Oil sorbents from plastic wastes and polymers: A review

Environmental and economic assessment of mixed plastic waste pelletization in the Gulf Cooperation Council region

Pelletizing mixed plastic wastes (MPW) has gained interest as an upcycling technology and an alternative to conventional recycling. To investigate its potential, we conducted a cost analysis and life-cycle assessment (LCA) for a conceptual pelletization facility designed to produce 1 kg of pellets per batch of MPW (comprising polyethylene-PE and polypropylene-PP). This work has the following merits: (i) evaluating environmental impact (EI), cost analysis, and mechanical strength based on actual experimental data and its comparison with local and international manufacturers; (ii) enabling the evaluation of LCA impacts of MPW pellets; and (iii) emphasizing the significance of waste management in reducing EIs. The following ten EIs were assessed: climate change (CC), net energy, particulate matter formation, natural land transformation, metal depletion, marine ecotoxicity, ionising radiation, freshwater ecotoxicity, freshwater eutrophication, and terrestrial ecotoxicity. The CC of the as-synthesized pellets is 1.26 kg CO2 eq., significantly lower than the data obtained from the Gulf Petrochemicals and Chemicals Association (GPCA) and an actual plant in Gulf Cooperation Council (GCC) countries. Additionally, the net energy required for the production of 1 kg of pellets is 54.1 MJ, while the cost is around 0.55 USD. The tensile strength of MPW pellets (24.63 MPa) falls between that of PE virgin pellets (21.12 MPa) and PP virgin pellets (28.12 MPa). This suggests that the MPW pellets exhibit competitive strength characteristics, warranting its consideration for applications where moderate strength is required. Overall, the competitive cost, coupled with the reduced EIs, demonstrates the potential of pelletization as a sustainable and economically viable waste management solution.

Anthropogenic stressors and the marine environment: From sources and impacts to solutions and mitigation

Human-released contaminants are often poorly understood wholistically in marine ecosystems. This review examines the sources, pathways, impacts on marine animals, and mitigation strategies of five pollutants (plastics, per- and polyfluoroalkyl substances, bisphenol compounds, ethynylestradiol, and petroleum hydrocarbons). Both abiotic and biotic mechanisms contribute to all five contaminants' movement. These pollutants cause short- and long-term effects on many biological processes genetically, molecularly, neurologically, physiologically, reproductively, and developmentally. We explore the extension of adverse outcome pathways to ecosystem effects by considering known inter-generational and trophic relations resulting in large-scale direct and indirect impacts. In doing so, we develop an understanding of their roles as environmental stressors in marine environments for targeted mitigation and future work. Ecosystems are interconnected and so international collaboration, standards, measures preceding mass production, and citizen involvement are required to protect and conserve marine life.

Recycling and high-value utilization of polyethylene terephthalate wastes: A review

Polyethelene terephthalate (PET) is a well-known thermoplastic, and recycling PET waste is important for the natural environment and human health. This study provides a comprehensive overview of the recycling and reuse of PET waste through energy recovery and physical, chemical, and biological recycling. This article summarizes the recycling methods and the high-value products derived from PET waste, specifically detailing the research progress on regenerated PET prepared by the mechanical recycling of fiber/yarn, fabric, and composite materials, and introduces the application of PET nanofibers recycled by physical dissolution and electrospinning in fields such as filtration, adsorption, electronics, and antibacterial materials. This article explains the energy recovery of PET through thermal decomposition and comprehensively discusses various chemical recycling methods, including the reaction mechanisms, catalysts, conversion efficiencies, and reaction products, with a brief introduction to PET biodegradation using hydrolytic enzymes provided. The analysis and comparison of various recycling methods indicated that the mechanical recycling method yielded PET products with a wide range of applications in composite materials. Electrospinning is a highly promising recycling strategy for fabricating recycled PET nanofibers. Compared to other methods, physical recycling has advantages such as low cost, low energy consumption, high value, simple processing, and environmental friendliness, making it the preferred choice for the recycling and high-value utilization of waste PET.

Production of Highly Efficient Activated Carbons for Wastewater Treatment from Post-Consumer PET Plastic Bottle Waste

Chemical activated carbons (PET-H2SO4 and PET-KOH) were prepared from post-consumer polyethylene terephthalate (PET) wastes using pyrolysis under moderate reaction temperatures by changing pyrolysis time and chemical activating agents. The produced carbons were characterized and tested in adsorption reactions of manganese, chromium, and cobalt ions in aqueous solutions. Results showed a high percentage removal of these inorganic ions from water: 98 % for Mn2+, 87 % for Cr3+, and 88 % for Co2+. Freundlich isotherms gave a better fit to the experimental data obtained with good correlation coefficient values in the range of 0.99-1 compared to other isotherms. The pseudo-second order kinetic model best described the chemical adsorption process as an exchange of electrons between the carbon and inorganic ions in solutions. The diffusion models showed that the process is controlled by a multi-kinetic stage adsorption process. In summary, this work demonstrates that the production of activated carbon from PET waste bottles is a potential alternative to commercial activated carbon and can be considered a sustainable waste management technology for removing these non-biodegradable plastic wastes from the environment.

Transforming polypropylene waste into transparent anti-corrosion weather-resistant and anti-bacterial superhydrophobic films

The global pollution crisis arising from the accumulation of plastic in landfills and the environment necessitates addressing plastic waste issues. Notably, polypropylene (PP) waste accounts for 20% of total plastic waste and holds promise for hydrophobic applications in the realm of recycling. Herein, the transparent and non-transparent superhydrophobic films made from waste PP are reported. A hierarchical structure with protrusions is induced through spin-casting and thermally induced phase separation. The films had a water contact angle of 159° and could vary in thickness, strength, roughness, and hydrophobicity depending on end-user requirements. The Bode plot indicated enhanced corrosion resistance in the superhydrophobic films. Antibacterial trials with Escherichia coli and Staphylococcus aureus microbial solutions showed that the superhydrophobic film had a significantly lower rate of colony-forming units compared to both the transparent surface and the control blank sample. Moreover, a life cycle assessment revealed that the film production resulted in a 62% lower embodied energy and 34% lower carbon footprint compared to virgin PP pellets sourced from petroleum. These films exhibit distinctiveness with their dual functionality as coatings and freestanding films. Unlike conventional coatings that require chemical application onto the substrate, these films can be mechanically applied using adhesive tapes on a variety of surfaces. Overall, the effective recycling of waste PP into versatile superhydrophobic films not only reduces environmental impact but also paves the way for a more sustainable and eco-friendly future.

3D Oleophilic Sorbent Films Based on Recycled Low-Density Polyethylene

Recycling low-end, one-time-use plastics-such as low-density polyethylene (LDPE)-is of paramount importance to combat plastic pollution and promote sustainability in the modern green economy. This study valorizes LDPE waste by transforming it into 3D oleophilic swellable thin films through a process involving dissolution, phase separation, and extraction. These films are subsequently layered using a customized polypropylene (PP) based nonwoven fabric separator and securely sealed in a zigzag pattern. The zigzag-shaped seal enhances the adhesion of pollutants to the sorbent by providing wire curvatures that increase retention time and uptake capacity. As a result, the sorbent exhibits impressive oil uptake capacities, with immediate and equilibrium values of 120 g/g and 85 g/g, respectively. Notably, the as-prepared sorbent demonstrates low water retention and high selectivity for oil, outperforming commercially available oil sorbents. The unique design involving a 3D-film structure, superposed films, and a zigzag-shaped seal offers a sustainable and value-added solution to the issues of LDPE waste and oil spills on water surfaces.

Repurposing the single-used-plastic for development of hydrophobic aerogels for remediation of oil spill and organic solvents

Currently, around 400 million tonnes of synthetic polymers are being dumped as waste annually and by this rate by 2050 the ocean would contain more such waste compared to the total weight of fish. As recycling could solve part of this problem, recently such waste is being reused for various purposes like composite preparation, oil production and various other use such as production of foams, sponges, and aerogels. However, there is a relatively limited literature available on the utilization of polyethylene polymer (like LDPE). The study presented in this article indicated that LDPE-based polymers could be reused (after modification) for preparation of hydrophobic, lightweight, and porous aerogels that have oil-spills and organic solvent adsorption capacity. The aerogels showed contact angle of 121.9o, bulk density below 0.25 g/cm3, and were found to be semi-crystalline. The aerogels showed oil and solvent adsorption more than that for their untreated counterparts. Also, the aerogels were found to be recycled for more than five cycles with very minimum loss of efficacy. This area of producing oil sorbents from single used plastic wastes is still very open for further research and seems to be a promising route for both waste reduction, and the synthesis of value-added products. This could be one of the most sustainable approaches for efficient single-used plastic wase management and environment clean-up.

Environmentally benign, bright luminescent carbon dots from IV bag waste and chitosan for antimicrobial and bioimaging applications

Luminescent carbon dots have gained significant attention in various fields due to their unique optical properties and potential applications. Here, the study was aimed to propose a novel and sustainable approach for the synthesis of luminescent carbon dots (ICDs) using IV (Intravenous) medical bag waste. The ICDs were synthesized through a facile and cost-effective method that involved the carbonization of IV bag waste followed by surface functionalization with chitosan. The synthesized ICDs were characterized using UV-Visible spectrum (UV-Vis), Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction analysis (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The size of the ICDs is between 2 and 8 nm. The ICDs effectively inhibited the growth of both gram positive and gram negative bacterial strains with the inhibitory activity in the range of 11-14 mm and 12-18 mm, respectively. Results of antibiofilm activity of ICDs varying concentrations (50 and 100 μg/ml) showed that it effectively distorted the biofilm architecture and thereby validated its promising potentials. In vitro antioxidant activity showed remarkable DPPH radical scavenging potentials of ICDs (33.4%-70.1%). Results of MTT assay revealted that ICDs showed potent cytotoxic effect on HeLa cells in a dose dependant matter (25-400 μg/ml). Furthermore, when HeLa cells were excited at wavelengths of 380 nm, 440 nm and 540 nm, cell-imaging experiments using ICDs revealed the presence of blue, green, and red fluorescence. This innovative method not only addresses the issue of IV bag waste in a sustainable manner but also opens up exciting possibilities for the advancement of versatile carbon-based materials in the field of biomedicine.

Designing super-fast trimodal sponges using recycled polypropylene for organics cleanup

Sorbent pads and films have been commonly used for environmental remediation purposes, but designing their internal structure to optimize access to the entire volume while ensuring cost-effectiveness, ease of fabrication, sufficient strength, and reusability remains challenging. Herein, we report a trimodal sorbent film from recycled polypropylene (PP) with micropores, macro-voids, and sponge-like 3D cavities, developed through selective dissolution, thermally induced phase separation, and annealing. The sorbent has hundreds of cavities per cm2 that are capable of swelling up to twenty-five times its thickness, allowing for super-fast saturation kinetics (within 30 s) and maximum oil sorption (97 g/g). The sorption mechanism follows a pseudo-second-order kinetic model. Moreover, the sorbent is easily compressible, and its structure is retained during oil sorption, desorption, and resorption, resulting in 96.5% reuse efficiency. The oil recovery process involves manually squeezing the film, making the cleanup process efficient with no chemical treatment required. The sorbent film possesses high porosity for effective sorption with sufficient tensile strength for practical applications. Our integrated technique results in a strengthened porous polymeric structure that can be tailored according to end-use applications. This study provides a sustainable solution for waste management that offers versatility in its functionality.

Sustainable Solution for Plastic Pollution: Upcycling Waste Polypropylene Masks for Effective Oil-Spill Management

The use of Polypropylene PP in disposable items such as face masks, gloves, and personal protective equipment has increased exponentially during and after the COVID-19 pandemic, contributing significantly to microplastics and nanoplastics in the environment. Upcycling of waste PP provides a useful alternative to traditional thermal and mechanical recycling techniques. It transforms waste PP into useful products, minimizing its impact on the environment. Herein, we synthesized an oil-sorbent pouch using waste PP, which comprises superposed microporous and fibrous thin films of PP using spin coating. The pouch exhibited super-fast uptake kinetics and reached its saturation in fewer than five minutes with a high oil uptake value of 85 g/g. Moreover, it displayed high reusability and was found to be effective in absorbing oil up to seven times when mechanically squeezed between each cycle, demonstrating robust oil-sorption capabilities. This approach offers a potential solution for managing plastic waste while promoting a circular economy.

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.

Up-cycling plastic waste into swellable super-sorbents

Environmental pollution caused by plastic waste and oil spills has emerged as a major concern in recent years. Consequently, there has been a growing interest in exploring innovative solutions to address these challenges. Herein, we report a method to upcycle polyolefins-based plastic waste by converting it into a bimodal super-oleophilic sorbent using dissolution, spin-coating, and annealing techniques. The resulting sorbent possesses an extensive network of pores and cavities with a size range from 0.5 to 5 µm and 150-200 µm, respectively, with an average of 600 cavities per cm². Each cavity can swell up to twenty times the thickness of the sorbent, exhibiting sponge-like behavior. The sorbent had an oil uptake capacity of 70-140 g/g, depending on the type of sorbate and dripping time. Moreover, the sorbent can be mechanically or manually squeezed to recover the sorbed oil. Our integrated methodology provides a promising approach to upcycling plastic waste as an abundant source of value-added materials.

Adsorbents obtained from recycled polymeric materials for retention of different pollutants: A review

Polymeric waste is an environmental problem, with an annual world production of approximately 368 million metric tons, and increasing every year. Therefore, different strategies for polymer waste treatment have been developed, and the most common are (1) redesign, (2) reusing and (3) recycling. The latter strategy represents a useful option to generate new materials. This work reviews the emerging trends in the development of adsorbent materials obtained from polymer wastes. Adsorbents are used in filtration systems or in extraction techniques for the removal of contaminants such as heavy metals, dyes, polycyclic aromatic hydrocarbons and other organic compounds from air, biological and water samples. The methods used to obtain different adsorbents are detailed, as well as the interaction mechanisms with the compounds of interest (contaminants). The adsorbents obtained are an alternative to recycle polymeric and they are competitive with other materials applied in the removal and extraction of contaminants.

Corn stalk pith-based hydrophobic aerogel for efficient oil sorption

Bio-based aerogel has become an attractive sorbent for spilled oil and organic pollutants because of its light weight, high porosity and strong sorption capacity. However, the current fabrication process is mainly "bottom-up" technology, which is cost-expensive, time-consuming, and energy-intensive. Herein, we report a top-down, green, efficient and selective sorbent prepared from corn stalk pith (CSP) using the deep eutectic solvent (DES) treatment, followed by TEMPO/NaClO/NaClO₂ oxidization and microfibrillation, and then hexamethyldisilazane coating. Such chemical treatments selectively removed lignin and hemicellulose, broke the thin cell walls of natural CSP, forming an aligned porous structure with capillary channels. The resultant aerogels had a density of 29.3 mg/g, a porosity of 98.13%, and a water contact angle of 130.5^◦, exhibiting excellent oil/organic solvents sorption performance, with a high sorption capacity in the range of 25.4-36.5 g/g, approximately 5-16-fold higher than CSP, and with fast absorption speed and good reusability.

Review of polymer technologies for improving the recycling and upcycling efficiency of plastic waste

Human society has become increasingly reliant on plastic because it allows for convenient and sanitary living. However, recycling rates are currently low, which means that the majority of plastic waste ends up in landfills or the ocean. Increasing recycling and upcycling rates is a critical strategy for addressing the issues caused by plastic pollution, but there are several technical limitations to overcome. This article reviews advancements in polymer technology that aim to improve the efficiency of recycling and upcycling plastic waste. In food packaging, natural polymers with excellent gas barrier properties and self-cleaning abilities have been introduced as environmentally friendly alternatives to existing materials and to reduce food-derived contamination. Upcycling and valorization approaches have emerged to transform plastic waste into high-value-added products. Recent advancements in the development of recyclable high-performance plastics include the design of super engineering thermoplastics and engineering chemical bonds of thermosets to make them recyclable and biodegradable. Further research is needed to develop more cost-effective and scalable technologies to address the plastic pollution problem through sustainable recycling and upcycling.

Preparation of superhydrophobic, green, and eco-friendly modified polylactic acid foams for separation oil from water

Developing a facile and green strategy to fabricate polymer foams with super hydrophobicity and eco-friendliness for large-scale oil-water separation remains a challenge. In this study, biocompatible polylactic acid polymer foam modified by nanochitosan and stearic acid was used to remove petroleum and organic contaminants in water. All three materials used to prepare and modify this foam are green and inexpensive. F₄d foam (prepared by solvent displacement method) and F₈d foam (prepared by freeze dryer) can selectively remove oil pollutants in water with a contact angle of 164.01° and 168.51°, respectively. The maximum absorption capacity of oil pollutants by F₄d and F₈d are related to chloroform with values of 32.7 g/g and 48.51 g/g, respectively. Also, the minimum absorption capacity is related to n-hexane with values of 24.83 g/g and 32.06 g/g. The absorption percentage range of F₄d and F₈d foams after 15 cycles of absorption-desorption for chloroform is 82.56 % and 87.81 %, respectively, and for n-hexane, is 77.28 % and 85.99 %, respectively. During the continuous water-oil pumping test, the efficiency of foam can be maintained for >15 h, which shows promising hope for large-scale oil pollution cleaning.

Photothermal and Concus Finn capillary assisted superhydrophobic fibrous network enabling instant viscous oil transport for crude oil cleanup

Rapid and effective removal of highly viscous oil spills from the sea remains a great challenge globally. Superhydrophobic materials are attractive candidates for handling oil spills, but they are restrained to recover oils with low viscosity exclusively. Herein, we report a novel polypyrrole wrapped superhydrophobic fibrous network using cross-shaped polyester fibers as starting blocks. The polypyrrole coating enables the absorbent to convert light to heat, ensuring that the viscosity of heavy oils in the proximity can be easily controlled. In the meanwhile, the special structure of the starting fibers initiates Concus Finn (CFin) capillary allowing instant oil transport in the network. When the absorbent is exposed to light oils (0-500 mPa.s), the oils can be transported instantly via CFin capillary. Interestingly, under synergistic effect of light-to-heat conversion and CFin capillary, a drawing-sticking crude oil strip (10⁵ mPa.s) is sucked instantly against gravity by the absorbent. The absorbent is successfully applied to efficiently separate both oil/water mixtures and oil/water emulsions (efficiency > 99%). Such absorbent can absorb 62.99-74.23 g/g light oils on average and up to 123.3 g/g crude oil under 0-2 sun illumination, holding a huge potential in managing oil spills.

Smoke filtration performances of membranes produced from commercial PVA and recycled PET by electrospinning method and ANN modeling

Plastic waste and air pollution are becoming a great concern due to their adverse effect on human health and the environment. There is increasing number of evidence showing that recycling plastic and filtering harmful air pollutants are one of the most effective and promising way to eliminate their hazard on the environment. In this purpose, we developed eco-friendly filtration materials from recycled PET by electrospinning method to be used in air filtration and compared them with conventional PVA membranes. Filtration efficiency of prepared membranes were tested homemade membrane system using cigarette smoke source. Characterization results and smoke filtration performance of recycled PET and PVA membranes before and after smoke filtration were examined. The results demonstrated that the removal efficiencies of PVA-5 wt.%, PVA-10 wt.%, and PVA-15 wt.% were 4.11%, 11.32%, and 12.14%, respectively. A similar trend was also observed in recycled PET-5 wt.%, PET-10 wt.%, and PET-15 wt.% membranes with 4.32%, 10.79%, and 11.68% of filtration efficiency, respectively. Based on this result, using recycled PET can be an alternative way to produce a higher value product compared to traditional polymer membranes used commercially. This result is also supported by the neural network model of this study.

Reusable Macroporous Oil Sorbent Films from Plastic Wastes

Plastic waste comprises 15% of the total municipal solid waste and can be a rich source for producing value-added materials. Among them, polyethylene (PE) and polypropylene (PP) account for 60% of the total plastic waste, mainly due to their low-end and one-time-use applications. Herein, we report reusable oil sorbent films made by upcycling waste PE and PP. The as-prepared oil sorbent had an uptake capacity of 55 g/g. SEM analysis revealed a macroporous structure with a pore size range of 1-10 µm, which facilitates oil sorption. Similarly, the contact angle values reflected the oleophilic nature of the sorbent. Moreover, thermal properties and crystallinity were examined using DSC, while mechanical properties were calculated using tensile testing. Lastly, 95% of the sorbed oil could be easily recovered by squeezing mechanically or manually.

An Overview into Polyethylene Terephthalate (PET) Hydrolases and Efforts in Tailoring Enzymes for Improved Plastic Degradation

Plastic or microplastic pollution is a global threat affecting ecosystems, with the current generation reaching as much as 400 metric tons per/year. Soil ecosystems comprising agricultural lands act as microplastics sinks, though the impact could be unexpectedly more far-reaching. This is troubling as most plastic forms, such as polyethylene terephthalate (PET), formed from polymerized terephthalic acid (TPA) and ethylene glycol (EG) monomers, are non-biodegradable environmental pollutants. The current approach to use mechanical, thermal, and chemical-based treatments to reduce PET waste remains cost-prohibitive and could potentially produce toxic secondary pollutants. Thus, better remediation methods must be developed to deal with plastic pollutants in marine and terrestrial environments. Enzymatic treatments could be a plausible avenue to overcome plastic pollutants, given the near-ambient conditions under which enzymes function without the need for chemicals. The discovery of several PET hydrolases, along with further modification of the enzymes, has considerably aided efforts to improve their ability to degrade the ester bond of PET. Hence, this review emphasizes PET-degrading microbial hydrolases and their contribution to alleviating environmental microplastics. Information on the molecular and degradation mechanisms of PET is also highlighted in this review, which might be useful in the future rational engineering of PET-hydrolyzing enzymes.

High Quality and Maximizing the Production of CNTs from the Pyrolysis of Waste Polypropylene

Thermal decomposition of plastics by pyrolysis into oil is a successful way of treating wastes. Nevertheless, the production of carbon nanotubes (CNTs) from wastes improves the feasibility of the waste management process. An experimental setup was developed to study the influence of different heating rates on the produced oil by pyrolysis of waste polypropylene (WPP), and the influence of using foamed nickel on the produced CNTs as a function of operating temperature and heating rate. Different heating rates of 5, 10, and 20 °C/min were examined, as well as the different carbon vapor deposition (CVD) temperatures of 600, 700, and 800 °C were studied. It has been found that increasing the heating rate from 5 to 20 °C/min increases the oil yield from 59.3 to 71%, but on the other hand it decreases the quality of the oil. It has been also found that increasing the heating rate decreases the quality of CNTs, i.e., uniform CNTs with small diameter and small wall thickness, and as well as the quantity. The physical properties of the produced CNTs have been improved by increasing the CVD temperature; however, the quantity of CNTs decreased. The highest yield of CNTs produced was 43.12% at the lowest CVD temperature and heating rate examined, i.e., 600 and 5 °C/min, respectively. The optimum heating rate and CVD temperature for the pyrolysis of waste polypropylene to achieve the highest quality of CNTs with moderate production of 39.34%, is the lowest heating rate examined, i.e., 5 °C/min, with a moderate CVD temperature of 700 °C.

Understanding of synergy in non-isothermal microwave-assisted in-situ catalytic co-pyrolysis of rice husk and polystyrene waste mixtures

Rice husk (RH) and polystyrene (PS) wastes were converted into value-added products using microwave-assisted catalytic co-pyrolysis. The graphite susceptor (10 g) along with KOH catalyst (5 g) was mixed with the feedstock to understand the products and energy consumption. RH promoted the char yield (20-34 wt%) and gaseous yields (16-25 wt%) whereas PS enhanced the oil yield (23-70 wt%). Co-pyrolysis synergy induced an increase in gaseous yields (14-53 wt%) due to excessive cracking. The specific microwave energy consumption dramatically decreased in co-pyrolysis (5-22 kJ/g) compared to pyrolysis (56-102 kJ/g). The pyrolysis index increased (17-445) with the increase in feedstock quantity (5-50 g). The obtained oil was composed of monoaromatics (74%) and polyaromatics (18%). The char was rich in carbon content (79.5 wt%) and the gases were composed of CO (24%), H₂ (12%), and CH₄ (22%).

Temperature effects on ageing properties and diffusivity of a HDPE GM in landfill

High-density polyethylene (HDPE) geomembranes (GMs) play a crucial role in preventing the leakage and migration of pollutants. GM service life and ageing properties are the main concerns for the choice of materials. However, it is not clear how the mechanical properties and anti-fouling performance of geomembranes change with ageing time. To solve this problem, a HDPE GM was selected for testing under exposed air condition. The tests included oxidation induction time (OIT), melt flow index (MFI), tensile properties and diffusivity under four temperature conditions for 1½ years. The test results showed that the GM has higher OIT degradation rates. Stage I - depletion of antioxidants occurred at only 10 years for the GM, which was approximately 1/4 that of the GM-GSE. The GM engineering properties index showed the same changes as those of the GM-GSE. However, MI rapidly decreased with the incubation time. The molecular weight degradation of the GM was approximately 57% and far greater than that of GM-GSE after 15 months, but the tensile properties of the two GMs showed little change. The diffusion coefficient D_i of GM increases gradually with the increase of temperature in methane and trichloromethane. Under the same conditions, the diffusion coefficient D_i of the GM in methane is significantly higher than that in trichloromethane, indicating that the GM has better barrier to trichloromethane.

Mussel-Inspired Durable TiO2/PDA-Based Superhydrophobic Paper with Excellent Self-Cleaning, High Chemical Stability, and Efficient Oil/Water Separation Properties

Oceanic oil spill and the discharge of industrial oily wastewaters can cause significant threats to the ecological environment and human health. Herein, we design a durable TiO₂/PDA-based superhydrophobic paper for efficient oil/water separation. Bioinspired from mussel adhesive proteins, the mechanical durability of the as-prepared superhydrophobic paper is enhanced by the deposition of polydopamine (PDA) onto cellulosic fibers via self-polymerization of dopamine. The TiO₂/PDA-based superhydrophobic paper shows a high water contact angle of 168.2° and an oil contact angle of ∼0°, exhibiting excellent superhydrophobicity and superoleophilicity. Furthermore, the as-prepared superhydrophobic paper possesses excellent chemical stability, thermal stability, and mechanical durability in terms of being immersed in corrosive solutions and solvents and boiling water and being subjected to the sandpaper abrasion test, respectively. More importantly, the separation efficiency of the TiO₂/PDA-based superhydrophobic paper for an oil/water mixture is 97.2%, and it maintains a separation efficiency above 94.3% even after 15 cyclic separation processes. Furthermore, the separation efficiency for water-in-oil emulsions is higher than 93.7% after 15 cyclic separation tests, showing its excellent recyclable stability for water-in-oil emulsions. Therefore, the rationally designed TiO₂/PDA-based superhydrophobic paper shows great potential in the practical applications of self-cleaning, antifouling, and oil/water separation.

Advancements in Bioelectricity Generation Through Nanomaterial-Modified Anode Electrodes in Microbial Fuel Cells

The use of nanotechnology in bioelectrochemical systems to recover bioelectricity and metals from waste appears to be a potentially appealing alternative to existing established procedures. This trend exactly characterizes the current renewable energy production technology. Hence, this review focuses on the improvement of the anode electrode by using different functional metal oxide-conducting polymer nanocomposites to enhance microbial fuel cell (MFC) performance. Enhancement of interfacial bioelectrocatalysis between electroactive microorganisms and hierarchical porous nanocomposite materials could enhance cost-effective bioanode materials with superior bioelectrocatalytic activity for MFCs. In this review, improvement in efficiency of MFCs by using iron oxide- and manganese oxide-based polypyrrole hybrid composites as model anode modifiers was discussed. The review also extended to discussing and covering the principles, components, power density, current density, and removal efficiencies of biofuel cell systems. In addition, this research review demonstrates the application of MFCs for renewable energy generation, wastewater treatment, and metal recovery. This is due to having their own unique working principle under mild conditions and using renewable biodegradable organic matter as a direct fuel source.

Recycling and Reutilizing Polymer Waste via Electrospun Micro/Nanofibers: A Review

The accumulation of plastic waste resulting from the increasing demand for non-degradable plastics has led to a global environmental crisis. The severe environmental and economic drawbacks of inefficient, expensive, and impractical traditional waste disposal methods, such as landfills, incineration, plastic recycling, and energy production, limit the expansion of their applications to solving the plastic waste problem. Finding novel ways to manage the large amount of disposed plastic waste is urgent. Until now, one of the most valuable strategies for the handling of plastic waste has been to reutilize the waste as raw material for the preparation of functional and high-value products. Electrospun micro/nanofibers have drawn much attention in recent years due to their advantages of small diameter, large specific area, and excellent physicochemical features. Thus, electrospinning recycled plastic waste into micro/nanofibers creates diverse opportunities to deal with the environmental issue caused by the growing accumulation of plastic waste. This paper presents a review of recycling and reutilizing polymer waste via electrospinning. Firstly, the advantages of the electrospinning approach to recycling plastic waste are summarized. Then, the studies of electrospun recycled plastic waste are concluded. Finally, the challenges and future perspectives of electrospun recycled plastic waste are provided. In conclusion, this paper aims to provide a comprehensive overview of electrospun recycled plastic waste for researchers to develop further studies.

Multifunctional Carbon Fibers from Chemical Upcycling of Mask Waste

Over the past years, disposable masks have been produced in unprecedented amounts due to the COVID-19 pandemic. Their increased use imposes significant strain on current waste management practices including landfilling and incineration. This results in large volumes of discarded masks entering the environment as pollutants, and alternative methods of waste management are required to mitigate the negative effects of mask pollution. While current recycling methods can supplement conventional waste management, the necessary processes result in a product with downgraded material properties and a loss of value. This work introduces a simple method to upcycle mask waste into multifunctional carbon fibers through simple steps of thermal stabilization and pyrolysis. The pre-existed fibrous structure of polypropylene masks can be directly converted into carbonaceous structures with high degrees of carbon yield, that are inherently sulfur-doped, and porous in nature. The mask-derived carbon product demonstrates potential use in multiple applications such as for Joule heating, oil adsorption, and the removal of organic pollutants from aqueous environments. We believe that this process can provide a useful alternative to conventional waste management by converting mask waste generated during the COVID-19 pandemic into a product with enhanced value.

Facile Preparation of Robust Superhydrophobic/Superoleophilic TiO2-Decorated Polyvinyl Alcohol Sponge for Efficient Oil/Water Separation

Oily wastewater and oil spills pose a threat to the environment and human health, and porous sponge materials are highly desired for oil/water separation. Herein, we design a new superhydrophobic/superoleophilic TiO₂-decorated polyvinyl alcohol (PVA) sponge material for efficient oil/water separation. The TiO₂-PVA sponge is obtained by firmly anchoring TiO₂ nanoparticles onto the skeleton surface of pristine PVA sponge via the cross-linking reactions between TiO₂ nanoparticles and H₃BO₃ and KH550, followed by the chemical modification of 1H,1H,2H,2H-perfluorodecyltrichlorosilane. The as-prepared TiO₂-PVA sponge shows a high water contact angle of 157° (a sliding angle of 5.5°) and an oil contact angle of ∼0°, showing excellent superhydrophobicity and superoleophilicity. The TiO₂-PVA sponge exhibits excellent chemical stability, thermal stability, and mechanical durability in terms of immersing it in the corrosive solutions and solvents, boiling it in water, and the sandpaper abrasion test. Moreover, the as-prepared TiO₂-PVA sponge possesses excellent absorption capacity of oils or organic solvents ranging from 4.3 to 13.6 times its own weight. More importantly, the as-prepared TiO₂-PVA sponge can separate carbon tetrachloride from the oil-water mixture with a separation efficiency of 97.8% with the aid of gravity and maintains a separation efficiency of 96.5% even after 15 cyclic oil/water separation processes. Therefore, the rationally designed superhydrophobic/superoleophilic TiO₂-PVA sponge shows great potential in practical applications of dealing with oily wastewater and oil spills.

Synthesis and performance evaluation of plastic waste aerogel as sustainable and reusable oil absorbent

Direct utilization of waste polyethylene terephthalate (PET) from the environment to form highly porous aerogel technology for oil absorption is an attractive approach from the view point of green chemistry. However, the oil absorption reaction is limited by low oil absorption capacity and less stability. For now, silica aerogel are used to solve these problem. Our goal is to substitute to these silica aerogel with PET aerogel technology. Herein, we have prepared an environmental waste PET based aerogel with 1.0:0.5 wt% PET, polyvinyl alcohol (PVA), and glutaraldehyde (GA) 0.2% v/v were dispersed in 10 mL DI water, followed by homogenization (30 min), sonication (10 min), and ageing (2 h) at 70 °C. To escape macroscopic cracking, cooling (8 h) at 4 °C was followed by freezing (6 h), freeze drying at -80 °C, and 5 mTorr for 18 h. The hybrid PET aerogel displays excellent performance towards oil absorption. Notably it showed high absorption capacity towards the different oils about 21-40 times its own weight, depending on the viscosity and density of the oil and solvents within 15-35 s, 25 °C, and 2 × 2 cm aerogel size. In addition, the aerogel shows there is no change in structure after several recycles due to high mechanical strength. Furthermore, because of the PET aerogel's high porosity (99.74%) and low density (0.0311 g/cm³), close bonding between PET-PVA occurs. Therefore, aerogel shows hydrophobic nature, good mechanical strength, high thermal stability, arrangement of the interconnected fibrillar pore network offers a high surface to volume ratio, low surface energy, high surface roughness, and more reusability. All these parameters are responsible for high oil absorption.

Utilization of Plastic Wastes for Sustainable Environmental Management: A Review

The advancement and modernization of industries have provided numerous benefits to human life including diversification of manufacturing a wide range of products made from plastic materials, thereby leading to the generation of huge quantities of plastic waste. Owing to the increasing issues related with plastic waste, recycling methods have attracted much interest. Recycling not only protects the environment and resources for future generations but also reduces energy consumption and greenhouse gas emissions. A wide range of valuable products including char, oil, fuels, sorbent materials, and chemicals can be obtained through different techniques. This Review highlights various sustainable research avenues and potential routes to reduce the environmental impact of plastic waste based on both traditional and potential approaches for its utilization.

Reusable organosilicon hybrid sorbents with tunable oil interest via PEG-PPG copolymer

Synthetic polymers having hydrophobic cross-linked structures in order to remove oil spills have been gaining interest in environmental applications. Herein, a series of sorbents were produced by using PEG-b-PPG and PEG-co-PPG triols and organosilane cross-linker via bulk polymerization. The polymer sorbents were characterized by FTIR, thermal gravimetric analysis, scanning electron microscopy (SEM), and their interests towards polar and nonpolar solvents were examined via swelling, absorption-desorption kinetics and reusability tests. Besides, the effect of block-, copolymer-of PEG and PPG triol macromonomer on oil and water absorbency is investigated. The obtained sorbents exhibited high and quick absorption abilities towards organic liquids that were in the range of 5-28 gg^-1. Moreover, they can selectively remove the oil from oil/water mixtures and can repeatedly be applied for absorbing oils. The reusability test shows that the polymer sorbents maintained their absorption-desorption loop with no structural change or capacity loss after 10 cycles. These results show the promising potential of the sorbents for the purging of water from oils in environmental applications.

Resolving the effects of environmental micro- and nanoplastics exposure in biota: A knowledge gap analysis

The pervasive spread of microplastics (MPs) and nanoplastics (NPs) has raised significant concerns on their toxicity in both aquatic and terrestrial environments. These polymer-based materials have implications for plants, wildlife and human health, threatening food chain integrity and ultimate ecosystem resilience. An extensive - and growing - body of literature is available on MP- and NP-associated effects, including in a number of aquatic biota, with as yet limited reports in terrestrial environments. Effects range from no detectable, or very low level, biological effects to more severe outcomes such as (but not limited to) increased mortality rates, altered immune and inflammatory responses, oxidative stress, genetic damage and dysmetabolic changes. A well-established exposure route to MPs and NPs involves ingestion with subsequent incorporation into tissues. MP and NP exposures have also been found to lead to genetic damage, including effects related to mitotic anomalies, or to transmissible damage from sperm cells to their offspring, especially in echinoderms. Effects on the proteome, transcriptome and metabolome warrant ad hoc investigations as these integrated "omics" workflows could provide greater insight into molecular pathways of effect. Given their different physical structures, chemical identity and presumably different modes of action, exposure to different types of MPs and NPs may result in different biological effects in biota, thus comparative investigations of different MPs and NPs are required to ascertain the respective effects. Furthermore, research on MP and NP should also consider their ability to act as vectors for other toxicants, and possible outcomes of exposure may even include effects at the community level, thus requiring investigations in mesocosm models.

Simple pyrolysis of polystyrene into valuable chemicals

Overuse of polymer products has led to severe environmental problems, which are threatening survival of creatures on earth. It is urgent to tackle enormous polymer wastes with proper cycling methods. Pyrolysis of polymers into high-value chemicals and fuels is displaying great potential to address the white pollution issue. In this study, we focus on chemical recycling of polystyrene, an important polymer in our everyday life, into valuable chemicals through simple pyrolysis strategy under nitrogen protection. It is found that yield of liquid product from polystyrene pyrolysis achieves as high as 76.24%, and there exists single component in the liquid product, which has been identified as styrene through hydrogen nuclear magnetic resonance spectra. Moreover, we propose monomer dissociation mechanism to explain the pyrolysis process of polystyrene based on the structure of polystyrene and experimental results.

Sorbent-based devices for the removal of spilled oil from water: a review

Always, oil spills do cause serious and dire consequences for the environment, nature, and society that it consumes much time and socio-economic resources to overcome such consequences. Oil spills, hence, posed a big challenge in searching the advanced technologies and devices to recover spilled oil rapidly and efficiently. Indeed, sorbents have been found to play an extremely critical role in the spilled-oil remediation processes. Recently, a large number of various advanced sorbents and sorbent-based oil-collecting devices/technologies have been developed to enhance the oil-recovery capacity. Therefore, it is necessary to have a comprehensive assessment of the application of sorbent-based oil-collecting devices/technologies in recovering spilled oil. Due to this reason, this paper aims to provide a comprehensive review of the advanced technologies of the combination of sorbents and oil-collecting devices in the oil cleanup strategies. Two main oil-collecting devices such as booms and skimmers that could conjunct with sorbents were critically evaluated on the basis of the applicability and technological features, indicating that the capacity of oil spill recovery could achieve 90%. Moreover, oil-storage and oil-collecting devices were also completely mentioned. Last but not least, technical directions, concerns over the application of sorbents in oil recovery, and existing challenges relating to storage, transport, and disposal of used sorbents were discussed in detail. In the future, the automatic process of spilled oil recovery with the conjunction between advanced devices and environmentally friendly high-efficiency sorbents should be further investigated to minimize the environmental impacts, reduce the cost, as well as maximize the collected oil spill.

In Situ Oil Separation and Collection from Water under Surface Wave Condition

Removal of oil from water is strongly desired due to environmental pollution, and related studies are mainly limited to the material itself. Here, we propose an oil-water separation device, called a floating well, which includes a container for oil collection and a modified mesh screen for oil separation. The mesh screen is superhydrophilic to oil and superhydrophobic to water. The oil removal experiment was performed in a basin. Under the calm surface condition, the oil collection efficiency is shown to be 42-69%. The inadequate oil collection is explained by the breakdown of a thin oil film above water to form an oil-free area, preventing direct contact between the separator and the oil. Sustained by a wave generator, we are surprised to find that with a low-frequency surface wave, the oil collection efficiency is increased to 98%, and the collection speed reaches 2.5 times that under the calm surface condition. The almost complete collection is due to the sustained contact between the separator and the oil, under which the surface wave continuously drives the oil film toward the separator from elsewhere, thus the oil-free area cannot be formed. Our work presents a new clue for large-scale in situ applications, in which the nature wave energy of river/sea can be the driving force for continuous oil separation and collection.

Sorption as a rapidly response for oil spill accidents: A material and mechanistic approach

Accidents involving oil transportation has increase due to directly connection with the elevation of global energy demand. The environmental losses are tremendous and brings huge economic issues to remediate the spilled oil. This report presents an up-to-date review on an overall aspects of oil spill remediation techniques, the fundamentals and advantages of sorption, the most applied materials through diverse types of oil spill sites and oils with variety features, highlight to natural materials and future prospective. As the environment preservation progressively becomes a major social concern issue, the achievement of a worldwide distribution process aligned with environmental legislation and economic viability is crucial to the oil industry. For this, a specific preparation considering several scenarios must be carried out regarding minimization of oil spillages. Since the sorbent materials are decisive for sorption, it was approached the main sorbents: natural, graphenic, nano, polymeric and waste materials, and future trends.

Recovery of oil from palm oil mill effluent using polypropylene micro/nanofiber

Residual palm oil that goes into the river untreated can become detrimental to the environment. Residual oil discharge during milling process into palm oil mill effluent (POME) is unavoidable. About 1 wt% of residual oil in POME causes major problems to the mills, in terms of environment, wastewater treatment and economy losses. This paper reports the recovery of residual oil from POME by adsorption on polypropylene micro/nanofiber (PP-MNF) and desorption of oil by hands pressing, and oil extraction from the PP-MNF using solvent and supercritical-CO₂ extraction techniques. The characterization of the PP-MNF and the quality of oil extracted were analyzed using analytical instruments. The reusability of the PP-MNF was also investigated. The experimental results showed the adsorption capacity of the PP-MNF was 28.65 g of oil/g of PP-MNF on average using refined palm oil, whilst recovery of oil from POME was 10.93 g of oil/g of PP-MNF. The extraction yield of oil from PP-MNF using hand pressing was 89.62%. The extraction of residual oil from the pressed PP-MNF showed comparable yield between solvent and supercritical CO₂ techniques. The quality of recovered oil was similar with the quality of the crude oil, and no trace of polypropylene contamination was detected in the oil recovered. The PP-MNF showed no significant physical change after the extraction process. In conclusion, the PP-MNF has great potential to be used commercially in residual oil recovery from POME.

Biosorbent with superhydrophobicity and superoleophilicity for spilled oil removal

The development of efficient and sustainable sorbents for emergent oil cleanup has attracted tremendous attention. In this study, the feasibility of enzymatic grafting of octadecylamine (ODA) on corn stalk pith (CSP) by laccase-TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) treatment for enhanced oil-water separation was investigated. The dynamic contact angle tests suggest that the modified CSP (LCSP) had higher hydrophobicity (WCA, 157.2˚) and lipophilicity (OCA, 0˚) than the CSP did. In addition, the introduction of ODA onto the surface of modified CSP was verified by a variety of characterization techniques including SEM, FT-IR, and XPS. Compared with the control, laccase-TEMPO treatment of CSP coupled with octadecylamine grafting greatly improved the oil sorption capacity from 13.24 g/g to 44.25 g/g, while substantially reduced the water sorption capacity from 15.52 g/g to 2.76 g/g. LCSP has fast kinetic (sorption equilibrium reached before 60 min) and high fits to the pseudo-second-order kinetic model. The results obtained in this study reveal the feasibility of using Laccase-TEMPO treatment to graft the ODA onto the surface of CSP, thereby enhancing the rate and capacity of oil separation from oily water. The method and sorbent developed in this study hold promise for green, simple and cost-effective oil cleanup during oil spillage emergency events.