Low-density Polyethylene Particles Research Articles

Biodegradable microplastics: Uptake by and effects on the rockpool shrimp Palaemon elegans (Crustacea: Decapoda)

Ingestion of microplastics can lead to deleterious consequences for organisms, as documented by numerous laboratory studies. The current knowledge is based on a multitude of effect studies, conducted with conventional fossil-based and non-degradable plastics. However, there is a lack of information about the acceptance and the effects of novel bio-based and biodegradable plastics. Biodegradable plastics are considered an alternative to conventional plastics and are showing rapidly growing production rates. Biodegradable plastics can disperse into the environment in the same way as conventional plastics do, becoming available to marine organisms. This study aims to provide new insights into the uptake and effects of biodegradable microplastics on marine invertebrates. Rockpool shrimp, Palaemon elegans, were fed with algal flakes coated with polylactic acid (PLA), polyhydroxybutyrate-co-valerate (PHBV) and conventional low-density polyethylene (LDPE) microparticles. Live observations showed that all of the different types of microplastics were ingested. After dissection of the shrimp, less LDPE particles were found in the stomachs than PLA and PHBV particles. This indicates a longer retention time of biodegradable microplastics compared to conventional microplastics. Presumably, less LDPE particles were ingested or evacuated from the stomach, probably by regurgitation. The ingestion of microparticles of all types of plastics induced enzymatic activity of short-chain carboxylesterases in the midgut glands of the shrimp. However, only PLA induced enzymatic activity of medium-chain carboxylesterases. Palaemon elegans showed no oxidative stress response after ingestion of microparticles, irrespective of polymer type. From our results we conclude that biodegradable plastics might have different effects than conventional plastics. The longer retention times of biodegradable plastics might enhance exposure to leaching additives and other harmful substances. Our study provides new insights into how biodegradable plastics might affect aquatic fauna and indicate that the use of biodegradable plastics needs to be reconsidered to some extent.

Spectroscopic evidence for adsorption of natural organic matter on microplastics

AbstractThe interaction of microcroplastics (MP) with dissolved organic matter, especially humic substances, is of great importance in understanding the behavior of microplastics in aquatic ecosystems. Surface modification by humic substances plays an essential role in transport and interaction of MP with abiotic and biotic components. Previous studies on the interaction between MP and humic substances were largely based on a model compound, humic acid (Sigma‐Aldrich). In our work, we therefore investigated the interaction of natural organic matter (NOM) sampled from a German surface water with low‐density polyethylene particles (LDPE). High‐pressure size exclusion chromatography (HPSEC) and UV/vis absorption and fluorescence spectroscopy were used to characterize the incubation solutions after modifications due to the presence of LDPE, and Raman spectroscopy was used to characterize the incubated microplastics. While the studies of the solutions generally showed only very small effects, Raman spectroscopic studies allowed clear evidence of the binding of humic fractions to MP. The comparison of the incubation of NOM and a lignite fulvic acid which also was tested further showed that specific signatures of the humic substances used could be detected by Raman spectroscopy. This provides an elegant opportunity to conduct broader studies on this issue in the future.

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.

Measuring binary fluidization of nonspherical and spherical particles using machine learning aided image processing

AbstractThe binary fluidization of Geldart D type nonspherical wood particles and spherical low density polyethylene (LDPE) particles was investigated in a laboratory‐scale bed. The experiment was performed for varying static bed height, wood particles count, as well as superficial gas velocity. The LDPE velocity field were quantified using particle image velocimetry (PIV). The wood particles orientation and velocity are measured using particle tracking velocimetry (PTV). A machine learning pixel‐wise classification model was trained and applied to acquire wood and LDPE particle masks for PIV and PTV processing, respectively. The results show significant differences in the fluidization behavior between LDPE only case and binary fluidization case. The effects of wood particles on the slugging frequency, mean, and variation of bed height, and characteristics of the particle velocities/orientations were quantified and compared. This comprehensive experimental dataset serves as a benchmark for validating numerical models.

Nile Red staining for detecting microplastics in biota: Preliminary evidence

Nile Red is a lipophilic, metachromatic and solvatochromic dye used as an alternative or complementary method to aid identification of microplastics in routine analysis of biological samples. It was rarely used in biota since organic residues after the digestion step can be co-stained with possible overestimation of microplastics. The limits of using Nile Red in biota were investigated in marine mussels experimentally contaminated with low-density polyethylene (LDPE) microplastics. Stained particles were detected through magnified images obtained by stitching together thirty photographs of the filter surface of each sample. LDPE particles appeared yellowish and fluorescent and could be confused with certain organic residues. The smaller the fragments, the greater the difficulty in recognizing them. In particular, it was difficult to recognize LDPE particles based on their fluorescence if <180 μm in size. Regardless of the size, fluorescence of the items aids the operator in LDPE particles identification also in biota.

The Effect of Polymer Waste Addition on the Compressive Strength and Water Absorption of Geopolymer Ceramics

The quantity of polymer waste in our communities is increasing significantly. It is therefore necessary to consider reuse or recycling waste to avoid an increase in the risk to public health. This project is aimed at using pulverized low-density polyethylene (LDPE) waste as a source to reinforce and improve compressive strength, and to reduce the water absorption of geopolymer ceramics (GC). Clay:LDPE composition consisting of 5%, 10%, and 15% LDPE was geopolymerized with an NaOH/Na2SiO3 solution and cured at 30 °C and 50 °C. Characterization of the geopolymer samples was carried out using XRF and XRD. The microstructure was analyzed by SEM and chemical bonding by FTIR. The SEM micrographs showed LDPE particle pull-out on the geopolymer ceramics’ fracture surface. The result showed that the compressive strength increases with the addition of pulverized polymer waste compared to the controlled without LDPE addition. Water absorption decreased with an increase in LDPE addition in the geopolymer ceramics composite.

Biofilm development of Bacillus siamensis ATKU1 on pristine short chain low-density polyethylene: A case study on microbe-microplastics interaction

A low-density polyethylene (LDPE) degrading bacterial strain (ATKU1) was isolated (99.86% similar with Bacillus siamensis KCTC 13613T) from a plastic dumping site to study interactions between microplastics (< 5 mm) and microorganisms. The strain was found (by scanning electron microscopy) to form biofilm on the microplastic surface after its interaction with LDPE (avg. Mw~4,000 Da and avg. Mn~1,700 Da) as a sole carbon source. Atomic force microscopy (AFM) showed the biofilm’s 3-D developmental patterns and significantly increased Young’s modulus of the LDPE surface after microbial treatment. Most of the viable bacteria attached to biofilms rather than media, which suggested their ability to utilize LDPE. Absorption bands of carbonyl, alkenyl, acyl, ester, primary-secondary alcohol, alkene groups and nitric oxides were found on the treated LDPE particles using Fourier-transform infrared spectroscopy. Fourier transform-ion cyclotron resonance mass spectrometry of the media indicated compositional shifts of the compounds after treatment (i.e., increase in the degree of unsaturation and increment in oxygen-to-carbon ratio) and presence of unsaturated hydrocarbons, polyketides, terpenoids, aliphatic/peptides, dicarboxylic acids, lipid-like compounds were hinted. The plastic degrading abilities of Bacillus siamensis ATKU1 suggest its probable application for large scale plastic bioremediation facility.

On Path Oscillation of a Particle–Laden Bubble in Stationary Liquid

The rise of particle–laden bubbles is a common phenomenon in many metallurgical refining processes as well as flotation processes. During its rise, it undergoes path oscillation, which is greatly affected by the mass of particles that are attached to the bubble surface. The experimental investigation was carried out to investigate the effect of coated particle fraction on the bubble, which is on the rise in a quiescent liquid medium. During the experiments, low-density polyethylene particles are coated on a bubble surface in water, which is generally used to mimic the steel in a cold model. The images (one mirror and direct image) of the particle–laden bubble were captured for all positions on its rising path. Further, these images were processed in MATLAB®. The effect of the different fraction of particle coatings such as 10% and 50% on the rising bubble was studied. It is found that the coating fraction has a considerable effect on the path of a rising bubble, which has been characterized by the phase shift of the oscillating path of a rising bubble.

Leaching of microplastics by preferential flow in earthworm (Lumbricus terrestris) burrows

Environmental contextMicroplastics found in soil pose several potential environmental risks. This study shows that microplastics on the soil surface can be ingested by earthworms and transported to the lower soil layers. In this way, microplastics may enter the food chain and find their way into groundwater systems, especially in cases where the water table is shallow. AbstractIn the current study, we examine how the activities of earthworms (Lumbricus terrestris) affect microplastic (MP) distribution and concentration in soil, with a focus on low density polyethylene (LDPE). We also want to determine if MPs can be flushed out with water. We used a laboratory sandy soil column (polyvinyl chloride tube) experimental set-up and tested five different treatments: (1) treatment with just soil (control) to check if the saturated conductivity (Ksat) could be impacted by MP, (2) treatment with MP, (3) treatment with MP and litter, (4) treatment with earthworms and litter as a second control for treatment 5 and (5) treatment with MPs, earthworms and litter. Each treatment consisted of eight replicates. For the treatments with MP, the concentration of MP added at the start of the experiment was 7% by weight (3.97g, polyethylene, 50% 1mm–250µm, 30% 250µm–150µm and 20% &amp;lt;150µm) based on 52.78g of dry litter from Populus nigra. In the treatments using earthworms, two adult earthworms, with an initial average weight of (7.14±0.26) g, were placed in each column. Results showed that LDPE particles could be introduced into the soil by the earthworms. MP particles were detected in each soil sample and within different soil layers for the earthworm treatments. Earthworms showed a tendency to transport the smaller MP particles and that the amount of MPs in size class &amp;lt;250μm increased in soil samples with increasing soil depth in comparison to the other size classes. After leaching, MPs were only detected in the leachate from the treatments with the earthworms, and the MP had similar size distributions as the soil samples in the 40–50cm layer of the treatment with MP, earthworms and litter. The results of this study clearly show that biogenic activities can mobilise MP transport from the surface into the soil and even be leached into drainage. It is highly likely that biogenic activities constitute a potential pathway for MPs to be transported into soil and groundwater.

Formulation and aging resistance of modified bio-asphalt containing high percentage of waste cooking oil residues

Waste cooking oil residues (WCOR) based bio-asphalt is a potential substitute for petroleum asphalt. This study aims to prepare a bio-asphalt with high percentage of WCOR derived from esterification reaction for biodiesel. According to the uniform design results, the optimum mass ratios of materials were determined as WCOR of 33.3%, resin (RE-1) of 30.3%, hard asphalt particles (HAP) of 31.8%, low density polyethylene particles (LDPE) of 4.6% and linear SBS (L-SBS) of 4%. Based on the orthogonal design results, the WCOR based bio-asphalt would have the best performance when stirred for 40 min and sheared for 50 min (4000 rpm) under the condition of 170 °C with the optimum mass ratios. Rotational viscosity (RV) test results indicated that the viscosity of optimal bio-asphalt (OBA) was between PEN 70 base asphalt (PEN 70) and SBS modified asphalt (SBS-MA). Dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test results proved that OBA exhibited excellent high-temperature performance similar with SBS-MA, and it had superior low-temperature performance to SBS-MA and PEN 70. Furthermore, the effect of thermo-oxidative aging on the properties of OBA was studied. DSR test results revealed that the complex modulus and phase angle of thin film oven (TFO)-aged OBA both increased with the elevated aging level, indicating an increase in viscosity during aging process. Fourier transform infrared spectroscopy (FTIR) test results showed that there was no obvious variation on the functional groups of OBA after 15 h TFOT aging process. It was confirmed that less aging susceptibility of OBA was found compared with PEN 70, which demonstrated that OBA had a better aging resistance performance.

Modelling Coalescence of a Particle Laden Bubble with a Bare Bubble in Steel Bath

The phenomenon of bubble coalescence is encountered along with the interaction of hydrophobic particles in metallurgical industries and flotation processes. In the context of steel making industries where inert gas bubbles are used to remove inclusions from steel, coalescence of bubbles was expected to show an effect on the stability of the particles or agglomerates at the bubble interface. This was verified by carrying out experiments using a cold model with polymeric low density polyethylene particles which are hydrophobic in nature. The effect of particle size and particle loading on coalescence of two equal sized bubbles, one bare and the other coated with particles has been investigated. It has been found that individual particles remained stable to bubble surface oscillations, however, agglomerated particles were unstable and their detachment had a dependency in particle size and loading fraction on the bubble.

Modification of LDPE molecular structure by gamma irradiation for bioapplications

The surface properties of low-density polyethylene (LDPE) can be modified by the grafting of 2-hydroxyethyl methacrylate (HEMA). This was done aiming at the production of new materials suitable for bioapplications. Samples with different monomer concentrations were prepared from LDPE particles by gamma irradiation, following different irradiation protocols, including irradiation in presence and absence of air. The samples were characterized by thermal analysis techniques (DSC and TGA) and by Fourier transform infrared spectroscopy (FTIR). The results obtained show a decrease in the crystallinity of the supporting matrix for copolymers with high yields of grafting. However, the new materials prepared maintain good structural order resulting from the protective effect of polyHEMA grafted onto LDPE backbone. These effects can improve the diffusion of other species deeper inside the matrix and increase the material hydrophilicity. The studies performed made possible the selection of experimental protocols adequate for the production of new copolymeric materials with high grafting yield. These were used in the production of new LDPE films with enhanced hydrophilic properties.

Atomic Layer Deposition of Al2O3 Films on Polyethylene Particles

Sequential exposures of Al(CH3)3 and H2O at 77 °C were used to encapsulate low-density polyethylene (LDPE) particles with an ultrathin Al2O3 film. FTIR studies revealed that the nucleation of Al2O3 atomic layer deposition (ALD) on the LDPE particles occurred primarily via adsorption of Al(CH3)3 onto the LDPE surface or absorption of Al(CH3)3 into the LDPE particle followed by the reaction with H2O. The FTIR spectra then revealed the progressive switching between AlCH3* and AlOH* species with alternating exposure to Al(CH3)3 and H2O. This nucleation of Al2O3 ALD did not require the existence of specific chemical functional groups on the polymer. The FTIR spectra also demonstrated that the sequential exposures of Al(CH3)3 and H2O led to an increase in Al2O3 bulk vibrational modes. The increase of the absorbance for the Al2O3 bulk vibrational modes was linear with the number of AB cycles. The presence of an Al2O3 film on the LDPE particles was confirmed using transmission electron microscopy (TEM). The TEM i...

Flash Vacuum Pyrolysis of Low Density Polyethylene in a Free-Fall Reactor

Polyethylene (PE) is the principal component of postconsumer plastic wastes. It is important to develop chemical techniques to decompose PE with a view to recycling and production of compounds that are valuable as fuel or industrial raw materials. The most common reactors in polymer pyrolysis are fluidized-bed types. Free-fall reactors do not suffer the disadvantages of fluidized beds related to inert gas employment. This flash pyrolysis study has shown that low density polyethylene (LDPE) can be continuously degraded in a free-fall reactor under vacuum to give a product quality superior to other methods. The total conversion (i.e., the sum of liquid and gas yield) is 43% at 875°C when the feed is 150–75 μm LDPE particles. Over 99% of the gaseous product is C1 to C4, the ethylene monomer exceeding 64%. The bulk of the liquid product is paraffinic; 96% of which is below C40, while over 55% is C12–C20. As is known, C12–C20 hydrocarbons are essential raw materials for the production of fatty acids, fatty alcohols, and detergents. Reduction in operation temperature down to 750°C causes the total conversion to fall from 40% to 25%. This is accompanied by a slight increase (from about 64% to 67%) in the ethylene monomer yield. Thus higher temperatures should be preferred. On the other hand, indications are that lowering the particle size down to −75 μm favorably influences the total conversion, with a gain of about 20%.

Effect of the Characteristic of Matrix on Deformation Mechanism of Polymer Blends

Polymer blends composed of low-density polyethylene (LDPE) as a dispersed phase, polystyrene (PS) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) constituting a matrix phase and a small amount of block copolymer poly(styrene-block-ethylene-co-butene-block-styrene)(SEBS) as a compatibilizer were studied for exploring deformation mechanism. The blend specimens prepared via solution-melt procedure were observed by transmission electron microscopy (TEM) under in-situ stretching. For the blend with PS matrix, crazing initiated by the dispersed LDPE is the deformation mode while micro-shear yielding becomes dominate when a certain amount of PPO is incorporated. In the latter case, the LDPE particles within the deformation zones deform to ellipsoids indicative of the molecular orientation in the microbands. The variation of the deformation mode can be attributed to the change of entanglement density of the matrix with changing composition of PS and PPO.