New Insights into Aggregation Behaviors of the UV-Irradiated Dissolved Biochars (DBioCs) in Aqueous Environments: Effects of Water Chemistries and Variation in the Hamaker Constant.

The aggregation behavior of ubiquitous dissolved black carbon (DBC) largely affects the fate and transport of its own contaminants and the attached contaminants. However, the photoaging processes and resulting effects on its colloidal stability remain yet unknown. Herein, dissolved biochars (DBioCs) were extracted from common wheat straw biochar as a proxy for an anthropogenic DBC. The influences of UV radiation on their aggregation kinetics were systematically investigated under various water chemistries (pH, electrolytes, and protein). The environmental stability of the DBioCs before and after radiation was further verified in two natural water samples. Hamaker constants of pristine and photoaged DBioCs were derived according to Derjaguin-Landau-Verwey-Overbeek (DLVO) prediction, and its attenuation (3.19 ± 0.15 × 10-21 J to 1.55 ± 0.07 × 10-21 J after 7 days of radiation) was described with decay kinetic models. Pearson correlation analysis revealed that the surface properties and aggregation behaviors of DBioCs were significantly correlated with radiation time (p < 0.05), indicating its profound effects. Based on characterization and experimental results, we proposed a three-stage mechanism (contended by photodecarboxylation, photo-oxidation, and mineral exposure) that DBioCs might experience under UV radiation. These findings would provide an important reference for potential phototransformation processes and relevant behavioral changes that DBC may encounter.

Non-radical activation of low additive periodate by carbon-doped boron nitride for acetaminophen degradation: Significance of high-potential metastable intermediates.

Metal-free environmental-friendly and cost-effective catalysts for periodate (PI) activation are crucial to popularize their application for micropollutant removal in water. Herein, we report that carbon-doped boron nitride (C-BN) can efficiently activate PI to degrade acetaminophen under very low oxidant doses (40 µM) and over a relatively wide pH range (3-9). As expected, the significant reduction in periodate addition is likely to be due to the higher chemical utilization efficiency achieved by a non-radical oxidation pathway. This involved two main mechanisms, the electron transfer process mediated by the high-potential metastable C-BN-900-PI* complex and singlet oxygen. In this case, the CO groups and defects on the C-BN surface were identified as key active sites for PI activation. Notably, the prepared C-BN-900 had good cycling performance and the degradation efficiency is recovered after simple annealing. The existence of HCO3- and HA significantly inhibited the reaction, whereas Cl-, SO42-, and NO3- had little effect on the degradation of ACE. Overall, this study provides a new alternative method to regulate the non-radical pathway of boron nitride/periodate system.

Systematic tracking of nitrogen sources in complex river catchments: Machine learning approach based on microbial metagenomics.

Tracking nitrogen pollution sources is crucial for the effective management of water quality; however, it is a challenging task due to the complex contaminative scenarios in the freshwater systems. The contaminative pattern variations can induce quick responses of aquatic microorganisms, making them sensitive indicators of pollution origins. In this study, the soil and water assessment tool, accompanied by a detailed pollution source database, was used to detect the main nitrogen pollution sources in each sub-basin of the Liuyang River watershed. Thus, each sub-basin was assigned to a known class according to SWAT outputs, including point source pollution-dominated area, crop cultivation pollution-dominated area, and the septic tank pollution-dominated area. Based on these outputs, the random forest (RF) model was developed to predict the main pollution sources from different river ecosystems using a series of input variable groups (e.g., natural macroscopic characteristics, river physicochemical properties, 16S rRNA microbial taxonomic composition, microbial metagenomic data containing taxonomic and functional information, and their combination). The accuracy and the Kappa coefficient were used as the performance metrics for the RF model. Compared with the prediction performance among all the input variable groups, the prediction performance of the RF model was significantly improved using metagenomic indices as inputs. Among the metagenomic data-based models, the combination of the taxonomic information with functional information of all the species achieved the highest accuracy (0.84) and increased median Kappa coefficient (0.70). Feature importance analysis was used to identify key features that could serve as indicators for sudden pollution accidents and contribute to the overall function of the river system. The bacteria Rhabdochromatium marinum, Frankia, Actinomycetia, and Competibacteraceae were the most important species, whose mean decrease Gini indices were 0.0023, 0.0021, 0.0019, and 0.0018, respectively, although their relative abundances ranged only from 0.0004 to 0.1 %. Among the top 30 important variables, functional variables constituted more than half, demonstrating the remarkable variation in the microbial functions among sites with distinct pollution sources and the key role of functionality in predicting pollution sources. Many functional indicators related to the metabolism of Mycobacterium tuberculosis, such as K24693, K25621, K16048, and K14952, emerged as significant important factors in distinguishing nitrogen pollution origins. With the shortage of pollution source data in developing regions, this suggested approach offers an economical, quick, and accurate solution to locate the origins of water nitrogen pollution using the metagenomic data of microbial communities.

Assisted wet deposition targeted synthesis of Co-N coordination single-atom catalysts for efficient Fenton-like catalytic degradation of micropollutants.

Assisted wet deposition methods to localize the active phase metal on the carrier surface and prevent atomic aggregation during conventional heat treatment are strongly preferred. Herein, single-atom cobalt catalysts (SA-Co-PCN) with different metal-central content were target-prepared using a combination of impregnation and secondary annealing on polymerized carbon nitride (PCN) through reticular confinement. Fitting the coordination configuration of the Co-N pathway within the first coordination shell according to quantitative EXAFS indicated that the ligancy of Co-N was 4. The removal efficiency of representative micropollutants in the SA-Co-PCN/PMS system achieved 100% within 15 min. The outstanding degradation properties of micropollutants were ascribed to the SA-Co-PCN boosts PMS to a 1O2-dominated system. Moreover, the effects of substituents on the degradation behavior and ecotoxicology of sulfonamides (SAs) in PMS-activated systems were investigated in depth. The combination of DFT theoretical calculations and LC-MS further confirmed that the similar electron-rich sites on the SAs molecules allowed for commonality in the degradation pathway. Both S-N bond and C-S bond fragments became the initial attack and cleavage sites in the series of SAs. Ecotoxicity predictions indicated that most intermediates of SAs exhibited lower acute and chronic toxicity, especially acute toxicity, than the parent compounds. ENVIRONMENTAL IMPLICATION: Assisted wet deposition to localize the active phase metal on the carrier surface allows easy target formation of single-atom cobalt catalysts (SA-Co-PCN), which could boost PMS to a 1O2-dominated system for efficient oxidation of typical micropollutants. The degradation behavior and ecotoxicology of sulfonamides in the SA-Co-PCN/PMS system were investigated in depth, revealing that most intermediates of sulfonamides exhibited lower acute and chronic toxicity, especially acute toxicity, than the parent compounds. This work provides a strategy for the development of facilely prepared single-atom catalysts and contributes to the development and application potential of PMS advanced oxidation technology for water pollution control.

Linkage Microenvironment of Azoles-Related Covalent Organic Frameworks Precisely Regulates Photocatalytic Generation of Hydrogen Peroxide.

Artificial H2 O2 photosynthesis by covalent organic frameworks (COFs) photocatalysts is promising for wastewater treatment. The effect of linkage chemistry of COFs as functional basis to photoelectrochemical properties and photocatalysis remains a significant challenge. In this study, three kinds of azoles-linked COFs including thiazole-linked TZ-COF, oxazole-linked OZ-COF and imidazole-linked IZ-COF were successfully synthesized. More accessible channels of charge transfer were constructed in TZ-COF via the donor-π-acceptor structure between thiazole linkage and pyrene linker, leading to efficient suppression of photoexcited charge recombination. Density functional theory calculations support the experimental studies, demonstrating that the thiazole linkage is more favorable for the formation of *O2 intermediate in H2 O2 production than that of the oxazole and imidazole linkages. The real active sites in COFs located at the benzene ring fragment between pyrene unit and azole linkage.

Regulation of tourmaline-mediated Fenton-like system by biochar: Free radical pathway to non-free radical pathway.

The heterogeneous Fenton-like systems induced by Fe-containing minerals have been largely applied for the degradation of organic pollutants. However, few studies have been conducted on biochar (BC) as an additive to Fenton-like systems mediated by iron-containing minerals. In this study, the addition of BC prepared at different temperatures was found to significantly enhance the degradation of contaminants in the tourmaline-mediated Fenton-like system (TM/H2O2) using Rhodamine B (RhB) as the target contaminant. Furthermore, the hydrochloric acid-modified BC prepared at 700 °C (BC700(HCl)) could achieve complete degradation of high concentrations of RhB in the BC700(HCl)/TM/H2O2 system. Free radical quenching experiments showed that TM/H2O2 system removed contaminants mainly mediated by the free radical pathway. After adding BC, the removal of contaminants is mainly mediated by the non-free radical pathway in BC700(HCl)/TM/H2O2 system which was confirmed by the Electron paramagnetic resonance (EPR) experiments and electrochemical impedance spectroscopy (EIS). In addition, BC700(HCl) had broad feasibility in the degradation of other organic pollutants (Methylene Blue (MB) 100%, Methyl Orange (MO) 100%, and tetracycline (TC) 91.47%) in the tourmaline-mediated Fenton-like system. Possible pathways for the degradation of RhB by the BC700(HCl)/TM/H2O2 system were also proposed.

Elaborating the mechanism of lead adsorption by biochar: Considering the impacts of water-washing and freeze-drying in preparing biochar.

This paper examined the impacts of different pretreatments on the characteristics of biochar and its adsorption behavior for Pb2+. Biochar with combined pretreatment of water-washing and freeze-drying (W-FD-PB) performed a maximum adsorption capacity for Pb2+ of 406.99 mg/g, higher than that of 266.02 mg/g on water-washing pretreated biochar (W-PB) and 188.21 mg/g on directly pyrolyzed biochar (PB). This is because the water-washing process partially removed the K and Na, resulting in the relatively enriched Ca and Mg on W-FD-PB. And the freeze-drying pretreatment broke the fiber structure of pomelo peel, favoring the development of a fluffy surface and large specific surface area during pyrolysis. Quantitative mechanism analysis implied that cation ion exchange and precipitation were the driving forces in Pb2+ adsorption on biochar, and both mechanisms were enhanced during Pb2+ adsorption on W-FD-PB. Furthermore, adding W-FD-PB to Pb-contaminated soil increased the soil pH and significantly reduced the availability of Pb.

Land-Water Transport and Sources of Nitrogen Pollution Affecting the Structure and Function of Riverine Microbial Communities.

The characterization of variations in riverine microbiota that stem from contaminant sources and transport modes is important for understanding biogeochemical processes. However, the association between complex anthropogenic nitrogen pollution and bacteria has not been extensively investigated owing to the difficulties faced while determining the distribution of nitrogen contaminants in watersheds. Here, we employed the Soil and Water Assessment Tool alongside microbiological analysis to explore microbial characteristics and their responses to complex nitrogen pollution patterns. Significant variations in microbial communities were observed in sub-basins with distinct land-water pollution transport modes. Point source-dominated areas (PSDAs) exhibited reduced microbial diversity, high number of denitrification groups, and increased nitrogen cycling compared with others. The negative relative deviations (-3.38) between the measured and simulated nitrate concentrations in PSDAs indicated that nitrate removal was more effective in PSDAs. Pollution sources were also closely associated with microbiota. Effluents from concentrated animal feeding operations were the primary factors relating to the microbiota compositions in PSDAs and balanced areas. In nonpoint source-dominated areas, contaminants from septic tanks become the most relevant sources to microbial community structures. Overall, this study expands our knowledge regarding microbial biogeochemistry in catchments and beyond by linking specific nitrogen pollution scenarios to microorganisms.

Construction of PDIsa/BiOBr type-I scheme heterojunction for efficient ciprofloxacin photocatalytic degradation.

Fabrication of heterojunction photocatalysts is a promising strategy for enhancing photocatalytic activity. However, the study about traditional type-I heterojunction still remains to be developed. Herein, a PDIsa/BiOBr traditional type-I heterojunction was constructed by electrostatic self-assembly method, which owned improved light absorption capacity and photogenerated charge separation efficiency. The interfacial electric field and the polarization electric field of PDIsa impelled the separation of excitons. The degradation rate of ciprofloxacin (CIP) was improved by 3.2 times over the optimal PDIsa/BiOBr composite than pure BiOBr. In addition, the TOC removal efficiency reached 67.34% within 120 min. Trapping experiments and electron spin resonance (ESR) tests showed that superoxide radical (•O2-) was the most active species, and singlet oxygen (1O2) and hole (h+) played a secondary role. The work may furnish a new reference for designing BiOBr-based type-I heterojunction.

The aggregation of natural inorganic colloids in aqueous environment: A review.

Natural inorganic colloids (NICs) are the most common and dominant existence in the ecosystem, with high concentration and wide variety. In spite of the low toxicity, they can alter activity and mobility of hazardous engineered nanoparticles (ENPs) through different interactions, which warrants the necessity to understand and predict the fate and transport of NICs in aquatic ecosystems. Here, this review summarized NICs properties and behaviors, interaction mechanisms and environmental factors at the first time. Various representative NICs and their physicochemical properties were introduced across the board. Then, the aggregation and sedimentation behaviors were discussed systematically, mainly concerning the heteroaggregation between NICs and ENPs. To speculate their fate and elucidate the corresponding mechanisms, the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) and extended DLVO (X-DLVO) theories were focused. Furthermore, a range of intrinsic and extrinsic factors was presented in different perspective. Last but not the least, this paper pointed out theoretical and analytical gaps in current researches, and put forward suggestions for further research, aiming to provide a more comprehensive and original perspective in the fields of natural occurring colloids.

Resource utilization of chicken manure to produce biochar for effective removal of levofloxacin hydrochloride through peroxymonosulfate activation: The synergetic function of graphitization and nitrogen functionality.

Transforming hazardous livestock manure into biochar as an advanced oxidation processes catalyst is a two-in-one strategy to treat waste by waste. In this work, a self-modified biochar catalyst obtained from chicken manure is developed for peroxymonosulfate activation to degrade levofloxacin hydrochloride. The deterioration rate of levofloxacin hydrochloride reached 89% in 40 min, after three cycles of the catalyst, the LFX still maintained 52% degradation rate. And under low levofloxacin hydrochloride concentration, the degradation rate can reach 99% within 40 min. Apart from catalyst characterization and optimization, the effects of catalyst, peroxymonosulfate, levofloxacin hydrochloride, co-existing anions, and natural organic matter concentrations during the reaction are investigated. Additionally, the quenching experiments and electron spin resonance spectroscopy both reveal the reaction mechanism. As the graphitic nitrogen combined with the sp2-hybridized carbon in biochar was highly electronegative, thus appealing electrons from neighboring carbon networks, making the adjoining carbon atoms to be positively charged, which facilitated the degradation process. The oxidative degradation of levofloxacin hydrochloride was ascribed to non-radical routes including surface-bound radicals, h+ and 1O2 mediated oxidation, the contribution rates were 91%, 93.5%, and 96.8%, respectively. Moreover, possible degradation pathways of levofloxacin hydrochloride are studied by Density Functional Theory (DFT) and LC-MS analysis. This work provides a novel method to produce chicken manure biochar by self-modified chicken manure during biochar pyrolysis for peroxymonosulfate activation in organic contaminations abatement and reveals the combined effect of graphitization and nitrogen functionalization while providing new ideas for the resource utilization of chicken manure.

Recycling of waste power lithium-ion batteries to prepare nickel/cobalt/manganese-containing catalysts with inter-valence cobalt/manganese synergistic effect for peroxymonosulfate activation.

Developing a high-efficiency peroxymonosulfate (PMS) activator is of great significance for the elimination and mineralization of organic contaminants. Herein, a catalyst (LiNi0.5Co0.2Mn0.3O2, NCM) was constructed using the cathode scrap of spent lithium-ion battery (LIB) for activation of PMS to remove Rhodamine B (RhB). The excellent catalytic capacity of NCM-650 was observed, as RhB was completely removed after 25 min. The NCM-650/PMS process could function effectively over a broad pH scope with favorable reusability and adaptability. The non-radical channels (singlet oxygen and mediated charge transfer) played a dominant role in the removal of RhB. Several reactive radical species (sulfate radicals, hydroxyl radicals and superoxide radicals) also facilitated the degradation of RhB, where the Co2+ and Mn4+ on the surface served as active sites to activate PMS. The synergistic effect of inter-valence cobalt and manganese in the catalyst was the predominant medium during the whole reaction process. According to the intermediates identified by High performance liquid chromatograph-mass spectrometry (HPLC-MS) and the analysis of density function theory (DFT) calculations, N-de-ethylation, chromophore cleavage, ring opening, and mineralization were regarded as the primary decomposition pathways. This research provided a novel perspective on the potential application of waste LIBs for the effective activation of PMS.

Identification of priority areas for water ecosystem services by a techno-economic, social and climate change modeling framework.

Water scarcity and quality deterioration often occur in economically developing regions, particularly during crises related to climate change or increasing human activities. The assignment of priority areas is considered a suitable strategy for stakeholders to mitigate water crises and cope with water stress. However, most studies focused on protecting water bodies in priority areas and did not consider the hydrological/hydrochemical/hydroecological interaction between aquatic and terrestrial ecosystems. We divided a watershed into manageable areas to select priority areas for multiple water-related ecosystem services (WES-priority areas), considering the aquatic-terrestrial interactions to predict the effects of climate change and human activities. The proposed novelty framework couples the soil and water assessment tool and maximum entropy models with a systematic conservation planning tool. It uses the gross domestic product as the economic cost to assess dynamic changes and social-environmental driving forces. A case study is conducted in the Xiangjiang River basin, a modified watershed of the main tributary of the Yangtze River, China. Results revealed that most of the WES-priority areas were located in the southern and southeastern regions of the upper reaches in all climatic scenarios. The conservation efficiency of the WES-priority areas decreased from 1.264 to 0.867 in 50 years, indicating that the level of protection declined as climate change accelerated. The precipitation was positively correlated with the WES-priority area selection in all climate scenarios. The temperature was only negatively correlated with the WES-priority areas when it exceeded 20 °C, and this effect became more pronounced as the temperature increased. The topographic factors had the most crucial impacts on the upstream priority areas selection. The water flow regulation service played a leading role in identifying WES-priority areas in the middle reaches because the priority areas' distribution here was closely related to the water yield, and its proportion decreased with the acceleration of global warming. The number of WES-priority areas was relatively low in the lower reaches. It was positively associated with the gross domestic product and the amount of built-up land. The proposed framework for WES-priority areas identification enables a sound trade-off between environmental protection and economic development.

Photocatalytic degradation of persistent organic pollutants by Co-Cl bond reinforced CoAl-LDH/Bi12O17Cl2 photocatalyst: mechanism and application prospect evaluation.

The widespread distribution of persistent organic pollutants (POPs) in natural waters has aroused global concern due to their potential threat to the aquatic environment. Photocatalysis represents a promising mean to remediate polluted waters with the simple assistance of solar energy. Herein, we fabricated a Co-Cl bond reinforced CoAl-LDH/Bi12O17Cl2 heterogeneous photocatalyst to investigate the feasibility of photocatalysis to treat POPs-polluted water under environmental conditions. The optimum CoAl-LDH/Bi12O17Cl2 (5-LB) composite photocatalyst exhibited excellent photocatalytic performance, which could degrade 92.47 % of ciprofloxacin (CIP) and 95 % of bisphenol A (BPA) with 2h of actual solar light irradiation in Changsha, China (N 28.12 °, E 112.59 °). In view of the synergistic influence of water constituents, various water matrices greatly affected the degradation rate of CIP (BPA), with the degradation efficiency of 82.17% (84.37%) in tap water, 69.67% (71.63%) in wastewater effluent, and 44.07% (67.7%) in wastewater inflow. The results of electron spin resonance, and chemical trapping experiment, HPLC-MS and density functional theory calculation reflected that the degradation of CIP was mainly attributed to h+ and 1O2 attacking the active atoms of CIP molecule with high Fukui index. Furthermore, the non-toxicity of both 5-LB photocatalyst and treated CIP solution was proved by E.coli and B.subtilis cultivation, which further demonstrated the feasibility of the 5-LB to treat POPs in real water under irradiation of solar light.

Evaluating the remediation potential of MgFe2O4-montmorillonite and its co-application with biochar on heavy metal-contaminated soils.

In this work, a novel and efficient magnesium ferrite-modified montmorillonite (MgFe2O4-MMT) compound was prepared. MgFe2O4-MMT and biochar were mixed at 0:10, 1:9, 3:7, 4:6, and 10:0 w/w combinations and were used for heavy metal immobilization in soil polluted with multiple heavy metals. MgFe2O4-MMT can significantly increase soil alkalinity, and it exhibited the most optimal effect in immobilization of heavy metals in soil. The amounts of Cd, Pb, Cu, and Zn that were extracted by the toxicity characteristic leaching procedure (TCLP) decreased by 58.4%, 50.3%, 42.9%, and 24.7%, respectively. MgFe2O4-MMT can immobilize heavy metals through electrostatic interactions and cation exchange processes. Although, the immobilization of potentially toxic elements by MgFe2O4-MMT and biochar was inferior to that by MgFe2O4-MMT. The combined application of MgFe2O4-MMT and biochar dramatically increased the diversity and richness of the soil bacterial community. The Chao1 index for M3B7 treatment group was 1.7 and 1.2 times higher than that for the control and MgFe2O4-MMT treatment groups, respectively. The combination of biochar and MgFe2O4-MMT might be a cost-effective and ecological remediation approach for mild Pb and Cd contamination.

Mechanistic insights of removing pollutant in adsorption and advanced oxidation processes by sludge biochar.

With the accelerated industrialization, more and more sewage sludge (SS) needs to be treated properly. The conversion of sludge into harmless biochar material with dual utilization value of adsorption and catalysis by pyrolysis is in line with the concept of sustainable development. However, the reaction mechanisms of pristine sludge biochar (SDBC) and its composites (SDBCs) in adsorption, persulfate (PS), and Fenton-like advanced oxidation processes (AOPs) are very closely related to its adsorption performance and catalytic efficiency. In this paper, from the application mechanisms of SDBC in adsorption and AOPs, we review in detail the common methods for synthesizing SDBC and their characteristics. We discuss the synthesis techniques that affect the structural, chemical, and catalytic properties of SDBC, including gasification, pyrolysis, and hydrothermal carbonation (HTC). The pyrolysis temperature, environmental factors, and sludge characteristics have important effects on the properties of SDBC, leading to different mechanisms in adsorption and catalytic processes. Furthermore, this paper systematically generalizes the mechanisms of SDBCs in adsorption, where π-π interactions and electrostatic attractions are the main adsorption mechanisms. Then, activation mechanisms of SDBCs in PS and Fenton-like AOPs systems are discussed, including free radical pathways and non-free radical pathways. Finally, we present several challenges and perspectives for the application of SDBC and SDBCs in the field of adsorption, PS, and Fenton-like AOPs from the mechanistic point of views.

Effect of Anoxic Atmosphere on the Physicochemical and Pelletization Properties of Pinus massoniana Sawdust during Storage.

The 34-day anoxic storage of Pinus massoniana sawdust (PS) in a sealed constant temperature and humidity chambers was carried out to simulate the limited-oxygen storage process inside piles at industrial scale. The effects of anoxic storage on feedstock's properties and pelletization process were investigated with respect to elemental composition, dry matter loss, thermogravimetric characteristics, energy consumption, pellets' density, and microbial communities, etc. After anoxic storage, the microbial community of PS samples was altered, such as the fungi content (Clonostachys, Strelitziana, and Orbilia, etc.), resulting the elemental composition of PS was altered. Thus, the cellulose and ash content of the stored PS were increased, while the hemicellulose, volatile, and fixed carbon were decreased. The energy consumption was increased 7.85-21.98% with the increase in anoxic storage temperature and with the additive of fresh soil collected from PS field in storage process. The single pellet density was altered slightly. Meanwhile, the moisture uptake of PS pellets was decreased. After anoxic storage, the combustion behavior of the stored PS became more stable. The results can be applied directly to guide the development of commercial PS storage and pelletization process currently under development in Asia, Europe and North America.

Recent advances in graphitic carbon nitride as a catalyst for heterogeneous Fenton-like reactions.

Graphitic carbon nitride (g-C3N4), an appealing metal-free polymer, has featured in extensive research in heterogeneous Fenton-like reactions owing to its advantages of stable chemical and thermal properties, ease of structural regulation and unique redox ability. However, there are still some gaps in the understanding of the mechanism and fate of g-C3N4 and its derivatives in heterogeneous Fenton reaction degradation of contaminants. This paper gives systematic emphasis to the development and progress of g-C3N4 and its composites as catalysts in heterogeneous Fenton-like reactions. The main synthesis strategies of g-C3N4 composites are discussed, including calcination, hydrothermal method and self-assembly method. Then, the key catalytic properties of g-C3N4 in Fenton-like applications, including anchoring nanoparticles, increasing specific surface area and exposed active surface sites, as well as regulating charge transfer reactions, are highlighted. Special emphasis is placed on its multifunctional role in heterogeneous Fenton-like reactions and the mechanisms involved in the activation of hydrogen peroxide, persulfates, and photocatalytic activation of persulfate. Lastly, the existing challenges and possible development direction of g-C3N4-coupling Fenton reactions are proposed. It is believed that this paper will bring useful information for the development of graphitic carbon nitride in both laboratory studies and practical applications.

Defect engineering in polymeric carbon nitride photocatalyst: Synthesis, properties and characterizations.

Polymer carbon nitride (CN) has unique structure and electronic properties, making it attractive in photocatalysis fields. However, the photocatalytic efficiency of the pristine CN photocatalyst is still unsatisfactory. In this regard, the introduction of vacancy defects can effectively tune photoelectric properties of CN photocatalyst through tailoring the electronic structure and bandgap engineering. In this review, the effect of vacancy defects on CN is reviewed from the aspects of light absorption, charge separation and surface photoreactivity of CN. Meanwhile, the current progress in the design of vacancy defects with the classified carbon vacancies (CVs), nitrogen vacancies (NVs), amino and cyano groups on CN to boost the photocatalytic performance is summarized. Furthermore, various characterization methods have been summarized and highlighted, including microscopic characterization (SEM, TEM, AFM, HAADF-STEM), spectroscopic characterization (XRD, FTIR, XAFS, XANES, EPR, PAS, XPS, raman spectroscopy, solid-state NMR spectroscopy), elemental analysis, and computational characterization. Finally, the future opportunities and challenges of CN photocatalysts designed with vacancies and defects are proposed to highlight the development direction of this research field.

Recovery of CuO/C catalyst from spent anode material in battery to activate peroxymonosulfate for refractory organic contaminants degradation.

It is critical to developing low-cost and efficient catalysts to activate peroxymonosulfate for the degradation of organic contaminants, whereas it remains challenging. In the study, a recycle method to synthesize efficient heterogeneous catalysts was developed by exploiting the anode electrode of spent lithium-ion batteries as the raw material based on a one-step calcination process. The recycled anode material (AM) composed of copper oxide and graphite carbon was capable of efficiently activating peroxymonosulfate (PMS) to degrade a wide range of organic contaminants. In addition, an investigation was conducted on the effect of reactive parameters (e.g., catalyst dose, PMS dose, RhB concentration, and coexisting matters). Besides, the AM/PMS process could exhibit high effectiveness at a broad pH range (3-10) and in a real water matrix. The redox cycle of Cu(II)/Cu(I) in the AM acted as the predominated force to effectively facilitate the PMS activation for the formation of oxygen species, in which the SO4·- and 1O2 exerted a primary effect. Moreover, the non-radical pathway of electron transfer between RhB and PMS facilitated the removal of RhB. In this study, a reclamation approach was developed for the recycling of spent LIBs anodes, and insights into the development of catalysts in SR-AOPs were gained.