Magnetic Extraction of Weathered Tire Wear Particles and Polyethylene Microplastics.

Magnetic extraction offers a rapid and low-cost solution to microplastic (MP) separation, in which we magnetize the hydrophobic surface of MPs to separate them from complex environmental matrices using magnets. We synthesized a hydrophobic Fe-silane based nanocomposite (Fe@SiO2/MDOS) to separate MPs from freshwater. Pristine and weathered, polyethylene (PE) and tire wear particles (TWP) of different sizes were used in the study. The weathering of MPs was performed in an accelerated weathering chamber according to ISO 4892-2:2013 standards that mimic natural weathering conditions. The chemical properties and morphology of the Fe@SiO2/MDOS, PE and TWP were confirmed by Fourier transform infrared spectroscopy and Scanning electron microscopy, respectively. The thermal properties of PE and TWP were evaluated by Thermogravimetric analysis. Using 1.00 mg of Fe@SiO2/MDOS nanocomposite, 2.00 mg of pristine and weathered PE were extracted from freshwater; whereas, using the same amount of the nanocomposite, 7.92 mg of pristine TWP and 6.87 mg of weathered TWP were extracted. The retrieval of weathered TWP was 13% less than that of pristine TWP, which can be attributed to the increasing hydrophilicity of weathered TWP. The results reveal that the effectiveness of the magnetic separation technique varies among different polymer types and their sizes; the weathering of MPs also influences the magnetic separation efficiency.

Synergistic Adsorption of Organic Pollutants on Weathered Polyethylene Microplastics.

Microplastics (MPs) are persistent tiny pieces of plastic material in the environment that are capable of adsorbing environmental organic pollutants from their surroundings. The interaction of MPs with organic pollutants alters their environmental behavior, i.e., their adsorption, degradation and toxicity, etc. Polyethylene (PE) is the most widely used plastic material. The environmental weathering of PE results in changes to its surface chemistry, making the polymer a much better vector for organic pollutants than virgin PE. In this study, a laboratory-accelerated weathering experiment was carried out with a virgin PE film and an oxidatively degradable PE (OXO-PE) film, i.e., PE modified by the addition of a pro-oxidant catalyst. The degradation of PE and OXO-PE was assessed through Fourier transform infra-red (FTIR) spectroscopy and their wettability was measured by contact angle (CA) measurements. Their thermal properties and morphology were studied using thermogravimetric analyses (TGA) and scanning electron microscopy (SEM), respectively. Further, the adsorption of two model organic pollutants onto weathered and virgin PE was analyzed. Triclosan (TCS) and methylparaben (MeP) were chosen as model organic pollutants for the adsorption experiment due to their frequent use in the cosmetics industry, their uncontrolled release into the environment and their toxicity. The adsorption of both model pollutants onto PE and OXO-PE MP was analyzed by using gas chromatography with a flame ionization detector (GC-FID). The adsorption of MeP onto OXO-PE was higher than onto PE MPs. However, TCS showed insignificant adsorption onto PE and OXO-PE. When both pollutants were present simultaneously, the adsorption of TCS onto both PE and OXO-PE was significantly influenced by the presence of MeP. This result demonstrates that the adsorption behavior of one pollutant can be significantly altered by the presence of another pollutant. Both the effect of weathering on the adsorption of organic pollutants as well as the interaction between organic pollutants adsorbing onto MPs is highly relevant to actual MP pollution in the environment, where MPs are exposed to weathering conditions and mixtures of organic pollutants.

Integral analysis of hydrodynamic cavitation effects on waste activated sludge characteristics, potentially toxic metals, microorganisms and identification of microplastics.

Wastewater treatment plants, the last barrier between ever-increasing human activities and the environment, produce huge amounts, of unwanted semi-solid by-product - waste activated sludge. Anaerobic digestion can be used to reduce the amount of sludge. However, the process needs extensive modernisation and refinement to realize its full potential. This can be achieved by using efficient pre-treatment processes that result in high sludge disintegration and solubilization. To this end, we investigated the efficiency of a novel pinned disc rotational generator of hydrodynamic cavitation. The results of physical and chemical evaluation showed a reduction in mean particle size up to 88%, an increase in specific surface area up to 300% and an increase in soluble COD, NH4-N, NO3-N, PO4-P up to 155.8, 126.3, 250 and 29.7%, respectively. Microscopic images confirmed flocs disruption and damage to yeast cells and Epistilys species due to mechanical effects of cavitation such as microjets and shear forces. The observed cell ruptures and cracks were sufficient for the release of small soluble biologically relevant dissolved organic molecules into the bulk liquid, but not for the release of microbial DNA. Cavitation treatment also decreased total Pb concentrations by 70%, which was attributed to the reactions triggered by the chemical effects of cavitation. Additionally, the study confirmed the presence of microplastic particles and fibers of polyethylene, polyethylene terephthalate, polypropylene, and nylon 6 in the waste activated sludge.

Plastic bag and facial cleanser derived microplastic do not affect feeding behaviour and energy reserves of terrestrial isopods.

Current data regarding the effects of microplastic (MP) on terrestrial organisms are very scarce. Isopods play an important role in plant litter decomposition processes and are commonly used test species in terrestrial ecotoxicity studies. Their altered feeding behaviour and energy reserves are established biomarkers of adverse effects upon stressor exposure. For this study we assessed the effects of MP derived from plastic bag film (mean size 183±93µm) and particles from a facial cleanser (mean size 137±51µm) on the terrestrial isopod, Porcellio scaber. Isopods were exposed to MP via feeding on food pellets (4mgg-1 dry weight; 0.4% w w-1) for 14days under laboratory conditions. A control group was exposed to food pellets with no MP added. In line with previously suggested modes of MP action on animal ingestion, we assessed the food ingestion rate, defecation rate, food assimilation rate and efficiency, body mass change, mortality and energy reserves (proteins, carbohydrates, and triglycerides) in the digestive glands (hepatopancreas) of individual isopods. Contrary to our expectations, no effects on either end-point were observed under the given exposure conditions. Further work should be carried out to investigate the potential longer-term effects of such exposure. We conclude that 14days exposure to plastic bag and facial cleanser MP is not severely hazardous to isopods.

Microplastics as a vector for the transport of the bacterial fish pathogen species Aeromonas salmonicida.

Microplastics is widespread in the marine environment where it can cause numerous negative effects. It can provide space for the growth of organisms and serves as a vector for the long distance transfer of marine microorganisms. In this study, we examined the sea surface concentrations of microplastics in the North Adriatic and characterized bacterial communities living on the microplastics. DNA from microplastics particles was isolated by three different methods, followed by PCR amplification of 16S rDNA, clone libraries preparation and phylogenetic analysis. 28 bacterial species were identified on the microplastics particles including Aeromonas spp. and hydrocarbon-degrading bacterial species. Based on the 16S rDNA sequences the pathogenic fish bacteria Aeromonas salmonicida was identified for the first time on microplastics. Because A. salmonicida is responsible for illnesses in fish, it is crucial to get answers if and how microplastics pollution is responsible for spreading of diseases.

Uptake and effects of microplastic textile fibers on freshwater crustacean Daphnia magna.

Microplastic fibers (MP) from textile weathering and washing are increasingly being recognized as environmental pollutants. The majority of studies on the bioavailability and effects of microplastic focused on small polystyrene spherical plastic particles, while less data are available for fibers and for other materials besides polystyrene. We investigated the ingestion and effects of ground polyethylene terephthalate (PET) textile microfibers (length range: 62-1400 µm, width 31-528 µm, thickness 1-21.5 µm) on the freshwater zooplankton crustacean Daphnia magna after a 48 h exposure and subsequent 24 h of recovery in MP free medium and algae. The majority of ingested fibers by D. magna were around 300 µm, but also some very large twisted MP fibers around 1400 µm were found inside the gut. Exposure to these fibers results in increased mortality of daphnids after 48 h only in the case where daphnids were not pre-fed with algae prior to experiment, but no effect was found when daphnids were fed before the experiments. Regardless of the feeding regime, daphnids were not able to recover from MP exposure after additional 24 h incubation period in a MP free medium with algae. The uptake and effects of PET textile MP on D. magna are presented here for the first time.

Sea surface microplastics in Slovenian part of the Northern Adriatic.

Plastics are the most common material of marine litter and have become a global pollution concern. They are persistent in the environment where they gradually degrade into increasingly smaller particles-microplastics (MP). Our study presents results of sea-surface monitoring for MP in the Slovenian part of the Trieste Bay in the Northern Adriatic Sea. In 17 trawls conducted over a 20-month period we found a high average concentration of 406×103MPparticles/km2. Over 80% of the particles were identified as polyethylene. The significant variability of MP concentrations obtained on different sampling dates is explained by use of surface current maps and a recently developed Markov chain marine litter distribution model for the Adriatic Sea.

Synthesis of Dendronized Poly(l-Glutamate) via Azide-Alkyne Click Chemistry.

Poly(l-glutamate) (PGlu) was modified with a second-generation dendron to obtain the dendronized polyglutamate, P(Glu-D). Synthesized P(Glu-D) exhibited a degree of polymerization (DPn) of 46 and a 43% degree of dendronization. Perfect agreement was found between the P(Glu-D) expected structure and the results of nuclear magnetic resonance spectroscopy (NMR) and size-exclusion chromatography coupled to a multi-angle light-scattering detector (SEC-MALS) analysis. The PGlu precursor was modified by coupling with a bifunctional building block (N3-Pr-NH2) in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) coupling reagent. The second-generation polyamide dendron was prepared by a stepwise procedure involving the coupling of propargylamine to the l-lysine carboxyl group, followed by attaching the protected 2,2-bis(methylol)propionic acid (bis-MPA) building block to the l-lysine amino groups. The hydroxyl groups of the resulting second-generation dendron were quantitatively deprotected under mild acidic conditions. The deprotected dendron with an acetylene focal group was coupled to the pendant azide groups of the modified linear copolypeptide, P(Glu-N3), in a Cu(I) catalyzed azide-alkyne cycloaddition reaction to form a 1,4-disubstituted triazole. The dendronization reaction proceeded quantitatively in 48 hours in aqueous medium as confirmed by ¹H NMR and Fourier transform infrared spectroscopy (FT-IR) spectroscopy.

Protocol for Microplastics Sampling on the Sea Surface and Sample Analysis.

Microplastic pollution in the marine environment is a scientific topic that has received increasing attention over the last decade. The majority of scientific publications address microplastic pollution of the sea surface. The protocol below describes the methodology for sampling, sample preparation, separation and chemical identification of microplastic particles. A manta net fixed on an ¼A frame« attached to the side of the vessel was used for sampling. Microplastic particles caught in the cod end of the net were separated from samples by visual identification and use of stereomicroscopes. Particles were analyzed for their size using an image analysis program and for their chemical structure using ATR-FTIR and micro FTIR spectroscopy. The described protocol is in line with recommendations for microplastics monitoring published by the Marine Strategy Framework Directive (MSFD) Technical Subgroup on Marine Litter. This written protocol with video guide will support the work of researchers that deal with microplastics monitoring all over the world.

Liquefied Wood as Inexpensive Precursor-Feedstock for Bio-Mediated Incorporation of (R)-3-Hydroxyvalerate into Polyhydroxyalkanoates.

Liquefied wood (LW) prepared in a microwave process was applied as a novel; inexpensive precursor feedstock for incorporation of (R)-3-hydroxyvalerate (3HV) into polyhydroxyalkanoate (PHA) biopolyesters in order to improve the biopolyester's material quality; Cupriavidus necator was applied as microbial production strain. For proof of concept, pre-experiments were carried out on a shake flask scale using different mixtures of glucose and LW as carbon source. The results indicate that LW definitely acts as a 3HV precursor, but, at the same time, displays toxic effects on C. necator at concentrations exceeding 10 g/L. Based on these findings, PHA biosynthesis under controlled conditions was performed using a fed-batch feeding regime on a bioreactor scale. As major outcome, a poly(3HB-co-0.8%-3HV) copolyester was obtained displaying a desired high molar mass of Mw = 5.39 × 105 g/mol at low molar-mass dispersity (DM of 1.53), a degree of crystallinity (Xc) of 62.1%, and melting temperature Tm (176.3 °C) slightly lower than values reported for poly([R]-3-hydroxybutyrate) (PHB) homopolyester produced by C. necator; thus, the produced biopolyester is expected to be more suitable for polymer processing purposes.

Determination of the interactions between Zn2+ and water soluble polymer ligands with potential use in controlled drug delivery.

Biodegradable copolymers of aspartic and lactic acids were synthesized for potential use in controlled drug release. The proportion of aspartic acid moieties in the copolymers was 0.9 and 0.1, the molecules were partially branched and had absolute molar masses over 100,000 g/mol. The drug could be attached to the copolymer via metal (particularly zinc) ions, so a method to estimate the interactions between zinc ions and the water-soluble polymers by fluorescence spectroscopy was developed. The stability constants of binding of zinc and the concentrations of zinc bound to polymer were determined. The results confirm that zinc ions at pH 6 preferentially bind to side groups of aspartic acid units of the copolymers.

Atomic volume as a descriptor for carbon electronic structure and stability.

Electron density at the carbon atom is a significant factor determining the stability of molecules, but it is difficult to quantify. Using the Atoms in Molecules (AIM) quantum theory, we calculated the atomic charges and volumes of carbon atoms in highly oxidized compounds. The two parameters are shown to be good quantitative descriptors of electron depletion and can be used as an indicator for stability/reactivity of such compounds.

Microwave driven wood liquefaction with glycols.

Wood liquefaction with glycols using p-toluenesulfonic acid as the catalyst was carried out under microwave heating. With rapid heating and temperatures in the 190-210 degrees C range complete liquefaction was achieved in 7 min. Liquefaction efficiency was dependent on the choice of glycol. Simple glycols such as ethylene glycol and propylene glycol were more effective than higher analogues. The use of glycerol in mixtures with glycols showed a synergistic effect. Size exclusion chromatography was used to follow the gradual emergence of liquefaction products in solution as well as the recondensation products that start forming early in the reaction and precipitate from solution when molar masses of approx. 1x10(4) g/mol are reached.

Microwave catalysis through rotationally hot reactive species.

In this contribution we propose a novel physical mechanism for microwave catalysis based on rotationally excited reactive species and verify its validity through a computer simulation of a realistic chemical reaction-neutral ester hydrolysis. This nonequilibrium system is formally described by introducing rotational temperature, which is higher than the translational temperature. A Born-Oppenheimer surface was constructed on the density functional theory level and applied to a modified Monte Carlo scheme. The simulation gave a reduced activation free energy when the rotational temperature was higher than the translational temperature, which constitutes a catalytic effect. For example, our calculation predicts that with rotational and translational temperatures of 310 and 300 K, respectively, the reaction should proceed 4.5 times faster than when both temperatures are 300 K. Moreover, this microwave catalytic effect is less pronounced at higher temperatures, which may have serious implications for the interaction of microwaves with living organisms in the context of widespread mobile telephony.

Ability of fungi to degrade synthetic polymer nylon-6.

Fifty-eight fungi have been tested for their ability to degrade a recalcitrant synthetic polymer polyamide-6, generally known as nylon-6. Most of them were isolated from a factory producing nylon-6. After preliminary screening, 12 strains were selected for submerged culture in a medium with nylon fibres as the only N-source. No degradation was observed with the isolates from the factory. Wood degrading fungi from a culture collection, however, degraded nylon after incubation for several weeks. Bjerkandera adusta disintegrated the fibres most efficiently, starting with the small transverse grooves, which deepened into cracks. The superficial layers crumbled to leave a thin inner core of the fibre, which finally broke down into fragments. The remaining insoluble part of the nylon showed a decrease in number average molecular mass from 16900 to 5600 during a 60-day incubation. Its thermal properties, such as shifts in melting points and broadening of the melting endotherms, were altered. The reduction of the amount of nylon and the composition of the liquid phase indicated that part of the polymer was degraded into soluble products. After 50 days, the total nitrogen content of the soluble fraction was 10-fold higher than in the control sample. Manganese peroxidase, presumably responsible for the degradation, was detected in the liquid phase. The study shows that only white rot fungi are able to break down nylon-6. For the first time this polymer was shown to be disrupted by B. adusta. The extent of the biodegradation indicates its potential for application in nylon waste reduction.

Sequence distribution in microbial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) co-polyesters determined by NMR and MS.

The microstructure of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolyesters (PHBV) as well as a mixture of two PHBV copolyesters of different comonomer composition and sequence distribution was studied by 13C NMR based on dyad and triad analysis and multistage electrospray ionization mass spectrometry (ESI-MSn). Both techniques gave results that were in good agreement for all investigated samples. The effect of microstructure on PHBV thermal properties was investigated from the melting behavior of samples. A PHBV copolyester with randomly distributed hydroxyvalerate units (12.0 mol % HV) showed a single melting peak, whereas samples with nonrandom composition distribution showed multiple melting peaks in their thermograms. Such complex melting behavior suggested that the 12.9 and 27.1 mol % PHBV copolyesters were actually blends of several copolymers with widely different comonomer-unit composition.

SEC-MALS characterization of microbial polyhydroxyalkanoates.

Characterization of poly-3-hydroxybutyric acid (PHB) and poly-3-hydroxybutyric-co-valeric acid (PHBV, 13% valerate) in chloroform was performed using size exclusion chromatography coupled to a multi-angle light scattering detector (SEC-MALS). Absolute molar mass averages, molar mass distribution, and the radius of gyration were determined. Three sample preparation methods were examined: dissolution in chloroform (1) at room temperature, (2) at 60 degrees C, and (3) after thermal pretreatment of samples (annealing at 180 degrees C with subsequent quenching in liquid nitrogen). Dissolution at 60 degrees C and dissolution of thermally pretreated samples gave molecularly dissolved PHB and PHBV. At 60 degrees C using acid free chloroform, there was no indication of degradation for up to 120 min dissolution time, whereas thermal degradation of polymers did take place during annealing at 180 degrees C. The degradation rate constants for number and weight average degree of polymerization at 180 degrees C were slightly higher for PHB (5.19 x 10(-5) min(-1), 4.95 x 10(-5) min(-1)) than for PHBV (4.99 x 10(-5) min(-1), 4.54 x 10(-5) min(-1)). The dependence of the radii of gyration on molar mass showed that both polymers form random coils in chloroform. The relationship between the absolute molar masses and relative SEC results was determined. DSC and NMR characterization also gave evidence of the progress of degradation.