Tunable schiff-based networks with different bonding sites for enhanced photocatalytic activity under visible-light irradiation: The effects of steric hindrance.

Organic polymers hold great potential in photocatalysis considering their low cost, structural tailorability, and well-controlled degree of conjugation for efficient electron transfer. Among the polymers, Schiff base networks (SNWs) with high nitrogen content have been noticed. Herein, a series of SNWs is synthesized based on the melamine units and dialdehydes with different bonding sites. The chemical and structural variation caused by steric hindrance as well as the related photoelectric properties of the SNW samples are investigated, along with the application exploration on photocatalytic degradation and energy production. The results demonstrate that only SNW-o based on o-phthalaldehyde responds to visible light, which extends to over 550 nm. SNW-o shows the highest tetracycline degradation rate of 0.02516 min-1, under 60-min visible light irradiation. Moreover, the H2O2 production of SNW-o is 2.14 times higher than that of g-C3N4. The enhanced photocatalytic activity could be ascribed to the enlarged visible light adsorption and intramolecular electron transfer. This study indicates the possibility to regulate the optical and electrical properties of organic photocatalysts on a molecular level, providing an effective strategy for rational supramolecular engineering to the applications of organic materials in photocatalysis.

Microplastics in landfill and leachate: Occurrence, environmental behavior and removal strategies.

Plastic wastes buried in landfill are gradually broken and decomposed into microplastics under physical, chemical and biological effects, bringing environmental risks to the exploitation of waste resources. Landfill leachate as a potential source of environmental microplastics has not good attention. Microplastics in leachate carry toxic and harmful pollutants and antibiotic resistance genes, and these vectors pose greater risks to human and environmental health without systematic treatment. Recently, the main technologies of landfill leachate treatment process include order batch activated sludge process, membrane biological reaction process, flocculation process, combined filtration process, and constructed wetland process. However, there is still little knowledge about microplastic removal of the existing leachate treatment facilities, and some technologies to alleviate the sources of such microplastics should be timely developed. This paper systematically summarizes the occurrence of plastics, microplastics and nanoplastics in leachate and their interactive pollution with other toxic pollutants. Meanwhile, the prospects of their environmental behaviors in landfill and leachate are put forward. The microplastic removal by existing leachate treatment equipment and the limitations and challenges to upgrading process of development and implementation are also discussed. The paper can provide a scientific basis for studying the fate of microplastics in landfill and leachate.

Recent advances in impacts of microplastics on nitrogen cycling in the environment: A review.

Nitrogen cycling plays a decisive role in biogeochemistry, and largely depends on microbial driven nitrogen transformation. The environmental problems caused by microplastics are becoming more serious, and the analysis and control of its pollution in the environment have become a research hotspot in the field. The nitrogen transformation and nitrogen cycling in the environment are mainly driven by microorganisms in the environment, and the existence of microplastics can affect the microbial population, abundance and type, thus affecting the transformation of nitrogen. The effect of microplastics on microorganisms involved in nitrogen transformation is briefly described. This paper mainly reviews the research progress on the impacts of microplastics on nitrogen transformation and nitrogen cycling in water, soil, sediment and sewage sludge. Microplastic type, size and concentration can cause obvious difference in the impacts of microplastics on nitrogen transformation. Then, response and mechanism of microplastics to microorganism mediated nitrogen transformation and nitrogen cycling are introduced. Processes of nitrogen transformation are affected by interfering with microorganism diversity and structure, enzyme activities and related coding genes and oxygen flux. Additionally, additives released from microplastics can also affect the microbial activity. However, mechanisms of microplastics on environmental nitrogen transformation and nitrogen cycling are not fully understood due to the lack of relevant research. There are effective strategies to evaluate complex environmental systems, prolong action time, strengthen multi factor and multi-level research, and assist molecular biology and stable isotope technology. This review article can provide valuable insights into the impact of microplastics on microorganisms mediated nitrogen transformation processes and evaluate the impact on ecological and environmental health.