Turning plastics/microplastics into valuable resources? Current and potential research for future applications.

Plastics are a wide range of synthetic or semi-synthetic materials, mainly consisting of polymers. The use of plastics has increased to over 300 million metric tonnes in recent years, and by 2050, it is expected to grow to 800 million. Presently, a mere 10% of plastic waste is recycled, with approximately 75% ended up in landfills. Inappropriate disposal of plastic waste into the environment poses a threat to human lives and marine species. Therefore, this review article highlights potential routes for converting plastic/microplastic waste into valuable resources to promote a greener and more sustainable environment. The literature review revealed that plastics/microplastics (P/MP) could be recycled or upcycled into various products or materials via several innovative processes. For example, P/MP are recycled and utilized as anodes in lithium-ion (Li-ion) and sodium-ion (Na-ion) batteries. The anode in Na-ion batteries comprising PP carbon powder exhibits a high reversible capacity of ∼340 mAh/g at 0.01 A/g current state. In contrast, integrating Fe3O4 and PE into a Li-ion battery yielded an excellent capacity of 1123 mAh/g at 0.5 A/g current state. Additionally, recycled Nylon displayed high physical and mechanical properties necessary for excellent application as 3D printing material. Induction heating is considered a revolutionary pyrolysis technique with improved yield, efficiency, and lower energy utilization. Overall, P/MPs are highlighted as abundant resources for the sustainable production of valuable products and materials such as batteries, nanomaterials, graphene, and membranes for future applications.

Degradation Product-Promoted Depolymerization Strategy for Chemical Recycling of Poly(bisphenol A carbonate).

The accumulation of waste plastics has a severe impact on the environment, and therefore, the development of efficient chemical recycling methods has become an extremely important task. In this regard, a new strategy of degradation product-promoted depolymerization process was proposed. Using N,N'-dimethyl-ethylenediamine (DMEDA) as a depolymerization reagent, an efficient chemical recycling of poly(bisphenol A carbonate) (BPA-PC or PC) material was achieved under mild conditions. The degradation product 1,3-dimethyl-2-imidazolidinone (DMI) was proven to be a critical factor in facilitating the depolymerization process. This strategy does not require catalysts or auxiliary solvents, making it a truly green process. This method improves the recycling efficiency of PC and promotes the development of plastic reutilization.

Recent advances on solar-driven valorization of polyethylene terephthalate plastics into value-added chemicals.

The random disposal and immature recycling of post-consumer polyethylene terephthalate (PET) packages lead to a severe threaten to the ecological system owing to slow natural degradation kinetics of PET plastic, and meanwhile cause a waste of carbon resources stored in PET plastics. Many methods have been developed to recycle PET plastics, such as mechanical recycling, which induces a reduced quality relative to the virgin PET. In recent years, the photocatalytic conversion of PET plastic wastes into chemicals has received considerable attention due to their unique advantages, including mild conditions, less energy consumption, and simple operation. In this review, we have summarized the latest achievements in photoreforming of PET plastics into value-added chemicals. Primarily, we described the mechanism for bond cleavage during PET photoreforming, the emerging pretreatment methodologies for PET plastics, and the advantages of photocatalytic PET plastics conversion. Then, we introduced electro-/bio-assisted photocatalysis technologies for PET disposal and commented their strengths and limitations. Finally, we put forward the challenges and potential advances in the domain of photocatalytic PET plastics conversion.

Characterization of microparticles derived from waste plastics and their bio-interaction with human lung A549 cells.

Microplastics (MPs) represent a worldwide emerging relevant concern toward human and environmental health due to their intentional or unintentional release. Human exposure to MPs by inhalation is predicted to be among the most hazardous. MPs include both engineered, or primary MPs, and secondary MPs, materials obtained by fragmentation from any plastic good. The major part of the environmental MPs is constituted by the second ones that are irregular in size, shape and composition. These features make the study of the biological impact of heterogenous MPs of extremely high relevance to better estimate the real toxicological hazards of these materials on human and environmental organisms. The smallest fractions of plastic granules, relying on the micron-sized scale, can be considered as the most abundant component of the environmental MPs, and for this reason, they are typically used to perform toxicity tests using in vitro systems representative of an inhalation exposure scenario. In the present work, MPs obtained from industrial treatment of waste plastics (wMPs < 50 µm) were investigated, and after the physico-chemical characterization, the cytotoxic, inflammatory and genotoxic responses, as well as the modality of wMPs interactions with alveolar lung cells, were determined. Obtained results indicated that, at high concentrations (100 µg/ml) and prolonged exposure time (48 h), wMPs affect biological responses by inducing inflammation and genotoxicity, as a result of the cell-wMP interactions, also including the uptake of the smaller particles.

A review of microwave pyrolysis as a sustainable plastic waste management technique.

The high demand for plastic has led to plastic waste accumulation, improper disposal and environmental pollution. Even though some of this waste is recycled, most ends up in landfills or flows down rivers into the oceans. Therefore, researchers are now exploring better ways to solve the plastic waste management problem. From a socio-economic perspective, there is also a concerted effort to enable energy recovery from plastic waste and convert it into useful products to generate income for targeted segments of the population. In fact, this concept of waste-to-wealth has been adopted by the United Nations as part of its Sustainable Development Goals strategies. The current article begins by reviewing the strengths and weaknesses of plastic recycling before focusing specifically on microwave pyrolysis as an alternative to conventional technologies in plastic waste management, due to its benefit in providing fast and energy-efficient heating. The key parameters that are reviewed in this paper include different types of plastic, types of absorbent, temperatures, microwave power, residence time, and catalysts. The yield of the final product (oil, gaseous and char) varies depending on the main process parameters. Key challenges and limitations of microwave pyrolysis are also discussed in this paper.

Catalytic pyrolysis of high-density polyethylene over nickel-waste chicken eggshell/HZSM-5.

The main objective of the current work is to investigate the effect of nickel-waste chicken eggshell modified Hydrogen exchanged Zeolite Socony Mobil-5 (Ni-WCE/HZSM-5) on pyrolysis of high-density polyethylene (HDPE). Ni-WCE/HZSM-5 was synthesized via the impregnation incipient wetness (IWI) method with Ni and WCE mass loading of 4 and 12 wt% respectively. HZSM-5, CaO, WCE, WCE/HZSM-5, and Ni/HZSM-5 were prepared for comparison purposes with Ni-WCE/HZSM-5. All the synthesized catalysts were characterized for phase analysis, metal loading, surface morphology, and textural properties. The impregnation of nickel and WCE had significantly affected the original framework of HZSM-5, where the crystallinity percentage and average crystal size of HZSM-5 dropped to 44.97% and increased to 47.90 nm respectively. The surface morphology of HZSM-5 has drastically changed from a cubic-like shape into a spider web-like surface after the impregnation of WCE. The BET surface area of HZSM-5 has been lowered due to the impregnation of nickel and WCE, but the total pore volume has increased greatly from 0.2291 cm3/g to 0.2621 cm3/g. The catalyst performance was investigated in the pyrolysis of HDPE via a fixed bed reactor and the pyrolysis oil was further analysed to evaluate the distribution of C6 to C9> hydrocarbons. Among the tested catalytic samples, the highest pyrolysis oil yield was achieved by WCE (80%) followed by CaO (78%), WCE/HZSM-5 (63%), HZSM-5 (61%), Ni/HZSM-5 (44%) and Ni-WCE/HZSM-5 (50%). For hydrocarbon distribution in pyrolysis oil, the Ni/HZSM-5 produced the highest of total C6 and C7 hydrocarbons at 12% and 27% respectively followed by WCE/HZSM-5 (4% and 20%), non-catalytic (5% and 13%), Ni-WCE/HZSM-5 (0% and 15%), WCE (0% and 10%), HZSM-5 (0% and 6%) and CaO (0% and 0%).

Potential Chemicals from Plastic Wastes.

Plastic is referred to as a "material of every application". From the packaging and automotive industries to the medical apparatus and computer electronics sectors, plastic materials are fulfilling demands efficiently. These plastics usually end up in landfills and incinerators, creating plastic waste pollution. According to the Environmental Protection Agency (EPA), in 2015, 9.1% of the plastic materials generated in the U.S. municipal solid waste stream was recycled, 15.5% was combusted for energy, and 75.4% was sent to landfills. If we can produce high-value chemicals from plastic wastes, a range of various product portfolios can be created. This will help to transform chemical industries, especially the petrochemical and plastic sectors. In turn, we can manage plastic waste pollution, reduce the consumption of virgin petroleum, and protect human health and the environment. This review provides a description of chemicals that can be produced from different plastic wastes and the research challenges involved in plastic waste to chemical production. This review also provides a brief overview of the state-of-the-art processes to help future system designers in the plastic waste to chemicals area.

Fast and Facile Biodegradation of Polystyrene by the Gut Microbial Flora of Plesiophthalmus davidis Larvae.

Polystyrene (PS), which accounts for a significant fraction of plastic wastes, is difficult to biodegrade due to its unique molecular structure. Therefore, biodegradation and chemical modification of PS are limited. In this study, we report PS biodegradation by the larvae of the darkling beetle Plesiophthalmus davidis (Coleoptera: Tenebrionidae). In 14 days, P. davidis ingested 34.27 ± 4.04 mg of Styrofoam (PS foam) per larva and survived by feeding only on Styrofoam. Fourier transform infrared spectroscopy confirmed that the ingested Styrofoam was oxidized. Gel permeation chromatography analysis indicated the decrease in average molecular weight of the residual PS in the frass compared with the feed Styrofoam. When the extracted gut flora was cultured for 20 days with PS films, biofilm and cavities were observed by scanning electron microscopy and atomic force microscopy. X-ray photoelectron spectroscopy (XPS) studies revealed that C-O bonding was introduced into the biodegraded PS film. Serratia sp. strain WSW (KCTC 82146), which was isolated from the gut flora, also formed a biofilm and cavities on the PS film in 20 days, but its degradation was less prominent than the gut flora. XPS confirmed that C-O and C=O bonds were introduced into the biodegraded PS film by Serratia sp. WSW. Microbial community analysis revealed that Serratia was in the gut flora in significant amounts and increased sixfold when the larvae were fed Styrofoam for 2 weeks. This suggests that P. davidis larvae and its gut bacteria could be used to chemically modify and rapidly degrade PS.IMPORTANCE PS is widely produced in the modern world, but it is robust against biodegradation. A few studies reported the biodegradation of PS, but most of them merely observed its weight loss; fewer were able to find its chemical modifications, which are rather direct evidence of biodegradation, by using limited organisms. Therefore, it is required to find an effective way to decompose PS using various kinds of organisms. Herein, we discovered a new PS-degrading insect species and bacterial strain, and we found that the genus that includes the PS-degrading bacterial strain occurs in significant amounts in the larval gut flora, and the proportion of this genus increased as the larvae were fed Styrofoam. Our research offers a wider selection of PS-degrading insects and the possibility of using a certain mixture of bacteria that resemble the gut flora of a PS-degrading insect to biodegrade PS, and thus could contribute to solving the global plastic crisis.

Degradation of plastics and plastic-degrading bacteria in cold marine habitats.

Synthetic plastics present in everyday materials constitute the main anthropogenic debris entering the Earth's oceans. The oceans provide important and valuable resources such as food, energy, and water. They are also the main way of international trade and the main stabilizer of the climate. Hence, changes in the marine ecosystem caused by anthropogenic influences such as plastic pollution can have a dramatic impact on a global scale. Although the problem of plastics still remains unsolved, different ways are being considered to reduce their impact on the environment. One of them is to use microorganisms capable of degradation of plastic. A particularly interesting area is the application of microorganisms isolated from cold regions in view of their unique characteristics. Nevertheless, the interactions between plastic and microorganisms are still poorly known. Here, we present a review of current knowledge on plastic degradation and plastic-microorganism interactions in cold marine habitats. Moreover, we highlight the advantages of microorganisms isolated from this environment for eliminating plastic waste from ecosystems.

Hydrodeoxygenation of Oxygen-Containing Aromatic Plastic Wastes into Cycloalkanes and Aromatics.

Chemical recycling and upcycling offer promising approaches for the management of plastic wastes. Hydrodeoxygenation (HDO) is one of the appealing ways for conversion of oxygen-containing plastic wastes, including polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polyphenyl ether (PPO), and polyether ether ketone (PEEK), into cyclic alkanes and aromatics in high yields under mild reaction conditions. The challenge lies in achieving C-O activation while preserving C-C bonds. In this review, we highlight the recent advancements in catalytic strategies and catalysts for the conversion of these oxygen-containing plastic wastes into cycloalkanes and aromatics. The reaction systems, including multi-step routes, direct HDO and transfer HDO methods, are exemplified. The design and performance of HDO catalysts are systematically summarized and compared. We comprehensively discuss the functions of the catalysts' components, reaction pathway and mechanism to gain insights into the HDO process for efficient valorization of oxygen-containing plastic wastes. Finally, we provide perspectives for this field, with specific emphasis on the non-noble metal catalyst design, selectivity control, reaction network and mechanism studies, mixed plastic wastes management and product functionalization. We anticipate that this review will inspire innovations on the catalytic process development and rational catalyst design for the HDO of oxygen-containing aromatic plastics to establish a low-emission circular economy.

Novel polyurethane-degrading cutinase BaCut1 from Blastobotrys sp. G-9 with potential role in plastic bio-recycling.

Environmental pollution caused by plastic waste has become global problem that needs to be considered urgently. In the pursuit of a circular plastic economy, biodegradation provides an attractive strategy for managing plastic wastes, whereas effective plastic-degrading microbes and enzymes are required. In this study, we report that Blastobotrys sp. G-9 isolated from discarded plastic in landfills is capable of depolymerizing polyurethanes (PU) and poly (butylene adipate-co-terephthalate) (PBAT). Strain G-9 degrades up to 60% of PU foam after 21 days of incubation at 28 â„ƒ by breaking down carbonyl groups via secretory hydrolase as confirmed by structural characterization of plastics and degradation products identification. Within the supernatant of strain G-9, we identify a novel cutinase BaCut1, belonging to the esterase family, that can reproduce the same effect. BaCut1 demonstrates efficient degradation toward commercial polyester plastics PU foam (0.5 mg enzyme/25 mg plastic) and agricultural film PBAT (0.5 mg enzyme/10 mg plastic) with 50% and 18% weight loss at 37 â„ƒ for 48 h, respectively. BaCut1 hydrolyzes PU into adipic acid as a major end-product with 42.9% recovery via ester bond cleavage, and visible biodegradation is also identified from PBAT, which is a beneficial feature for future recycling economy. Molecular docking, along with products distribution, elucidates a special substrate-binding modes of BaCut1 with plastic substrate analogue. BaCut1-mediated polyester plastic degradation offers an alternative approach for managing PU plastic wastes through possible bio-recycling.

Management of ibuprofen in wastewater using electrospun nanofibers developed from PET and PS wastes.

Electrospinning is a promising technique for the beneficial use and recycling of plastic waste polymers using simple methodologies. In this study, plastic bottles and Styrofoam wastes have been used to develop polyethylene terephthalate (PET) and polystyrene (PS) nanofibers using electrospinning technique separately without any further purification. The effect of the concentration onto the nanofiber's morphology was studied. The fabricated nanofibers were characterized using Field Emission Scanning Electron Microscope (FE-SEM), Fourier Transformed Infrared Spectroscopy (ATR-FTIR), N2 adsorption/desorption analysis, and water contact angle (WCA). Furthermore, the prepared nanofibers were applied for the adsorption of ibuprofen (IBU) from wastewater. Some parameters that can influence the adsorption efficiency of nanofibers such as solution pH, wt.% of prepared nanofibers, drug initial concentration, and contact time were studied and optimized. The results show that the equilibrium adsorption capacity was achieved after only 10 min for 12 wt% PET nanofibers which is equivalent to 364.83 mg/g. For 12 wt% PS nanofibers, an equilibrium adsorption capacity of 328.42 mg/g was achieved in 30 min. The experimental data was fitted to five isotherm and four kinetics models to understand the complicated interaction between the nanofibers and the drug. Langmuir-Freundlich isotherm model showed the best fit for experimental data for both PET and PS nanofibers. The adsorption process was characterized by predominantly physical reaction rather than chemical adsorption for both materials. The reusability study revealed that the synthesized nanofibers maintain their ability to adsorb/desorb IBU for up to five cycles. The results obtained demonstrated that fabricated nanofibers from plastic wastes could perform promising adsorbents for the management of IBU in wastewater. However, further research is needed for the scaling-up the fabrication which is required for real-world applications.

Two-stage thermal pyrolysis of plastic solid waste: Set-up and operative conditions investigation for gaseous fuel production.

In response to the escalating global challenge of mounting plastic waste and the imperative to adopt more sustainable practices for resource utilization, our study focuses on the utilization of plastic solid waste (PSW) through a two-stage thermal pyrolysis process. This aims to demonstrate its potential as a high-performance alternative to existing two-stage catalytic pyrolysis methods. The experimentation involved processing real scrap PSW material in a lab-scale batch set-up, emphasizing optimizing residence time in the cracking reactor to maximize gas yield and its lower heating value (LHV). The study underscores the advantages of the employed two-stage thermal pyrolysis apparatus through a comparative analysis with established set-up dedicated to maximizing gas yield. Once the operative conditions were explored, resulting pyrolysis products underwent detailed characterization to assess their suitability as a sustainable fuel source. The study also presents a practical application of the produced gaseous fuel, envisioning its combustion in an internal combustion engine (ICE), known for its flexibility regarding fuel properties. This application is demonstrated through a simulation conducted in Unisim Design©. The successful processing of real PSW material in the two-stage lab-scale experimental set-up showcased optimal gas yield achievements (>65 % w/w) with an LHV (∼41 MJ/kg), comparable to that of natural gas. This emphasizes the potential of these sustainable alternatives to replace fossil fuels, especially in the context of ICE applications. The integration of the pyrolysis plant with an ICE demonstrated promising prospects for generating electricity in the transportation sector and facilitating thermal power for heat integration in pyrolysis reactors.

Plastic wastes-derived N-doped carbon nanotubes for efficient removal of sulfamethoxazole in high salinity wastewater via nonradical peroxymonosulfate activation.

Peroxymonosulfate (PMS) catalytic activation is effective to eliminate organic pollutants from water, thus the development of low-cost and efficient catalysts is significant in applications. The resource conversion of plastic wastes (PWs) into carbon nanotubes (CNTs) is a promising candidate for PMS-based advanced oxidation processes (AOPs), and also a sustainable strategy to realize plastic management and reutilization. Herein, cost-effective PWs-derived N-doped CNTs (N-pCNTs) were synthesized, which displayed efficient activity for PMS activation through an electron transfer pathway (ETP) for sulfamethoxazole (SMX) degradation in high salinity water. The pyrrolic N induced the positively charged surface of N-pCNTs, favoring the electrostatic adsorption of PMS and subsequent generation of active PMS* . A galvanic oxidation process was developed to prove the electron-shuttle dominated ETP for SMX oxidation. Combined with theoretical calculations, the efficiency of ETP was determined by the potential difference between HOMO of SMX and LUMO of N-pCNTs. Such oxidation produced low-toxicity intermediates and resulted in selective degradation of specific sulfonamide antibiotics. This work reveals the feasibility of low-cost N-pCNTs catalysts from PWs serving as an appealing candidate for PMS-AOPs in water remediation, providing a new solution to alleviate environmental issues caused by PWs and also advances the understanding of ETP during PMS activation.

Kinetic and Thermodynamic Analyses of Co-Pyrolysis of Nylon-Polyethylene Pouch Wastes.

In this study, thermogravimetric measurements of nylon-6/polyethylene double-layer pouch wastes were conducted in N2 under a constant heating-rate mode, and the multiple heating-rate results were analyzed in terms of degradation features and specific temperatures. Experimental results show that the waste pyrolysis involves one reaction stage, and all specific parameters appear to increase with the heating rate. Kinetic analysis of non-isothermal data was thoroughly performed using various isoconversional model-free methods for the calculations of the activation energy, resulting in 143~215 kJ/mol over the whole pyrolysis process. By means of the model-fitting method, the reaction mechanism model g(α) and pre-exponential factor lnk0 are concurrently determined with the aid of the linear compensation effect. With such methodology proposed, the Avrami-Erofeev kinetic model A3/2 of g(α) = [-ln(1 - α)]2/3 is found to be the most appropriate mechanism function for describing the pyrolysis of the nylon-6/polyethylene waste along with lnk0 of 23.14 to 34.26 min-1. With the Arrhenius parameters thus obtained, the predictions were made and performed very satisfactorily to correlate experimental results. Additionally, the service life and thermodynamic parameters over the entire pyrolysis process were also estimated.

Optimization of diesel engine performance and emission using waste plastic pyrolytic oil by ANN and its thermo-economic assessment.

The current study focuses on the engine performance and emission analysis of a 4-stroke compression ignition engine powered by waste plastic oil (WPO) obtained by the catalytic pyrolysis of medical plastic wastes. This is followed by their optimization study and economic analysis. This study demonstrates the use of artificial neural networks (ANN) to forecast a multi-component fuel mixture, which is novel and reduces the amount of experimental effort required to determine the engine output characteristics. The engine tests were conducted using WPO blended diesel at various proportions (10%, 20%, 30% by volume) to acquire the required data for training the ANN model, which enables better prediction for the engine performance by making use of the standard back-propagation algorithm. Considering supervised data obtained from repeated engine tests, an artificial intelligence-based model of ANN was designed to select different parameters of performance and emission as output layers; at the same time, engine loading and different blending ratios of the test fuels were taken as the input layers. The ANN model was built up making use of 80% of testing outcomes for training. The ANN model forecasted engine performance and exhaust emission with regression coefficients (R) at 0.989-0.998 intervals and a mean relative error from 0.002 to 0.348%. Such results illustrated the effectiveness of the ANN model for estimating emissions and the performance of diesel engines. Moreover, the economic viability of the use of 20WPO as an alternative to diesel was justified by thermo-economic analysis.

Dechlorination of waste polyvinyl chloride (PVC) through non-thermal plasma.

Dechlorination is essential for the chemical recycling of waste polyvinyl chloride (PVC) plastics. This study investigated the use of non-thermal plasma (NTP) for chlorine removal, with a focus on the effects of treatment time and discharge power on dechlorination efficiency. The results showed that longer treatment times and higher discharge powers led to better dechlorination performance. The maximum efficiency (98.25%) and HCl recovery yield (55.72%) were achieved at 180 W power after 40 min of treatment where 96.44% of Cl existed in the form of HCl gas, 1.44% in the liquid product, and 2.12% in the solid residue product. NTP at a discharge power of 150 W showed better dechlorination performance compared to traditional thermal pyrolysis treatment in temperatures ranging from 200 to 400 °C. The activation energy analysis of the chlorine removal showed that compared to pyrolysis-based dechlorination (137.09 kJ/mol), NTP-based dechlorination (23.62 kJ/mol) was more easily achievable. This work presents a practical method for the dechlorination of waste PVC plastic using a novel technology without requiring additional thermal and pressure input.

Laccase driven biocatalytic oxidation to reduce polymeric surface hydrophobicity: An effective pre-treatment strategy to enhance biofilm mediated degradation of polyethylene and polycarbonate plastics.

Plastic pollution is a major global environmental issue due to its structural complexity and poor biodegradability. Biological approaches are appropriate due to cost effectiveness and environmental friendliness, however effective polymer degradation is still in its infancy. As biological treatments are slower than physical and chemical approaches, they could be applied in conjunction with pre-treatment techniques such as photo-oxidation, heat treatment, and chemical treatments. But these processes lead to high energy consumption and hazardous secondary pollution. To address these concerns, an enzymatic pre-treatment strategy has been proposed in this study, with an aim of promoting surface oxidation on the plastics leading to improved hydrophilicity. This in turn, facilitates the surface attachment of microbes, ultimately, accelerating biodegradation. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FT-IR) spectroscopy analyses confirmed the surface oxidation of the polyethylene (PE) and polycarbonate (PC) plastics mediated by the action of laccase enzyme. Contact angle measurement witnessed the increased hydrophilicity of the treated plastics. Following, a potential biofilm forming microbial consortium has been employed for the biodegradation of enzyme treated plastics. SEM analysis indicated the increased formation of corrosive pits and surface aberrations on the enzymatically pre-treated plastics and Confocal Laser Scanning microscopy (CLSM) analysis exhibited the enhanced biofilm formation and exopolysaccharide deposition on the pre-treated PE and PC. In addition, X-ray photoelectron spectroscopy (XPS) revealed the reduction in the elemental composition of carbon with an increment in the oxygen composition of plastics. Gel permeation chromatography (GPC) further confirmed the greater reduction in the molecular weights of the plastics subjected to integrated enzymatic and biofilm treatment than only biofilm treated plastics. This is the first report on the integration of enzymatic pre-treatment with the biofilm mediated microbial degradation to achieve enhanced treatment of plastics which demonstrated to be a promising technology for the effective mitigation of plastic pollution.

The interactions between mixed waste from discarded surgical masks and face shields during the degradation in supercritical water.

The widespread use of surgical masks made of polyolefin and face shields made of polyester during pandemics contributes significantly to plastic pollution. An eco-friendly approach to process plastic waste is using supercritical water, but the reaction of mixed polyolefin and polyester in this solvent is not well understood, which hinders practical applications. This study aimed to investigate the reaction of waste surgical masks (SM) and face shields (FS) mixed in supercritical water. Results showed that the optimal treatment conditions were 400 °C and 60 min, achieving a liquid oil yield of 823.03 mg·g-1 with 25 wt% FS. The interaction between polypropylene (PP), polyethylene terephthalate (PET), and iron (Fe) in SM and FS mainly determined the production of liquid oil products such as olefins and benzoic acid. The methyl-branched structure of PP enhanced PET hydrolysis, resulting in higher production of terephthalic acid (TPA). The degradation of PP was facilitated by the acidic environment created by TPA and benzoic acid in the reaction. Moreover, the hydrolysis of PET produced carboxylic acid, which coordinated with Fe3+ to form Fe-H that catalyzed the polymerization of small olefins, contributing to higher selectivity for C9 olefins. Therefore, this study provides valuable insights into the degradation mechanism of mixed PPE waste in supercritical water and guidance for industrial treatment.

Non-Wettable Microporous Sheets Using Mixed Polyolefin Waste for Oil-Water Separation.

Mixed polyolefin-based waste needs urgent attention to mitigate its negative impact on the environment. The separation of these plastics requires energy-intensive processes due to their similar densities. Additionally, these materials cannot be blended without compatibilizers, as they are inherently incompatible and immiscible. Herein, non-wettable microporous sheets from recycled polyethylene (PE) and polypropylene (PP) are presented. The methodology involves the application of phase separation and spin-casting techniques to obtain a bimodal porous structure, facilitating efficient oil-water separation. The resulting sheets have an immediate and equilibrium sorption uptake of 100 and 55 g/g, respectively, due to the presence of micro- and macro-pores, as revealed by SEM. Moreover, sheets possess enhanced crystallinity, as evidenced by XRD; hence, they retain their structure during sorption and desorption and are reusable with 98% efficiency. The anti-wetting properties of the sheets are enhanced by applying a silane coating, ensuring waterless sorption and a contact angle of 140°. These results highlight the importance of implementing sustainable solutions to recycle plastics and mitigate the oil spill problem.