ACS ES&T engineering最新文献

Acidic partial nitrification (a-PN) has great potential for efficient nitrite accumulation but may hinder subsequent anammox coupling due to its associated low pH. This study developed an acidic partial nitrification coupling anammox (a-PNA) in a single reactor to elucidate the metabolic interactions. As a prerequisite for anammox, a-PN driven by both Candidatus Nitrosoglobus and Nitrosomonas, maintains a pH below 6, achieving nondiscriminatory suppression of NOBs. Results demonstrate that a-PN is highly reproducible and has been demonstrated in biomass from four wastewater plants across China. During the a-PNA phase, 94.5% nitrogen removal efficiency (NRE) was realized, with effluent quality of 2.7 mg/L NH₄⁺–N, 0.4 mg/L NO₂^––N, and 1.1 mg/L NO₃^––N. The a-PNA could adapt to various stresses by evolving community structure, reconfiguring metabolic pathways, and regulating gene expression. Notably, the anammox community was drastically altered, with Candidatus Brocadia (4.9%), which has weak acid tolerance, being the only detectable genus. Under substrate-limited conditions, a-PNA greatly enhanced organic carbon utilization, energy metabolism, and denitrification capacity, ensuring community stability and metabolic function sustainability. Consequently, even as influent ammonia decreased to 24.2 mg/L, a robust nitrogen removal rate of 0.19 kg/m³/d and NRE of 89.3% was demonstrated. This study presents a novel, sustainable wastewater treatment approach, contributing to environmental sustainability.

Large-scale and sustainable photocatalytic water treatment requires semiconductors with appropriate band structures and efficient charge transfer properties. Motivated by this point, a facial method is reported for synthesizing an efficient single-atom photocatalyst (Fe_SA-PCN) consisting of polymeric graphitic carbon nitride (g-C₃N₄) rationally integrated with Fe single atoms (Fe SAs). Fe SAs not only enhance the oxidation ability of the holes on the valence band but also introduce a doping energy level directly into the band gap, significantly expanding the light absorption range of Fe_SA-PCN. The density functional theory (DFT) calculations and characterization results such as Kelvin probe force microscopy (KPFM) imply that a significant polarized distribution of surface charges is constructed owing to the electronic interaction between Fe SAs and g-C₃N₄. This enables the efficient separation and transfer of photogenerated charge carriers for surface reactions. Subsequently, high-oxidation-capability holes directly oxidize adsorbed pollutants, while electrons are captured by oxygen, reduced via a two-electron process to H₂O₂, and further activated into ^•OH for pollutant degradation. Consequently, Fe_SA-PCN demonstrates outstanding efficiency in pollutant degradation, resistance to interference, and stability, which proposes a promising strategy for developing g–C₃N₄–based photocatalysts for applications in environmental remediation.

Copper (Cu)-based catalysts have emerged as cost-effective and sustainable alternatives to noble metal systems (e.g., Pt, Pd) for catalytic CO oxidation. However, their practical application is hindered by insufficient low-temperature activity and rapid deactivation under wet conditions containing moisture. To address these challenges, this work introduces CeO₂-modified CuO/MgO-Al₂O₃ (Cu-Ce/MA) catalysts, strategically designed to enhance the catalytic performance and water resistance simultaneously. These catalytic materials were evaluated for CO oxidation under both dry and humid conditions, revealing that CeO₂ modification significantly improves the low-temperature activity. Specifically, the optimal catalyst, Cu-30Ce/MA, achieved a 50% CO conversion temperature (T₅₀) of 151 °C, a marked reduction from 218 °C on Cu/MA reference catalyst. Furthermore, the water resistance improves in a CeO₂ content-dependent manner, with higher CeO₂ loadings imparting greater stability in humid environments. Detailed characterizations demonstrate that CeO₂ promotes the dispersion of CuO and stabilizes Cu sites, while also enhancing the low-temperature reducibility and CO adsorption capacity. Crucially, CeO₂ modification suppresses the competitive H₂O adsorption, mitigating water-induced deactivation. These synergistic effects collectively rationalize the superior activity and durability of Cu-Ce/MA catalysts. By elucidating the dual role of CeO₂ in optimizing Cu-based systems, this study advances the rational design of cost-effective catalysts for real-world CO emission control, particularly under water-rich industrial conditions.

Microalgae can capture CO₂ from the air and convert it into biomass and valuable byproducts, positioning these organisms as the key in terms of sustainable carbon fixation technologies. However, cultivating microalgae efficiently and cost-effectively remains a significant challenge. In this study, we enhanced the cultivation of microalgal cells within a silk/alginate hydrogel, shielded by CO₂ adsorption/desorption functional fabrics, to generate an innovative sandwich-structured composite system. Additionally, carbonic anhydrase-encapsulated silk fibroin nanoparticles were synthesized and co-embedded with the microalgae in the hydrogel. This silk-based microencapsulation sustained enzymatic activity, improving the conversion of CO₂ to bicarbonate and providing vital inorganic carbon for microalgal growth. The integration of microchannels within the gel facilitated continuous flow of culture medium via a microinjection pump, addressing nutrient deficiencies during prolonged exposure to air. Our findings indicate that microalgae cultivated in this system exhibit a significantly higher growth rate and carbon fixation rate compared to control setups, highlighting their potential as a carbon fixation system.

Mechanical stirring is the most efficient method for enhancing solid-state anaerobic digestion (SS-AD). However, the current understanding of its mass and heat transfer is limited due to experimental constraints. Here, two 100 L SS-AD reactors were established: one with mechanical stirring and the other without. Temperature distributions were conducted to study heat transfer; computational fluid dynamics (CFD) was combined with the effective diffusion coefficient (D_eff) to validate mass transfer. Environmental parameters were incorporated to determine the influence of heat and mass transfer on the microenvironment. The results revealed that the cumulative CH₄ yield with mechanical stirring was increased by 32.21%. Mass transfer had a greater impact on the microenvironment and microbial communities’ distribution than heat transfer. During the start-up stage of AD, mechanical stirring facilitated the homogeneous dispersion of microorganisms. It promoted substrate hydrolysis, while reducing methanogenic potential on the peak CH₄ production phase, indicating a lower intensity of mechanical stirring is required in the following methanogenesis stage. For this case, metagenome analysis confirmed that mechanical stirring enhanced microbial mobility and environmental adaptability. However, it limited microbial DNA synthesis, ribosome, and functions related to microbial reproduction, resulting in a reduction in the CH₄ production potential of the reactor.

Volatile organic compounds (VOCs) have caused serious harm to human health and the ecological environment. As a promising strategy, the catalytic oxidation of VOCs into harmless products such as H₂O and CO₂ has been widely employed. Although many catalysts have been developed for VOC decomposition, the design and synthesis of functional catalysts toward multicomponent VOC purification in industrial exhaust gas under reality remains a great challenge. In the actual vent, the composition of multicomponent VOCs is complex and impurities such as NO_x, SO₂, and H₂O are also present. Traditional catalysts often suffer from poor stability, deactivation by impurities, and inefficient oxidation of complex VOC mixtures in industrial settings. Addressing these challenges requires a deeper understanding of the fundamental mechanisms and advanced catalyst design strategies. Therefore, elucidating the mechanism of multicomponent VOC oxidation and revealing the influential behavior of impurities are urgently required to guide researchers on how to synthesize effective and stable catalysts proactively for multicomponent VOC purification under reality. Accordingly, this review systematically summarizes the recent advances in the engineering of highly active and durable catalysts for the oxidation of multicomponent VOCs. The experimental and theoretical studies revealing the mixing effects occurring in the catalytic oxidation process of multicomponent VOCs are also highlighted. Further development of and research on catalysts to be adopted in multipollutant controlling are proposed. This review can help researchers to better understand the catalytic elimination of multicomponent VOCs and provide a great foundation for future design and practical industrial application of VOC oxidation catalysts.

Actualizing energy-efficient and sustainable activation of peroxymonosulfate (PMS) for advanced wastewater treatment remains a persistent challenge. While piezoelectric materials can harness mechanical energy to activate PMS, they often suffer from inefficient carrier separation, limited active sites, and poor recyclability. Here, we introduce a novel piezoelectric-driven approach for PMS activation using a chitosan hydrogel-encapsulated BaTiO₃/MoS₂ Z-scheme heterojunction (denoted as BTO/MS@CSH). The interfacial electric field within the BTO/MS heterojunction provides a strong driving force for electron–hole separation, ensuring a consistent supply of piezo-excited carriers for cleaving the O–O bonds in PMS. The hydrogel encapsulation is conducive to rapid PMS capture and electron transfer via its functional groups and 3D polymer chain spatial structure, further reducing catalyst consumption, preventing metal leaching, and allowing for easy recovery. This integrated system achieves a remarkable 96.1% degradation of levofloxacin (LEV) within 60 min, with a rate constant of 0.0446 min^–1, demonstrating the synergistic interaction between piezoelectric catalysis and PMS activation while enhancing reactive oxygen species (ROS) generation. Ultimately, the synergistic action of various ROS ensures the mineralization of LEV and safe, nontoxic disposal. This study provides insights into the design of advanced piezoelectric catalysts for sustainable environmental remediation.

Nitrogen oxides (NO_x) and methyl mercaptan (CH₃SH) are prevalent atmospheric pollutants that frequently coexist in industrial flue gases emitted from the petroleum chemical industry, municipal waste incineration, and biomass combustion. It is challenging to achieve the synergistic catalytic elimination of NO_x and CH₃SH in CaO-containing flue gases. A comprehensive investigation into the copoisoning mechanisms of CaO and CH₃SH is essential yet remains insufficiently explored. In this work, we unravel the antagonistic effects between CaO and sulfate species on a CuO/Al₂O₃ model catalyst during the synergistic catalytic elimination of NO_x and CH₃SH. In the absence of CaO, the SO₄^2– species generated from the oxidation of CH₃SH can occupy CuO sites, resulting in suboptimal CO₂ selectivity. However, in the presence of CaO, the SO₄^2– species can preferentially bind to CaO that is combined with the Al₂O₃ support. Such a CaO-induced shift in sulfate species bridging behavior not only liberates CuO active sites but also modulates their electronic structures, thereby enhancing the CO₂ selectivity. These findings demonstrate that CaO can mitigate the poisoning effects of CH₃SH on the catalyst during the synergistic catalytic elimination of NO_x and CH₃SH. This research offers valuable insights for designing catalysts capable of synergistically eliminating NO_x and sulfur-containing VOCs in complex flue gases containing alkaline impurities.