reductase. Thauera was always the core denitrifier demonstrating strong adaptability to various VFAs. This study provides mechanistic insights into organic carbon-regulated NO₂⁻ accumulation, filling the gap regarding dynamic changes in carbon utilization during PD.

Mercury (Hg) is largely emitted from coal-fired power plants. For Hg purification, the oxidation of elemental Hg (Hg⁰) to Hg²⁺ in the flue gas over selective catalytic reduction (SCR) catalysts with halogen involvement is the most important step. Based on laboratory tests of Hg⁰ oxidation over cerium (Ce)-modified regenerated V₂O₅-MoO₃/TiO₂ (V-Mo/Ti) SCR catalysts in the presence of HBr, it is necessary to investigate how the Ce-modified catalysts perform in real power plants for further industrial application. Therefore, a 1-year field verification was conducted in a 600 MW power plant unit. The results showed that with increased CaBr₂ addition to coal, the rate-determining factor for Hg⁰ oxidation shifted from the intrinsic catalytic properties of SCR catalysts to bromide concentrations. Meanwhile, owing to the decomposition of CaBr₂, bromide could participate in Hg⁰ oxidation via adsorptive, homogeneous, and heterogeneous chemical processes. For NO_x, its removal efficiency decreased from 96.22% to 61.10% over the Ce-modified catalyst after 1 year of operation, with little effect exerted by CaBr₂, compared with a decrease from 95.79% to 43.92% over the unmodified catalysts. For SO₃, only 41.78 mg/m³ of SO₃ was generated from 6174.27 mg/m³ of SO₂ over the Ce-modified catalysts after 1 year of operation compared with 97.29 mg/m³ of SO₃ over the unmodified catalysts. This study verifies the long-term commercial applicability of Ce-modified regenerated V-Mo/Ti SCR catalysts in power plants.

The improper disposal of marine bottom soft sediment poses significant risks to both ecological systems and human health. Due to its complex composition and contamination, sustainable remediation and reuse remain a major challenge. In tandem, the land limitation in some regions does not offer easy waste treatment, which in some cases hinders local governments in their waste management strategies. To overcome these challenges, this study proposes low-carbon treatments for contaminated marine mud, aimed at promoting efficient in-situ recycling and application as backfilling materials. The optimal treatments and long-term stability of the mud were attained by using aluminosilicate raw materials. Specifically, Unconfined Compressive Strengths (UCS) of up to 7.75, 4.24, 8.69, and 3.15 MPa were achieved respectively in mixtures containing 25% OPC, fly ash, slag, and 5% river sand. These mixtures not only improved the strength but also significantly immobilized the heavy metals efficiently, producing engineered-fill materials that meet both Chinese (GB36600-2018) and U.S. (EPA 540/2-86/001) standards, stipulated for health and environmental safety. Furthermore, the XRD analysis reveals a primary phase dominated by SiO₂ and secondary phases of Ca(CO₃), Mn_1.7Fe_1.3O₄ and a complex silicate mineral phase. Each phase contributes to distinct structural, chemical and mechanical development of the solidified mud, which was influenced by the supplemented raw minerals, as confirmed by the morphological analysis. The proposed treatment formulations not only facilitate large-scale recycling of contaminated marine mud into valuable construction materials, but also advance environmental protection, enhance resource efficiency, and support the goals of carbon reduction and neutrality.

Perfluorooctane sulfonate (PFOS) resists complete defluorination under ambient conditions. We developed a mechanochemical (MC) method using α-Al₂O₃ and Fe that achieved complete defluorination of PFOS. Among the tested metal oxides and zero-valent metals, the combination of α-Al₂O₃ and Fe enabled complete defluorination of PFOS while preventing overreduction of the sulfonate group to generate toxic H₂S. Instead, the reaction produced SO₃^2–, F^–, and amorphous carbon as the main products. The defluorination rate in this MC system was more than three times faster than that reported for other MC systems. This method could not only be applied to PFOS alternatives but also enabled the defluorination of PFOS in soil. During ball milling, the in situ generated coordinative unsaturated Fe³⁺ and Al³⁺ on the surface of the milling reagents bound the sulfonate group of PFOS to promote desulfonation. Fe has a moderate reducing ability that facilitated reductive desulfonation and subsequent defluorination while simultaneously inhibiting the overreduction of the sulfonate group. α-Al₂O₃ suppressed Fe aggregation and critically inhibited the protonation of the desulfonation fragment (i.e., C₈F₁₇^–) owing to the small amount of surface OH^–/H₂O. This ability enhanced the electron transfer from Fe to C₈F₁₇^–, leading to complete defluorination without the generation of hydrofluorocarbons.

The high energy consumption of conventional activated sludge process is posing significant challenge on the current wastewater industry worldwide. Therefore, the development of energy-efficient wastewater treatment processes is urgently needed. This study proposed an energy self-sufficient biosorption/partial nitrification/anammox process by using functionalized carriers to augment the efficiency of partial nitrification and anammox. Specifically, in biosorption stage, COD was captured into sludge, which could further be converted into bio-methane by anaerobic digestion for energy recovery. In the partial nitrification stage, nitrification-functionalized carriers were used for selective enrichment of ammonia-oxidizing bacteria (AOB) to maintain efficient and stable nitrite accumulation, while anammox-functionalized carriers were utilized in anammox stage for massive anammox bacteria accumulation. Long-term operation results showed that with an averaged influent COD concentration of 200.0 mg/L and total nitrogen (TN) concentration of 60.0 mg/L, the effluent consistently achieved an average COD concentration of 25.4 mg/L and an average TN concentration of 13.6 mg/L, which could meet the national discharge standard (GB18918-2002, China). The use of nitrification-functionalized carriers promoted the survival and enrichment of AOB, while anammox-functionalized carriers similarly facilitated the survival and enrichment of anammox bacteria. The effective colonization resulted in a significant upregulation of genes associated with nitrogen metabolism. This study proposes a novel approach for the in-situ selective enrichment of AOB and anammox bacteria to realize efficient partial nitrification-anammox process, which holds potential for achieving energy-neutral mainstream municipal wastewater treatment with low carbon emissions.

This study aims to reveal the seasonal variations in reactive oxygen species (ROS) for the size-resolved ambient particulate matter (PM) collected over one year in a coastal megacity in southeastern China. Through electron paramagnetic resonance (EPR), hydroxyl radicals (·OH) and organic radicals (·R) were measured, with ·OH identified as the dominant species. ROS concentrations exhibited evident seasonality in the following order: winter (6.58 × 10¹¹ spins/m³) > fall (4.17 × 10¹¹ spins/m³) > summer (3.38 × 10¹¹ spins/m³) > spring (2.02 × 10¹¹ spins/m³). Fine-mode particles (PM_0–3.3) constitute less than 40% of PM mass but account for over 60% of the total ROS burden. A variety of water-soluble components such as Fe, Mn, Zn, NO₃⁻, and WSOC exhibited strong correlations with ROS (r > 0.6), of which FTIR confirmed the high aromaticity of WSOC, indicating the seasonal changes in photochemical aging. As revealed by positive matrix factorization (PMF) analysis, vehicle emissions (41.41%) and secondary aerosols (32.73%) contributed mainly to ROS formation, particularly for ·OH. Differently, combustion sources were a major contributor to ·R generation, especially in winter. Its toxicological significance is highlighted by the enrichment of redox-active and aromatic compounds in PM_0–3.3. These findings underscore the pressing need to develop seasonally adaptive control strategies targeting traffic-related and secondary emissions, with particular attention paid to ultrafine particle pollution in coastal urban environments.

In order to comprehensively evaluate potential GHG emissions and reduction of applied carbonized waste biomass, a Prospective Life Cycle Assessment (PLCA) was conducted. This evaluation quantified the carbon sequestration and GHG (CO₂, N₂O, CH₄) reduction effects of two crop residue biochar-based products (biochar and biochar-based fertilizer) from their production to application stages, including applications in diverse soils (black soil, loess, and laterite) for cultivating paddy and other crops respectively. Results showed that the slow pyrolysis process was the main source of GHG emissions due to electricity consumption. Biochar-based fertilizers exhibited higher GHG emissions than biochar because of the additional energy required for extra processing steps. In addition, under the low-carbon scenario with a higher share of clean energy, GHG emissions at the production stage were significantly reduced compared to those under the baseline scenario. At the usage stage, the GHG emissions varied significantly with soil and crop types. In laterite, biochar-based fertilizers for paddy cultivation effectively reduced GHG emissions, while biochar for other crops increased GHG emissions; in black soil, the GHG emissions reduction of biochar in paddy fields was superior to that of biochar-based fertilizers; in loess, for both paddy and other crops, the GHG emissions reduction of biochar was more pronounced. This study indicates that soil physicochemical properties directly affect the GHG reduction efficiency of biochar-based products, resulting in potentially different GHG emissions or reduction in different soil-crop systems.

Amine-containing particles play a critical role in atmospheric chemistry, new particle formation, and haze episodes, but their mixing states and atmospheric processes remain poorly understood, resulting in significant uncertainties in accurately assessing their global budget by models. Here we investigated the seasonal differences in the mixing states and evolution processes of particulate amines in Liaocheng, a heavily polluted city in the North China Plain (NCP), during winter and summer. The dominant amine markers were diethylamine (DEA), trimethylamine (TMA), and triethylamine (TEA) particles, with DEA particles constituting over 70% of total amines. Winter amine-containing particles exhibited higher abundances (winter: 23.0% vs. summer: 17.5%) and elevated biomass–burning indicators (e.g., ⁴⁵CHO₂⁻, ⁵⁹C₂H₃O₂⁻, ⁷³C₃H₅O₂⁻, and ¹¹⁵K₂Cl⁺), along with broader size distributions (0.6–0.9 μm), attributed to anthropogenic sources and particle aging. Conversely, summer amine particles showed fresher signatures (unimodal 0.42 μm peak) with dominant carbonaceous fragments and weaker secondary inorganic signals, reflecting less aging. The gas-to-particle partitioning of amines was significantly influenced by temperature, particle acidity (R_ra), and acid-base reactions, with lower temperatures and higher acidity promoting the amine uptake. DEA particles presented stronger associations with sulfate (r² = 0.87) and nitrate (r² = 0.69) compared to TMA particles. Winter haze events significantly enhanced particulate amines, driven by elevated humidity, lower temperatures, and enhanced R_ra, with random forest and multiple linear regression analyses identifying temperature, R_ra, and O₃ (≥ 15%) as dominant controls. Photochemical processes and sulfate interactions also played critical roles in amine transformations. These findings highlight the complex interplay of environmental and chemical factors governing amine behavior in atmospheric particles, providing essential insights for urban air quality management and climate modeling in the NCP.

This study used ethanol and acetate as substrates, anaerobic digestion sludge as inoculum, and selected bamboo charcoal with three particle size conditions (< 25, 45–75, 100–250 μm) as the mediating material. While maintaining consistent electrical conductivity levels of bamboo charcoal, we investigated the effect of specific surface area on the chain elongation reactions. Experimental results demonstrated that when bamboo charcoal served as the mediating material, larger specific surface area significantly enhanced the chain elongation for the production of medium-chain fatty acids. Microbial community composition analysis via 16S rRNA sequencing demonstrated that bamboo charcoal intervention promoted the enrichment of Clostridium_sensu_stricto_12, a keystone functional microbe exhibiting statistically significant positive correlations with the yield, electron transfer efficiency, and selectivity of MCFAs. Metagenomic analysis identified the simultaneous presence of reverse β-oxidation and fatty acid biosynthesis pathways, with reverse β-oxidation pathway serving as the dominant route. Notably, the Candidatus_Microthrix genus exhibited dual functionality by engaging in both pathways for MCFAs production.

Landfills, serving as the primary disposal sites for municipal solid waste, are increasingly recognized for their potential to contribute to arsenic (As) contamination. The As toxicity and mobility are closely associated with its chemical speciation, with inorganic As species—arsenate [As(V)] and arsenite [As(III)]—being the most prevalent and problematic. The transformation of these species poses substantial risks to both ecosystems and human health. This study delves into the biomineralization behaviors of As(V) and As(III) under the influence of sulfate-reducing bacteria (SRB) isolated from refuse. Results indicate that SRB facilitate the dissimilatory sulfate (SO₄^2–) reduction process, converting SO₄^2– to hydrogen sulfide (H₂S)/hydrosulfide (HS^–), which subsequently reacts with As(III) to form insoluble arsenic-sulfide minerals like As₂S₃, AsS, and As₄S₄. As(III) demonstrated a superior biomineralization potential, with mineralization rates reaching 16.09% (T3) and 20.43% (T4) in As(III)-amended reactors, significantly exceeding those in As(V)-amended reactors (T1 and T2). X-ray diffraction and scanning electron microscopy analyses confirmed the predominant formation of AsS in the presence of As(III) reactor, while As(V) reactor contributed to the formation of As₄S₄. Both environmental parameters, such as pH and SO₄^2– concentration, and the microbial community composition critically influenced the As biomineralization behaviors. Metagenomic sequencing uncovered the pivotal roles of SRB and As(V)-reducing bacteria, including Clostridium and Desulfitobacterium, in mediating SO₄^2– reduction and the detoxification of As(V). This research offers novel insights into the biomineralization mechanisms of As within landfills and lays a theoretical groundwork for the remediation of As pollution.

Methylsiloxanes (MSs) are anthropogenic substances that do not occur naturally, and most studies have focused on their presence in indoor environments. To date, there is limited information regarding their prevalence in road dust across broad geographical scales, with even fewer studies identifying the sources of MSs. This research investigates the levels, regional distributions, and potential origins of MSs in road dust collected from major cities throughout China. The results indicate that these chemicals are prevalent in road dust, with total concentrations of the target MSs ranging from 6.36 to 8618 ng/g dw. Tetradecamethylcycloheptasiloxane was identified as the dominant methylsiloxane. Spatial variations were primarily associated with traffic flow, the value added by the secondary industry, and local population density. Principal component analysis combined with multiple linear regression and positive matrix factorization revealed that vehicle emissions (41.8%–42.3%), industrial activities (38.9%–47.2%), and the use of personal care and consumer products (11.0%–18.8%) were the major contributors to MSs in road dust. The overall source contributions identified by both methods were consistent. These findings highlight the significant role of vehicle emissions and industrial activities and provide valuable insights for developing policies aimed at managing MSs in urban areas.

The co-occurrence of N,N-dimethylformamide (DMF) and residual nitrogen in industrial wastewater presents significant challenges for conventional biological treatment. To overcome these limitations, this study developed an innovative zero-valent iron (ZVI) enhanced nitrate-reducing bioreactor (ZVI-NR) that establishes an efficient electron transfer pathway for simultaneous DMF mineralization and nitrate removal. The ZVI-NR system achieved complete DMF removal (100%) and high nitrate reduction efficiency (96.17% ± 1.50%), representing 40.37% ± 2.30% and 34.23% ± 1.30% improvements over conventional NR system. The key innovation involves establishing an Fe²⁺/Fe³⁺ electron shuttle system, coupled with the selective enrichment of iron-cycling genera (such as Dojkabacteria and Denitratisoma). These genera maintain iron bioavailability and facilitate extracellular electron transfer. The increased enzymatic activity (136.96%–161.23% for nitrate/nitrite reductases), and dynamic extracellular polymeric substance (EPS) secretion (154.73 ± 4.65 mg/g VSS) featuring α-helix-dominated protein structures that improve microbial aggregation (Dojkabacteria, Chryseobacterium and Arenimonas, etc.). The superior performance of the system is further attributed to dual metabolic regulation through feoAB-mediated Fe²⁺ transport and a formate dehydrogenase mediated mechanism that is hypothesized to contribute to the proton motive force. This study demonstrates a technological breakthrough in industrial wastewater treatment, which achieves stable and complete DMF mineralization at high loading rates. The unique iron-mediated electron transfer that enhances efficient DMF degradation and optimized nitrogen removal, addressing the challenge of treating refractory wastewater containing high organic and nitrogen loads.

Bioelectrochemical systems have been widely studied as an enhanced anaerobic digestion (AD) technology for regulating electron transfers during organic degradation and methane production using bioelectrodes. However, owing to their limited interactions with bioelectrodes, suspended microbial communities are relatively less effective than biofilm communities. In this study, a magnetic composite electrode-driven bioelectrochemical reactor is constructed and the synergistic optimization mechanism of magnetic-field-coupled magnetite particles is elucidated. The combined effects of magnetic fields and Fe₃O₄ particle–anode contact on methane production were examined using five membrane-free reactors with different magnetic and particle-size conditions. The magnetic field with 20–40 mesh Fe₃O₄ shortened the start-up time to 48.7 d (32.8% less than the control) and achieved the highest methane rate (1.70 mol CH₄/(m³·d)), chemical oxygen demand (COD) removal (94.34%), and current-driven methane conversion efficiency (68.1%). Electrochemical analysis showed improvements in direct and mediated electron transfer due to increased Fe₃O₄ active site exposure, with cathode coulombic efficiency rising by 90.3%. Microbial analysis revealed that fine particles promoted rapid transfer mediated by Proteobacteria, whereas coarse particles enriched Desulfobacterota through stable mineral–microbe interfaces. These findings demonstrate that regulating magnetic particle–anode interfaces can accelerate start-up, enhance electron transfer, and improve the stability of bioelectrochemical methane production.

Extracellular polymeric substances (EPS) play a crucial role in maintaining the colloidal structure of sewer sludge, which can lead to significant siltation in sewage systems. In this study, a sodium pyrophosphate (SP)-mediated divalent cation chelation strategy was proposed for disrupting divalent cation bridging and macromolecular material entanglement in EPS structure in sewer sludge to achieve adhesion degradation. At the SP dosage of 0.25 g/g TS, the total amount of extractable EPS was found to have increased 2.17 times significantly, accompanied by disruption and outward migration of gelatinous EPS. Concurrently, the functional groups transfer of macromolecules and the structural transformation of aromatic proteins were initiated. In this instance, the microbial cells were lysed, facilitating the molecular deconstruction and solubilization of aromatic proteins, humic acids and carbohydrates. The deterioration of the EPS network and the breakdown of gelatinous biopolymers resulted in significantly reduced sludge cohesion. As a consequence, the mean adhesion force decreased from 4.00 to 2.37 nN, while the total suspended solids (TSS) concentration in the effluent increased by 48.59 times, indicating substantial sludge dissolution and flotation. The loss of divalent cation bridging further increased the surface electronegativity of the sludge matrix, reducing its resistance to hydraulic erosion. In this case, sewer sludge particles could be transported downstream by gravity scouring of the effluent flow. This study demonstrates the feasibility of SP-mediated EPS disruption as an effective in-situ self-cleaning strategy for sewer system management, providing a sustainable solution for mitigating siltation and improving sewer hydraulic efficiency.