Conversion Of Waste Plastics Research Articles

Mineralizing Biofilm towards Sustainable Conversion of Plastic Wastes to Hydrogen

AbstractThe integration of inorganic materials with biological machinery to convert plastics into fuels offers a promising strategy to alleviate environmental pollution and energy crisis. Herein, we develop a type of hybrid living material via biomineralization of CdS onto Shewanella oneidensis‐based biofilm, which is capable of sustainable hydrogen production from poly(lactic acid) (PLA) wastes under daylight. We reveal that the formed biofilm microstructure provides an independent anaerobic microenvironment that simultaneously supports cellular viability, maintains hydrogenase activity, and preserves the functional stability of CdS, giving rise to the efficient plastic‐to‐hydrogen conversion efficiency as high as 3751 μmol H2 g‐1 PLA. Besides, by genetically engineering transmembrane pili conduit and incorporating conductive nanomaterials to strengthen the electron transfer across cellular interface and biofilm matrices, we show that the conversion efficiency is further enhanced to 5862 μmol H2 g‐1 PLA. Significantly, we exhibit that a long‐term sustainable plastic‐to‐hydrogen conversion of 63 d could be achieved by periodically replenishing PLA wastes. Overall, by the synergistic integration of biotic‐abiotic characteristics the developed biofilm‐based biomineralized hybrid living material is anticipated to provide a new platform toward the efficient conversion of plastic wastes into valuable fuels, and bridge the gap between environmental contamination and green energy production.

Advancing Sustainability through Energy Innovation and Climate Action: Insights from ETUT

This study explores the potential of sustainable energy solutions to address global energy challenges and mitigate climate change. Oguz Han Engineering and Technology University (ETUT) serves as a case study, displaying its innovative approaches to energy efficiency, waste management, and renewable energy production. The university's implementation of energy-saving devices, smart building automation systems, and LED lighting demonstrates a commitment to reducing carbon emissions and promoting sustainable practices. Additionally, the study investigates the conversion of plastic waste into liquid fuel and the production of bioethanol from cotton stalks as potential solutions for waste management and renewable energy generation. Further, the research explores the deposition of thin film bismuth vanadium tetraoxide for hydrogen production, highlighting its potential as a clean energy source. Overall, this study emphasizes the importance of sustainable energy solutions and the role of academic institutions in driving innovation and promoting a greener future.

Mineralizing Biofilm towards Sustainable Conversion of Plastic Wastes to Hydrogen.

The integration of inorganic materials with biological machinery to convert plastics into fuels offers a promising strategy to alleviate environmental pollution and energy crisis. Herein, we develop a type of hybrid living material via biomineralization of CdS onto Shewanella oneidensis-based biofilm, which is capable of sustainable hydrogen production from poly(lactic acid) (PLA) wastes under daylight. We reveal that the formed biofilm microstructure provides an independent anaerobic microenvironment that simultaneously supports cellular viability, maintains hydrogenase activity, and preserves the functional stability of CdS, giving rise to the efficient plastic-to-hydrogen conversion efficiency as high as 3751 μmol H2 g-1 PLA. Besides, by genetically engineering transmembrane pili conduit and incorporating conductive nanomaterials to strengthen the electron transfer across cellular interface and biofilm matrices, we show that the conversion efficiency is further enhanced to 5862 μmol H2 g-1 PLA. Significantly, we exhibit that a long-term sustainable plastic-to-hydrogen conversion of 63 d could be achieved by periodically replenishing PLA wastes. Overall, by the synergistic integration of biotic-abiotic characteristics the developed biofilm-based biomineralized hybrid living material is anticipated to provide a new platform toward the efficient conversion of plastic wastes into valuable fuels, and bridge the gap between environmental contamination and green energy production.

Photocatalytic Upcycling of Plastic Waste into Syngas by ZnS/Ga2O3 Z-Scheme Heterojunction.

The photocatalytic conversion of plastic waste into value-added products using solar energy presents a promising approach for promoting environmental sustainability. Nonetheless, the emission of CO2 during the conventional photocatalytic degradation process remains a major hurdle that impedes its further development. In this study, we propose an efficient photocatalytic conversion of polyethylene plastic into syngas (CO+H2 mixtures) by using a ZnS/Ga2O3 Z-scheme heterojunction photocatalyst. It is found that the strong redox capability of photogenerated holes and electrons in the Z-scheme heterojunction photocatalyst can promote the oxidative depolymerization of PE plastic, concurrently enabling the efficient reduction of the intermediate product CO2 into syngas. Furthermore, this system also demonstrates applicability in the conversion and upcycling of other polyolefin plastics including polypropylene and polyvinyl chloride. Our findings highlight the potential of polyolefin plastics photoreforming for the production of syngas under environmentally benign conditions.

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 pathways are first summarized, 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.

In situ formation of oxygen-deficient WO3-x nanosheets for enhanced photocatalytic activity in water splitting and plastic reforming

Photocatalytic pathways are essential for the sustainable production of chemicals and fuels, pivotal for achieving a pollution-free planet. Electron-hole recombination is a critical problem that has, so far, limited the efficiency of the photocatalytic materials. Here, oxygen-deficient WO3-x nanosheets were in situ grown in a polymeric carbon nitride (PCN) support during the thermal polycondensation of melamine. The introduction of defect in WO3-x, accompanied by spin polarization and the formed WO3-x/PCN heterostructure, greatly accelerated the charge separation and transfer. The synthesized WO3-x/PCN composite exhibited a tenfold increase in hydrogen generation activity than pure PCN under visible-light (420 ≤ λ ≤ 780 nm). The WO3-x/PCN also demonstrated consecutive 24 h and stable photocatalytic H2 production in the aqueous plastic-containing [poly(vinyl alcohol) (PVA), poly(ethylene terephthalate) (PET) and the PET bottle] solutions under visible light. The hydrogen production rates were determined to be 111.2, 50.5, and 7.8 μmol·h−1·g−1 in PVA, PET and PET bottle, respectively. In addition, the oxygen vacancies WO3 with their localized surface plasmon resonance effect, facilitated efficient utilization of NIR photon and the hydrogen evolution rate over WO3-x/PCN reached to 120 μmol h−1·g−1 under NIR light (700 ≤ λ ≤ 780 nm). This research not only advances the potential applications of WO3-x/PCN in sustainable energy production but also provides insights into environmental remediation through the conversion of plastic wastes.

The Potential Use of Plastic Waste as Sustainable Construction Material

Solid waste management is one of the major process which our country has to be given importance. One of the major threats in the solid waste is due to the Plastic Waste generation which are released to the open environment without any proper care. Since the plastic waste take more years to get degraded, the major issue arises is management of plastic waste among the total solid waste produced. They even cause environmental as well as health issues to the living being.The project elucidates about the use of LDPE waste as the construction material i.e., paving tile which is an innovative method for the conversion of plastic waste to a useful product. The pavement tiles showed best results of compressive strength and breaking load when tested. As a result, the so made pavement tile can be used either as pedestrian paving tile or can also be used as paving tile for residential driveways there by showing a compressive strength of 42 N/mm2 and a breaking load of 3 KN.

Rapid Surface Reconstruction of Amorphous‐Crystalline NiO for Industrial‐Scale Electrocatalytic PET Upcycling

The conversion of plastic waste into valuable chemicals through innovative and selective nano‐catalysts offers significant economic benefits and positive environmental impacts. However, our current understanding of catalyst design capable of achieving industrial‐grade current densities is limited. Herein, we develop a self‐supported amorphous‐crystalline NiO electrocatalyst for the electrocatalytic upcycling of polyethylene terephthalate (PET) into formate and hydrogen (H2) fuel. The catalyst achieves an industrial current density of over 1 A cm‐2 at 1.5 V vs. RHE, with an 80% Faradaic efficiency and a formate production rate of 7.16 mmol cm‐2 h‐1. In situ Raman spectroscopy, X‐ray absorption spectroscopy, and density functional theory calculations reveal that the rapid transformation of amorphous‐crystalline NiO into γ‐NiOOH at the amorphous‐crystalline interface provides a thermodynamic advantage for formate desorption, leading to the high activity required for industrial applications, which is difficult to achieve for fully crystalline NiO. A techno‐economic analysis indicates that recycling waste PET using this catalytic process could generate a profit of $501 per ton. This work presents a cost‐effective and highly efficient approach to promoting the sustainable utilization of waste PET.

Rapid Surface Reconstruction of Amorphous-Crystalline NiO for Industrial-Scale Electrocatalytic PET Upcycling.

The conversion of plastic waste into valuable chemicals through innovative and selective nano-catalysts offers significant economic benefits and positive environmental impacts. However, our current understanding of catalyst design capable of achieving industrial-grade current densities is limited. Herein, we develop a self-supported amorphous-crystalline NiO electrocatalyst for the electrocatalytic upcycling of polyethylene terephthalate (PET) into formate and hydrogen (H2) fuel. The catalyst achieves an industrial current density of over 1 A cm-2 at 1.5 V vs. RHE, with an 80% Faradaic efficiency and a formate production rate of 7.16 mmol cm-2 h-1. In situ Raman spectroscopy, X-ray absorption spectroscopy, and density functional theory calculations reveal that the rapid transformation of amorphous-crystalline NiO into γ-NiOOH at the amorphous-crystalline interface provides a thermodynamic advantage for formate desorption, leading to the high activity required for industrial applications, which is difficult to achieve for fully crystalline NiO. A techno-economic analysis indicates that recycling waste PET using this catalytic process could generate a profit of $501 per ton. This work presents a cost-effective and highly efficient approach to promoting the sustainable utilization of waste PET.

Nanocatalysts convert waste plastic bottles into value-added products

Nanocatalysts convert waste plastic bottles into value-added products

Efficient photoreforming of plastic waste using a high-entropy oxide catalyst

Simultaneous catalytic hydrogen (H2) production and plastic waste degradation under light, known as photoreforming, is a novel approach to green fuel production and efficient waste management. Here, we use a high-entropy oxide (HEO), a new family of catalysts with five or more principal cations in their structure, for plastic degradation and simultaneous H2 production. The HEO shows higher activity than that of P25 TiO2, a benchmark photocatalyst, for the degradation of polyethylene terephthalate (PET) plastics in water. Several valuable products are produced by photoreforming of PET bottles and microplastics including H2, terephthalate, ethylene glycol and formic acid. The high activity is attributed to the diverse existence of several cations in the HEO lattice, lattice defects, and appropriate charge carrier lifetime. These findings suggest that HEOs possess high potential as new catalysts for concurrent plastic waste conversion and clean H2 production.

Sustainable recovery of monomers from PET and PC waste via Thermocatalytic depolymerization for synthesis of polycarbonates and co-polycarbonates

The increasing global demand for sustainable plastics recycling methods has propelled the research and development of innovative depolymerization processes. The Thermocatalytic depolymerization (TCDP) of polyethylene terephthalate (PET) and polycarbonate (PC) has been performed at 200 ℃. Ethylene glycol (EG) is used as a reactant and as well a polymer bond-cleaving agent and Yttrium Oxide (Y2O3) is used as an effective catalyst. Y2O3 acted as a dual role during depolymerization reaction, which converts EG into cyclic ethylene oxide (CEO) and as well as to break the ester and carbonate bonds in the polymer structure of PET and PC respectively. The TCDP reaction conditions were optimized and the maximum quantity of Bis(2-hydroxyethyl) terephthalate (BHET) (80%) and (Bisphenol A (BPA)) (83%) has been recovered by TCDP reaction of PET and PC respectively. The polycarbonate and co-polycarbonate (Co-PC) were synthesized using recovered BPA and BHET with triphosgene via polycondensation reaction. The structure of monomers and polymers was confirmed by existing analytical (FTIR, NMR, XRD and GPC) techniques. The thermal properties of PC and Co-PC were performed by TG analysis. The TGA results reveal that the degradation temperature (Td) of PC and Co-PC are observed at 420.5 and 442.8 °C respectively, which shows that the Td of Co-PC has been increased by 22 ℃ than PC. The TCDP process is an effective method to recover specific value-added products from waste plastics, which could be made into a new versatile material for different applications. This research finding will provide a new direction to convert plastic waste into useful chemicals, which could reduce waste plastic and their carbon footprint and contribute to a more sustainable future by reusing plastic materials and achieving a circular economy.

Producing aromatic‐rich oil through microwave‐assisted catalytic pyrolysis of low‐density polyethylene over Ni/Co/Cu‐doped Ga/ZSM‐5 catalysts

AbstractMicrowave (MW)‐assisted catalytic pyrolysis represents a promising method for transforming petroleum‐based plastic waste into valuable chemicals, offering a pathway towards more sustainable circular economy. In this study, catalytic pyrolysis of low‐density polyethylene (LDPE) was conducted under MW irradiation. The influence of various catalyst types (HZSM‐5, Ga/ZSM‐5, Ga/Ni/ZSM‐5, Ga/Co/ZSM‐5, and Ga/Cu/ZSM‐5) on product yield and distribution was examined. The results revealed that the Ga/ZSM‐5 catalyst yielded the maximum liquid oil, approximately 41%. Ga/Ni/ZSM‐5 performed excellently in the production of long‐chain olefins, constituting about 27% of the liquid fraction. However, Ga/Co/ZSM‐5 led to the production of heavy pyrolysis oil containing nearly 25% long‐chain paraffins, rendering it unsuitable for producing high‐value chemicals. Conversely, the Ga/Cu/ZSM‐5 catalyst yielded an aromatic‐rich pyrolysis oil, with benzene derivatives constituting approximately 90% of the liquid oil fraction, thus proving to be a suitable catalyst for the intended application. The liquid product distribution was compared with a petroleum assay by SimDist, and this suggested that utilizing the HZSM‐5 catalyst could yield an 86.4% naphtha fraction. The study also revealed that the Ga/Cu/ZSM‐5 catalyst generated the largest amounts of hydrogen and syngas, as determined by a MicroGC analysis of the gas products. This catalyst also exhibited the maximum coke deposition (1.35%) postreaction, which was attributed to its high aromatic hydrocarbon content in the pyrolysis oil and maximal hydrogen release. A comparison of fresh and spent catalyst properties was conducted to gain insights into catalyst activity and to correlate the effects of metal doping on product distribution. These findings underscore the potential of MW‐assisted catalytic pyrolysis, particularly with the Ga/Cu/ZSM‐5 catalyst, for the efficient conversion of plastic waste into valuable chemicals, thereby contributing to sustainable resource utilization and environmental conservation.

Optimizing process parameters and materials for the conversion of plastic waste into hydrogen

Abstract This study has investigated hydrogen production from waste plastics using pyrolysis, steam methane reforming, and water-gas-shift reactions modelled via Aspen Plus. After evaluating multiple alternatives, polypropylene (PP) was selected as the feedstock. The research has been focused on how reformer temperature, steam-to-fuel ratio (S/F), reformer pressure, and pyrolysis temperature impact syngas composition, heating values, syngas (H2/CO) ratios, and yields of hydrogen (H2), methane (CH4), and carbon dioxide (CO2). Key findings have indicated that raising reformer temperatures to around 1000°C maximizes hydrogen production in syngas, reaching peak levels of 2360 Nm3/Ton and 2525 Nm3/Ton for reformer temperature and steam-to-fuel ratio (S/F) ratios, respectively, via processes like steam methane reforming and the water-gas-shift reaction. Moreover, other parameters like steam-to-fuel (S/F) ratio and reformer pressure have produced the highest amount of hydrogen at 0.25 and 1 atm, respectively. Optimizing reformer temperature and steam-to-fuel ratio (S/F) have been selected as key in hydrogen production, with peak lower heating values (LHV) of 1.15 MJ/kg for temperature and 1.035 MJ/kg for S/F ratios, highlighting the importance of balancing these parameters for efficiency. Additionally, syngas' hydrogen (H2) composition increased with pyrolysis temperature, peaking at 8.5% at 700°C. Finally, this research has provided valuable insights into optimizing process parameters for sustainable hydrogen production. Moreover, the simulation process has provided cost-effective adjustments and informed decision-making for sustainable and scalable technologies, benefiting researchers, investors, engineers, and policymakers involved in innovative hydrogen generation.

Aquathermolysis of polyolefin plastic wastes over a MOF-derived TiO2 anatase catalyst: Enhancing C–N bond cleavage and coke suppression

Plastics are ubiquitous in modern society owing to their cost-effectiveness, low weight, and durability. However, the disposal and recycling of plastic waste remain significant challenges. Aquathermolysis has emerged as a promising strategy for converting contaminant-rich polyolefin plastic waste into value-added liquid fuels. This study investigates the plastic-waste aquathermolysis potential of a TiO2 catalyst derived from the sacrificial precursor Ti-containing MIL-125 via a MOF-mediated synthesis pathway combined with calcination. The TiO2 catalyst retained its mesoporous properties and predominantly anatase phase on calcination at 450 ℃. The aquathermolysis catalysis and stability of the newly synthesized catalyst for plastic-waste conversion were evaluated and compared with those of other catalytic systems. Additionally, the role of water in the N removal efficiency and coke suppression properties of the catalyst were analyzed. Water significantly improved the removal of N and S impurities, with a N reduction of 80–95% at the optimal water content (20–40 wt%). The robustness of the as-synthesized catalyst was confirmed by deconvoluted X-ray photoelectron spectroscopy patterns, which indicated the persistence of the TiO2 phase, even after prolonged catalysis in aqueous environments, and transmission electron microscopy results, which showed that the anatase phase remained well-dispersed under aquathermolysis conditions with a significant reduction in the C/Ti ratio and a corresponding increment in the N/C ratio. The results of this study could guide future research on the development of catalysts, similar to the MIL-125-derived TiO2 catalyst investigated here, with high potential for efficient plastic-waste conversion and impurity removal in aqueous environments.

Probing the influence of synthesized hierarchical ZSM-5 catalyst in ex-situ catalytic conversion of real-world plastic waste into aromatic rich liquid oil

Plastic waste management has become a vitally important environmental and economic concern for researchers and technologists worldwide. Currently, catalytic pyrolysis of plastic waste emerged as a promising plastic waste management technique, further aiding the full-scale development of an alternate innovation to convert plastic waste into fuel (liquid oil) energy. Lately, zeolites have been one of the most suitable and versatile catalysts in converting plastic waste into fuel grade hydrocarbons via catalytic pyrolysis. The present work exhibits an attempt to synthesize and study the performance of a hierarchical ZSM-5 in a fixed bed reactor to convert the real-world (LDPE, HDPE, PP and PS) plastic wastes into higher quality fuel grade liquid oil. The hierarchical ZSM-5 catalyst having both mesopores and micropores (dual porosity) in its framework is synthesized by using a single organic template i.e., 10 % tetra propylammonium hydroxide (TPAOH). The catalyst performance study displays remarkable selectivity and increase in the yield of the aromatic component in the liquid oil obtained from different plastic wastes. The results indicate that presence of hierarchical catalyst has exceptionally lowered the reaction temperature in the range of 400–430 °C and increased the liquid oil yield in comparison with that of the thermal pyrolysis. Also, the obtained liquid oils have comparable fuel properties with that of kerosene and diesel.

Waste to Energy; Conversion of Plastic Waste into Liquid Fuel Equivalent to Diesel and Gasoline Using the Pyrolysis Method

Abstract The aim of this research is to produce oil equivalent to diesel and gasoline from plastic waste using the pyrolysis method, examining its physico-chemical properties and comparing it with conventional diesel and gasoline. The production of diesel oil and gasoline from plastic waste is a topic that has received increasing attention in recent years, due to increasing awareness of the environmental problems caused by plastic waste and the need for alternative energy sources. Methods for converting plastic waste into liquid fuel, separating diesel and gasoline equivalents and examining their physico-chemical properties are the main focus of this research. Pyrolysis is the process chosen because the technology is simpler than other methods, such as gasification for example. A total of 6000 grams of plastic chips were pyrolyzed in an LPG-fueled reactor. Pyrolysis was carried out at temperatures of 200, 250, 300, 350, 400 °C, then the yield of oil produced at each temperature was weighed. It was found that the optimum temperature for pyrolysis was 300 because the increase in yield afterwards was very small. Next, 2000 grams of pyrolysis oil was distilled by gradually increasing the temperature from 100 to 300. The resulting 1520 grams or 79.17% gasoline equivalent fraction, 320 grams or 16.67% diesel fraction, the remaining 80 grams or 4.17% residual oil. The results of the physico-chemical properties examination showed that the diesel and gasoline fractions were similar to conventional diesel and gasoline.

Temperature-dependent highly active LaCaMgAl2O4 catalyst effect on carbon nanomaterial and hydrogen generation from polymethyl methacrylate plastic

The increasing accumulation of waste polymethyl methacrylate (PMMA) plastics presents a significant environmental challenge, while the demand for renewable energy sources continues to rise. Thermochemical recycling is a prospective technique for converting waste plastics into high-value chemicals, both economically and environmentally. In this work, the catalytic pyrolysis of waste PMMA plastics over LaCaMgAl2O4 nanosheets (NSs) catalyst is being investigated for its potential to produce hydrogen and carbon nanotubes (CNTs) in a two-stage fixed-bed reactor. The yield and purity of the gaseous products, as well as carbon deposition, concerning the effects of temperature during the catalysis process. Additionally, a small portion of LaCa was incorporated into the MgAl2O4 composite in the pre-catalysts under investigation. Analyzing the physicochemical properties of the carbon nanomaterials that form provides valuable insights into the workings of different catalysts. It's noteworthy that LaCaMgAl2O4 NSs showed such large yields of H2 (82.71 vol% H2) and CNTs (388 mg g−1) at 750 °C. The LaCaMgAl2O4 NSs catalyst's impressive ability to produce CNTs and H2 gas at high yields underscores its efficacy and potential for real-world catalytic pyrolysis applications. This study emphasizes the Nanocatalyst's potential for large-scale catalytic pyrolysis operations, providing a workable and efficient way of converting waste plastics into high-value products and renewable energy.

Supercritical CO2-promoted degradation of polystyrene to aromatic oils with NiO@C catalyst

Exploring new system for chemical recycling of plastic is an effective way to convert plastic waste into energy. Herein, the use of supercritical CO2 (ScCO2) to promote the catalytic degradation of polystyrene (PS) with high yield of aromatic oils was proposed. ScCO2 provided a homogeneous environment for the reaction, which not only facilitated the swelling of PS, but also inhibited the formation of coke, beneficial for the degradation of PS to aromatic oils. In addition, CO2 as an oxidant reacted with PS or intermediates to generate new products. NiO@C catalyst prepared by doping carbon material in NiO had a simple preparation process, an abundance of porous structure and strong acidic sites, thus improving the catalytic activity. Under the co-action of ScCO2 and NiO@C, the yield of aromatic oils produced from PS was up to 89.3 ± 0.6 wt% at 300 °C with a reaction time of 2 h and a catalyst loading amount of 10 wt%. Moreover, the NiO@C catalyst was used for three cycles without obvious change in the catalytic performance. The efficient catalytic degradation of PS to aromatic oils by ScCO2 promoted NiO@C catalysis provides a potential route for simultaneously recycling plastic and sequestering carbon.

Surface-Activated Mechano-Catalysis for Ambient Conversion of Plastic Waste.

Improved recycling technologies can offer sustainable end-of-life options for plastic waste. While polyolefins can be converted into small hydrocarbons over acid catalysts at high temperatures, we demonstrate an alternative mechano-catalytic strategy at ambient conditions. The mechanism is fundamentally different from classical acidity-driven high-temperature approaches, exploiting mechanochemically generated radical intermediates. Surface activation of zirconia grinding spheres creates redox active surface sites directly at the point of mechanical energy input. This allows control over mechano-radical reactivity, while powder catalysts are not active. Optimized milling parameters enable the formation of 45% C1-10 hydrocarbons from polypropylene within 1 h at ambient temperature. While mechanochemical bond scission is undesired in plastic production, we show that it can also be exploited for chemical recycling.