New methods to remove volatile organic compounds from post-consumer plastic waste

Analysis and removal of bisphenols in recycled plastics using polyethylene glycol

This study examines the presence of bisphenol A (BPA), S (BPS), F (BPF), and M (BPM) in various recycled plastics readily available on the market (LDPE, HDPE, PET, and PP), in light of European Food Safety Authority (EFSA) limits. Twenty samples of different origin are analyzed, cleaning treatments are applied, and the migration potential of these bisphenols into food is studied. BPM is absent in all samples, but a post-consumer recycled LDPE sample reveals high bisphenol concentrations, raising concerns, reaching 8540 ng/g, 370 ng/g, and 29 ng/g of BPA, BPS, and BPF, respectively. Migration tests show substantial migration of these contaminants into food simulants. Using a cleaning treatment with polyethylene glycol (PEG 400) reduces BPA in LDPE, HDPE, PP, and PET samples by 95%, 99%, 97% and 28%, respectively, highlighting the importance of cleaning treatments across various polymers in plastic recycling. These findings not only protect food safety but addressing environmental challenges associated with plastic recycling.

Pulmonary evaluation of whole-body inhalation exposure of polycarbonate (PC) filament 3D printer emissions in rats

During fused filament fabrication (FFF) 3D printing with polycarbonate (PC) filament, a release of ultrafine particles (UFPs) and volatile organic compounds (VOCs) occurs. This study aimed to determine PC filament printing emission-induced toxicity in rats via whole-body inhalation exposure. Male Sprague Dawley rats were exposed to a single concentration (0.529 mg/m3, 40 nm mean diameter) of the 3D PC filament emissions in a time-course via whole body inhalation for 1, 4, 8, 15, and 30 days (4 hr/day, 4 days/week), and sacrificed 24 hr after the last exposure. Following exposures, rats were assessed for pulmonary and systemic responses. To determine pulmonary injury, total protein and lactate dehydrogenase (LDH) activity, surfactant proteins A and D, total as well as lavage fluid differential cells in bronchoalveolar lavage fluid (BALF) were examined, as well as histopathological analysis of lung and nasal passages was performed. To determine systemic injury, hematological differentials, and blood biomarkers of muscle, metabolic, renal, and hepatic functions were also measured. Results showed that inhalation exposure induced no marked pulmonary or systemic toxicity in rats. In conclusion, inhalation exposure of rats to a low concentration of PC filament emissions produced no significant pulmonary or systemic toxicity.

Application of chemometric tools in the QSAR development of VOC removal in plastic waste recycling

Deodorization and, in a broader sense, the removal of volatile organic compounds (VOCs) from plastic waste have become increasingly important in the field of plastic recycling, and various new decontamination techniques have been developed. Both in research and industrial practice, the selection of VOCs has been random or unsubstantiated, making it difficult to compare studies and assess decontamination processes objectively. Thus, this study proposes the use of Statistical Molecular Design (SMD) and Quantitative Structure - Activity Relationship (QSAR) as chemometric tools for the selection of representative VOCs, based on physicochemical properties. Various algorithms are used for SMD; hence, several frequently used D-Optimal Onion Design (DOOD) and Space-Filling (SF) algorithms were assessed. Hereby, it was validated that DOOD, by dividing the layers based on the equal-distance approach without so-called 'Adjacent Layer Bias', results in the most representative selection of VOCs. QSAR models that describe VOC removal by water-based washing of plastic waste as a function of molecular weight, polarizability, dipole moment and Hansen Solubility Parameters Distance were successfully established. An adjusted-R2 value of 0.77 ± 0.09 and a mean absolute error of 24.5 ± 4 % was obtained. Consequently, by measuring a representative selection of VOCs compiled using SMD, the removal of other unanalyzed VOCs was predicted on the basis of the QSAR. Another advantage of the proposed chemometric selection procedure is its flexibility. SMD allows to extend or modify the considered dataset according to the available analytical techniques, and to adjust the considered physicochemical properties according to the intended process.

Unraveling the cytotoxicity and cellular uptake of low, medium and high molecular weight polyethylene glycol polymers in MCF-7 cells by green UPLC-MS/MS methods

Unraveling the cytotoxicity and cellular uptake of low, medium and high molecular weight polyethylene glycol (PEG) in cells is important for evaluation of therapeutic efficacy and toxicity of PEGylated drug delivery systems. In this study, cellular uptake of PEG600, PEG2K, PEG4K and PEG10K in MCF-7 cells was first studied by an UPLC-MS/MS assay coupled with collision induced dissociation (CID) in source technique. The CID of PEG in source with high values of declustering potentials generates numerous PEG-related product ions. These PEG-related fragment ions can be further broken into specific product ions in the collision cell as alternative ions for detection of PEG. The quantification of PEG was finally performed with the MRM transition (m/z 221.0 → 89.0). The experimental results indicated that the toxicity of PEG600, PEG2K, PEG4K and PEG10K was not significant at concentrations of 5-1200 μg/mL and the amounts of PEG polymers entry into MCF-7 cells at was small. The greenness of the developed analytical methods was also assessed by Analytical Eco-Scale, Analytical Greenness calculator (AGREE) and Green Analytical Procedure Index (GAPI) in this study.

Development of ultra-high surface area polyaniline-based activated carbon for the removal of volatile organic compounds from industrial effluents

Removing volatile organic compounds (VOCs) from aqueous solutions is critical for reducing VOC emissions in the environment. Activated carbons are widely used for removal of VOCs from water. However, they show less application feasibility and low removal due to less surface area. Here, a cost-effective and high surface area activated carbonized polyaniline (ACP) was synthesized to sustainable removal of VOCs from water. The ACP microstructure, surface properties, and pore structure were investigated using Brunauer-Emmett-Teller (BET) theory, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The specific surface area of ACP6:1 (2988.13 m2/g) was greater than that of commercial activated carbon (PAC) (1094.49 m2/g), indicating that it has excellent VOC adsorption capacity. The effects of pH, initial VOC concentration, time, temperature, and ionic strength were studied. According to kinetic and thermodynamic studies on VOCs adsorption, it is an exothermic and spontaneous process involving rate-limiting kinetics. Adsorption isotherms follow the Freundlich isotherm model, suggesting that the adsorbent surface is heterogeneous with multilayer adsorption and maximum ACP adsorption capacities of 1913.9, 2453.3, 1635.8, and 3327.0 mg/g at 293 K for benzene, toluene, ethylbenzene, and perchloroethylene, respectively, representing a 3- to 5-fold improvement over PAC. ACP is a promising adsorbent with a high adsorption efficiency for VOC removal.

Special Packaging Materials from Recycled PET and Metallic Nano-Powders

The European methodology for plastics, as a feature of the EU's circular economy activity plan, ought to support the decrease in plastic waste. The improvement of recycled plastics' economics and quality is one important part of this action plan. Additionally, achieving the requirement that all plastic packaging sold in the EU by 2030 be recyclable or reusable is an important objective. This means that food packaging materials should be recycled in a closed loop at the end. One of the most significant engineering polymers is polyethylene terephthalate (PET), which is widely used. Due to its numerous crucial qualities, it has a wide variety of applications, from packaging to fibers. The thermoplastic polyolefin, primarily polyethylene and polypropylene (PP), is a popular choice utilized globally in a wide range of applications. In the first phase of the current experiment, the materials were obtained by hot pressing with the press machine. The reinforcer is made of Al nanopowder 800 nm and Fe nanopowder 790 nm and the quality of the recycled polymer was examined using Fourier transform infrared spectroscopy (FTIR), a scanning electron microscope (SEM), and differential scanning calorimetry (DSC). From DSC variation curves as a function of temperature, the values from the transformation processes (glass transition, crystallization, and melting) are obtained. SEM measurements revealed that the polymer composites with Al have smooth spherical particles while the ones with Fe have bigger rough spherical particles.

Tracing the origin of VOCs in post-consumer plastic film bales

Volatile organic compounds (VOCs), including odors, are still a key issue in plastic recycling, especially in case of flexible packaging. Therefore, this study presents a detailed qualitative and quantitative VOC analysis by applying gas chromatography on 17 categories of flexible plastic packaging that are manually sorted from bales of post-consumer flexible packaging (e.g., beverage shrink wrap, packaging for frozen food, packaging for dairy products, etc.). A total of 203 VOCs are identified on packaging used for food products, while only 142 VOCs are identified on packaging used for non-food products. Especially, more oxygenated compounds (e.g., fatty acids, esters, aldehydes) are identified on food packaging. With more than 65 VOCs, the highest number of VOCs is identified on packaging used for chilled convenience food and ready meals. The total concentration of 21 selected VOCs was also higher on packaging used for food products (totally 9187 μg/kg plastic) compared to packaging used for non-food packaging (totally 3741 μg/kg plastic). Hence, advanced sorting of household plastic packaging waste, e.g., via tracer-based sorting or watermarking, could open the door towards sorting on other properties than polymer type, such as mono- versus multi-material packaging, food versus non-food packaging or even their VOC profile, which might allow for tailoring washing procedures. Potential scenarios showed that sorting the categories with the lowest VOC load, which corresponds to half of the total mass of flexible packaging, could result in a VOC reduction of 56%. By producing less contaminated plastic film fractions and by tailoring washing processes recycled plastics can ultimately be used in a broader market segment.

Assessment of Melt Compounding with Zeolites as an Effective Deodorization Strategy for Mixed Plastic Wastes and Comparison with Degassing

The emission of off-odors from mechanically recycled plastics severely limits their re-introduction into the market for the production of new objects, for the same use or even for less demanding applications, thus hindering the implementation of an effective circular economy for plastics. The addition of adsorbing agents during the extrusion of polymers represents one of the most promising strategy to reduce the odorous emissions of plastics, due to its characteristics of cost-effectiveness, flexibility and low energy consumption. The novelty of this work lies in the assessment of zeolites as VOC adsorbents during the extrusion of recycled plastics. They appear more suitable than other types of adsorbents, due to their ability to capture and "hold" the adsorbed substances at the high temperatures of the extrusion process. Moreover, the effectiveness of this deodorization strategy was compared with the traditional degassing technique. Two types of mixed polyolefin wastes, coming from completely different collection and recycling processes, were tested: Fil-S (Film-Small), deriving from post-consumer flexible films of small size, and PW (pulper waste), which is the residual plastic waste obtained from the paper recycling process. The melt compounding of the recycled materials with two micrometric zeolites (zeolite 13X and Z310) resulted as more effective in the off-odors removal with respect to degassing. In particular, the highest reduction (-45%) of the Average Odor Intensity (AOI) was measured for both PW/Z310 and Fil-S/13X systems at 4 wt% of the zeolites' amount, compared with the corresponding untreated recyclates. Finally, by combining degassing and melt compounding with zeolites, the best result was obtained for the composite Fil-S/13X, whose Average Odor Intensity resulted as quite close (+22%) to the one of the virgin LDPE.

Use of Fourier-Transform Infrared Spectroscopy for DNA Identification on Recycled PET Composite Substrate

Fourier-transform infrared (FTIR) spectroscopy has been extensively used in plastic pollution research, since it has the advantages of great simplicity, rapidity, and low cost, being widely employed in the fingerprint identification of molecular composition and structure. The present study evaluates attenuated total reflection (ATR)–FTIR spectroscopy as a sensitive and effective assay for the identification of deoxyribonucleic acid (DNA) isolated from experimental animals. Various composite materials based on recycled polyethylene terephthalate (PET) as the main component, along with high-density polyethylene (HDPE), polypropylene (PP), and aluminum nanopowder obtained using an injection-molding machine, were used as substrate contaminants. The contamination was performed using quantified nucleic acid solution added in droplets to the clean, decontaminated samples, which were then dried and kept in a protective environment until the analysis. ATR–FTIR (with an FTIR spectrometer equipped with an ATR accessory) spectroscopy was used to analyze the bare composite materials’ substrates and the DNA-contaminated samples. To the best of our knowledge, the evaluation of PET packaging contamination with DNA species by FTIR has not been reported previously. This study demonstrated that FTIR spectroscopy could provide a rapid, sensitive, and reliable approach for screening of biochemical contaminants on composite materials based on recycled PET.

Deodorization of post-consumer plastic waste fractions: A comparison of different washing media

An important impediment to the acceptance of recyclates into a broader market is their unwanted odor after reprocessing. Different types of washing procedures are already in place, but fundamental insights into the deodorization efficiencies of different washing media are still relatively scarce. Therefore, in this study, the deodorization efficiencies of different types of plastics after washing with different media were determined via gas chromatography and mass spectrometry analysis. A total of 169 compounds subdivided into various chemical classes, such as alkanes, terpenes, and oxygenated compounds, were detected across all packaging types. Around 60 compounds were detected on plastic bottles, and around 40 were detected on trays and films. Owing to the differences in physicochemical properties of odor compounds, different deodorization efficiencies were obtained with different washing media. Water and caustic soda were significantly more efficient for poly(ethylene terephthalate) bottles with deodorization efficiencies up to 80%, whereas for polyethylene (PE) and polypropylene bottles, the washing media were relatively inefficient (around 30-40%). Adding a detergent or an organic solvent could increase deodorization efficiencies by up to 70-90% for these packaging types. A similar trend was observed for PE films having deodorization efficiencies in the range of 40-50% when washing with water or caustic soda and around 70-80% when a detergent was added. Polystyrene trays were most effectively deodorized with a detergent, achieving efficiencies up to 67%. Hence, this study shows that optimal washing processes should be tailored to specific packaging types to further improve deodorization and to eventually be able to meet ambitious European recycling targets.

Chemical Characterization of Recycled Consumer Products Using Suspect Screening Analysis

Recycled materials are found in many consumer products as part of a circular economy; however, the chemical content of recycled products is generally uncharacterized. A suspect screening analysis using two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOFMS) was applied to 210 products (154 recycled, 56 virgin) across seven categories. Chemicals in products were tentatively identified using a standard spectral library or confirmed using chemical standards. A total of 918 probable chemical structures identified (112 of which were confirmed) in recycled materials versus 587 (110 confirmed) in virgin materials. Identified chemicals were characterized in terms of their functional use and structural class. Recycled paper products and construction materials contained greater numbers of chemicals than virgin products; 733 identified chemicals had greater occurrence in recycled compared to virgin materials. Products made from recycled materials contained greater numbers of fragrances, flame retardants, solvents, biocides, and dyes. The results were clustered to identify groups of chemicals potentially associated with unique chemical sources, and identified chemicals were prioritized for further study using high-throughput hazard and exposure information. While occurrence is not necessarily indicative of risk, these results can be used to inform the expansion of existing models or identify exposure pathways currently neglected in exposure assessments.

PAH and POP Presence in Plastic Waste and Recyclates: State of the Art

The presence of different pollutants in recycled plastics is reviewed in this article. The desirable circular economy of plastics should be linked to the availability of clean recycled plastics with a non-significant and small to nil amount of substances of concern. Different researchers found polycyclic aromatic hydrocarbons (PAHs) and Persistent Organic Pollutants (POPs), such as brominated flame retardants (BFRs), pesticides, dioxins and furans (PCDD/Fs and PBDD/Fs) in plastic recyclates. This represents an added difficulty to the effective recycling process of plastics that reduces the demand for energy and materials, in addition to posing a great environmental danger since they represent a vector of accumulation of the contaminants that will finally appear in the most unexpected products. Life Cycle Analysis of the plastic wastes recycling process indicates a great saving of energy, water and CO2 emissions.