Addition Of High-density Polyethylene Research Articles

Moisture damage resistance of pyro-oil modified bitumen with hydrated lime using surface free energy approach

Moisture damage (MD) in bituminous mixtures occurs due to the loss of cohesion in the bitumen or adhesion between the binder and aggregates. The existence of moisture may influence the bonding between aggregates and bitumen, which may affect the moisture susceptibility of the bituminous mix. Therefore, there is a need to understand the bonding-debonding properties and the moisture susceptibility of binders and mixes, at the material selection stage. Surface free energy (SFE) method is one of the proven techniques to quantify the moisture susceptibility of bituminous mixtures, by using contact angle (CA) determination of the component materials of the mix. This study aimed to evaluate the effect of hydrated lime (HL) on the moisture susceptibility of bituminous mixtures, with control (VG30) bitumen and pyro-oil modified bitumen (POMB) having different percentages of pyro oil, using the SFE approach. Also, the study compared the SFE characteristics of VG30 and POMB with and without the optimum content of HL. POMB binders were prepared by the addition of high-density polyethylene (HDPE) pyro oil in percentages of 1, 3, and 5% in a control bitumen. HL was added as 20%, 25%, and 30% by weight of bitumen in VG30 and POMB bitumen. The aggregates used in the study were limestone, basalt, gravel, and their SFE components were directly considered from the literature. The sessile drop method was used to measure the CA of bitumen and, in turn, determine the various SFE parameters using Van Oss–Chaudhury–Good theory. The moisture susceptibility of mixtures with and without HL was evaluated and compared. From the results, the MD resistance of the bituminous mixtures with modified and unmodified bitumen was found to be increased after the optimum of HL, depending upon the type of aggregates used. Basalt has a 27.41%, 23.38%, and 10.48% greater energy ratio (ER) with POMB1/25, POMB3/25, and POMB5/30, respectively, than VG30/30, the highest ER in modified base bitumen. This indicates that HDPE pyro-oil treatment improves MD resistance for basalt. Whereas for limestone and gravel, VG30/30 gives a maximum value of ER as compared to any other combination of HL modified POMB. The ER values would assist highway agencies in selecting the most compatible binder–aggregate combinations.

Thermoformed products from high-density polyethylene and Softwood kraft pulp.

Plastic recycling, waste minimization such as process outfall valorization promotes a circular economy. Herein, food trays have been produced in the moulded pulp thermoforming process. To this end, high-density polyethylene (HDPE) outfall has been dispersed in water via Poly vinyl alcohol (PVA) addition in a Northern Bleached Softwood KraftPulp (NBSKP) slurry. Samples physical and mechanical properties have been evaluated. With an increasing HDPE content, parts air permeability was drastically reduced to a minimum of 2.4±0.8 mL min-1. In addition, water and grease hold out properties have been increased with minimum waterCobb1800 value of 10.9±5.4 gm-2 and oil Cobb1800 value of13.18±6.5 gm-2. Samples with high HDPE content demonstrated hydrophobic surface with water contact angle value above 90°. HDPE melting and binding to wood pulp fibers was monitored by SEM images. Regarding the mechanical properties, HDPE induced plastic deformation with a reduced Young modulus by 17 %. Moreover, the addition of HDPE increased wet strength by 81 %. However, the produced foodtray composites with high HDPE content demonstrated low repulpability index.

Performance evaluation of SBS-modified asphalt mixtures incorporating waste tire rubber and HDPE

Based on the functional complementarity of waste tire rubber (WTR) and waste high-density polyethylene (HDPE) in asphalt, this study presents a novel approach that simultaneously utilizes WTR and HDPE for modification and substitution of styrene-butadiene-styrene (SBS) modified asphalt. Through experiments on three major indicators, the dosage ratios of the three polymers are scientifically designed using the response surface methodology, and four different ratios of SBS-HDPE-WTR are selected to prepare modified asphalt mixtures. Performance evaluations are conducted on various pavement properties, including high-temperature stability, low-temperature crack resistance, water stability, fatigue resistance, and aging resistance, by comparing them to the reference 4% SBS-modified asphalt mixture. The results demonstrate that the addition of WTR significantly improves the elastic properties and fatigue resistance of the mixture, while the addition of HDPE enhances its high-temperature stability and aging resistance. The SBS-HDPE-WTR asphalt mixtures, designed with appropriate ratios, exhibit superior high-temperature stability, low-temperature crack resistance, and fatigue resistance. Therefore, the use of these waste materials in asphalt mixtures offers a sustainable and environmentally friendly solution for the construction industry.

Effects of process conditions and nano-fillers on the cell structure and mechanical properties of co-injection molded polypropylene-polyethylene composites

Compared with traditional injection foaming, co-injection foaming serves as a method to prepare products with high-quality surfaces and enhanced mechanical properties, demonstrating excellent technical advantages and economic benefits. The effects of high-density polyethylene (HDPE) content, foaming agent content, melting temperature of core material, and nano-organic montmorillonite (OMMT) content on the cell structure, mechanical properties, and crystallization behavior of isotactic polypropylene (iPP)/HDPE composite foam prepared by co-injection foaming were systematically studied. At a foaming agent content of 2 wt.%, HDPE content of 30 wt.%, OMMT content of 3 wt.%, and the melting temperature of core material of 190 °C, the composite foam exhibited a cell size measuring 85 μm, a cell density of 2.5 × 105 cells/cm3, a tensile strength of 25.8 MPa, and an impact strength of 12.5 kJ/m2. The addition of HDPE reduced the crystallinity of iPP matrix, while enhancing the solubility of carbon dioxide within the matrix. The non-miscible interface between HDPE and iPP helped reduce the energy barrier for cell nucleation. Furthermore, the introduction of OMMT as a nucleating agent in iPP/HDPE composite material dramatically decreased the energy barrier for cell nucleation. These synergistic effects result in foam with the smaller cell size and the higher cell density, exhibiting excellent comprehensive mechanical properties. This work provides a feasible method for preparing composite foam with excellent comprehensive performance.

Selected properties of MDF boards bonded with various fractions of recycled HDPE particles

Selected properties of MDF boards bonded with various fractions of recycled HDPE particles.The substitution of non-renewable, formaldehyde-based amine wood binders in the wood-based composites industry is one of the main directions of trials and research. On the other hand, a bigger effort should be put into carbon capture and storage (CCS) activity, especially in the case of oil-based plastics, to extend their life in the products. The aim of the research was to use waste high-density polyethylene (HDPE) in MDF panels and determine their selected properties, including modulus of elasticity in bending, bending strength, internal bond, thickness swelling, water absorption, screw withdrawal resistance, density profile when referred to the fraction of used HDPE.The panels were created in laboratory conditions with a 50% weight content of HDPE particles of different fractions (<1 mm, <2 mm, <4 mm, and a mixed fraction containing 25% of each fraction and unsorted waste). The results show that the highest strength and modulus of elasticity were obtained for panels with plastic fractions below 1 mm. This fraction also achieved the lowest results for water absorption and thickness swelling. The fraction of the used plastic has no significant effect on screw withdrawal resistance. The negative impact of using larger fractions in the board is noticeable, however, for the mixed fraction, the results are similar to the finest fraction in terms of the internal bond, thickness swelling, and water absorption. The addition of HDPE can have a beneficial effect on the parameters of MDF panels. It is possible to create fibreboards from wasted plastic, store carbon dioxide in them, and upcycle them. In the discussed panels, the only binder for wood fibres was HDPE, so panels should not emit formaldehyde from the binder.

Analysis of the thermal characteristics of the paraffin wax/high-density polyethylene (HDPE) composite as a form-stable phase change material (FSPCM) for thermal energy storage

The present work is specifically focused on the form stability of paraffin as a phase change material (PCM) through the addition of high-density polyethylene (HDPE). The aim of adding HDPE is to obtain a stable form of paraffin during the phase transition. Moreover, improving the performance of PCM leads to an advanced operation of the latent heat storage unit with an excellent charging duration and response time. The study uses HDPE at a ratio of 5 wt %, 10 wt % and 15 wt %. The results indicate significant differences between the form-stable PCM (FSPCM) and pure paraffin. For instance, the supercooling degree is decreased with the addition of HDPE, where paraffin has a supercooling degree of 8.01 °C while FSPCM with 15 wt % HDPE has a supercooling degree of 3.73 °C. The latent heat of fusion by adding 10 wt % and 15 wt % HDPE is slightly decreased by 1.85 %, which is much lower compared to adding 5 wt % HDPE, which reduces the latent heat of fusion by about 6.02 %. Adding HDPE leads to a faster charging process and a better response time during the discharging process. The charging rate is increased significantly by adding 15 wt % HDPE with a substantial increment of around 40 % with an average charging rate of 2.39 °C/min. The heat release during the discharging process is increased for FSPCM with 5 wt % HDPE where the temperature drops by more than 70 °C within 20 minutes. The findings indicate that adding HDPE contributed positively to reducing the supercooling degree and providing a steady phase transition. Thus, the heat exchange process of paraffin is more favorable, which improves the performance of the latent heat storage unit. Furthermore, the operation can be improved significantly by providing a faster charging and discharging process

Co-pyrolysis of pinewood and HDPE: pyrolysis characteristics and kinetic behaviors study

Abstract Co-pyrolysis of lignocellulosic biomass and hydrogen-rich petroleum-based polyolefin plastics is a promising to way to improve bio-oil quality and alleviate the waste plastic pollution issues. In this study, co-pyrolysis of pinewood and HDPE was systematically investigated. The addition of HDPE decreased yield of char and gas while increased that of bio-oil, enhancing the selectivity to alcohols and hydrocarbons. The most obvious synergistic effect was observed at the HDPE mixing proportion of 0.25, at which hydrocarbon selectivity derived from co-pyrolysis experiments was 41.19% higher than the calculated weighted average values. As pyrolysis temperature increased from 500°C to 700°C, the yield of bio-oil from co-pyrolysis at the HDPE mixing proportion of 0.25 decreased from 69.11 wt.% to 50.33 wt.%, alkanes selectivity decreased from 27.41% to 3.67% and olefins selectivity increased from 14.96% to 47.12%. At 700°C, aromatics started to produce with a selectivity of 15.50%. The surface morphologies of char were not significantly affected by the HDPE mixing proportion and pyrolysis temperature. The thermogravimetric analysis results revealed that the global co-pyrolysis process can be divided into two major degradation stages, based on which multi-step method was adopted to analyze the kinetics of the process. The average apparent activation energies of stage I and stage II were 167.73 kJ/mol and 274.74 kJ/mol, respectively. The results from this work provide a theoretical guide for further development of co-pyrolysis of pinewood and high-density polyethylene (HDPE).

Effect of Vegetable Oil on the Properties of Asphalt Binder Modified with High Density Polyethylene.

Economic development results in increased traffic and higher traffic loads that often cause serious asphalt pavement problems, such as permanent deformation, fatigue cracking, and reduced lifetime. Polymers are seen as viable asphalt additives to minimize these problems. However, their incorporation reduces the workability of the material due to the increase in the viscosity of the blend. This study evaluates the effect of the addition of soybean oil on the physical, rheological, and thermal properties of high-density polyethylene (HDPE)-modified asphalt binder. The HDPE was kept at 5 wt.% and the soybean oil the asphalt was varied from 1 to 7 wt.%. A series of tests was conducted to evaluate the binders, comprising conventional tests (penetration, softening point, and ductility) rheological performance tests (dynamic viscosity and short-term aging (RTFO), and thermogravimetric analysis (TGA). The addition of HDPE reduced the penetration and increased the softening point and viscosity. The oil reduced steadily the viscosity, improved the workability and the thermal susceptibility of the modified asphalt up to 3 wt.% of oil, and reduced about 92% mass gain after aging. Hence, the oil is considered a good modifier agent for the improvement of polymer-modified asphalt's workability under service conditions.

Effects of single and combined contamination of microplastics and cadmium on soil organic carbon and microbial community structural: A comparison with different types of soil

Microplastics (MPs) are an emerging contaminant that have attracted a growing concern about their behavior in soil environment in recent years. However, the research on the interaction between MPs and heavy metal pollution in the soil environment is still scarce. This study investigated the effects of high–density polyethylene (HDPE) and Cd on two soil types (phaeozem and fluvo–aquic soil), and explored their interaction mechanisms. The addition of HDPE significantly increased the content of available Cd in the phaeozem and enhanced the soil organic carbon (SOC) content and the abundance of microbial available carbon source. The presence of Cd reduced the content of SOC and dissolved organic carbon (DOC) in phaeozem and changed the soil bacteria community structure. The combined pollution of HDPE and Cd had a superimposed effect on the increment of DOC content in fluvo–aquic, and in phaeozem, the combined pollution had an antagonistic effect on SOC and DOC. In conclusion, the coexistence of MPs and Cd would affect soil carbon cycling and microbial community structure, especially in phaeozem. These results contribute to understanding the effects of MPs and/or Cd on soil biological properties.

Comprehensive Study on the Performance of Waste HDPE and LDPE Modified Asphalt Binders for Construction of Asphalt Pavements Application.

This research is aimed at investigating the mechanical behavior of the bitumen by the addition of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) obtained from waste plastic bottles and bags. Polymers (HDPE and LDPE) with percentages of 0%, 2%, 4%, and 6% in shredded form by weight of bitumen were used to evaluate the spectroscopic, structural, morphological, and rheological properties of polymer-modified binders. The rheological properties for different factors; viscosity (ἠ) from Rotational Viscometer (RV), rutting factor G*/Sin (δ), fatigue characteristics G*. Sin (δ), for the modified binder from dynamic shear rheometer (DSR), Short and long-term aging from rolling thin film oven (RTFO), and pressure aging vessel (PAV) was determined. The thermal characteristics, grain size, and texture of polymers for both LDPE and HDPE were found using bending beam rheometer (BBR) and X-ray diffraction (XRD), respectively. Fourier transform infrared (FTIR) analysis revealed the presence of polymer contents in the modified binder. Scanning electron microscopy (SEM) images revealed the presence of HDPE and LDPE particles on the surface of the binder. Creep Rate (m) and Stiffness (S) analysis in relationship with temperature showed a deduction in stress rate relaxation. Results have revealed the best rutting resistance for 6% HDPE. It also showed an improvement of 95.27% in G*/Sin (δ) which increased the performance of the bituminous mix. Similarly, the addition of 4% LDPE resulted in maximum dynamic viscosity irrespective of the temperatures. Moreover, fatigue resistance has shown a significant change with the HDPE and LDPE. The festinating features of waste plastic modified binder make it important to be used in the new construction of roads to address the high viscosity and mixing problems produced by plastic waste and to improve the performance of flexible pavements all over the world.

Pelletizing ultra-high molecular weight polyethylene (UHMWPE) powders with a novel tapered die and addition of high density polyethylene (HDPE): Processing, morphology, and properties

The extremely high molecular weight and molecular entanglement have rendered ultra-high molecular weight polyethylene (UHMWPE) superior properties. However, poor inter-particle diffusion makes it difficult to pelletize UHMWPE powders for easy processing/handling. A novel tapered die with air cooling was proposed to pelletize UHMWPE and a UHMWPE blend with 5 wt% high-density polyethylene (HDPE) for compression molding and material characterization. The tensile strength of samples prepared with the tapered die outperformed those by the regular die or from virgin powders. The addition of HDPE further improved the tensile strength. Fourier transform infrared spectroscopy (FTIR) revealed little chain scission and the lowest amount of oxidation from the tapered die. Intrinsic viscosity (IV) measurements confirmed the negligible chain scission and showed an increment in IV for the UHMWPE/HDPE blend. Multi-angle light scattering with size-exclusion chromatography (SEC-MALS) indicated no change in the UHMWPE molecular weight distribution, but some crosslinking in the blend. Polarized optical microscopy (POM) showed that the HDPE and extrusion led to a finer UHMWPE domain size and better fusion between UHMWPE and HDPE. The combined effect of enhanced molecular chain diffusion, improved consolidation, and lower oxidation using the tapered die led to 40% improvement of tensile strength for the UHMWPE/HDPE blend.

Conversion Of GeNose C-19 Plastic Waste And HDPE (High Density Poly Ethylene) Into Alternative Energy Bio-Oil Using The Co-Pyrolysis Method

Background: Covid-19 has spread to various countries in the world, one of which is Indonesia. The positive cases until March 29, 2021, have reached one and a half million cases and still increasing. GeNose is the latest Covid-19 testing tool that is able to detect the presence of Covid-19 with a sensitivity level of 89-92% and a specification of 95-96%. The ease of using GeNose C-19 has increased so that GeNose C-19 plastic waste also increases. If this is not considered, it will cause a new problem, such as the accumulation of plastic waste caused by the use of the GeNose C-19 tool. Method: As solution to handling that problem, we utilize GeNose plastic waste with addition of HDPE (High Density Poly Ethylene) plastic to produce alternative bio-oil energy products. The methods used in this research are quantitative and qualitative methods with literature studies and research, where we collect data from various scientific journal including Garuda Ristekdikti, SINTA, and Google Scholar using the keywords GeNose waste, Pyrolysis, Plastic waste. In addition, we use the research process using a pyrolysis reactor. Result: The resulting liquid from pyrolysis method is in the form of bio oil which can be used as an alternative energy material. However, the bio oil produced from the pyrolysis process does not produce high quantitative results. So, we combine with HDPE plastic with a ratio of 1:1 (Co-Pyrolysis) to get better results quantitative or qualitative and also have a better indication. Conclusion: GeNose plastic waste treatment with the pyrolysis method with the addition of HDPE raw materials produces bio-oil products in larger quantities. In addition, the pyrolysis of GeNose plastic waste with the addition of HDPE, has a better and longer fuel power than bio oil from the pyrolysis of pure GeNose plastic waste. Keywords: Covid, GeNose, HDPE, Pyrolysis.

Improvement of coke strength by HDPE addition

ABSTRACT Plastic waste of different origin has been proposed and used as an additive in coal blends in metallurgical coke production for trace amounts for about two decades. Previous studies have suggested that high-density polyethylene (HDPE) can be used as an additive in coking blends for small quantities (2–3 wt% of the blend) without considerably damaging the strength properties of coke. Here, one HDPE-free and five HDPE-bearing laboratory-made cokes were produced and tested for their compressive cold strength and compressive hot strength. The temperature in the hot compressive strength tests was 1,700°C, corresponding to the temperature of the blast furnace bosh area near the tuyeres. The results showed that the trend of the cold compressive strength of coke increased as the amount of HDPE in the coking blend was increased from 0 wt% to 5 wt%. In hot compressive strength tests, cokes containing 3 wt% to 5 wt% of HDPE in the raw material blend showed non-breaking behavior, while the reference coke samples were crushed to pieces in the tests. Image analysis performed for the microscopic images of all experimental coke types revealed that the high number and area percentage of large pores impacted negatively on compressive strength of coke.

Increasing the rating performance of paraffin up to 5000 cycles for active latent heat storage by adding high-density polyethylene to form shape-stabilized phase change material

The unstable phase transition of pure paraffin limits its application, particularly for active latent heat storage (ALHS). In passive latent heat storage, the addition of high-density polyethylene (HDPE) can decrease paraffin's leakage rate, which is associated with unstable phase transition and increase its durability after a large thermal number. This study aims to discover the possibility to use HDPE as a shape-stabilizer to increase the paraffin's performance for the ALHS system. Pure paraffin and composite paraffin/HDPE (80:20 wt%) are prepared as the reference material. The evaluation is focused on thermal properties, stability and performance during charging and discharging under different thermal cycles. Thermal cycle treatment uses temperature as a working boundary where the sample is heated from 30°C to 150°C, then cooled back to 30°C and repeated until 5000 cycles. Three different cycle references are chosen (1, 1000 and 5000 cycles) for each evaluation. The melting temperature of paraffin is decreased from 61.6°C to 59.8°C after 5000 cycles where Paraffin/HDPE slightly decreased from 60.4°C to 60.1°C. The heat fusion is decreased by 8.7% and 2.9% for paraffin and Paraffin/HDPE, respectively. The isothermal phase change is observed for paraffin/HDPE even after 5000 cycles with a higher rating performance by 30% faster to complete one cycle than pure paraffin. The other thermal performance is discussed in detail within the article, including the phase transition model during charging and discharging for the sample.

Heat Transfer Modeling of Oriented Sorghum Fibers Reinforced High-Density Polyethylene Film Composites during Hot-Pressing.

A one-dimensional heat transfer model was developed to simulate the heat transfer of oriented natural fiber reinforced thermoplastic composites during hot-pressing and provide guidance for determining appropriate hot-pressing parameters. The apparent heat capacity of thermoplastics due to the heat of fusion was included in the model, and the model was experimentally verified by monitoring the internal temperature during the hot-pressing process of oriented sorghum fiber reinforced high-density polyethylene (HDPE) film composites (OFPCs). The results showed that the apparent heat capacity of HDPE accurately described its heat fusion of melting and simplified the governing energy equations. The data predicted by the model were consistent with the experimental data. The thermal conduction efficiency increased with the mat density and HDPE content during hot-pressing, and a higher mat density resulted in a higher mat core temperature. The addition of HDPE delayed heat transfer, and the mat had a lower core temperature at a higher HDPE content after reaching the melting temperature of HDPE. Both the experimental and simulated data suggested that a higher temperature and/or a longer duration during the hot-pressing process should be used to fabricate OFPC as the HDPE content increases.

Investigation of Biochar Production from Copyrolysis of Rice Husk and Plastic.

Biomass renewable energy has become a major target of the Thailand Alternative Energy Development Plan (AEDP) since the country’s economy is largely based on agricultural production. Rice husk (RH) is one of the most common agricultural residues in Thailand. This research aims to investigate yields and properties of biochar produced from copyrolysis of RH and plastic (high-density polyethylene (HDPE)) at different ratios, temperatures, and holding times. For both individual and copyrolysis, the temperature variation generated more pronounced effects than the holding time variation on both biochar yields and properties. For individual pyrolysis of RH, the maximum biochar yield of ∼54 wt % was obtained at 400 °C. A shift in temperature from 400 to 600 °C resulted in RH biochars with higher fixed carbon (FC) and carbon (C) contents by ∼1.11–1.28 and 1.06–1.22 times, respectively, while undetectable changes in higher heating values (HHVs) were noticed. For copyrolysis, obvious negative synergistic effects were observed due to the radical interaction between the rich H content of HDPE and RH biochars, which resulted in lower biochar yields as compared to the theoretical estimation based on individual pyrolysis values. However, the addition of HDPE positively impacted the FC and C contents, especially when 10 and 20 wt % HDPE were added to the feedstock. Besides, higher HDPE blending ratios resulted in biochars with improved HHVs, and >1.5 times improvement in HHV was reported in the biochar with 50 wt % HDPE addition in comparison with RH biochar obtained under the same conditions. In summary, biochars generated in this study have the potential to be utilized as a solid fuel or soil amendment.

Torrefaction and Pelleting of Wheat and Barley Straw for Biofuel and Energy Applications

Microwave (MW)-assisted torrefaction and pelleting could enhance biomass fuel properties and energy applications. Plastic wastes are considered as a replacement source binder in pellets to minimize their effect on the environment as pollutants. High-density polyethylene (HDPE), an extractable plastic from recycling waste, was investigated as a binder for torrefied wheat and barley straw pellets. Fuel pellet characteristics, such as durability, density, tensile strength, and water absorption, were used to evaluate the pellets produced from a single pelleting test. The results showed that the addition of HDPE as a binder significantly increased the pellet quality in terms of density (686.12–982.93 kg/m3), tensile strength (3.68 and 4.53 MPa) for wheat and barley straw, and reduced ash content of the pellet from 10.34 to 4.59% for barley straw pellet and 10.66 to 3.88% for wheat straw pellets. The higher heating value (HHV) increased with increasing biochar mix and HDPE binder blend. The highest HHV value observed for barley straw was 28.34 MJ/kg, while wheat straw was 29.78 MJ/kg. The study further indicated that MW torrefaction of biomass-biochar mix with HDPE binder reduced the moisture adsorption of wheat and barley straw pellets, which can significantly improve their storage capability in humid locations. The moisture uptake ratio for MW-torrefied barley straw pellets was 0.10–0.25 and wheat straw pellets 0.11–0.25 against a moisture uptake ratio of 1.0 for untreated biomass. MW torrefaction of wheat and barley straw with biochar and HDPE binder addition during pelleting is a promising technique to improve biomass fuel pellet properties.

Effects of plastics on reactor performance and microbial communities during acidogenic fermentation of food waste for production of volatile fatty acids

The aim of this work was to study the effects of plastics (high-density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET)) on reactor performance and microbial communities during acidogenic fermentation of food waste for the production of volatile fatty acids (VFA). The addition of HDPE and PS increased total VFA yields by 28% and 47%, respectively, whereas the addition of PP and PET decreased total VFA yields by 6% and 2%, respectively. The highest enhancing performance of PS could be ascribed to its highly porous structure that could provide immobilization effects for microbial growth. Degradation of various plastics was confirmed by FESEM results, but the degrees were limited (i.e., 3.9–8.7%). Bacterial analysis showed that the addition of various plastics altered the community diversity. Phylum Thermotogae and genus Defluviitoga dominated all the reactors. Potential HDPE- and PS-degrading microbes could belong to genus Clostridium_sensu_stricto_8, while Tepidanaerobacter_syntrophicus could be PET-degrading microbes.

Influences of different source microplastics with different particle sizes and application rates on soil properties and growth of Chinese cabbage (Brassica chinensis L.)

The potentially negative effects of microplastics (MP) on agroecosystems have raised worldwide concerns. However, little is known about the negative effects of MP exposure on the soil–plant system. To fill up this knowledge gap, a pot experiment was set up, and two different MP types [high density polyethylene (HDPE) and general purpose polystyrene (GPPS)] were used, which had four particle sizes (<25, 25–48, 48–150, and 150–850 µm) at four application rates (2.5, 5, 10, and 20 g MP kg−1 soil). Some soil properties and the growth of Chinese cabbage (Brassica chinensis L.) were monitored. The results showed that (1) MP application with high application rates and relatively small particle sizes significantly enhanced the soil urease activity, which accompanied with enhanced soil pH and decreased soil available concentrations of phosphorus and potassium in some cases. (2) The exposure of MP did not significantly affect the activity of soil catalase regardless of their application rates and sizes. MP with different application rates and small sizes significantly reduced the soil sucrase activity, but the largest size of MP enhanced the activity of soil sucrase. (3) GPPS at 10–20 g kg−1 or with the sizes of <25 and 48–150 µm significantly reduced the fresh weight of Chinese cabbage, but the addition of HDPE had no remarkable effects on the fresh weight regarding of its application rates or sizes. (4) MP with high application rates and large sizes enhanced but small sizes of MP reduced the leaf soluble sugar concentration. The increasing application rates of MP and small size HDPE significantly reduced the starch concentration in the leaves of Chinese cabbage, however, the different sizes of GPPS showed limited effects on the leaf starch. The addition of MP with increasing application rates and different sizes always reduced the concentration of leaf chlorophyll. These parameters regarding to plant and soil could be used to assess the risks of MP pollution in the soil–plant systems. We found that the risks resulting from MP pollution were MP type-dependent and particle size-dependent. These findings indicate that overaccumulation of MP in the agriculture may possess an ecology risk and will negatively affect the agricultural sustainability and the food safety.

Insight into co-pyrolysis interactions of Pingshuo coal and high-density polyethylene via in-situ Py-TOF-MS and EPR

In-situ detection on primary volatiles interactions and stable radical evolution behaviors during co-pyrolysis of Pingshuo coal (PC) and high-density polyethylene (HDPE) were systematically investigated via a novel in-situ pyrolysis time-of-flight mass spectrometry (in-situ Py-TOF-MS) combined with electron paramagnetic resonance (EPR) spectroscopy. TG results demonstrated that the mixing ratio 7:3 for PC/HDPE has the better positive interaction performances. Accordingly, in-situ Py-TOF-MS results revealed that more short-chain alkenes such as butene and heptadiene are formed in co-pyrolysis, and the addition of HDPE remarkably enhances the transfer of hydrogen (H) to react with the phenoxy group from PC to form diphenol. According to the EPR analysis, HDPE has a remarkable effect on the stable radical concentration (Ng) in PC pyrolysis residue, especially for oxygen (O)-centered and C-centered radicals. Meanwhile, higher temperature is favorable to the generation of O-centered radicals in PC/HDPE (7:3) pyrolysis residue, its radical concentration increases from 3.42 × 1018 to 20.85 × 1018 spins/g. Furthermore, the peak of CO bond exists at a higher temperature, which is consistent with the changes of O-centered radical concentration, and this result can provide effective supplements for understanding the stable radical interactions.