Photocatalytic degradation of (micro)plastics using TiO2-based and other catalysts: Properties, influencing factor, and mechanism

Nuclease-Mimetic Nanomaterials: From Fundamentals to Bioapplications

With the rapid development of nanozymes and nanomedicine, designing novel nanostructures directly acting on deoxyribonucleic acid (DNA) has great therapeutic potential because DNA is the carrier of genetic information and plays a vital role on life activities of the organism. Specifically, DNA cleavage is an important step in most of these DNA engineering technologies. While nucleases play crucial roles in the cell metabolism by efficient DNA cutting, the practical applications of natural nucleases suffer from some intrinsic shortcomings such as high cost and intolerance to harsh environments. In the past 20 years, great varieties of engineered nanostructures with DNA cleavage (nuclease-mimetic nanomaterials, abbreviated as nuclease mimics) have been developed rapidly and widely used in biomedical fields. In view of the significant progress of nuclease-mimetic nanomaterials, the possible DNA cleavage mechanism mediated by nuclease-mimetic nanomaterials is systematically discussed in this review, and the classification of nuclease-mimetic nanomaterials is illustrated. Their potential biomedical applications, especially in anti-biofilms and cancer treatment, are also comprehensively summarized. Finally, the current opportunities and challenges are discussed to stimulate the research of understanding and development of nuclease-mimetic nanomaterials.

Current Advances in the Photoconversion of Plastics: the Catalysts and Reaction Pathways

Plastic waste has caused severe global environmental pollution and health issues due to the high production rate and lack of proper disposal technology. Traditional methods to deal with plastic waste, such as incineration and landfilling, are deemed unsustainable and energy-intensive. A promising alternative is the photocatalytic conversion of plastic waste, using sunlight as a sustainable and carbon-neutral energy source to break down plastic waste under ambient pressure and low temperatures. This review aims to provide a comprehensive summary of recent advancements in plastic photoconversion, with an emphasis on the catalysts and reaction pathways. The mechanisms and reaction routes are first reviewed, followed by a detailed discussion of strategies to design catalysts for improved performance in photoconversion. Then, examples of photothermal degradation processes are presented. Finally, current strategies, challenges, and possible future directions of plastic photoconversion are summarized and discussed.

Innovative materials that behave like robots to combat plastic pollution

The growing plastic pollution crisis demands novel approaches, with innovative materials that mimic robotic behaviors emerging as a promising solution. This approach explores the development and application of smart materials that can autonomously engage in plastic waste removal, functioning like robots under various environmental conditions. We focus on materials activated by light, magnetic fields, chemical fuels, and ion exchange, which are designed to target and remove plastic waste efficiently. The key properties of these materials, such as self-activation, adaptability, and precision that enable them to function autonomously in waste management systems, are examined. The integration of these innovative materials offers significant advantages, including faster waste processing, reduced human exposure to hazardous waste, and enhanced sorting accuracy. Additionally, this review evaluates the environmental impact, scalability, and cost-effectiveness of these materials in comparison to traditional methods. Finally, the potential of these materials to play a central role in sustainable plastic waste management and contribute to a circular economy is discussed.

Review and future outlook for the removal of microplastics by physical, biological and chemical methods in water bodies and wastewaters

Microplastics (MPs) have become a major global environmental problem due to their accelerated distribution throughout different environments. Their widespread presence is a potential threat to the ecosystems because they alter the natural interaction among their constituent elements. MPs are considered as emergent pollutants due to the huge amount existing in the environment and by the toxic effects they can cause in living beings. The removal of MPs from water bodies and wastewaters is a control strategy that needs to be implemented from the present on and strictly constantly in the near future to control and mitigate their distribution into other environments. The present work shows a detailed comparison of the current potential technologies for the remediation of the MPs pollution. That is, physical, biological, and chemical methods for the removal of MPs from water bodies and wastewaters. Focusing mainly on the discussion of the perspective on the current innovative technologies for the removal or degradation of the MPs, rather than in a deep technical discussion of the methodologies. The selected novel physical methods discussed are adsorption, ultrafiltration, dynamic membranes and flotation. The physical methods are used to modify the physical properties of the MPs particles to facilitate their removal. The biological methods for the removal of MPs are based on the use of different bacterial strains, worms, mollusks or fungus to degrade MPs particles due to the hydrocarbon chain decrease of the particles, because these kinds of microorganisms feed on these organic chains. The degradation of MPs in water bodies and wastewaters by chemical methods is focusing on coagulation, electrocoagulation, photocatalysis, and ozonation. Chemical methods achieve the degradation of MPs by the modification of the chemical structure of the particles either by the change of the surface of the particles or by attacking radicals with a high oxidation capacity. Additionally, some interesting combinations of physical, chemical, and biological methods are discussed. Finally, this work includes a critical discussion and comparison of several novel methods for the removal or degradation of MPs from water bodies and wastewaters, emphasizing the areas of opportunity and challenges to be faced.

Impact of plastic pollution on ecosystems: a review of adverse effects and sustainable solutions

The primary source of the growing concern regarding marine, aquatic, and land pollution is plastic products, the majority of which are made of synthetic or semi-synthetic organic compounds. These combinations include materials like coal and natural gas that are obtained through petrochemical processes. As these two types of plastic-derived products are produced and disposed of, they have a major impact on the ecosystems. According to recent figures, around 400 million tons of plastic and related products derived from plastic are produced annually, and it became double in the last two decades. Plastic pollutants are introduced into ecosystems by a variety of stakeholders at different points in their daily lives, whether intentionally or accidentally. They have become a major source of adverse effects, toxicity development in natural entities, and problems. The aquatic, marine, and land ecosystems are vital to human existence, which emphasizes how difficult it is to stop pollution from it. This review highlights the adverse impacts of plastics, plastic-based products, and micro-nanoplastics on aquatic, terrestrial, and marine ecosystems while addressing advances in biodegradable plastics, recycling innovations, plastic-degrading enzymes, and sustainable solutions to reduce environmental risks.

Investigating the polyethylene degradation mechanism using docking and molecular dynamics simulations

Polyethylene (PE), widely utilized in everyday life, is notorious for its protracted degradation period, extending over decades, presenting an environmental hazard. Recently, there has been growing interest in utilizing microorganisms to aid in PE decomposition. Molecular docking and molecular dynamics simulations are valuable tools for understanding specific mechanisms and conducting initial screenings to support experimental research in this context. In this study, various enzymes, including lignin peroxidase, laccase, manganese peroxidase, and cutinase, sourced from Phanerodontia chrysosporium, Melanocarpus albomyces, and Fusarium vanettenii, were investigated. The docking simulations revealed that lignin peroxidase exhibited the most substantial binding interaction with PE, displaying a binding energy of - 4.69162 kcal mol-1 and an RMSD value of 0.93428 Å. Following lignin peroxidase in binding strength were laccase, manganese peroxidase, and cutinase. Furthermore, molecular dynamics simulations provided insights into the binding mechanisms. These simulations demonstrated stability over a 200-ns period, as indicated by RMSD and RMSF values below 0.2 nm. Additionally, the study delved into the interaction mechanisms between microorganisms and plastic molecules, enriching our understanding of this process. While the findings of this study may be considered modest, they contribute to a broader perspective and have the potential to influence more profound and significant research in the field.

Selection of engineered degradation method to remove microplastics from aquatic environments

Microplastics (MPs) in the aquatic environment are difficult to degrade naturally due to their hydrophobicity and structure. A variety of engineered degradation methods were developed to treat MPs contamination in the aquatic environment. Current reviews of MPs degradation methods only provided an inventory but lacked systematic comparisons and application recommendations. However, selecting suitable degradation methods for different types of MPs contamination may be more effective. This work examined the present engineered degradation methods for MPs in the aquatic environment. They were categorized into chemical degradation, biodegradation, thermal degradation and photodegradation. These degradation methods were systematically summarized in terms of degradation efficiency, technical limitations and production of environmental hazards. Also, the potential influences of different environmental factors and media on degradation were analyzed, and the selection of degradation methods were suggested from the perspectives of contamination types and degradation mechanisms. Finally, the development trend and challenges for studying MPs engineered degradation were proposed. This work will contribute to a better selection of customized degradation methods for different types of MPs contamination scenarios in aquatic environments.

Visible-light-sensitive microrobots using H2O as fuel for highly efficient capture and precise detection of nanoplastics

Nanoplastics, which are small plastic particles resulting from the decomposition of plastic waste, can accumulate and adsorb toxic chemicals in aquatic environments, leading to detrimental effects on the environment and human health. Consequently, there is an urgent demand for the development of an efficient method to accurately quantify and effectively remove nanoplastics. Here, we prepared a novel "cage-like" microrobot for effective dynamic capture and highly sensitive surface-enhanced Raman scattering detection of nanoplastics in situ. The microrobot utilizes water as fuel under visible light and achieves efficient capture of nanoplastics within 2 min on the basis of the stacking structure between layers and electrostatic action. The microrobot could be recovered by an external magnetic field, and the SERS activity was greatly enhanced through the coupling of multilayer hot spots, with a detection limit of 1.27 μg/mL. We built a simple device to demonstrate the feasibility of the microrobot strategy of capturing plastic in real wastewater and further extended this technology to single-use plastic cups in everyday life. Moreover, many different types of plastic spectra can also be quickly distinguished when combined with machine learning. This work provides new ideas for improving the dynamic capture and effective monitoring of nanoplastics.

Elimination of torasemide from aqueous medium: influence of sorption and photocatalytic processes parameters supported by DFT analysis

The sorption and photocatalytic activity of pharmaceutical torasemide using an immobilized TiO2 photocatalyst were investigate. The experimental design included optimization of reaction conditions such as pH and initial pharmaceutical concentration in aqueous solution using the response surface modeling approach, scavenger tests to gain insight into the photocatalysis mechanism, and application of the process to more complex water matrices. TiO2 in the role of sorbent showed a low capacity for torasemide (12.23-29.83 μg/g within 24 h of contact), making this type of removal inefficient on its own. Investigating the sorption process influenced by different process parameters such as pH, temperature, ionic strength, and dosage of TiO2 applied, the low tendency to this kind of material was affirmed by low Kd values (0.70 to 6.78 mL/g) obtained by linear isotherms. Photocatalysis proved to be the better choice for the removal of torasemide from water, with the best kinetics at pH 4 and concentration of 5 mg/L with half-time for degradation of 34.83 min. Computational DFT analysis identified the zwitterionic torasemide structure as predominant under neutral and acidic conditions. It also showed that negatively charged areas around nitrogen-containing fragments probably have the highest potential to promote the TiO2 sorption at low pH conditions, where it is highest, through electrostatic attractions and N-H∙∙∙∙∙OTiO2 hydrogen-bonding contacts.

A convenient strategy for mitigating microplastics in wastewater treatment using natural light and ZnO nanoparticles as photocatalysts: A mechanistic study

Polypropylene microplastics (PPMPs) are one of the major emerging contaminants in the ecosystem due to their frequent usage and improper disposal practices. These PPMPs enter ecosystems via wastewater effluent plants and cause severe environmental health issues. In addition, quantifying PPMPs smaller than 50 μm in wastewater plant extraction is very difficult. Thus, the current study was designed to mitigate the PPMPs using zinc oxide nanoparticles (ZnONPs) as a photocatalyst under sunlight. The photocatalytic reaction was examined using spectroscopic techniques and microscopic imaging. The findings indicated that the weight loss percentage of PPMPs increased, and a decrease in UV-Vis DRS peak intensities was observed. The spectroscopic results elucidated the formation of free radicals, which affect the PPMPs and lead to the formation of carbonyl, allylic, and unsaturated groups. Further, EDS reports clarified that there is increased oxygen content due to the photooxidation process and the disintegration of the polymer chain owing to decreased carbon levels. Overall, ZnO photocatalyst absorbs photons from the visible spectrum of sunlight and forms free radicals, which affect the PPMPs to initiate polymer deterioration. Also, the current study revealed the mechanistic pathway of PPMP degradation under the photocatalytic reaction as proposed in the results obtained above.

Improved photodegradation of a superabsorber via carbon dots as electron transfer stations

Superabsorbers have been widely used in industrial and daily chemical products. Polymerized sodium acrylate (PAA-Na) is the most popular superabsorber used in diapers. Here we report the enhanced photodegradation of PAA-Na via carbon dots (CDs) in aqueous solutions. For a system comprising PAA-Na and CDs, CDs act as photosensitizers which improve the photodegradation efficiency by ∼5.6% compared with PAA-Na alone. Moreover, for PAA-Na+TiO2+CDs system, CDs also play the role of transfer stations of excited electrons which facilitate electron transfer from TiO2 nanoparticles (NPs) to PAA-Na and further boost the photodegradation efficiency of PAA-Na by ∼9.8%. Based on the spectral results, electrons can hardly transfer from TiO2 NPs to PAA-Na directly even with a bigger driving force compared with CDs; however, CDs can provide effective electron transfer channels within CDs-TiO2 NPs and CDs-PAA-Na which finally build an efficient pathway for electron transfer from TiO2 NPs to PAA-Na. This study reveals the great potential applications of CDs in photodegradation fields as photosensitizers or mediators to promote electron transfer efficiency.

Hydroborative Depolymerization of Polyesters and Polycarbonates to Diols Catalyzed by Heterogeneous Lanthanum Materials La(CH2C6H4NMe2-o)3@SBA-15

Chemical recycling is a promising strategy to establish a circular plastic economy, and it is still in an early stage of development. In this work, the reductive depolymerization of polyesters and polycarbonates into their corresponding borylated alcohols promoted by heterogeneous lanthanum materials was described. Grafting the easily accessible lanthanum tris(aminobenzyl) complex La(CH2C6H4NMe2-o)3 (1) onto the partially dehydroxylated silica support SBA-15 (SBA-15500 or SBA-15700) gave the inorganic-organic hybrid materials 1@SBA-15500 and 1@SBA-15700. These hybrid lanthanum materials, in combination with pinacolborane (HBpin), could serve as highly active heterogeneous catalysts for the selective depolymerization of aliphatic and aromatic polyesters, as well as polycarbonates into their corresponding borylated diols through a hydroboration reaction under mild conditions. The lanthanum materials exhibited a practical application in plastic waste recycling for their easy preparation, high catalytic efficiency, and recyclable property.

Innovative solutions for the removal of emerging microplastics from water by utilizing advanced techniques

Microplastic pollution is one of the most pressing global environmental problems due to its harmful effects on living organisms and ecosystems. To address this issue, researchers have explored several techniques to successfully eliminate microplastics from water sources. Chemical coagulation, electrocoagulation, magnetic extraction, adsorption, photocatalytic degradation, and biodegradation are some of the recognized techniques used for the removal of microplastics from water. In addition, membrane-based techniques encompass processes propelled by pressure or potential, along with sophisticated membrane technologies like the dynamic membrane and the membrane bioreactor. Recently, researchers have been developing advanced membranes composed of metal-organic frameworks, MXene, zeolites, carbon nanomaterials, metals, and metal oxides to remove microplastics. This paper aims to analyze the effectiveness, advantages, and drawbacks of each method to provide insights into their application for reducing microplastic pollution.

Co-photoaging inhibited the heteroaggregation between polystyrene nanoplastics and different titanium dioxide nanoparticles

Heteroaggregation between nanoplastics (NPs) and titanium dioxide nanoparticles (TiO2NPs) determines their environmental fates and ecological risks in aquatic environments. However, the co-photoaging scenario of NPs and TiO2NPs, interaction mechanisms of TiO2NPs with (aged) NPs, as well as the dependence of their heteroaggregation on TiO2NPs facets remain elusive. We found the critical coagulation concentration (CCC) of polystyrene nanoplastics (PSNPs) with coexisting RTiO2NPs was 1.9 - 2.2 times larger than that with coexisting ATiO2NPs, suggesting a better suspension stability of PSNPs+RTiO2NPs. In addition, CCC of TiO2NPs with coexisting photoaged PSNPs (APSNPs) was larger 1.7 - 2.2 times than that with PSNPs coexisting, indicating photoaging inhibited their heteroaggregation due to increasing electrostatic repulsion derived from increased negative charges on APSNPs and the polymer-derived dissolved organic carbon. Coexisted TiO2NPs promoted oxidation of PSNPs with the action of HO· and O2·- under UV light, leading to inhibited heteroaggregation. Moreover, Van der Waals and Lewis-acid interaction dominated the formation of primary heteroaggregates of PSNPs-TiO2NPs (ESE = ‒2.20 ∼ ‒2.78 eV) and APSNPs-TiO2NPs (ESE = ‒3.29 ∼ ‒3.67 eV), respectively. The findings provide a mechanistic insight into the environmental process of NPs and TiO2NPs, and are significant for better understanding their environmental risks in aquatic environments.

Nano-based remediation strategies for micro and nanoplastic pollution

Due to rapid urbanization, there have been continuous environmental threats from different pollutants, especially from microplastics. Plastic products rapidly proliferate significantly contributing to the occurrence of micro-plastics, which poses a significant environmental risk. These microplastics originated from diverse sources and are characterized by their persistent and widespread occurrence; human health and the entire ecosystem are adversely affected by them. The removal of microplastics not only requires innovative technologies but also efficient materials capable of effectively eliminating them from our environment. The progress made so far has highlighted the advantages of utilizing the dimensional and structural properties of nanomaterials to increase the effectiveness of existing methods for micro-plastic treatment, aiming for a more sustainable approach to their removal. In the current review, we demonstrate a thorough overview of the sources, occurrences, and potential harmful effects of microplastics, followed by a further discussion of promising technologies used for their removal. An in-depth examination of both advantages and a few limitations of all these given technologies, including physical, chemical, and biological approaches, has been discussed. Additionally, the review explores the use of nanomaterials as an effective means to overcome obstacles and improve the efficiency of microplastic elimination methods. n conclusion, this review addresses, current challenges in this field and outlines the future perspectives for further research in this domain.

Microplastics removal in wastewater treatment plants: A review of the different approaches to limit their release in the environment

In last 10 years, the interest about the presence of microplastics (MPs) in the environment has strongly grown. Wastewaters function as a carrier for MPs contamination from source to the aquatic environment, so the knowledge of the fate of this emerging contaminant in wastewater treatment plants (WWTPs) is a priority. This work aims to review the presence of MPs in the influent wastewater (WW) and the effectiveness of the treatments of conventional WWTPs. Moreover, the negative impacts of MPs on the management of the processes have been also discussed. The work also focuses on the possible approaches to tackle MPs contamination enhancing the effectiveness of the WWTPs. Based on literature results, despite WWTPs are not designed for MPs removal from WW, they can effectively remove the MPs (up to 99 % in some references). Nevertheless, they normally act as "hotspots" of MPs contamination considering the remaining concentration of MPs in WWTPs' effluents can be several orders of magnitude higher than receiving waters. Moreover, MPs removed from WW are concentrated in sewage sludge (potentially >65 % of MPs entering the WWTP) posing a concern in case of the potential reuse as a soil improver. This work aims to present a paradigm shift intending WWTPs as key barriers for environmental protection. Approaches for increasing effectiveness against MPs have been discussed in order to define the optimal point(s) of the WWTP in which these technologies should be located. The need of a future legislation about MPs in water and sludge is discussed.

A broad horizon for sustainable catalytic oxidation of microplastics

Microplastics (MPs) have attracted tremendous attention due to their widespread appearance in the environment and biota, and their adverse effects on organisms. Since plastics are substantially produced to meet human needs, primary and secondary MPs are extensively trapped in wastewater treatment plants, freshwater, drinking water, ocean, air, and soil. The serious MPs pollution calls for efficient treatment strategies Herein, we discuss three catalytic processes (photocatalysis, electrocatalysis, and biocatalysis) for the sustainable management of MPs, and the relevant catalytic mechanisms are clarified. For photocatalysis, three categories (organic, inorganic, hybrid) of photocatalysts are listed, with degradation efficiency of 23%-100%. Next, relative impact factors on photocatalysis, such as characteristics of MPs and photocatalysts, are discussed. Then, some promising electrocatalysts for the degradation/conversion of (micro)plastics and standard electrolyzer designs are briefly introduced. This electrocatalytic method has achieved over 77% of Faradaic efficiency. Next, potential organisms with abundant biocatalysts for degrading different types of MPs are reviewed. Advances in three bioremediation techniques including biositimulation, bioaugmentation, and biosurfactant are outlined. Lastly, perspectives are put forward to promote scientific development in solving environmental issues on MPs pollution in broad fields. This paper provides insights into the development of next-generation techniques for MPs pollution management in a sustainable manner.

Photocatalytic degradation of different types of microplastics by TiOx/ZnO tetrapod photocatalysts

We investigated the use of titania coated ZnO tetrapods for photocatalytic degradation of two common types of microplastics, namely polyethylene (PE) microparticles and polyester (PES) microfibers. We found that the plastics morphology affects the rate of degradation, and that the use of electron scavengers is needed to maintain the reactivity of the photocatalysts over a prolonged period of time. Complete mass loss of PE and PES is achieved under UV illumination for 480 h and 624 h, respectively. In addition to pristine microplastics, the degradation of environmental microplastics sample (consisting primarily of polypropylene) was also demonstrated, though in this case longer degradation time (∼816 h) was needed to achieve complete mass loss of the samples.

Microplastics in soils during the COVID-19 pandemic: Sources, migration and transformations, and remediation technologies

The COVID-19 pandemic has led to a notable upsurge of 5-10 % in global plastic production, which could have potential implications on the soil quality through increased microplastics (MPs) content. The elevated levels of MPs in the soil poses a significant threat to both the environment and human health, hence necessitating the remediation of MPs in the environment. Despite the significant attention given to MPs remediation in aqueous environments, less consideration has been given to MPs remediation in the soil. Consequently, this review highlights the major sources of MPs in the soil, their migration and transformation behaviors during the COVID-19 pandemic, and emphasizes the importance of utilizing remediation technologies such as phytoremediation, thermal treatment, microbial degradation, and photodegradation for MPs in the soil. Furthermore, this review provides a prospective outlook on potential future remediation methods for MPs in the soil. Although the COVID-19 pandemic is nearing its end, the long-term impact of MPs on the soil remains, making this review a valuable reference for the remediation of MPs in the post-pandemic soil.

Black carbon derived from pyrolysis of maize straw and polystyrene microplastics affects soil biodiversity

Understanding the environmental correlation of microbial community under external stimulation is significant for ecological restoration. However, few studies focused on the response of soil biodiversity induced by black carbon (BC) derived from pyrolysis of straw and microplastics (MPs) due to their widespread existence in natural environment. In this study, polystyrene MPs (PS) and maize straw with different mass ratios were used as raw materials to prepare BC by pyrolysis. The surface morphology, chemical composition and sequential variations of different functional groups of BC were systematically analyzed. The leachate from BC was identified by three-dimensional excitation emission matrice (3D-EEM). The corresponding results showed that yield, value of O/C and N element content of BC decreased with more PS. The changed C content and oxygen-containing functional groups occurred. The order of functional groups of BC formed by co-pyrolysis was: C=C > C-O > C-H > Si-O-Si. The main component of leaching from BC was humic-like and fulvic-like acid. Simultaneously, the input of exogenous BC into soil affected abundance, composition and metabolic pathways of microorganisms. The study helps to understand environmental implication of BC which was pyrolyzed from maize straw and MPs, providing an idea for improving biogeochemical cycle process in soil.

Waste self-heating bag derived iron-based composite with abundant oxygen vacancies for highly efficient Fenton-like degradation of micropollutants

In this study, iron-rich waste self-heating bag was reutilized as the raw material to prepare oxygen vacancies (OV) functionalized iron-based composite (iron oxide (Fe₃O₄)-carbon-vermiculite, viz. OV-ICV), which exhibited excellent performance in the Fenton-like degradation of micropollutants via peroxydisulfate (PDS) activation. Above 95% of 1.0 mg/L carbaryl (CB) was efficiently eliminated in the presence of 0.1 g/L of OV-ICV and 0.5 mmol/L of PDS over a wide pH range of 3-10 within 30 min. Besides, OV-ICV also showed acceptable adaptability, stability, and renewability. Imbedding OV into Fe₃O₄ structure significantly generated more active iron sites and localized electrons, promoted the charge transfer ability, and assisted the redox cycle of ≡Fe(III)/≡Fe(II) for PDS activation. Mechanism investigation demonstrated that superoxide radicals (O₂^•-) derived from the activation of molecular oxygen mediated the generation of H₂O₂, and both of them further enhanced the formation of more sulfate radicals (SO₄^•-) and hydroxyl radicals (^•OH), which led to the efficient degradation and mineralization of CB. Furthermore, the degradation pathways of CB were proposed based on the intermediates identification. This work lays a foundation for the rational reutilization of iron-containing wastes modified with defect engineering in heterogeneous Fenton-like catalysis for the remediation of micropollutants wastewater.

Enhanced ozonation of polystyrene nanoplastics in water with CeOx@MnOx catalyst

The nanoplastics released into the environment pose a critical threat to creatures, and thus it is necessary to remove them. However, their natural decomposition usually takes years or even decades, which raises an imminent demand for an efficient removal technology. Herein we report a core-shell CeOx@MnOx catalyst for enhancing ozonation of polystyrene nanoplastics in water. Ozonation achieves 31.67% molecular weight removal of polystyrene nanoplastics in the first 10 min reaction, which is increased to 51.67% in catalytic ozonation by MnOx and further improved to 73.33% in catalytic ozonation via CeOx@MnOx. The remarkable thing is the CeOx@MnOx could achieve almost 96.70% molecular weight removal after 50 min reaction. The specific catalytic mechanism is ozone decomposes into reactive oxygen radicals (•OH, •O₂^- and ¹O₂) after capturing electrons from MnOx, improving the polystyrene nanoplastics removal. Meanwhile, the Mn averaged valence state increases, making it harder to donate electrons to ozone. This can be alleviated by encapsulating the CeOx core in the MnOx, enabling electrons replenishment from the CeOx core to the MnOx shell, which is verified by the experiment and density functional theory calculations. The repeated experiment demonstrates the CeOx@MnOx possesses excellent stability, maintaining 95.25-96.70% removal efficiency of polystyrene nanoplastics. This research provides a possibility for the efficient removal of nanoplastics in water.

Removing microplastics from aquatic environments: A critical review

As one of the typical emerging contaminants, microplastics exist widely in the environment because of their small size and recalcitrance, which has caused various ecological problems. This paper summarizes current adsorption and removal technologies of microplastics in typical aquatic environments, including natural freshwater, marine, drinking water treatment plants (DWTPs), and wastewater treatment plants (WWTPs), and includes abiotic and biotic degradation technologies as one of the removal technologies. Recently, numerous studies have shown that enrichment technologies have been widely used to remove microplastics in natural freshwater environments, DWTPs, and WWTPs. Efficient removal of microplastics via WWTPs is critical to reduce the release to the natural environment as a key connection point to prevent the transfer of microplastics from society to natural water systems. Photocatalytic technology has outstanding pre-degradation effects on microplastics, and the isolated microbial strains or enriched communities can degrade up to 50% or more of pre-processed microplastics. Thus, more research focusing on microplastic degradation could be carried out by combining physical and chemical pretreatment with subsequent microbial biodegradation. In addition, the current recovery technologies of microplastics are introduced in this review. This is incredibly challenging because of the small size and dispersibility of microplastics, and the related technologies still need further development. This paper will provide theoretical support and advice for preventing and controlling the ecological risks mediated by microplastics in the aquatic environment and share recommendations for future research on the removal and recovery of microplastics in various aquatic environments, including natural aquatic environments, DWTPs, and WWTPs.

Panax notoginseng powder -assisted preparation of carbon-quantum-dots/BiOCl with enriched oxygen vacancies and boosted photocatalytic performance

Low activity of photocatalysts is a serious bottleneck to the practical application of photocatalytic technology. In this paper, a series of BiOCl composite photocatalysts containing carbon quantum dots (CQDs) were successfully prepared by adding Panax notoginseng powder (PNP) to the solvothermal synthesis system of BiOCl as a template agent and a raw material for 0D CQDs. CQDs/BiOCl exhibit 2D flake structures and 3D flower-like microspheres self-assembled from thin flakes, holding rich oxygen vacancies (OVs). After detailed characterization, it was found that the amount of OVs on BiOCl could be regulated according to the amount of PNP added. The CQDs/OVs-BiOCl photocatalysts exhibit higher photogenerated charge separation efficiency and photocatalytic activity than the bare BiOCl. When the mass ratio of PNP/BiOCl is 1.0%, the photocatalyst demonstrates the maximum degradation activity for rhodamine B (RhB) and perfluorooctanoic acid (PFOA). In view of the solid observations, a photocatalytic enhancement mechanism of CQDs/BiOCl was elucidated.

Prospects of TiO2-based photocatalytic degradation of microplastic leachates related disposable facemask, a major COVID-19 waste

COVID-19 is one of the serious catastrophes that have a substantial influence on human health and the environment. Diverse preventive actions were implemented globally to limit its spread and transmission. Personnel protective equipment (PPE) was an important part of these control approaches. But unfortunately, these types of PPE mainly comprise plastics, which sparked challenges in the management of plastic waste. Disposable face masks (DFM) are one of the efficient strategies used across the world to ward off disease transmission. DFMs can contribute to micro and nano plastic pollution as the plastic present in the mask may degrade when exposed to certain environmental conditions. Microplastics (MPs) can enter the food chain and devastate human health. Recognizing the possible environmental risks associated with the inappropriate disposal of masks, it is crucial to avert it from becoming the next plastic crisis. To address this environmental threat, titanium dioxide (TiO2)-based photocatalytic degradation (PCD) of MPs is one of the promising approaches. TiO2-based photocatalysts exhibit excellent plastic degradation potential due to their outstanding photocatalytic ability, cost efficiency, chemical, and thermal stability. In this review, we have discussed the reports on COVID-19 waste generation, the limitation of current waste management techniques, and the environmental impact of MPs leachates from DFMs. Mainly, the prominence of TiO2 in the PCD and the applications of TiO2-based photocatalysts in MPs degradation are the prime highlights of this review. Additionally, various synthesis methods to enhance the photocatalytic performance of TiO2 and the mechanism of PCD are also discussed. Furthermore, current challenges and the future research perspective on the improvement of this approach have been proposed.

Nano-architectural design of TiO2 for high performance photocatalytic degradation of organic pollutant: A review

In the past several decades, significant efforts have been paid toward photocatalytic degradation of organic pollutants in environmental research. During the past years, titanium dioxide nano-architectures (TiO2 NAs) have been widely used in water purification applications with photocatalytic degradation processes under Uv/Vis light illumination. Photocatalysis process with nano-architectural design of TiO2 is viewed as an efficient procedure for directly channeling solar energy into water treatment reactions. The considerable band-gap values and the subsequent short life time of photo-generated charge carriers are showed among the limitations of this approach. One of these effective efforts is the using of oxidation processes with advance semiconductor photocatalyst NAs for degradation the organic pollutants under UV/Vis irradiation. Among them, nano-architectural design of TiO2 photocatalyst (such as Janus, yolk-shell (Y@S), hollow microspheres (HMSs) and nano-belt) is an effective way to improve oxidation processes for increasing photocatalytic activity in water treatment applications. In the light of the above issues, this study tends to provide a critical overview of the used strategies for preparing TiO2 photocatalysts with desirable physicochemical properties like enhanced absorption of light, low density, high surface area, photo-stability, and charge-carrier behavior. Among the various nanoarchitectural design of TiO2, the Y@S and HMSs have created a great appeal given their considerable large surface area, low density, homogeneous catalytic environment, favorable light harvesting properties, and enhanced molecular diffusion kinetics of the particles. In this review was summarized the developments that have been made for nano-architectural design of TiO2 photocatalyst. Additional focus is placed on the realization of interfacial charge and the possibility of achieving charge carriers separation for these NAs as electron migration is the extremely important factor for increasing the photocatalytic activity.

Photocatalytic Inactivation of Bacillus subtilis Spores by Natural Sphalerite with Persulfate under Visible Light Irradiation

Bacterial spores are highly resistant to be inactivated by conventional water disinfection methods. In this study, the inactivation efficiency and mechanisms of Bacillus subtitles (B. subtilis) spores by natural sphalerite (NS) with persulfate (PS) under visible light (Vis) irradiation were investigated for the first time. The NS was composed of ZnS doped with trace amounts of metal ions, including As, Fe, Cd, and Mn. The results showed that 7 log of B. subtilis spores could be completely inactivated within 5 h in the Vis/NS/PS photocatalytic system, and the inactivation efficiency was about four and seven times higher than that of the NS/PS system and the Vis/PS system, respectively. The photo-generated electrons are generated by the excitation of NS under the illumination activated PS to form PS radicals (∙SO4−) and hydroxyl radicals (∙OH), which are the main active species for spore inactivation. Mechanism studies further showed that spore inactivation was related to physiological responses, including the increase in intracellular reactive oxygen species, the change of induced antioxidant enzyme activity, and the change of total protein. Furthermore, the dynamic changes of cells during spore inactivation were observed by SEM. These results not only clarify the relationship between the cell physiological stress response and inactivation mechanism of spores, but also reveal the interaction between minerals and PS under Vis, which provides technical methods for the inactivation of bacterial spores in the field of water disinfection.