Biochar-compost as a new option for soil improvement: Application in various problem soils.

Due to the synergistic effects of biochar and compost/composting, the combined application of biochar and compost (biochar-compost) has been recognized as a highly promising and efficient method of soil improvement. However, the willingness to apply biochar-compost for soil improvement is still low compared to the use of biochar or compost alone. This paper collects data on the application of biochar-compost in several problem soils that are well-known and extensively investigated by agronomists and scientists, and summarizes the effects of biochar-compost application in common problem soils. These typical problem soils are classified based on three different characteristics: climatic zones, abiotic stresses, and contaminants. The improvement effect of biochar-compost in different soils is assessed and directions for further research and suggestions for application are made. Generally, biochar-compost mitigates the high mineralization rate of soil organic matter, phosphorus deficiency and aluminum toxicity, and significantly improves crop yields in most tropical soils. Biochar-compost can help to achieve long-term sustainable management of temperate agricultural soils by sequestering carbon and improving soil physicochemical properties. Biochar-compost has shown positive performance in the remediation of both dry and saline soils by reducing the threat of soil water scarcity or high salinity and improving the consequent deterioration of soil conditions. By combining different mechanisms of biochar and compost to immobilize or remove contaminants, biochar-compost tends to perform better than biochar or compost alone in soils contaminated with heavy metals (HMs) or organic pollutants (OPs). This review aims to improve the practicality and acceptability of biochar-compost and to promote its application in soil. Additionally, the prospects, challenges and future directions for the application of biochar-compost in problem soil improvement were foreseen.

Recent advances in application of heterogeneous electro-Fenton catalysts for degrading organic contaminants in water.

Over the last decades, advanced oxidation processes (AOPs) have been widely used in surface and ground water pollution control. The heterogeneous electro-Fenton (EF) process has gained much attention due to its properties of high catalytic performance, no generation of iron sludge, and good recyclability of catalyst. As of October 2022, the cited papers and publications of EF are around 1.3 × 10-5 and 3.4 × 10-3 in web of science. Among the AOP techniques, the contaminant removal efficiencies by EF process are above 90% in most studies. Current reviews mainly focused on the mechanism of EF and few reviews comprehensively summarized heterogeneous catalysts and their applications in wastewater treatment. Thus, this review focuses on the current studies covering the period 2012-2022, and applications of heterogeneous catalysts in EF process. Two kinds of typical heterogeneous EF systems (the addition of solid catalysts and the functionalized cathode catalysts) and their applications for organic contaminants degradation in water are reviewed. In detail, solid catalysts, including iron minerals, iron oxide-based composites, and iron-free catalysts, are systematically described. Different functionalized cathode materials, containing Fe-based cathodes, carbonaceous-based cathodes, and heteroatom-doped cathodes, are also reviewed. Finally, emphasis and outlook are made on the future prospects and challenges of heterogeneous EF catalyst for wastewater treatments.

Constructing functional metal-organic frameworks by ligand design for environmental applications.

Metal-organic frameworks (MOFs) with unique physical and chemical properties are composed of metal ions/clusters and organic ligands, including high porosity, large specific surface area, tunable structure and functionality, which have been widely used in chemical sensing, environmental remediation, and other fields. Organic ligands have a significant impact on the performance of MOFs. Selecting appropriate types, quantities and properties of ligands can well improve the overall performance of MOFs, which is one of the critical issues in the synthesis of MOFs. This article provides a comprehensive review of ligand design strategies for functional MOFs from the number of different types of organic ligands. Single-, dual- and multi-ligand design strategies are systematically presented. The latest advances of these functional MOFs in environmental applications, including pollutant sensing, pollutant separation, and pollutant degradation are further expounded. Furthermore, an outlook section of providing some insights on the future research problems and prospects of functional MOFs is highlighted with the purpose of conquering current restrictions by exploring more innovative approaches.

Peroxydisulfate activation by sulfur-doped ordered mesoporous carbon: Insight into the intrinsic relationship between defects and 1O2 generation.

The carbon-catalyzed persulfate-based advanced oxidation process (PS-AOP) has recently received much focus owing to the green, economical, and sustainable nature of carbon catalysts. In this study, sulfur-doped ordered mesoporous carbons (S-OMCs) were utilized to activate peroxydisulfate (PDS) for ciprofloxacin (CIP) removal. A synthesis temperature gradient was set to regulate the defect level of S-OMCs, since the thermal decomposition of oxygen- and sulfur-containing groups at different temperatures could release S and O and then create defects. In all S-OMCs/PDS systems, 1O2 dominated CIP degradation. Interestingly, a high linear correlation (R2 = 0.9091) between defect level and 1O2 yield was found, confirming the structure-activity relationship between defects and 1O2 generation. Moreover, the impacts of several important reaction conditions and water matrix on S-OMC-1000/PDS activation system were surveyed. In the S-OMC-1000/PDS activation system, CIP removal could attain 85.84% under the condition of unadjusted pH (pH = 5.3) and small amount of S-OMC-1000 (50 mg/L). The S-OMC-1000/PDS activation system also exhibited relatively stable or even better performance in the presence of common inorganic anions and natural organic matter (NOM), manifesting its good potential for practical applications. In addition, the reusability of S-OMC-1000 was investigated. This study provides a practical and high-efficiency way for decontaminating antibiotic-polluted water, and gives an alternative approach for identifying the active site of catalysts.

The dynamics of phosphorus fractions and the factors driving phosphorus cycle in Zoige Plateau peatland soil.

Phosphorus (P) is an essential nutrient, limiting plant growth and microbial activity in many ecosystems. However, a few studies have been conducted to investigate P dynamics and the factors driving P dynamics in peatland soils. Therefore, this study chose Zoige Plateau peatland (the largest peatland in China) to reveal P dynamics and the possible driving factors through fractionating soil P and investigating a series of abiotic and biotic factors. It is found that season, peatland type, and soil depth could strongly affect P dynamics. H2O-P and NaHCO3-P (labile P) had lower content, while NaOH-P, HCl-P, Mix-P, and Residual-P (non-labile P) were the dominant fractions. Besides, the sum of P fractions was higher than the traditional measurement of total P, suggesting P storage might be underestimated in peatland soils. Moreover, it is observed that biotic factors affected P fractions more than abiotic factors, and fungi affected refractory P more than bacteria. This study provides essential information for understanding P cycling in peatland soils and emphasizes specific microbes related to P cycling, which should be paid more attention to in the future.