Solar-driven methanogenesis with ultrahigh selectivity by turning down H2 production at biotic-abiotic interface

Dual-mode harvest solar energy for photothermal Cu2-xSe biomineralization and seawater desalination by biotic-abiotic hybrid

Biotic-abiotic hybrid photocatalytic system is an innovative strategy to capture solar energy. Diversifying solar energy conversion products and balancing photoelectron generation and transduction are critical to unravel the potential of hybrid photocatalysis. Here, we harvest solar energy in a dual mode for Cu2-xSe nanoparticles biomineralization and seawater desalination by integrating the merits of Shewanella oneidensis MR-1 and biogenic nanoparticles. Photoelectrons generated by extracellular Se0 nanoparticles power Cu2-xSe synthesis through two pathways that either cross the outer membrane to activate periplasmic Cu(II) reduction or are directly delivered into the extracellular space for Cu(I) evolution. Meanwhile, photoelectrons drive periplasmic Cu(II) reduction by reversing MtrABC complexes in S. oneidensis. Moreover, the unique photothermal feature of the as-prepared Cu2-xSe nanoparticles, the natural hydrophilicity, and the linking properties of bacterium offer a convenient way to tailor photothermal membranes for solar water production. This study provides a paradigm for balancing the source and sink of photoelectrons and diversifying solar energy conversion products in biotic-abiotic hybrid platforms.

Abiotic Methane Production Driven by Ubiquitous Non-Fenton-Type Reactive Oxygen Species

Abiotic CH4 production driven by Fenton-type reactive oxygen species (ROS) has been confirmed to be an indispensable component of the atmospheric CH4 budget. While the chemical reactions independent of Fenton chemistry to ROS are ubiquitous in nature, it remains unknown whether the produced ROS can drive abiotic CH4 production. Here, we first demonstrated the abiotic CH4 production at the soil-water interface under illumination. Leveraging this finding, polymeric carbon nitrides (CNx) as a typical analogue of natural geobattery material and dimethyl sulfoxide (DMSO) as a natural methyl donor were used to unravel the underlying mechanisms. We revealed that the ROS, photocatalytically produced by CNx, can oxidize DMSO into CH4 with a high selectivity of 91.5 %. Such an abiotic CH4 production process was further expanded to various non-Fenton-type reaction systems, such as electrocatalysis, pyrocatalysis and sonocatalysis. This work provides insights into the geochemical cycle of abiotic CH4, and offers a new route to CH4 production via integrated energy development.

Proposed mechanisms of electron uptake in metal-corroding methanogens and their potential for CO2 bioconversion applications

Some methanogens are electrotrophic bio-corroding microbes that can acquire electrons from solid surfaces including metals. In the laboratory, pure cultures of methanogenic cells oxidize iron-based materials including carbon steel, stainless steel, and Fe0. For buried or immersed pipelines or other metallic structures, methanogens are often major components of corroding biofilms with complex interspecies relationships. Models explaining how these microbes acquire electrons from solid donors are multifaceted and include electron transfer via redox mediators such as H2 or by direct contact through membrane proteins. Understanding the electron uptake (EU) routes employed by corroding methanogens is essential to develop efficient strategies for corrosion prevention. It is also beneficial for the development of bioenergy applications relying on methanogenic EU from solid donors such as bioelectromethanogenesis, hybrid photosynthesis, and the acceleration of anaerobic digestion with electroconductive particles. Many methanogenic species carrying out biocorrosion are the same ones forming the extensive abiotic-biological interfaces at the core of these bio-applications. This review will discuss the interactions between corrosive methanogens and metals and how the EU capability of these microbes can be harnessed for different sustainable biotechnologies.

External Electrons Directly Stimulate Escherichia coli for Enhancing Biological Hydrogen Production

External electric field has the potential to influence metabolic processes such as biological hydrogen production in microorganisms. Based on this concept, we designed and constructed an electroactive hybrid system for microbial biohydrogen production under an electric field comprised of polydopamine (PDA)-modified Escherichia coli (E. coli) and Ni foam (NF). In this system, electrons generated from NF directly migrate into E. coli cells to promote highly efficient biocatalytic hydrogen production. Compared to that generated in the absence of electric field stimulation, biohydrogen production by the PDA-modified E. coli-based system is significantly enhanced. This investigation has demonstrated the mechanism for electron transfer in a biohybrid system and gives insight into precise basis for the enhancement of hydrogen production by using the multifield coupling technology.

Solar-driven sugar production directly from CO2 via a customizable electrocatalytic-biocatalytic flow system

Conventional food production is restricted by energy conversion efficiency of natural photosynthesis and demand for natural resources. Solar-driven artificial food synthesis from CO2 provides an intriguing approach to overcome the limitations of natural photosynthesis while promoting carbon-neutral economy, however, it remains very challenging. Here, we report the design of a hybrid electrocatalytic-biocatalytic flow system, coupling photovoltaics-powered electrocatalysis (CO2 to formate) with five-enzyme cascade platform (formate to sugar) engineered via genetic mutation and bioinformatics, which achieves conversion of CO2 to C6 sugar (L-sorbose) with a solar-to-food energy conversion efficiency of 3.5%, outperforming natural photosynthesis by over three-fold. This flow system can in principle be programmed by coupling with diverse enzymes toward production of multifarious food from CO2. This work opens a promising avenue for artificial food synthesis from CO2 under confined environments.

Rumen microbes, enzymes, metabolisms, and application in lignocellulosic waste conversion - A comprehensive review

The rumen of ruminants is a natural anaerobic fermentation system that efficiently degrades lignocellulosic biomass and mainly depends on synergistic interactions between multiple microbes and their secreted enzymes. Ruminal microbes have been employed as biomass waste converters and are receiving increasing attention because of their degradation performance. To explore the application of ruminal microbes and their secreted enzymes in biomass waste, a comprehensive understanding of these processes is required. Based on the degradation capacity and mechanism of ruminal microbes and their secreted lignocellulose enzymes, this review concentrates on elucidating the main enzymatic strategies that ruminal microbes use for lignocellulose degradation, focusing mainly on polysaccharide metabolism-related gene loci and cellulosomes. Hydrolysis, acidification, methanogenesis, interspecific H2 transfer, and urea cycling in ruminal metabolism are also discussed. Finally, we review the research progress on the conversion of biomass waste into biofuels (bioethanol, biohydrogen, and biomethane) and value-added chemicals (organic acids) by ruminal microbes. This review aims to provide new ideas and methods for ruminal microbe and enzyme applications, biomass waste conversion, and global energy shortage alleviation.

Nitrate removal by anammox bacteria utilizing photoexcited electrons via inward extracellular electron transfer channel

Dissimilatory nitrate reduction to ammonium (DNRA) has been found to occur in some anammox bacteria species, and the DNRA metabolites (nitrite and ammonium) can further be removed to nitrogen from water. However, the activation of DNRA pathway of anammox bacteria is usually limited by the access to electron donors. Herein, we constructed a photosensitized hybrid system combining anammox bacteria (Candidatus Kuenenia stuttgartiensis and Candidatus Brocadia anammoxidans) with CdS nanoparticles semiconductor for energy-efficient NO3- removal. Such photosensitized anammox-CdS hybrid systems achieved NO3- removal with an average efficiency of 88% (the maximum of 91%) and a N2 selectivity of 72%, only with photoexcited electrons as donors. The DNRA-anammox metabolism of anammox bacteria was proved to responsible for NO3- removal via inward extracellular electron transfer channel. The greatly up-regulated genes encoding c-type cytochrome proteins (5 or 11 hemes) in the outer membrane, c-type cytochrome protein (4 hemes) and electron transport protein RnfA-E in the inner membrane, ferredoxin (2Fe-2S) in the cytoplasm and c-type cytochrome bc1 in anammoxosome membrane were supposed to play key roles in the inward extracellular electron transfer pathway. This work provides a novel insight into the design of the biotic-abiotic hybrid photosynthetic systems, and opens a new strategy for light-driven NO3- removal from the perspective of light energy input.

A hybrid photocatalytic system enables direct glucose utilization for methanogenesis

Integration of methanogenic archaea with photocatalysts presents a sustainable solution for solar-driven methanogenesis. However, maximizing CH4 conversion efficiency remains challenging due to the intrinsic energy conservation and strictly restricted substrates of methanogenic archaea. Here, we report a solar-driven biotic-abiotic hybrid (biohybrid) system by incorporating cadmium sulfide (CdS) nanoparticles with a rationally designed methanogenic archaeon Methanosarcina acetivorans C2A, in which the glucose synergist protein and glucose kinase, an energy-efficient route for glucose transport and phosphorylation from Zymomonas mobilis, were implemented to facilitate nonnative substrate glucose for methanogenesis. We demonstrate that the photo-excited electrons facilitate membrane-bound electron transport chain, thereby augmenting the Na+ and H+ ion gradients across membrane to enhance adenosine triphosphate (ATP) synthesis. Additionally, this biohybrid system promotes the metabolism of pyruvate to acetyl coenzyme A (AcCoA) and inhibits the flow of AcCoA to the tricarboxylic acid (TCA) cycle, resulting in a 1.26-fold augmentation in CH4 production from glucose-derived carbon. Our results provide a unique strategy for enhancing methanogenesis through rational biohybrid design and reprogramming, which gives a promising avenue for sustainably manufacturing value-added chemicals.

Peracetic acid pretreatment improves biogas production from anaerobic digestion of sewage sludge by promoting organic matter release, conversion and affecting microbial community

Peracetic acid (PAA) pretreatment is considered as a novel and effective chemical pretreatment method for sludge. However, there is little information available on potential mechanisms of how PAA pretreatment affects sludge anaerobic digestion (AD). To fill the knowledge gap, this study investigated the effects and potential mechanisms of PAA pretreatment on sludge AD systems from physicochemical and microbiological perspectives. Batch experiments resulted that biogas production was enhanced by PAA pretreatment and the highest cumulative biogas yield (297.94 mL/g VS (volatile solid)) was obtained with 2 mM/g VS of PAA pretreatment. Kinetic model analysis illustrated that the PAA pretreatment improved the biogas potential (Pt) of sludge AD, but prolonged the lag phase (λ) of AD. Mechanistic studies revealed that reactive oxygen species (ROS) (HO•, O2-•, 1O2 and CH3C(O)OO•) were the major intermediate products of PAA decomposition. These ROS effectively promoted the decomposition and solubilization of sludge, and provided more biodegradable organic matter for the following AD reactions. 16S rRNA amplicon sequencing showed that some functional microorganisms associated with hydrolysis, acidogenesis, acetogenesis as well as methanogenesis, such as Hydrogenispora, Romboutsia, Longivirga, Methanosarcina and Methanosaet, were significantly enriched in reactors pretreated with PAA. Redundancy analysis and variation partitioning analysis indicated that functional microorganisms were significantly correlated with intermediate metabolites (soluble carbohydrate, soluble protein, soluble chemical oxygen demand and volatile fatty acids) and cumulative biogas production. This study provides a fresh understanding of the effects and mechanisms of PAA pretreatment on sludge AD, updates the insights into the response of functional microorganisms to PAA pretreatment, and the findings obtained might provide a fundamental basis for chemical pretreatment of sludge AD using oxidants.

Enhanced azo dye reduction at semiconductor-microbe interface: The key role of semiconductor band structure

Low-energy environmental remediation could be achieved by biocatalysis with assistance of light-excited semiconductor, in which the energy band structure of semiconductor has a significant influence on the metabolic process and electron transfer of microbes. In this study, direct Z-scheme and type II heterojunction semiconductor with different energy band structure were successfully synthesized for constructing semiconductor-microbe interface with Shewanella oneidensis MR-1 to achieve acid orange7 (AO7) biodegradation. UV-vis diffuse reflection spectroscopy, photoluminescence spectra and photoelectrochemical analysis revealed that the direct Z-scheme heterojunction semiconductor had stronger reduction power and faster separation of photoelectron-hole, which was beneficial for the AO7 biodegradation at semiconductor-microbe interface. Riboflavin was also involved in electron transfer between the semiconductor and microbes during AO7 reduction. Transcriptome results illustrated that functional gene expression of Shewanella oneidensis MR-1 was upregulated significantly with photo-stimulation of direct Z-scheme semiconductor, and Mtr pathway and conductive pili played the important roles in the photoelectron utilization by Shewanella oneidensis MR-1. This work is expected to provide alternative ideas for designing semiconductor-microbial interface with efficient electron transfer and broadening their applications in bioremediation.

Enhancing electricity-driven methanogenesis by assembling biotic-abiotic hybrid system in anaerobic membrane bioreactor

Biotic-abiotic hybrid systems are promising technologies to enhance methane production in anaerobic wastewater treatment. However, the dense structure of the extracellular polymeric substances (EPS) present in anaerobic granular sludge (AGS) poses challenges with respect to the implementation of hybrid systems and efficient interspecies electron transfer. In this study, the use of AGS with a Ni/Fe layered double hydroxide@activated carbon (Ni/Fe LDH@C-AGS) was investigated in an anaerobic membrane bioreactor (AnMBR). The hybrid system showed a significant increase of 82% in methane production. Further research revealed that Ni/Fe LDH@C regulated the dense structure of EPS, stimulated the production of cytochromes, and facilitated the decomposition of nonconductive substances. Surprisingly, the hybrid system also promoted resistance to membrane fouling and extended membrane life by 81%. This study provides insights into the operation of a biotic-abiotic hybrid system by regulating the dense structure of EPS ultimately resulting in an enhanced methane production.

Revealing Co-N4 @Co-NP Bridge-Enabled Fast Charge Transfer and Active Intracellular Methanogenesis in Bio-Electrochemical CO2 -Conversion with Methanosarcina Barkeri

To significantly advance the bio-electrochemical CO2 -conversion rate and unfold the correlation between the abiotic electrode and the attached microorganisms, an atomic-nanoparticle bridge of Co-N4 @Co-NP crafted in metal-organic frameworks-derived nanosheets is integrated with a model methanogen of Methanosarcina barkeri (M. barkeri). The direct bonding of N in Co-N4 and Fe in member protein of Cytochrome b (Cytb) activates a fast direct electron transfer path while the Co nanoparticles further strengthen this bonding via decreasing the energy gap between the p-band center of N and the d-band center of Fe. This multiorbital tuning operation of Co nanoparticles also enhances the coenzyme F420-mediated electron transfer by enabling the electron flow direct to the hydrogenation sites. Particularly, the increased surface electric field of the Co-N4 @Co-NP bridge-based nanosheet electrode facilitates the interfacial Na+ accumulation to expedite ATPase transport for powering intracellular CO2 conversion. Remarkably, the self-assembled M.barkeri-Co-N4 @Co-NP biohybrid achieves a high methane production rate of 3860 mmol m-2 day-1 , which greatly outperforms other reported biohybrid systems. This work demonstrates a comprehensive scrutinization of biotic-abiotic energy transfer, which may serve as a guiding principle for efficient bio-electrochemical system design.

Unexpected metabolic rewiring of CO2 fixation in H2-mediated materials-biology hybrids

A hybrid approach combining water-splitting electrochemistry and H2-oxidizing, CO2-fixing microorganisms offers a viable solution for producing value-added chemicals from sunlight, water, and air. The classic wisdom without thorough examination to date assumes that the electrochemistry in such a H2-mediated process is innocent of altering microbial behavior. Here, we report unexpected metabolic rewiring induced by water-splitting electrochemistry in H2-oxidizing acetogenic bacterium Sporomusa ovata that challenges such a classic view. We found that the planktonic S. ovata is more efficient in utilizing reducing equivalent for ATP generation in the materials-biology hybrids than cells grown with H2 supply, supported by our metabolomic and proteomic studies. The efficiency of utilizing reducing equivalents and fixing CO2 into acetate has increased from less than 80% of chemoautotrophy to more than 95% under electroautotrophic conditions. These observations unravel previously underappreciated materials' impact on microbial metabolism in seemingly simply H2-mediated charge transfer between biotic and abiotic components. Such a deeper understanding of the materials-biology interface will foster advanced design of hybrid systems for sustainable chemical transformation.

Construction of Core-shell Sb2 s3 @Cds Nanorod with Enhanced Heterointerface Interaction for Chromium-Containing Wastewater Treatment

How to collaboratively reduce Cr(VI) and break Cr(III) complexes is a technical challenge to solve chromium-containing wastewater (CCW) pollution. Solar photovoltaic (SPV) technology based on semiconductor materials is a potential strategy to solve this issue. Sb2 S3 is a typical semiconductor material with total visible-light harvesting capacity, but its large-sized structure highly aggravates disordered photoexciton migration, accelerating the recombination kinetics and resulting low-efficient photon utilization. Herein, the uniform mesoporous CdS shell is in situ formed on the surface of Sb2 S3 nanorods (NRs) to construct the core-shell Sb2 S3 @CdS heterojunction with high BET surface area and excellent near-infrared light harvesting capacity via a surface cationic displacement strategy, and density functional theory thermodynamically explains the breaking of SbS bonds and formation of CdS bonds according to the bond energy calculation. The SbSCd bonding interaction and van der Waals force significantly enhance the stability and synergy of Sb2 S3 /CdS heterointerface throughout the entire surface of Sb2 S3 NRs, promoting the Sb2 S3 -to-CdS electron transfer due to the formation of built-in electric field. Therefore, the optimized Sb2 S3 @CdS catalyst achieves highly enhanced simulated sunlight-driven Cr(VI) reduction (0.154 min-1 ) and decomplexation of complexed Cr(III) in weakly acidic condition, resulting effective CCW treatment under co-action of photoexcited electrons and active radicals. This study provides a high-performance heterostructured catalyst for effective CCW treatment by SPV technology.

Advances in understanding entire process of medium chain carboxylic acid production from organic wastes via chain elongation

Chain elongation is an environmentally friendly biological technology capable of converting organic wastes into medium chain carboxylic acids (MCCAs). This review aims to offer a comprehensive analysis of MCCA production from organic wastes via chain elongation. Seven kinds of organic wastes are introduced and classified as easily degradable and hardly degradable. Among them, food waste, fruit and vegetable waste are the most potential organic wastes for MCCA production. Combined pretreatment technologies should be encouraged for the pretreatment of hardly degradable organic wastes. Furthermore, the mechanisms during MCCA production are analyzed, and the key influencing factors are evaluated, which affect the MCCA production and chain elongation efficiency indirectly. Extracting MCCA simultaneously is the most important way to improve MCCA production efficiency, and technologies for sequentially extracting different kinds of MCCAs are recommended. Finally, some perspectives for future chain elongation researches are proposed to promote the large-scale application of chain elongation.

High-Crystallinity BiOCl Nanosheets as Efficient Photocatalysts for Norfloxacin Antibiotic Degradation

Semiconductor photocatalysts are essential materials in the field of environmental remediation. Various photocatalysts have been developed to solve the contamination problem of norfloxacin in water pollution. Among them, a crucial ternary photocatalyst, BiOCl, has attracted extensive attention due to its unique layered structure. In this work, high-crystallinity BiOCl nanosheets were prepared using a one-step hydrothermal method. The obtained BiOCl nanosheets showed good photocatalytic degradation performance, and the degradation rate of highly toxic norfloxacin using BiOCl reached 84% within 180 min. The internal structure and surface chemical state of BiOCl were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, Fourier transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance (UV-vis), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectra (XPS), and photoelectric techniques. The higher crystallinity of BiOCl closely aligned molecules with each other, which improved the separation efficiency of photogenerated charges and showed high degradation efficiency for norfloxacin antibiotics. Furthermore, the obtained BiOCl nanosheets possess decent photocatalytic stability and recyclability.

Volatile fatty acid production in anaerobic fermentation of food waste saccharified residue: Effect of substrate concentration

In this study, food waste saccharified residue was used to produce volatile fatty acids (VFAs), and the effects of substrate concentration on VFA production, VFA composition, acidogenic efficiency, microbial community, and carbon transfer were investigated. Interestingly, chain elongation from acetate to n-butyrate played an important role with a substrate concentration of 200 g/L in the acidogenesis process. Results showed that 200 g/L was a suitable substrate concentration for both VFA and n-butyrate production, the highest VFA production, and n-butyrate composition were 280.87 mg COD/g vS and more than 90.00 %, respectively, and VFA/SCOD reached 82.39 %. Microbial analysis showed that Clostridium_Sensu_Stricto_12 promoted n-butyrate production by chain elongation. Carbon transfer analysis indicated that chain elongation made a contribution of 43.93 % to n-butyrate production. Totally 38.47 % of organic matter in food waste saccharified residue was further utilized. This study provides a new way for n-butyrate production with waste recycling and low cost.

Biodegradation of p-hydroxybenzoic acid in Herbaspirillum aquaticum KLS-1 isolated from tailing soil: Characterization and molecular mechanism

The wide distribution of p-hydroxybenzoic acid (PHBA) in the environments has attracted great concerns due to its potential risks to organisms. Bioremediation is considered a green way to remove PHBA from environment. Here, a new PHBA-degrading bacterium Herbaspirillum aquaticum KLS-1was isolated and its PHBA degradation mechanisms were fully evaluated. Results showed that strain KLS-1 could utilize PHBA as the sole carbon source and completely degrade 500 mg/L PHBA within 18 h. The optimal conditions for bacterial growth and PHBA degradation were pH values of 6.0-8.0, temperatures of 30 °C-35 °C, shaking speed of 180 rpm, Mg²⁺ concentration of 2.0 mM and Fe²⁺ concentration of 1.0 mM. Draft genome sequencing and functional gene annotations identified three operons (i.e., pobRA, pcaRHGBD and pcaRIJ) and several free genes possibly participating in PHBA degradation. The key genes pobA, ubiA, fadA, ligK and ubiG involved in the regulation of protocatechuate and ubiquinone (UQ) metabolisms were successfully amplified in strain KLS-1 at mRNA level. Our data suggested that PHBA could be degraded by strain KLS-1 via the protocatechuate ortho-/meta-cleavage pathway and UQ biosynthesis pathway. This study has provided a new PHBA-degrading bacterium for potential bioremediation of PHBA pollution.

Surfactant aggravated the antibiotic's stress on antibiotic resistance genes proliferation by altering antibiotic solubilization and microbial traits in sludge anaerobic fermentation

The excessive application of antibiotics and surfactants resulted in their massive accumulation in waste activated sludge (WAS), but the co-occurrent impacts of antibiotics and surfactants on the antibiotic resistant genes (ARGs) fates have seldom reported. This work mainly revealed the roles and critical mechanisms of sodium dodecyl benzene sulfonate (SDBS) on the sulfadiazine (SDZ) stressing for ARGs distribution during WAS anaerobic fermentation. High-throughput qPCR and metagenomic analysis revealed that SDBS aggravated the SDZ selective pressure, and accelerated the proliferation of ARGs. The total abundance of ARGs was increased from 8.81 × 10¹⁰ in SDZ to 1.17 × 10¹¹ copies/g TSS in the SDBS/SDZ co-occurrence system. Specifically, the absolute abundances of ermF (MLSB), mefA (MLSB), tetM-01 (tetracycline), tetX (tetracycline), sul2 (sulfonamide) and strB (aminoglycoside) were risen from 4.60 × 10⁸-7.44 × 10⁹ copies/g TSS in the SDZ reactor to 1.02 × 10⁹-4.63 × 10¹⁰ copies/g TSS in SDBS/SDZ reactor. SDBS was contributed to the SDZ solubilization and simultaneously effective in disintegrating extracellular polymeric substances and improving cell membrane permeability, which would facilitate the SDZ transport and its interactions with ARGs hosts. Consequently, the microbial community structure was evidently altered, and the typical ARGs hosts (i.e., Saccharimonadales and Ahniella) were greatly enriched. Also, the cell signal transduction systems (i.e., glnL, glrK and pilG), oxidative stress response (i.e., frmA and recA) and bacterial secretion systems (i.e., VirB4), which were related with ARGs propagation, were all provoked in the co-occurred SDBS/SDZ reactor compared with that of sole SDZ. PLS-PM analysis suggested that the bacterial community was the predominant factor that determined the ARGs fates, followed by mobile genetic elements and metabolic pathway. This work demonstrated the interactive effects of surfactants and antibiotics on the ARGs fates in WAS fermentation systems and gave insightful implications on the ecological risks of different exogenous pollutants.

Ciprofloxacin degradation performances and mechanisms by the heterogeneous electro-Fenton with flocculated fermentation biochar

Antibiotic fermentation residue flocculated by polymeric ferric sulfate (PFS) has been classified as a "hazardous waste" in China. In this study, it was recycled into antibiotic fermentation residue biochar (AFRB) by pyrolysis and used as a heterogeneous electro-Fenton (EF) catalyst for ciprofloxacin (CIP) degradation. The results show that PFS was reduced to Fe⁰ and FeS during pyrolysis, which was beneficial for the EF process. The AFRB with mesoporous structures exhibited soft magnetic features, which were convenient for separation. CIP was completely degraded within 10 min by the AFRB-EF process at an initial concentration of 20 mg/L. Increasing the working current and catalyst dosage within a certain range could improve the degradation rate. ·OH and O₂^·- were the dominant reactive oxygen species that played critical roles for CIP degradation. The antibacterial groups of CIP have been destroyed by the heterogeneous electro-Fenton process and its toxicity was negligible. The AFRB showed satisfactory performance, even though it was recycled five times. This study provide new insights into the resourceful treatment of antibiotic fermentation residues.

Chelated Ion-Exchange Strategy toward BiOCl Mesoporous Single-Crystalline Nanosheets for Boosting Photocatalytic Selective Aromatic Alcohols Oxidation

The photoresponse and photocatalytic efficiency of bismuth oxychloride (BiOCl) are greatly limited by rapid recombination of photogenerated carriers. The construction of porous single-crystal BiOCl photocatalyst can effectively alleviate this issue and provide accessible active sites. Herein, a facile chelated ion-exchange strategy is developed to synthesize BiOCl mesoporous single-crystalline nanosheets (BiOCl MSCN) using acetic acid and ammonia solution respectively as chelating agent and ionization promoter. The strong chelation between acetate ions and Bi³⁺ ions introduces acetate ions into the precipitated product to exchange with Cl^- ions, resulting in large lattice mismatch, strain release, and formation of void-like mesopores. The prepared BiOCl MSCN photocatalyst exhibits excellent catalytic performance with 99% conversion and 98% selectivity for oxidation of benzyl alcohol to benzaldehyde and superior general adaptability for various aromatic alcohols. The theoretical calculations and characterizations confirm that the superior performance is mainly attributed to the abundant oxygen vacancies, plenty of accessible adsorption/active sites and fast charge transport path without grain boundaries.

Independent and synergistic bio-reductions of uranium (VI) driven by zerovalent iron in aquifer

Zerovalent iron [Fe(0)] can donate electron for bioprocess, but microbial uranium (VI) [U(VI)] reduction driven by Fe(0) is still poorly understood. In this study, Fe(0) supported U(VI) bio-reduction was steadily achieved in the 160-d continuous-flow biological column. The maximum removal efficiency and capacity of U(VI) were 100% and 46.4 ± 0.52 g/(m³·d) respectively, and the longevity of Fe(0) increased by 3.09 times. U(VI) was reduced to solid UO₂, while Fe(0) was finally oxidized to Fe(III). Autotrophic Thiobacillus achieved U(VI) reduction coupled to Fe(0) oxidation, verified by pure culture. H₂ produced from Fe(0) corrosion was consumed by autotrophic Clostridium for U(VI) reduction. The detected residual organic intermediates were biosynthesized with energy released from Fe(0) oxidation and utilized by heterotrophic Desulfomicrobium, Bacillus and Pseudomonas to reduce U(VI). Metagenomic analysis found the upregulated genes for U(VI) reduction (e.g., dsrA and dsrB) and Fe(II) oxidation (e.g., CYC1 and mtrA). These functional genes were also transcriptionally expressed. Cytochrome c and glutathione responsible for electron transfer also contributed to U(VI) reduction. This study reveals the independent and synergistic pathways for Fe(0)-dependent U(VI) bio-reduction, providing promising remediation strategy for U(VI)-polluted aquifers.

Build-in electric field in CuWO4/covalent organic frameworks S-scheme photocatalysts steer boosting charge transfer for photocatalytic CO2 reduction

Covalent organic frameworks (COFs) are crystalline porous materials with enormous potential for realizing solar-driven CO₂-to-fuel conversion, yet the sluggish transfer/separation of photoinduced electrons and holes remains a compelling challenge. Herein, a step (S)-scheme heterojunction photocatalyst (CuWO₄-COF) was rationally fabricated by a thermal annealing method for boosting CO₂ conversion to CO. The optimal CuWO₄/COF composite sample, integrating 10 wt% CuWO₄ with an olefin (C═C) linked COF (TTCOF), achieved a remarkable gas-solid phase CO yield as high as 7.17 ± 0.35 μmol g^-1h^-1 under visible light irradiation, which was significantly higher than the pure COF (1.6 ± 0.29 μmol g^-1h^-1). The enhanced CO₂ conversion rate could be attributable to the interface engineering effect and the formation of internal electric field (IEF) directing from TTCOF to CuWO₄ according to the theoretical calculation and experimental results, which also proves the electrons transfer from TTCOF to CuWO₄ upon hybridization. In addition, driven by the IEF, the photoinduced electrons can be steered from CuWO₄ to TTCOF under visible light irradiation as well-elucidated by in-situ irradiated X-ray photoelectron spectroscopy, verifying the S-scheme charge transfer pathway over CuWO₄/COF composite heterojunctions, which greatly foster the photoreduction activity of CO₂. The preparation technique of the S-scheme heterojunction photocatalyst in this study provides a paradigmatic protocol for photocatalytic solar fuel generation.

Recent Advances in Thallium Removal from Water Environment by Metal Oxide Material

Thallium is widely used in industrial and agricultural development. However, there is still a lack of systematic understanding of its environmental hazards and related treatment methods or technologies. Here, we critically assess the environmental behavior of thallium in aqueous systems. In addition, we first discuss the benefits and limitations of the synthetic methods of metal oxide materials that may affect the practicality and scalability of TI removal from water. We then assess the feasibility of different metal oxide materials for TI removal from water by estimating the material properties and contaminant removal mechanisms of four metal oxides (Mn, Fe, Al, and Ti). Next, we discuss the environmental factors that may inhibit the practicality and scalability of Tl removal from water. We conclude by highlighting the materials and processes that could serve as more sustainable alternatives to TI removal with further research and development.

Complete pentachlorophenol biodegradation in a dual-working electrode bioelectrochemical system: Performance and functional microorganism identification

Bioelectrochemical system (BES) can effectively promote the reductive dechlorination of chlorophenols (CPs). However, the complete degradation of CPs with sequential dechlorination and mineralization processes has rarely achieved from the BES. Here, a dual-working electrode BES was constructed and applied for the complete degradation of pentachlorophenol (PCP). Combined with DNA-stable isotope probing (DNA-SIP), the biofilms attached on the anodic and cathodic electrode in the BES were analyzed to explore the dechlorinating and mineralizing microorganisms. Results showed that PCP removal efficiency in the dual-working BES (84% for 21 days) was 4.1 and 4.7 times higher than those of conventional BESs with a single anodic or cathodic working electrode, respectively. Based on DNA-SIP and high-throughput sequencing analysis, the cathodic working electrode harbored the potential dechlorinators (Comamonas, Pseudomonas, Methylobacillus, and Dechlorosoma), and the anodic working enriched the potential intermediate mineralizing bacteria (Comamonas, Stenotrophomonas, and Geobacter), indicating that PCP could be completely degraded under the synergetic effect of these functional microorganisms. Besides, the potential autotrophic functional bacteria that might be involved in the PCP dechlorination were also identified by SIP labeled with ¹³C-NaHCO₃. Our results proved that the dual-working BES could accelerate the complete degradation of PCP and enrich separately the functional microbial consortium for the PCP dechlorination and mineralization, which has broad potential for bioelectrochemical techniques in the treatment of wastewater contaminated with CPs or other halogenated organic compounds.

Efficient chain elongation synthesis of n-caproate from shunting fermentation of food waste

Food waste was used to produce ethanol by yeast fermentation and volatile fatty acids (VFAs) by hydrolytic acidogenesis for chain elongation. Effectiveness of mole ratio of ethanol in yeast fermentation effluent (YFE) to VFAs in hydrolytic acidification effluent (HAE) on chain elongation was examined. The ideal YFE to HAE ratio for chain elongation was 2:1, the highest n-caproate production was 169.76 mg COD/g vS and the food waste utilization was 65.43 %. Electron transfer and carbon distribution did not completely correspond to n-caproate production, suggesting timely product extraction. The abundance of Romboutsia and Clostridium_sensu_stricto_12 increased as chain elongation progressed, which was critical for the chain elongation to n-caproate. The food waste shunting ratio of yeast fermentation to hydrolytic acidogenesis was 6:5, and 572.6 CNY can be created through chain elongation from shunting fermentation of 1 t food waste. This study proposed a new approach for efficient producing n-caproate from food waste.

Functionalized MOF-Based Photocatalysts for CO2 Reduction

Metal-organic frameworks (MOFs) materials have become a research forefront in the field of photocatalytic CO₂ reduction attributed to their ultra-high specific surface area, adjustable structure, and abundant catalytic active sites. Particularly, MOFs can be facilely tuned to match CO₂ photoreduction by utilizing post-modification of metal nodes, functionalization of organic linkers, and combination with other active materials. Herein, the recent advances in the construction strategy of MOF-based photocatalysts materials for CO₂ reduction are highlighted. Some systematic modification strategies on MOF-based photocatalysts are also discussed, such as modification of metal sites and organic ligands, construction of heterojunction, introduction of single/dual-atom, and strain engineering. Finally, the future development directions of MOF-based photocatalysts in the field of CO₂ reduction are presented.