New Strategies for Nitrogen Fixation and Pollution Control

Unveiling novel pathways and key contributors in the nitrogen cycle: Validation of enrichment and taxonomic characterization of oxygenic denitrifying microorganisms in environmental samples

Microorganisms play a crucial role in both the nitrogen cycle and greenhouse gas emissions. A recent discovery has unveiled a new denitrification pathway called oxygenic denitrification, entailing the enzymatic reduction of nitrite to nitric oxide (NO) by a putative nitric oxide dismutase (nod) enzyme. In this study, the presence of the nod gene was detected and subsequently enriched in anaerobic-activated sludge, farmland soil, and paddy soil samples. After 150 days, the enriched samples exhibited significant denitrification, and concomitant oxygen production. The removal efficiency of nitrite ranged from 64.6 % to 79.0 %, while the oxygen production rate was between 15.4 μL/min and 18.6 μL/min when exposed to a sole nitrogen source of 80 mg/L sodium nitrite. Additionally, batch experiments and kinetic analyses revealed the intricate pathways and underlying mechanisms governing the oxygenic denitrification reaction by using CARBOXY-PTIO, 18O-labelled water, and acetylene to unravel the intricacies of the reaction. The quantitative polymerase chain reaction (qPCR) results indicated a significant surge in the abundance of nod genes, escalating from 7.59 to 10.12-fold. Moreover, analysis of 16S ribosomal DNA (rDNA) amplicons revealed Proteobacteria as the dominant phylum and Thauera as the main genus, with the presumed affiliation. In this study, a new nitrogen conversion pathway, oxygenic denitrification, was discovered in environmental samples. This process provides the possibility for the control of nitrous oxide in the treatment of nitrogenous wastewater.

Oxygen vacancies-rich Cu-W18O49 nanorods supported on reduced graphene oxide for electrochemical reduction ofN2to NH3

High-performance nitrogen fixation is severely limited by the efficiency and selectivity of a catalyst of electrochemical nitrogen reduction reaction (NRR) under ambient conditions. Here, the RGO/WOCu (reduced graphene oxide and Cu-doping W₁₈O₄₉) composite catalysts with abundant oxygen vacancies are prepared by the hydrothermal method. The obtained RGO/WOCu achieves an enhanced NRR performance (NH₃ yield rate:11.4 μg h^-1 mg_cat^-1, Faradaic efficiency: 4.4%) at -0.6 V (vs. RHE) in 0.1 mol L^-1 Na₂SO₄ solution. Furthermore, the NRR performance of the RGO/WOCu still keeps at 95% after four cycles, demonstrating its excellent stability. The Cu⁺-doping increases the concentration of oxygen vacancies, which is conducive to the adsorption and activation of N₂. Meanwhile, the introduction of RGO further improves the electrical conductivity and reaction kinetics of the RGO/WOCu due to the high specific surface area and conductivity. This work provides a simple and effective method for efficient electrochemical reduction ofN₂.

Oxyanion-modified zero valent iron with excellent pollutant removal performance

Oxyanion-modified zero valent iron (OM-ZVI), including oxyanion-modified microscale ZVI (OM-mZVI) and nanoscale zero valent iron (OM-nZVI), has attracted growing interest in recent years for their excellent pollutant removal performance. This feature article summarizes the recent progress of OM-ZVI materials, including their synthesis, characterization, enhanced pollutant removal performance, and structure-property relationships. Generally, OM-ZVI could be synthesized with wet chemical and mechanochemical (ball-milling) methods and then characterized with state-of-the-art characterization techniques (e.g., X-ray-based spectroscopy, electron microscopy) to reveal their structure and physicochemical properties. We found that phosphate modification could form iron-phosphate on the nZVI surface, facilitating Cr(VI) removal, while the phosphorylation process could induce tensile hoop stress to produce numerous radial nanocracks in the structurally-dense spherical nZVI for enhanced Ni(II) removal via a boosted Kirkendall effect. Oxalate modification could trigger electron delocalization to increase electron cloud density and surface-bound Fe(II) of mZVI for enhanced Cr(VI) removal, while oxalated mZVI exhibited more efficient Cr(VI) removal performance via an in situ formed FeC₂O₄·2H₂O shell of high proton conductivity, favoring Cr(VI) reduction. Differently, the mechanochemical treatment of mZVI with B₂O₃ could exert tensile strain on it through interstitial boron doping, thereby promoting the release and transfer of electrons from its Fe(0) core to its iron oxide shell for dramatic Cr(VI) reduction. This article aims to demonstrate the potential of OM-ZVI for pollution control and environmental remediation.

Demonstration and Suggestion on the Communication Efficiency of New Media of Environmental Education Based on Ideological and Political Education

With the rapid development of the economy, we are facing more and more problems, and the construction of ecological civilization has become the focus of our national concern. With the rapid development of network technology, the immediacy of the new media and the huge audience have brought new development trends to the dissemination of environmental information. The number of new environmental media is increasing, but there are still some problems, such as formality, rigid content and lack of innovation, which make it difficult to achieve better communication effects. However, the research on new environmental media is still in its infancy, and there is not yet a set of targeted and specialized new media evaluation systems. Based on the social function of new environmental news media and the social responsibility of media as the entry point, the article establishes a set of index systems to measure the efficiency of environmental news dissemination and proposes corresponding improvement measures accordingly. The results of the study show that the best use of environmental education publicity is at 81.3%. In terms of cognitive efficiency and attitudinal efficacy, the scores of environmental education weibo public numbers were not high, at 60.7% and 71.5%, respectively. From the perspective of ideological and political education, the environmental protection class of WeChat plays a good role in attracting the attention of college students, and can provide ideological and political education to them and improve their ideological awareness. In terms of cognition, new media is responsible for conveying environmental knowledge and concepts to college students, so the development of new media centers on environmental information, and the content directly affects the cognitive level of college students, fully reflecting the importance of cognitive efficacy in new media of environmental education. On attitude efficacy, only one indicator is set for identity shaping, which has the highest score, but the lowest is 4.0, showing that the public number is still not obvious enough in terms of identifying with college student groups, influencing college students' emotions and attitudes. Based on this, this paper points out the problems of the current communication efficiency of environmental education new media through the analysis of the evaluation results and puts forward suggestions to improve its communication efficiency in this regard.

Surface Boronizing Can Weaken the Excitonic Effects of BiOBr Nanosheets for Efficient O2 Activation and Selective NO Oxidation under Visible Light Irradiation

The photocatalytic O₂ activation for pollutant removal highly depends on the controlled generation of desired reactive oxygen species (ROS). Herein, we demonstrate that the robust excitonic effect of BiOBr nanosheets, which is prototypical for singlet oxygen (¹O₂) production to partially oxidize NO into a more toxic intermediate NO₂, can be weakened by surface boronizing via inducing a staggered band alignment from the surface to the bulk and simultaneously generating more surface oxygen vacancy (V_O). The staggered band alignment destabilizes excitons and facilitates their dissociation into charge carriers, while surface V_O traps electrons and efficiently activates O₂ into a superoxide radical (^•O₂^-) via a one-electron-transfer pathway. Different from ¹O₂, ^•O₂^- enables the complete oxidation of NO into nitrate with high selectivity that is more desirable for safe indoor NO remediation under visible light irradiation. This study provides a facile excitonic effect manipulating method for layered two-dimensional photocatalysts and sheds light on the importance of managing ROS production for efficient pollutant removal.

High-Efficiency Photocatalytic Ammonia Synthesis by Facet Orientation-Supported Heterojunction Cu2O@BiOCl[100] Boosted by Double Built-In Electric Fields

In this work, the advantages of in situ loading, heterojunction construction, and facet regulation were integrated based on the poly-facet-exposed BiOCl single crystal, and a facet-oriented supported heterojunction of Cu₂O and BiOCl was fabricated (Cu₂O@BiOCl[100]). The photocatalytic nitrogen reduction reaction (pNRR) activity of Cu₂O@BiOCl[100] was as high as 181.9 μmol·g^-1·h^-1, which is 4.09, 7.13, and 1.83 times that of Cu₂O, BiOCl, and Cu₂O@BiOCl-ran (Cu₂O randomly supported on BiOCl). Combined with the results of the photodeposition experiment, X-ray photoelectron spectroscopy characterization, and DFT calculation, the mechanism of Cu₂O@BiOCl[100] for pNRR was discussed. When Cu₂O directionally loaded on the [100] facet of BiOCl, electrons generated by Cu₂O will be transmitted to the [100] facet of BiOCl through Z-scheme electron transmission. Due to the directional separation characteristics of charge in BiOCl, the electrons transmitted from Cu₂O are enriched on the [001] facet of BiOCl, which will together with the original electrons generated by pristine BiOCl act on pNRR, thus greatly improving the activity of photocatalytic ammonia synthesis. Thus, a new construction scheme of biphasic semiconductor heterojunction was proposed, which provides a reference research idea for designing and synthesizing high-performance photocatalysts for nitrogen reduction.