Biodegradable Plastics Research Articles

Enhancing degradation of PLA-made rigid biodegradable plastics with non-thermal plasma treatment

This study evaluated the efficacy of Dielectric Barrier Discharge Non-Thermal Plasma (DDBD-NTP) as a pretreatment method to enhance the degradation of rigid biodegradable plastics (RBP) during composting, specifically focusing on polylactic acid (PLA) products such as drinking cups (CS) and spoon handles (SH). Using a Single-Factor-At-A-Time (SFAT) design, the impact of NTP parameters, including input voltage and treatment duration, on the physicochemical properties was evaluated, and the subsequent degradation rate of RBP was assessed by measuring the degree of disintegration in a home-scale composter. The filamentary discharge mode of the DDBD plasma system selectively altered the surface characteristics of RBP without significantly affecting their bulk properties. High-voltage treatments significantly increased surface roughness and accelerated degradation rates, while low-voltage and short-duration treatments enhanced oxidation, as indicated by the increased O/C ratio (85.5% for SH and 66.1% for CS), showing a non-linear response to plasma intensity. Furthermore, NTP treatment reduced water contact angles (up to a 39.79% reduction for SH and 82.65% for CS), indicating enhanced hydrophilicity. All NTP-treated samples demonstrated significantly higher degradation rates compared to both untreated and thermally treated counterparts. Notably, ‘high-voltage for short-duration’ treatments, such as CS-3 and SH-3, exhibited the highest degradation rates among the samples. CS-3 achieved complete disintegration (100%) within 20 days, markedly exceeding the 2% observed in untreated CS samples. Similarly, SH-3 reached 36% disintegration after 35 days, considerably surpassing the 9% seen in untreated SH samples. The findings indicate that NTP treatment is a viable and sustainable method to enhance the biodegradation of plastic waste.

Bio-based polylactic acid labware as a sustainable alternative for microbial cultivation in life science laboratories

Single-use plastics (SUPs) in life science laboratories account for approximately 5.5 million tonnes of waste per year globally. Of SUPs used in life science laboratories, Petri dishes, centrifuge tubes, and inoculation loops are some of the most common. In order to reduce the reliance on petrochemical-based SUPs in the life science research laboratory and minimize the negative environmental impacts associated with SUPs, this research investigates the applicability of polylactic acid (PLA) in single-use labware as a replacement for petrochemical-based plastics. PLA is one of the most well-studied biodegradable plastics that can be produced from sustainable resources. Commercially available PLA was used to 3D print a select range of labware to test the suitability of PLA-based material for routine microbiology work. An injection moulded PLA-based Petri dish was also designed and produced, for increased optical clarity. The biocompatibility was tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus epidermidis) strains of bacteria. The PLA-based labware did not negatively impact the cell growth, viability, and metabolic activity of the bacterial cultures. The injection moulded PLA Petri dish showed a reduced colony forming unit count for the Gram-negative E. coli strain compared to the polystyrene Petri dish, ∼1.5 × 109 CFU/mL and ∼3.0 × 109 CFU/mL respectively, during late-exponential growth. The colony counts were, however, in the same order of magnitude. This observed difference may be due to the internal environment inside the Petri dish, hence the internal O2 concentration, humidity, and temperature during bacterial growth were investigated. This work demonstrates, for the first time, a full successful workflow of bacterial growth using a sustainable bioplastic, providing a pathway to reducing the environmental impacts of SUPs in life science laboratories.

Combined use of Bacteria and Enzymes in the Degradation of Polymer Materials

The development of the plastics industry, pro-ecological directives and environmental problems related to the decomposition of biodegradable plastics create necessity to develop a way to properly manage waste from materials that should not be deposited in the environment. A bioproduct has been developed to be used for accelerating the biodegradation of polymer materials. The bioproduct includes carefully selected microorganisms and enzymes. It has been observed that metabolic activity of selected bacteria increases significantly in the presence of plastic material, causing degradative changes. In addition, enzymes were used that also stimulate the decomposition of polymer materials. Impact of bacteria and enzymes on polymer biodegradation was analyzed using different methods: BOD, mass loss, SEM-EDX and FTIR-ATR. Also the effect on plant growth was examined. Five bacterial strains were selected as the active ingredients of the bioproduct, including two bacterial strains from the designated collection and three isolated from environment. Four hydrolytic enzymes have been selected that have the potential to accelerate the decomposition of polymer materials. Keywords: bacteria, enzymes, biodegradation, polymer materials

Preliminary study of synthesis and characterization of biodegradable avocado seed starch-chitosan plastic with glycerol plasticizer

Mechanical characteristics were studied for biodegradable plastics derived from avocado seed starch, emphasizing the influence of chitosan and glycerol. The extraction of starch from avocado seeds began with filtration. Different amounts of glycerol and chitosan were added to the extracted starch of up to 3% by weight. Because this method just uses distilled water instead of chemical chemicals, it was highly environmentally friendly. Tensile testing was done on the generated samples to assess the mechanical properties of this bioplastic; the results indicated that the samples’ elongation rates ranged from 21.9% to 134.7%. In spite of this, the bioplastic showed a comparatively low tensile strength, peaking at 3,381 MPa when chitosan-starch ratio was 2:1 and 1.5% glycerol was added.

Production of Defragmentable Bioplastic using Starch Extracted from Annona Muricata (Soursoup) Seed Reinforced with Bentonite Nanoclay

Abstract Seeds of Annona Muricata, often called soursop or guyabano were used as a source of starch for the production of defragmentable bioplastic. The researchers used mixture of water and starch content of 10 and 20 grams respectively from Annona Muricata (soursop) seeds with various concentration (20%, 25%, 30%) of glycerol (plasticizer) and reinforced with three different concentrations (0%, 3%, 6%) of bentonite nanoclay (filler). The characterization of the bioplastic was carried out by determining the effect of variation of the ratio between the quantity of starch from soursop seeds, bentonite nanoclay, and glycerol. The starch-based defragmentable bioplastic was evaluated with its water retention, degradation, and mechanical properties. The result showed that the tensile strength improved significantly with the addition of bentonite nanoclay and the elongation at break with the addition of glycerol. Same way in water retention test, where the presence of the bentonite nanoclay increased the strength of the bioplastic with its water solubility. In soil burial test, a higher level of glycerol concentration increased the rate of the bioplastic degradation. By adding the bentonite nanoclay as a filler, the rate of bioplastic degradation decreased compared to the bioplastic without filler. In shelf-life test, adding glycerol as plasticizer improved the shelf life of bioplastics. A high concentration of glycerol served as an anti-fungal for bioplastics.

Assessing the impact of weathered polystyrene collected from the marine environment on oxidative stress responses in Zophobas morio larvae: A preliminary study

Foamed polystyrene (PS) is a prevalent material in consumer products and thus represents one of the largest constituents of marine litter. PS may interact with and be ingested by various organisms, including insects, which are starting to be used in biodegradation of plastic wastes. This study examines the physiological performances and the potential oxidative stress related to dietary environmental PS exposure of Z. morio larvae. Experimental groups were fed different diets: bran and oatmeal (control), weathered PS collected from the marine environment, and virgin PS. Over a 30-day feeding period, larvae growth, survival, and PS consumption were measured, together with antioxidant enzymatic activities and gene expression profiles. Results showed that PS ingestion supports larval growth similarly to bran, but the two PS-fed groups consumed a different amount of plastic, suggesting that weathered PS might affect the patterns of PS consumption by larvae. We denoted that PS consumption was associated with a decline in total antioxidant capacity, which showed the highest decrease in the environmental PS group. Marked increases in oxidative stress biomarkers such as superoxide dismutase (SOD) activity/mRNA levels and malondialdehyde content were also observed in the environmental PS-fed group, indicating an elevated oxidative stress response, probably due to pollutants adsorbed/absorbed on PS. Differently to SOD, catalase at both mRNA and enzyme activity levels was found to be significantly reduced by PS digestion, regardless of PS type. The mRNA levels of glutathione s-transferase (GST) were significantly higher in the environmental PS-fed larvae compared to the virgin PS-fed group. In addition, Principal Component Analysis clearly distinguished between larvae fed different PS types, highlighting the enhanced oxidative stress caused by the ingestion of PS collected from marine environments. These results support the potential of insects in plastic biodegradation processes but also demonstrate the health hazards of using environmental PS as principal dietary component in Z. morio larvae, thus questioning their use in downstream productions.

Challenges and opportunities in managing biodegradable plastic waste: A review.

Biodegradable plastics have certain challenges in a waste management perspective. The existing literature reviews fail to provide a consolidated overview of different process steps of biodegradable plastic waste management and to discuss the support provided by the existing legislation for the same. The present review provides a holistic overview of these process steps and a comprehensive relative summary of 13 existing European Union (EU) laws related to waste management and circular economy, and national legislations plus source separation guidelines of 13 countries, to ensure the optimal use of resources in the future. Following were the major findings: (i) numerous types and low volumes of biodegradable plastics pose a challenge to developing cost-effective waste management infrastructure; (ii) biodegradable plastics are promoted as food-waste collection aids, but consumers are often confused about their proper disposal and are prone to greenwashing from manufacturers; (iii) industry-level studies demonstrating mechanical recycling on a full scale are unavailable; (iv) the existing EU legislation dealt with general topics related to biodegradable plastics; however, only the new proposal on plastic packaging waste and the EU policy framework for bioplastics clearly mentioned their disposal and (v) clear disparities were observed between disposal methods suggested by national legislation and available source separation guidelines. Thus, to appropriately manage biodegradable plastic waste, it is necessary to develop waste processing and material utilization infrastructure as well as create consumer awareness. In the end, recommendations were provided for improved biodegradable plastic waste management from the perspective of systemic challenges identified from the literature review.

Innovations to overcome the current waste problem caused by single-use plastics in the pursuit of a circular economy

Plastic production continues to increase each year, yet only 9% are successfully recycled. This has impacted natural habitats and ecosystems, due to an uncontrolled amount of waste. The food industry is a major contributor to plastic waste. To counter this problem, the demand for environmentally sustainable alternatives, i.e. bio-based plastics, in the pursuit of a circular economy is increasing. As such, this problem is interconnected and at the resource nexus of particularly, food, material, waste, and ecosystem. This systematic review provides an overview of different innovations regarding materials and additives for bio-based plastics for packaging in the food industry. The paper argues that a majority of materials for bio-based plastics originate from the food industry’s value chain and utilizing these resources is essential to reduce waste and to create more value, essentially addressing the problem with a focus on the resource nexus. Moreover, the importance of developing biodegradable and recyclable plastics to reduce the environmental impact of plastic waste is also highlighted, especially in the context of single-use food packaging. These findings and conclusions cumulated into a framework to differentiate the various materials and classify them regarding their biodegradability properties, origin (plant- or animal-based industry by-products and raw materials) and end-of-life scenarios. This contributes to the academic literature and practice by categorizing different kinds of materials, which might be labelled environmentally sustainable, particularly biodegradable, but which might not always be the case and critically discussing implications of this.

Pengaruh Compatibilizer Polyvinyl Alcohol-graft-Maleic Anhydride (PVA-g-MAH) terhadap Karakteristik Plastik Degradable Berbasis Pati Sagu dan Pati Biji Nangka

Degradable plastics may be employed as a substitute for conventional plastics in various commercial applications. Plastics made from starch and PVA-g-MAH are biodegradable. This research uses sago and jackfruit starch, a maleic anhydride compatibilizer, and PVA to make degradable plastics stronger. The research method consists of several stages, making sago starch and jackfruit seed starch, preparing degradable plastic synthesis, and testing the resulting degradable plastic. The test of mechanical characteristics of degradable plastics carried out is the tensile strength test of 4.41 Mpa - 6.02 MPa on sago starch-based degradable plastic with PVA-g-MAH, while the tensile strength of 6.86 - 8.43 MPa on jackfruit seed starch-based degradable plastic with PVA-g-MAH. The test shows that the compound is hydrophilic, meaning it binds to water and is easily degraded by soil. The DSC thermogram shows that the plastic samples degrade when heated, both thermogram peaks occur which indicate physical changes. The swelling value obtained in sago starch degradable plastic with PVA-g-MAH is (28.14-72.17%) while in jackfruit seed starch degradable plastic, the swelling obtained ranges from (25.91-84.72%) showing a good result. Sago starch and jackfruit seed starch degradable plastics degraded in 6-18 days using PVA-g-MAH. Sago starch and jackfruit seed starch-based plastics using PVA-g-MA meet the ASTM 6400 standard for biodegradable plastics. The plastic should be able to biodegrade up to 60% within six months or 90% within one year.

Environmental impacts of biodegradable microplastics

Biodegradable plastics, perceived as ‘environmentally friendly’ materials, may end up in natural environments. This impact is often overlooked in the literature due to a lack of assessment methods. This study develops an integrated life cycle impact assessment methodology to assess the climate-change and aquatic-ecotoxicity impacts of biodegradable microplastics in freshwater ecosystems. Our results reveal that highly biodegradable microplastics have lower aquatic ecotoxicity but higher greenhouse gas (GHG) emissions. The extent of burden shifting depends on microplastic size and density. Plastic biodegradation in natural environments can result in higher GHG emissions than biodegradation in engineered end of life (for example, anaerobic digestion), contributing substantially to the life cycle GHG emissions of biodegradable plastics (excluding the use phase). A sensitivity analysis identified critical biodegradation rates for different plastic sizes that result in maximum GHG emissions. This work advances understanding of the environmental impacts of biodegradable plastics, providing an approach for the assessment and design of future plastics.

Properties of poly(butylene adipate-co-terephthalate)/thermoplastic starch filled with treated and untreated sugarcane bagasse fiber

Sugarcane bagasse, comprising fibrous rind and spongy pith, is frequently employed as a reinforcing agent in both concrete and plastic composites. In thin plastic films, sugarcane bagasse is typically utilized as finely ground particles within the composite film. The integration of this agricultural byproduct into biodegradable plastic films could potentially lower production expenses and promote the film's biodegradability. This study presents the development of poly(butylene adipate-co-terephthalate) (PBAT)/thermoplastic starch (TPS) (90/10) formulations incorporating varying loadings of sugarcane bagasse fibers. The impact of alkaline and silane surface treatments on tensile strength, thermal properties, and water barrier properties was investigated. Upon the inclusion of sugarcane bagasse (5%, 10%, 15%, and 20%), a decrease in tensile strength from 23.47 to 8.41 MPa and elongation at break from 1135% to 55.83% was observed. Conversely, the Young's modulus increased from 47.12 to 188.50 MPa following the addition of 20% sugarcane bagasse in the PBAT/TPS matrix. Modest enhancements in tensile properties, thermal characteristics, and water barrier properties were noted after treating the bagasse fibers with alkaline and silane. Scanning Electron Microscope (SEM) analysis revealed that silane-treated sugarcane bagasse exhibited increased surface roughness due to the removal of lignin and hemicellulose, facilitating better adhesion between the fibers and the PBAT/TPS matrix.

Physico-Chemical and Microbiological Characterization of Starch-Based Biodegradable Films

Research on the manufacturing of experimental biodegradable films (EBF) was carried out in the laboratory. Recipes containing 8, 10, and 15% of corn and potato starch were analyzed. It was found that the EBF based on potato starch with a 10% concentration is more plastic and retains its shape well compared to other samples. Microbiological, mechanical, physicochemical, and infrared spectroscopic studies of the EBF and the biodegradable plastics (BP) available on the market in the form of packaging bags that are positioned as biodegradable (BP from ATB, BP from Silpo, BP from Roshen) were performed. The isolation of enrichment soil microbial cultures and their identification by microscopy of permanent mounts were studied. The ability of the isolated microbial cultures to biodegrade starch-based EBFs was experimentally investigated and determined, as well as the peculiarities of biodegradation of starch-based EBFs and BPs, as a result of the activity of microorganisms of different taxonomic groups, were studied.

The effect of low-temperature plasma pretreatment on the biodegradability of polyethylene films

ABSTRACT With the increasing focus on environmental friendliness and sustainable development, extensive research has been conducted on the biodegradation of plastics. The non-hydrolyzable, highly hydrophobic, and high-molecular-weight properties of polyethylene (PE) pose challenges for cell interaction and biodegradation of PE substrates. To overcome these obstacles, PE films were treated with low-temperature plasma before biodegradation. The morphology, surface chemistry, molecular weight, and weight loss of PE films after plasma treatment and biodegradation were studied. The plasma treatment decreased the surface water contact angle, formed C–O and C = O groups, and decreased the molecular weight of PE films. With the increased pretreatment time, the biodegradation efficiency rose to 2.6% from 0.63% after 20 days of incubation. The mechanism was proposed that the surface oxygen-containing groups formed by plasma treatment can facilitate the bio-accessibility and be further decomposed and utilised by the microbes. This study provided an effective and rapid pretreatment strategy for improving biodegradation of PE.

Adsorption and desorption of nonylphenol on the biodegradable microplastics in seawater

Biodegradable plastics have been widely used and their interaction with endocrine disrupting chemicals in the environment is worth exploring. This study selected poly (butylene adipate-co-terephthalate), poly (butylene succinate), polylactic acid (PLA) and a non-biodegradable microplastics (PE) as control to explore the adsorption-desorption behavior of nonylphenol (NP) on the biodegradable microplastics in seawater. The adsorption capacity of NP on PLA (60.78 μg g−1) was approximately 50% lower than that on PE (116.53 μg g−1) which was the non-biodegradable microplastic control. Almost all biodegradable microplastics showed negligible desorption capacity compared to PE, indicating a lower environmental risk of biodegradable microplastics. The pH could influence the interaction between the NP and biodegradable microplastics through the formation of hydrogen bonds. The adsorption-desorption capacity of microplastics might increase at the condition of the high salinity and seawater erosion. Physical adsorption was the major adsorption processes based on the Gibbs free energy changes that calculated. The adsorption mechanism of microplastics was determined by calculating the crystallinity of microplastics, simulating the surface electrostatic potential of microplastics and conducting hydrophilicity tests of microplastics. The adsorption and desorption capacities of NP on biodegradable microplastics were mainly influenced by various mechanisms, including the crystallinity of the microplastics, hydrogen bonding and hydrophobic effects. These results will offer new perspectives on the interaction between biodegradable microplastics and NP in the ocean.

Stochastic dynamics mass spectrometric and Fourier transform infrared spectroscopic structural analyses of composite biodegradable plastics

<p>The (partial) replacement of synthetic polymers with bioplastics is due to increased production of conventional packaging plastics causing for severe environmental pollution with plastics waste. The bioplastics, however, represent complex mixtures of known and unknown (bio)polymers, fillers, plasticizers, stabilizers, flame retardant, pigments, antioxidants, hydrophobic polymers such as poly(lactic acid), polyethylene, polyesters, glycol, or poly(butylene succinate), and little is known of their chemical safety for both the environment and the human health. Polymerization reactions of bioplastics can produce no intentionally added chemicals to the bulk material, which could be toxic, as well. When polymers are used to food packing, then the latter chemicals could also migrate from the polymer to food. This fact compromises the safety for consumers, as well. The scarce data on chemical safety of bioplastics makes a gap in knowledge of their toxicity to humans and environment. Thus, development of exact analytical protocols for determining chemicals of bioplastics in environmental and food samples as well as packing polymers can only provide warrant for reliable conclusive evidence of their safety for both the human health and the environment. The task is compulsory according to legislation Directives valid to environmental protection, food control, and assessment of the risk to human health. The quantitative and structural determination of analytes is primary research task of analysis of polymers. The methods of mass spectrometry are fruitfully used for these purposes. Methodological development of exact analytical mass spectrometric tools for reliable structural analysis of bioplastics only guarantees their safety, efficacy, and quality to both humans and environment. This study, first, highlights innovative stochastic dynamics equations processing exactly mass spectrometric measurands and, thus, producing exact analyte quantification and 3D molecular and electronic structural analyses. There are determined synthetic polymers such as poly(ethylenglycol), poly(propylene glycol), and polyisoprene as well as biopolymers in bags for foodstuffs made from renewable cellulose and starch, and containing, in total within the 20,416–17,495 chemicals per sample of the composite biopolymers. Advantages of complementary employment in mass spectrometric methods and Fourier transform infrared spectroscopy is highlighted. The study utilizes ultra-high resolution electrospray ionization mass spectrometric and Fourier transform infrared spectroscopic data on biodegradable plastics bags for foodstuffs; high accuracy quantum chemical static methods, molecular dynamics; and chemometrics. There is achieved method performance |<em>r</em>| = 0.99981 determining poly(propylene glycol) in bag for foodstuff containing 20,416 species and using stochastic dynamics mass spectrometric formulas. The results highlight their great capability and applicability to the analytical science as well as relevance to both the fundamental research and to the industry.</p>

Effect of plastic additives on anaerobic biological reutilization of biodegradable plastics and sludge: Focusing on the digestion process, microbial composition and metabolic traits

The inevitable release of plastic additives (PAs) from biodegradable plastics (BPs) might affect the ensuing biological reutilization, and the impact of PAs on anaerobic co-digestion performance is still controversial. This study evaluated the impacts of three typical PAs (bis(2-ethylhexyl) phthalate (DEHP), acetyl tributylcitrate (ATBC), tributyl citrate (TBC)) on the BPs anaerobic co-digestion with waste-activated sludge (WAS). Results indicated that the BPs type had a significant effect on methane production, but the effect of PAs was negligible within a concentration range (0.5–50 mg/g TSS). Mechanistic exploration revealed that PAs addition exhibited insignificant effects on solubilization, hydrolysis, and acidification stage. Microbial communities' analyses suggested that PAs did not change the diversity and composition of microbial communities. Furthermore, the addition of PAs has no direct effect on the metabolic function of microorganisms. This study shed light on the effects of PAs on BPs biological reutilization and help to gain a better understanding of the potential environmental hazards of plastics.

Highly degradable bio-based plastic with water-assisted shaping process and exceptional mechanical properties

The fabrication of biodegradable and recyclable bio-based plastic by complexing carboxymethyl cellulose (CMC) and cationic polymeric ionic liquid (PILCl) assisted with KNO3 is offered to utilize plastics sustainably and mitigate serious threats to the environment. The CMC/PIL plastic film, formed via electrostatic interactions, exhibits exceptional mechanical properties that surpass those of most conventional plastics. It demonstrates a tensile strength of approximately 200 MPa and a Young's modulus of around 5.5GPa. Even after recycling and regeneration, they essentially retain the original mechanical characteristics with a tensile strength of about 190 MPa. These CMC/PIL plastic films can be processed into three-dimensional (3D) shapes assisted with water and their fundamental qualities maintain after numerous shaping. Besides, they possess excellent biodegradability and can finish biodegrading in a few hours with cellulase and within a few days when exposed to soil. This innovation provides a fresh and practical way to produce degradable plastics.

Comparative life cycle assessment of PBAT from fossil-based and second-generation generation bio-based feedstocks

With the increasing demand for plastics, plastic pollution is growing rapidly. A significant amount of plastic has leaked into the environment, leading to severe environmental issues. Biodegradable plastics are considered promising alternatives to conventional durable plastics, and the environmental impacts of biodegradable plastics have received increasing attention. Poly (butylene adipate-co-terephthalate) (PBAT) is a commercial and cost-competitive biodegradable polymer and has been applied in the packaging and agriculture sectors. The environmental performances of PBAT with second-generation feedstocks from forestry waste have been rarely investigated. Since China is the leading global producer and exporter of PBAT polymer, Chinese cradle-to-gate life cycle inventories of PBAT were compiled in this study. A comparative life cycle assessment (LCA) was conducted to explore the potential for environmental performance of PBAT with second-generation bio-based feedstock compared to fossil-based PBAT and conventional plastics. The results showed that feedstocks contributed to more than 70 % of 18 environmental impact categories of fossil-based PBAT. In comparison, PBAT with second-generation bio-based feedstock reduces the environmental loads in 16 impact categories by 15–85 %, and renewable energy substitution has the potential to reduce environmental impacts by 10 %. Bio-based PBAT performs better than PVC, PP, HDPE, LDPE, and PET in 16 impact categories by 15–80 %. Bio-based PBAT has GWP of 3.72 kg CO2 eq, which is 37 % lower than fossil-based PBAT (5.89 kg CO2 eq) and 18–32 % lower than conventional plastics. Since feedstock dominates the environmental performance of PBAT, the development of biomanufacturing technologies for bio-based polymers and chemicals could significantly improve environmental performance of biodegradable plastics and promote the sustainable development of the plastic industry. Results could serve as the basis for environmental impact and mitigation strategies for biodegradable plastics with bio-based feedstocks, as well as the sustainable development of the PBAT industry.

Novel insights into photoaging mechanisms and environmental persistence risks of polylactic acid (PLA) microplastics: Direct and indirect photolysis

Polylactic acid (PLA), as a biodegradable plastic, exhibits high sensitivity to ultraviolet (UV) radiation, yet the mechanisms and environmental risks of its photoaging remain unclear. This study uses quantum chemical calculations (DFT and TD-DFT) and kinetic simulations to explore the direct and indirect photoaging of PLA. Direct photoaging indicates that the highest oscillator intensity absorption peaks occurred at 172 and 246 nm, corresponding to the 13th singlet (S13) and 48th triplet (T48) states, thereby initiating the Norrish I and Norrish II mechanisms. The innovative “electron-hole” technology effectively clarifies the variations in photoaging mechanisms under different wavelengths. Indirect photoaging involves multiple reactive oxygen species (ROS) like •OH, 1O2, •O2−, and •HO2. The study confirms the anhydride production hypothesis and proposes two novel •OH-induced mechanisms: carbonyl carbon addition and branched methyl hydrogen dehydrogenation. Both mechanisms are thermodynamically advantageous, but their products pose potential environmental risks. ROS species and concentrations impact both PLA's photoaging mechanisms and environmental persistence. Low •OH concentration in northeast China, especially in winter, suggests a significant photoaging risk. This study offers pioneering insights into photoaging mechanisms and emphasizes the pivotal role of ROS, offering recommendations for managing PLA environmental impacts and fates in China.

Effect of iron oxidation state on the catalytic performance of Fe/C in liquid phase flow hydrogenation of 2-butyne-1,4-diol

Cis-2-butene-1,4-diol and 1,4-butanediol are crucial precursors in producing bioplastics and biodegradable plastics. Moreover, cis-2-butene-1,4-diol is used in the production of vitamins A and B6, fungicides and insecticides. On an industrial scale, they are produced by hydrogenation of 2-butyne-1,4-diol with Ni Raney as catalyst at > 160 °C and > 15 MPa. Herein, the effect of mesoporous carbon, iron loading (2, 6, 10 and 14 wt%), and metal oxidation state on the activity and selectivity of iron catalysts in the liquid phase continuous flow 2-butyne-1,4-diol hydrogenation at mild conditions (at temperature range 10–65 °C and pressure range 1–20 bar) was performed. Catalytic investigations supported by statistical modeling and physicochemical characterization (TPR, H2-TPD, physisorption, TEM, XPS, and Mössbauer spectroscopy), showed that the activity of the Fe/C can be determined by the presence of functional groups in mesoporous support which are responsible for high metal dispersion and strong metal-support interaction, which boosts the catalytic activity of iron catalysts. Additionally, the formation of metastable iron carbides which are active in hydrogenation cannot be excluded. All of the catalysts showed 100% selectivity toward cis-2-butene-1,4-diol at the lowest temperature. However, the best compromise between selectivity and activity (TOF=336 h−1) was achieved with 2 wt% Fe at 1 bar and 25 °C.