Surface functional groups and biofilm formation on microplastics: Environmental implications.

Microplastics (MPs) contamination is becoming a significant environmental issue, as the widespread omnipresence of MPs can cause many adverse consequences for both ecological systems and humans. Contrary to what is commonly thought, the toxicity-inducing MPs are not the original pristine plastics; rather, they are completely transformed through various surface functional groups and aggressive biofilm formation on MPs via aging or weathering processes. Therefore, understanding the impacts of MPs' surface functional groups and biofilm formation on biogeochemical processes, such as environmental fate, transport, and toxicity, is crucial. In this review, we present a comprehensive summary of the distinctive impact that surface functional groups and biofilm formation of MPs have on their significant biogeochemical behavior in various environmental media, as well as their toxicity and biological effects. We place emphasis on the role of surface functional groups and biofilm formation as a means of influencing the biogeochemical processes of MPs. This includes their effects on pollutant fate and element cycling, which in turn impacts the aggregation, transport, and toxicity of MPs. Ultimately, future research studies and tactics are needed to improve our understanding of the biogeochemical processes that are influenced by the surface functional groups and biofilm formation of MPs.

Single cobalt atom anchored on carbon nitride with cobalt nitrogen/oxygen active sites for efficient Fenton-like catalysis.

As one of the tactics to produce reactive oxygen radicals, the Fenton-like process has been widely developed to solve the increasingly severe problem of environmental pollution. However, establishing advanced mediators with sufficient stability and activity for practical application is still a long-term objective. Herein, we proposed a facile strategy through polymeric carbon nitride (pCN) in-situ growth single cobalt atom for efficient degradation of antibiotics by peroxymonosulfate (PMS) activation. X-ray absorption spectroscopy and high-angle annular dark field-scanning transmission electron microscopy prove the single cobalt atoms are successfully anchored on pCN. Moreover, extended X-ray absorption fine structure analysis shows that the embedded cobalt atoms are constructed by covalently forming the Co-N bond and Co-O bond, which endow the single-atom cobalt catalyst with high stability. Experiment results indicate that the prepared single-atom cobalt catalyst can be used for efficient PMS activation catalytic degradation of tetracycline with a high degradation rate of 98.7 % in 60 min. And the CoN/O sites with single cobalt atoms serve as the active site for generating active radical species (singlet oxygen) from PMS activation. This work may expand the strategy for constructing single-atom catalysts and extend its application for the advanced oxidation process.

Phage-host interactions: The neglected part of biological wastewater treatment.

In wastewater treatment plants (WWTPs), the stable operation of biological wastewater treatment is strongly dependent on the stability of associated microbiota. Bacteriophages (phages), viruses that specifically infect bacteria and archaea, are highly abundant and diverse in WWTPs. Although phages do not have known metabolic functions for themselves, they can shape functional microbiota via various phage-host interactions to impact biological wastewater treatment. However, the developments of phage-host interaction in WWTPs and their impact on biological wastewater treatment are overlooked. Here, we review the current knowledge regarding the phage-host interactions in biological wastewater treatment, mainly focusing on the characteristics of different phage populations, the phage-driven changes in functional microbiota, and the potential driving factors of phage-host interactions. We also discuss the efforts required further to understand and manipulate the phage-host interactions in biological wastewater treatment. Overall, this review advocates more attention to the phage dynamics in WWTPs.

Swift reduction of nitroaromatics by gold nanoparticles anchored on steam-activated carbon black via simple preparation.

Gold (Au) nanoparticles supported on certain platforms display highly efficient activity on nitroaromatics reduction. In this study, steam-activated carbon black (SCB) was used as a platform to fabricate Au/SCB composites via a green and simple method for 4-nitrophenol (4-NP) reduction. The obtained Au/SCB composites exhibit efficient catalytic performance in reduction of 4-NP (rate constant kapp = 2.1925 min-1). The effects of SCB activated under different steam temperature, Au loading amount, pH, and reaction temperature and NaBH4 concentration were studied. The structural advantages of SCB as a platform were analyzed by various characterizations. Especially, the result of N2 adsorption-desorption method showed that steam activating process could bring higher surface area (from 185.9689 to 249.0053 m2/g), larger pore volume (from 0.073268 to 0.165246 cm3/g), and more micropore for SCB when compared with initial CB, demonstrating the suitable of SCB for Au NP anchoring, thus promoting the catalytic activity. This work contributes to the fabrication of other supported metal nanoparticle catalysts for preparing different functional nanocomposites for different applications.

Activation of persulfate by swine bone derived biochar: Insight into the specific role of different active sites and the toxicity of acetaminophen degradation pathways.

Recently, persulfate (PS) activation system has grown up as a primary branch of advanced oxidation processes, and biochar has been recognized as a potential nonmetal material in this field. However, few studies have focused on the corresponding relationship between actives sites on biochar and active species in AOPs. To pave this way, similar biochar (obtained from different pyrolysis temperature) with different functional structures were involved. In this study, biochar derived from swine bone (BBC) was applied in PS activation system to degrade acetaminophen (ACT). The results showed that both radical and non-radical pathway worked in the PS/BBCs systems, and the degradation rate (from 0.1042 to 0.4364 min-1) climbed with the increase of pyrolysis temperature (from 700 to 900 °C). To probe into the corresponding relationship between functional structure and active species, the effect of pyrolysis temperature on functional structure was analyzed. It came out that 1) defects could act as active sites for various active species; 2) persistent free radicals could do favor to the generation of 1O2 and O2-; 3) hydroxyapatite in swine bone only served as hard templet for the porous structure. ACT degradation process was measured by Liquid chromatograph-mass spectrometer, and Scendesmus obliquus was applied to investigate the toxicity of PS/BBCs system. It illustrated that the existence of SO4- mainly contributed to the generation of high toxic intermediates (such as biphenyl and diphenyl ether) in the PS/BBCs system. Furthermore, the enhancement of adsorption capacity would mitigate the toxicity of PS/BBCs systems to some extent.

Recent progress of noble metals with tailored features in catalytic oxidation for organic pollutants degradation.

With the increasing serious water pollutions, an increasing interest has given for the nanocomposites as environmental catalysts. To date, noble metals-based nanocomposites have been extensively studied by researchers in environmental catalysis. In detail, serving as key functional parts, noble metals are usually combined with other nanomaterials for rationally designing nanocomposites, which exhibit enhanced catalytic properties in pollutants removal. Noble metals in the nanocomposites possess tailored properties, thus playing different important roles in catalytic oxidation reactions for pollutants removal. To motivate the research and elaborate the progress of noble metals, this review (i) summarizes advanced characterization techniques and rising technology of theoretical calculation for evaluating noble metal, and (ii) classifies the roles according to their disparate mechanism in different catalytic oxidation reactions. Meanwhile, the enhanced mechanism and influence factors are discussed. (iii) The conclusions, facing challenges and perspectives are proposed for further development of noble metals-based nanocomposites as environmental catalysts.

Boron nitride quantum dots decorated MIL-100(Fe) for boosting the photo-generated charge separation in photocatalytic refractory antibiotics removal.

Metal organic frameworks (MOFs) have great potential for photocatalysis, but only possess moderate activity due to their slow charge transfer and low solar energy conversion. Herein, heterostructures photocatalysts constructed by boron nitride quantum dots (BNQDs) and MIL-100(Fe) (MNB) were successfully fabricated for overcoming these shortcomings. It was indicated that the composites possessed large surface area, mesoporous structure, and enhanced visible light absorption. The MNB photocatalysts exhibited excellent photocatalytic activity for tetracycline hydrochloride (TC-HCl) degradation under visible light irradiation. Compared with MIL-100(Fe), the photodegradation rate of TC-HCl by MNB-1 was 0.02383 min-1, which was 5.3 times higher than that of pure MIL-100(Fe). The close contact of MIL-100(Fe) with BNQDs and the synergistic effect between them were the main reasons for the improved photodegradation performance. This study reveals that a rational combination of MIL-100(Fe) and BNQDs can improve photocatalytic activity to enhance molecular oxygen activation. Therefore, it is reasonable to believe that quantum dots/MOFs photocatalysts have great potential in environmental remediation.

Facile one-pot synthesis of carbon self-doped graphitic carbon nitride loaded with ultra-low ceric dioxide for high-efficiency environmental photocatalysis: Organic pollutants degradation and hexavalent chromium reduction.

In the present study, an innovative carbon self-doped g-C3N4 (CCN) loaded with ultra-low CeO2 (0.067-0.74 wt%) composite photocatalyst is successfully synthesized via a facile one-pot hydrothermal and calcination method. The CeO2/CCN exhibits superior photocatalytic performance for tetracycline degradation (78.9% within 60 min), H2O2 production (151.92 µmol L-1 within 60 min), and Cr(VI) reduction (99.5% within 40 min), which much higher than that of g-C3N4, CCN, CeO2, and CeO2/g-C3N4. The enhanced photocatalytic performance is originated from the fact that the doping of C can efficaciously broaden the utilization range of solar light and improve the reduction ability of photogenerated electrons. Meanwhile, the ultra-low loading of CeO2 can effectually promote the migration of photogenerated electrons and enhance the specific surface area. Besides, the experiments of pH effect and cycle ability indicate that CeO2/CCN has excellent durability and stability. Finally, the photocatalytic mechanism of CeO2/CCN is systematically discussed. This work proves that combining element doping and semiconductor coupling is a promising strategy to design high-efficiency g-C3N4-based photocatalysts.

MXenes as Superexcellent Support for Confining Single Atom: Properties, Synthesis, and Electrocatalytic Applications.

Single atom catalysts (SACs) have shown their noticeable potential and gradually become a new favorite in catalytic field due to the particular selectivity, high catalytic performance, and strong durability. The most important factor in the synthesis of SACs is the selection of appropriate support and formation of metal-support interaction. Among a large number of nanomaterials, MXenes can be utilized as benign supports for fixing SACs because of their expansive specific surface area, regulable bandgap, superior electronic conductivity, and strong mechanical stability. The structure and property of MXenes can be manipulated by changing transition metal elements and surface termination. Here, the uniqueness and superiority of MXenes as superexcellent supports for confining SACs are analyzed from structure and property. The synthetic strategy of MXene-supported SACs is also summarized, especially emphasizing the immobilization of isolated atom against aggregation by utilizing the formidable metal-support covalent coordination interaction. In addition, the applications of MXene-supported SACs in electrocatalytic field are highlighted, including hydrogen evolution reaction, oxygen evolution reaction, overall water splitting, oxygen reduction reaction, and nitrogen reduction reaction. Finally, the challenges and prospects are pointed out for the further understanding and practical application of MXene-supported SACs in electrocatalysis.

Critical review of advanced oxidation processes in organic wastewater treatment.

With the development of industrial society, organic wastewater produced by industrial manufacturing has caused many environmental problems. The vast majority of organic pollutants in water bodies are persistent in the environment, posing a threat to human and animal health. Therefore, efficient treatment methods for highly concentrated organic wastewater are urgently needed. Advanced oxidation processes (AOPs) are widely noticed in the area of treating organic wastewater. Compared with other chemical methods, AOPs have the characteristics of high oxidation efficiency and no secondary pollution. In this paper, the mechanisms, advantages, and limitations of AOPs are comprehensively reviewed. Besides, the basic principles of combining different AOPs to enhance the treatment efficiency are described. Furthermore, the applications of AOPs in various wastewater treatments, such as oily wastewater, dyeing wastewater, pharmaceutical wastewater, and landfill leachate, are also presented. Finally, we conclude that the main direction in the future of AOPs are the modification of catalysts and the optimization of operating parameters, with the challenges focusing on industrial applications.

Enhanced visible-light-driven photocatalytic activity of bismuth oxide via the decoration of titanium carbide quantum dots.

In Ti3C2 quantum dots (Ti3C2 QDs)/Bi2O3 photocatalysts system, Ti3C2 QDs can act as a co-catalyst to greatly boost the photocatalytic performance of Bi2O3. Ti3C2 QDs with excellent light adsorption ability can improve the light response of the system, and the fascinating electronic property can function as a channel for electron transfer. Moreover, Ti3C2 QDs possess larger specific area and more active edge atoms thanks to the size effect. The best Ti3C2 QDs/Bi2O3 composite with the loading amounts of 75 mL of Ti3C2 QDs solution showed much higher photocatalytic performance (nearly 5.85 times) for tetracycline (TC) degradation than that of pristine Bi2O3 under visible light irradiation. These different photocatalytic performances shed light on the key role of Ti3C2 QDs in stimulating the photocatalytic activity of Bi2O3. Moreover, Ti3C2 QDs/Bi2O3 composites exhibited excellent stability in recycling experiments and actual water sample treatment.

Stabilization of lead in polluted sediment based on an eco-friendly amendment strategy: Microenvironment response mechanism.

Stabilization is the most important remediation mechanisms for sediment polluted heavy metals. However, little research has been done on the identification of microenvironmental response and internal correlation, as well as synergistic mechanisms during heavy metal remediation. This study aims to investigate the inner response mechanisms of microenvironment after the lead (Pb) are gradually stabilized in sediment. An eco-friendly amendment strategy which firstly used 100% biodegradable sophorolipids (SOP) to modify chlorapatite (ClAP) for the fabrication of SOP@nClAP was applied in this study. The stabilization efficiency of Pb was significantly improved by SOP@nClAP compared with ClAP. Most importantly, the high-throughput sequencing showed that the dominant species in the sediment changed with the stabilization of Pb. The decrease of Proteobacteria and increase of Firmicutes, especially the Sedimentibacter within the phylum Firmicute directly suggested that large amounts of Pb were stabilized. This research is not only devoted to stabilize Pb in sediment by eco-friendly amendment strategy, but also keep a watchful eye on microenvironment response mechanisms during the Pb stabilization in sediment. Therefore, this study lays a foundation for the future application of more heavy metal amendment strategies in the sediment environment and improves the possibility of large-scale site amendment.

Oxygen vacancy-rich doped CDs@graphite felt-600 heterostructures for high-performance supercapacitor electrodes.

Carbon dots (CDs) have attracted much attention owing to their distinctive 0D chemical structure, ultra-small size, and intrinsic surface/edge defects, and have been widely used in many kinds of research fields. In this work, a facile method to synthesize an oxygen vacancy-rich doped CDs@graphite felt-600 heterostructure with outstanding electrochemical properties is presented. The electron spin resonance (ESR) provides clear evidence for the existence of abundant oxygen vacancies in the CDs@graphite felt-600 heterostructure. The as-synthesized CDs@graphite felt-600 shows superior areal specific capacitance (5.99 F cm-2), due to abundant oxygen vacancies and extensive surface/edge defects in the heterostructure. In addition, a home-made coin cell supercapacitor (SC) with CDs@graphite felt-600 as the electrode delivers a large areal energy density of 20.7 µW h cm-2 at a power density of 150.0 µW cm-2. To determine the charge storage mechanism at the interface of CDs@graphite felt-600, the binding energies between the CDs and graphite felt are calculated by density functional theory (DFT).

Gold nanoparticles-modified MnFe2O4 with synergistic catalysis for photo-Fenton degradation of tetracycline under neutral pH.

To decrease the adverse environmental and health-related effects of antibiotics, a series of MnFe2O4-Au (MFO-Au) composites were prepared by simple co-precipitation and photoreduction methods for efficient photo-Fenton degradation of tetracycline (TC). The synergistic effect of MFO and gold nanoparticles (AuNPs) with high absorption of visible light and strong photogenerated carrier separation efficiency endowed MFO-Au3 an outstanding photo-Fenton catalytic performance for TC degradation in neutral condition. The surface hydroxyl of MFO profited to generation of •OH, and negative charged or partially polarized AuNPs benefited to adsorption of H2O2, which had a synergistic effect on enhancing the photo-Fenton catalytic performance of MFO-Au. 88.3% of TC was efficiently removed and about 51.9% of TOC decreased within 90 min. The electron spin resonance and quenching tests suggested that h+ and e- were responsible for the high catalytic degradation and •OH and •O2- participated in the photo-Fenton reaction. The toxicity assessment by seed germination experiments showed efficient toxicity reduction of this system. Besides, MFO-Au exhibited high stability, good cycle, relatively economical and practical application performance, which is expected to provide potential guidance for the design and combination of noble nanoparticles with high stability and spinel bimetallic oxides with high catalytic activity in photo-Fenton reactions.

Enhancing iron redox cycling for promoting heterogeneous Fenton performance: A review.

Conventional water treatment methods are difficult to remove stubborn pollutants emerging from surface water. Advanced oxidation processes (AOPs) can achieve a higher level of mineralization of stubborn pollutants. In recent years, the Fenton process for the degradation of pollutants as one of the most efficient ways has received more and more attention. While homogeneous catalysis is easy to produce sludge and the catalyst cannot be cycled. In contrast, heterogeneous Fenton-like reaction can get over these drawbacks and be used in a wider range. However, the reduction of Fe (III) to Fe(II) by hydrogen peroxide (H2O2) is still the speed limit step when generating reactive oxygen species (ROS) in heterogeneous Fenton system, which restricts the efficiency of the catalyst to degrade pollutants. Based on previous research, this article reviews the strategies to improve the iron redox cycle in heterogeneous Fenton system catalyzed by iron materials. Including introducing semiconductor, the modification with other elements, the application of carbon materials as carriers, the introduction of metal sulfides as co-catalysts, and the direct reduction with reducing substances. In addition, we also pay special attention to the influence of the inherent properties of iron materials on accelerating the iron redox cycle. We look forward that the strategy outlined in this article can provide readers with inspiration for constructing an efficient heterogeneous Fenton system.

Facile synthesis of CeO2/carbonate doped Bi2O2CO3 Z-scheme heterojunction for improved visible-light photocatalytic performance: Photodegradation of tetracycline and photocatalytic mechanism.

CeO2 nanoparticles are successfully loaded on carbonate doped Bi2O2CO3 (CBOC) nanosheets by a facile hydrothermal and low-temperature calcination method. CeO2/CBOC heterojunction shows significantly enhanced photocatalytic activity, when 35 mg of CeO2/CBOC photocatalyst is added to tetracycline (TC) solution (20 mg/L, 100 mL), about 79.5% TC is degraded within 90 min under visible light irradiation, which is much higher than that of original CeO2 and CBOC. According to photoelectrochemical characterization and active radical capture experiments, the Z-scheme electron transfer mechanism is the reason for the significant enhancement of photocatalytic activity. Besides, the XPS results indicate that Ce4+/Ce3+ redox pairs are formed at the contact interface between CeO2 and CBOC, which is conducive to the transfer of photoexcited electrons and production of superoxide radicals. Additionally, the photocatalytic mechanism and possible degradation pathway of TC is proposed through free radical trapping experiments and liquid chromatography-mass (LC-MS) analysis. This study will accumulate experience for the combination of CeO2 and bismuth-based nanomaterials, and provide a feasible way to design wide band-gap bismuth-based photocatalysts, thereby achieving efficient visible light degradation of environmental pollutants.

Carbon Dots-Decorated Carbon-Based Metal-Free Catalysts for Electrochemical Energy Storage.

In the past ten years, carbon dots-decorated, carbon-based, metal-free catalysts (CDs-C-MFCs) have become the fastest-growing branch in the metal-free materials for energy storage field. However, the further development of CDs-C-MFCs needs to clear up the electronic transmission mechanism rather than primarily relying on trial-and-error approaches. This review presents systematically and comprehensively for the first time the latest advances of CDs-C-MFCs in supercapacitors and metal-air batteries. The structure-performance relationship of these materials is carefully discussed. It is indicated that carbon dots (CDs) can act as the electron-rich regions in CDs-C-MFCs owing to their unique properties, such as quantum confinement effects, abundant defects, countless functional groups, etc. More importantly, specific doping can effectively modify the charge/spin distribution and then facilitate electron transfer. In addition, present challenges and future prospects of the CDs-C-MFCs are also given.

Improving the Fenton-like catalytic performance of MnOx-Fe3O4/biochar using reducing agents: A comparative study.

In this work, a Fenton-like system with MnOx-Fe3O4/biochar composite (FeMn/biochar) and reducing agents (RAs) was constructed for pollutant degradation, aiming to enhance Fenton-like performance from both degradation efficacy and operational cost aspects. Batch experiments revealed that five well-characterized RAs (sodium borohydride (SBH), sodium thiosulfate (STS), ascorbic acid (AA), hydroxylamine (HA) and oxalic acid (OA)) could impact performance of FeMn/biochar-H2O2 system through multiple mechanisms, including variation of solution pH, competition for H2O2, electrostatic attraction and acceleration of metal redox cycle. Significantly, only OA and HA obviously enhanced the catalytic capacity of Fenton-like process and HA increased ciprofloxacin degradation efficiency from 38.2% to 92.8% with a low economic consumption as 4.16 US$/m3, well in agreement with the accelerated Fe(III/II) cycle and Mn(III/II) cycle in FeMn/biochar-H2O2-HA system. The accelerated metal redox cycle could enhance the decomposition of H2O2 into •OH and •O2-, which were verified to be the main reactive oxygen species responsible for ciprofloxacin degradation by radical trapping experiments. Meanwhile, FeMn/biochar-H2O2-HA system could also work effectively in real wastewaters, and exhibited favorable catalytic performance towards oxytetracycline, tetracycline, methyl orange, methylene blue, Rhodamine B, and naphthalene, indicating the applicability of FeMn/biochar-H2O2-HA system in oxidizing refractory pollutants in wastewaters.

How does the microenvironment change during the stabilization of cadmium in exogenous remediation sediment?

The pollution degree of heavy metals is closely related to the sediment microenvironment. This study aims to give a comprehensive account of the changes of microenvironment in sediment during the stabilization of cadmium (Cd) by the sodium lignosulphonate (SLS) modified chlorapatites (SLS@nClAP). Chemical speciation change demonstrated that SLS@nClAP possessed better stabilizing capacity (65.84 %-76.66 %) for Cd than unmodified chlorapatites (ClAP) (45.88 %). It might be since that the surface of SLS@nClAP presented a more dispersive thin sheet structure with sulfonate groups compared with the aggregate block structure of ClAP. High-throughput sequencing results displayed that succession of microbial community occurred after remediation in sediment. Most importantly, the dominant genus changed from massilia to phosphate-solubilizing bacterium-pseudomonas which might be due to the remediation of chlorapatites and the stabilization of Cd. Moreover, enzyme activity changes showed that the activity of catalase and urease were highly influenced by the stability and bioavailability of Cd during the incubation. This study not only provided a novel remediation technology for Cd-polluted sediment but also confirmed that the change of microenvironment was closely related to the stability and bioavailability of Cd in sediment.

Strategy to improve gold nanoparticles loading efficiency on defect-free high silica ZSM-5 zeolite for the reduction of nitrophenols.

Catalytic reduction of toxic and aqueous stable nitrophenols by gold nanoparticles (Au NPs) is hot issue due to the serious environmental pollution in recent years. But the expensive price and poor recycling performance of Au NPs limit its further application. Defect-free high silica zeolite is suitable support for Au NPs due to its cheaper price, higher stability and stronger adsorbability, but the low alumina content and defect sites usually lead to poor Au NPs loading efficiency. Herein, we reported the improved Au NPs loading efficiency on defect-free high silica ZSM-5 zeolite through the additional surface fluffy structure. The fluffy structure was created through the addition of multi-walled carbon nanotubes (MWCNTs) and ethanol into synthesis gel. Highly dispersed ca. 4 nm Au NPs on zeolite surface are prepared by the green enhanced sol-gel immobilization method. The Au NPs loading efficiency on conventional ZSM-5 zeolite is 10.7%, in contrast, this result can arrive to 82.6% on fluffy structure ZSM-5 zeolite. The fluffy structure ZSM-5 zeolite and Au NPs nanocomposites show higher efficiency than traditional Au/ZSM-5 nanocomposites towards catalytic reduction of nitrophenols. Additionally, the experiments with different affecting factors (MWCNTs dosage, aging time, catalysts dosage, pH, initial 4-NP concentration, storage time and recycling times) were carried out to test general applicability of the nanocomposites. And the degradation of nitrophenols experiment was operated to explore the catalytic performance of the prepared nanocomposites in further environmental application. The detailed possible relationship between zeolite with fluffy structure and Au NPs is also proposed in the paper.