Quinone Moieties Link the Microbial Respiration of Natural Organic Matter to the Chemical Reduction of Diverse Nitroaromatic Compounds

Efficacy and durability of cobalt sulfide nanoparticles and axial sulfur-coordinated cobalt single-atom composite sites in hydrogenative nitroaromatics decontamination

Emerging single-atom materials and metal sulfides hold significant promise as alternatives to precious metal catalysts for nitroaromatics conversion; however, their intrinsic activity and durability remain insufficiently understood. Herein, sulfur and nitrogen co-doped carbon matrices incorporating CoS nanoparticles and single-atom Co with Co-N4-S1 coordination were constructed through a facile pyrolysis approach. Advanced characterization techniques, such as X-ray absorption fine structure (XAFS) and aberration-corrected electron microscopy, unveiled unique structural features underpinning exceptional catalytic efficiency and recyclability. The catalyst achieved a specific catalytic rate of 134 min-1 g-1 L for p-nitrophenol (PNP) hydrogenation, outperforming many noble metal-based catalysts. Experimental and theoretical analyses identified the Co-N4-S1 single-atom moiety as the primary active site, demonstrating remarkable structural stability. Axial sulfur coordination was found to fine-tune the electronic state of the central Co atom, mitigating the overbinding of reaction intermediates and enhancing PNP conversion efficiency. In contrast, CoS nanoparticles exhibited limited recyclability, with agglomeration, cobalt hydroxide formation, and dissolution observed during repeated use. This study presents a highly efficient catalyst for nitroaromatics conversion and provides a foundational framework for understanding the durability and mechanistic roles of cobalt-based active sites.

Biochar applications for efficient removal of energetic compound contaminants

Military activities and the production or disposal of ammunition often lead to soil contamination with energetic compounds (ECs) such as dinitrotoluene, trinitrotoluene, and hexogen, posing significant threats to human health and the ecosystem. Biochar has emerged as a cost-effective and widely available solution for remediating contaminated sites characterized by its capacity for pollutant removal through adsorption and conversion process, along with minimal secondary pollution. This paper provides a comprehensive review of relevant literature on biochar's efficacy in eliminating ECs, including an analysis of the underlying mechanisms. The discussion addresses challenges and opportunities associated with biochar application in ECs remediation, offering insights for future research directions. In summary, the use of biochar for ECs removal presents a promising and eco-friendly approach, facilitating the remediation of contaminated sites while promoting soil function and ecosystem recovery.

Frequency-modulated alternating current-driven bioelectrodes for enhanced mineralization of Alizarin Yellow R

The alternating current (AC)-driven bioelectrochemical process, in-situ coupling cathodic reduction and anodic oxidation in a single electrode, offers a promising way for the mineralization of refractory aromatic pollutants (RAPs). Frequency modulation is vital for aligning reduction and oxidation phases in AC-driven bioelectrodes, potentially enhancing their capability to mineralize RAPs. Herein, a frequency-modulated AC-driven bioelectrode was developed to enhance RAP mineralization, exemplified by the degradation of Alizarin Yellow R (AYR). Optimal performance was achieved at a frequency of 1.67 mHz, resulting in the highest efficiency for AYR decolorization and subsequent mineralization of intermediates. Performance declined at both higher (3.33 and 8.30 mHz) and lower (0.83 mHz) frequencies. The bioelectrode exhibited superior electron utilization, bidirectional electron transfer, and redox bifunctionality, effectively aligning reduction and oxidation processes to enhance AYR mineralization. The 1.67 mHz frequency facilitated the assembly of a collaborative microbiome dedicated to AYR bio-mineralization, characterized by an increased abundance of functional consortia proficient in azo dye reduction (e.g., Stenotrophomonas and Shinella), aromatic intermediates oxidation (e.g., Sphingopyxis and Sphingomonas), and electron transfer (e.g., Geobacter and Pseudomonas). This study reveals the role of frequency modulation in AC-driven bioelectrodes for enhanced RAP mineralization, offering a novel and sustainable approach for treating RAP-bearing wastewater.

Coupling Fe-Co atomic pair to promote the selective reduction of nitroaromatics under mild conditions

Selectively reducing nitroaromatics into aromatic amines will not only remove nitroaromatic pollutants in waste effluents to reduce environmental risks, but also yield important feedstocks for chemical industrial manufactures. In this study, a FeCo-co-embedded N-doped Carbon (FeCo-N-C) catalyst with Fe-Co atomic pair has been identified with favorable activity, superior selectivity, excellent reusability, as well as outstanding performance in the treatment of real water. The combined results from theoretical study and experimental tests indicate that the improved catalytic performance of FeCo-N-C is owing to the narrowed band gap and electron delocalization caused by the Fe-Co atomic pair which can improve electron transport in its catalytic reaction. The results of isotope experiments and H* quenching experiments confirm that H2O is the source of hydrogen in catalytic reduction of PNP. FeCo-N-C is identified as a superior catalyst to replace multitudinous currently used noble-metal catalysts for the selective catalytic reduction of nitroaromatics in wastewater treatment.

Genome-Centric Metatranscriptomic Characterization of a Humin-Facilitated Anaerobic Tetrabromobisphenol A-Dehalogenating Consortium

Tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant in electronics manufacturing, has caused global contamination due to improper e-waste disposal. Its persistence, bioaccumulation, and potential carcinogenicity drive studies of its transformation and underlying (a)biotic interactions. This study achieved an anaerobic enrichment culture capable of reductively dehalogenating TBBPA to the more bioavailable bisphenol A. 16S rRNA gene amplicon sequencing and quantitative PCR confirmed that successive dehalogenation of four bromide ions from TBBPA was coupled with the growth of both Dehalobacter sp. and Dehalococcoides sp. with growth yields of 5.0 ± 0.4 × 108 and 8.6 ± 4.6 × 108 cells per μmol Br- released (N = 3), respectively. TBBPA dehalogenation was facilitated by solid humin and reduced humin, which possessed the highest organic radical signal intensity and reducing groups -NH2, and maintained the highest dehalogenation rate and dehalogenator copies. Genome-centric metatranscriptomic analyses revealed upregulated putative TBBPA-dehalogenating rdhA (reductive dehalogenase) genes with humin amendment, cprA-like Dhb_rdhA1 gene in Dehalobacter species, and Dhc_rdhA1/Dhc_rdhA2 genes in Dehalococcoides species. The upregulated genes of lactate fermentation, de novo corrinoid biosynthesis, and extracellular electron transport in the humin amended treatment also stimulated TBBPA dehalogenation. This study provided a comprehensive understanding of humin-facilitated organohalide respiration.

Use of qPCR to monitor 2,4-dinitroanisole degrading bacteria in water and soil slurry cultures

Prediction and process monitoring during natural attenuation, bioremediation, and biotreatment require effective strategies for detection and enumeration of the responsible bacteria. The use of 2,4-dinitroanisole (DNAN) as a component of insensitive munitions leads to environmental contamination of firing ranges and manufacturing waste streams. Nocardioides sp. strain JS1661 degrades DNAN under aerobic conditions via a pathway involving an unusual DNAN demethylase. We used the deeply branched sequences of DNAN degradation functional genes as a target for development of a molecular method for detection of the bacteria. A qPCR assay was designed for the junction between dnhA and dnhB, the adjacent genes encoding DNAN demethylase. The assay allowed reproducible enumeration of JS1661 during growth in liquid media and soil slurries. Results were consistent with biodegradation of DNAN, accumulation of products, and classical biomass estimates, including most probable number and OD600. The results provide a sensitive and specific molecular method for prediction of degradation potential and process evaluation during degradation of DNAN.

ONE-SENTENCE SUMMARY

A unique target sequence in functional genes enables the design of a simple and specific qPCR assay for enumeration of aerobic 2,4-dinitroanisole-degrading bacteria in soil and water.

Redox mediators stimulated chain elongation process in fluidized cathode electro-fermentation systems for caproate production

Medium chain fatty acids (MCFAs), the secondary products of traditional anaerobic fermentation, can be produced via chain elongation (CE), a process often retarded due to the difficulty during interspecies electron transfer (IET). This study employed redox mediators, neutral red (NR), methyl viologen (MV), and methylene blue (MB) as electron shuttles to expedite the electro-fermentation for caproate production by improving IET. Results showed that MV increased the MCFAs production by promoting acetate to ethanol conversion, leading to the highest MCFAs selectivity of 68.73%. While NR was indicated to improve CE by encouraging H2 production, and the biocathode had the highest electrical activity due to the smallest internal resistance and largest capacitance increase of 96% than the control. A higher proportion of Sutterella, Prevotella, and Hydrogenophaga, linked with the H2 mediated interspecies electron transfer (MIET) during CE process, was observed across redox mediators supplied groups compared to the control. The presence of mediators led to an elevated abundance of key enzymes for enhanced CE process and electron transfer. This study provided the perspective of the stimulated electron transfer for improved MCFAs production in electro-fermentation systems.