Purification of post-consumer polyolefins via supercritical CO2 extraction for the recycling in food contact applications

Chemical Modification of Oxidized Polyethylene Enables Access to Functional Polyethylenes with Greater Reuse

Polyethylene is a commodity material that is widely used because of its low cost and valuable properties. However, the lack of functional groups in polyethylene limits its use in applications that include adhesives, gas barriers, and plastic blends. The inertness of polyethylene makes it difficult to install groups that would enhance its properties and enable programmed chemical decomposition. To overcome these deficiencies, the installation of pendent functional groups that imbue polyethylene with enhanced properties is an attractive strategy to overcome its inherent limitations. Here, we describe strategies to derivatize oxidized polyethylene that contains both ketones and alcohols to monofunctional variants with bulk properties superior to those of unmodified polyethylene. Iridium-catalyzed transfer dehydrogenation with acetone furnished polyethylenes with only ketones, and ruthenium-catalyzed hydrogenation with hydrogen furnished polyethylenes with only alcohols. We demonstrate that the ratio of these functional groups can be controlled by reduction with stoichiometric hydride-containing reagents. The ketones and alcohols serve as sites to introduce esters and oximes onto the polymer, thereby improving surface and bulk properties over those of polyethylene. These esters and oximes were removed by hydrolysis to regenerate the original oxygenated polyethylenes, showing how functionalization can lead to materials with circularity. Waste polyethylenes were equally amenable to oxidative functionalization and derivatization of the oxidized material, showing that this low- or negative-value feedstock can be used to prepare materials of higher value. Finally, the derivatized polymers with distinct solubilities were separated from mechanically mixed plastic blends by selective dissolution, demonstrating that functionalization can lead to novel approaches for distinguishing and separating polymers from a mixture.

Endocrine modulating chemicals in food packaging: A review of phthalates and bisphenols

Phthalates and bisphenol chemicals have been widely used globally in packaging materials and consumer products for several decades. These highly functional chemicals have become a concern due to their toxicity (i.e., endocrine/hormone modulators) and ability to migrate from food contact materials (FCMs) into food matrices and the environment resulting in human and environmental health risks. FCMs, composed of postconsumer materials, are particularly high risk for containing these compounds. The evaluation of postconsumer recycled feedstocks in FCMs is compulsory and selection of an appropriate detection method to comply with applicable regulations is necessary to evaluate human and environmental safety. Numerous regulations have been proposed and passed globally for both compound classes that are recognized as priority pollutants by the United States Environmental Protection Agency and the European Union. Several brand owners and retailers have also released their own "restricted substance lists" due to the mounting consumer and regulatory concerns. This review article has two goals: (1) discuss the utilization, toxicology, human exposure routes, and occurrence levels of phthalates and bisphenols in FCMs and associated legislation in various countries and (2) discuss critical understanding and updates for detection/quantification techniques. Current techniques discussed include extraction and sample preparation methods (solid-phase microextraction [SPME], headspace SPME, Soxhlet procedure, ultrasound-assisted extraction), chromatographic techniques (gas, liquid, detectors), and environmental/blank considerations for quantification. This review complements a previous review of phthalates in foods from 2009 by discussing phthalate and bisphenol characteristics, analytical methods of determining concentrations in packaging materials, and their influence on the migration potential into food.

Recycling of polypropylene by supercritical carbon dioxide for extraction of contaminants from beverage cups. A comparison with polyethylene terephthalate and polylactic acid

BACKGROUND

EU policies towards a circular economy address plastic packaging as one of the significant concerns and sets ambitious recycling targets. Polyolefins (POs) cannot be recycled for food contact using conventional polyethylene terephthalate (PET) recycling approaches. Thermal degradation prevents the use of high temperatures and, consequently, decontamination of POs may be insufficient when using lower temperatures. Polypropylene (PP) beverage cups were decontaminated using supercritical fluid extraction with carbon dioxide (scCO₂ ). Decontamination efficiencies (DEs) of selected markers were determined in challenge tests following European Food Safety Authority guidelines. The effects of time (10-60 min) for PET, polylactic acid (PLA), and PP and temperature (60-80 °C) for PP were studied at constant pressure. The physical properties, sensorial properties, and overall migration of treated scCO₂ PP were analysed and compared with virgin PP.

RESULTS

PP showed the highest average DE, and PET the lowest, for all the surrogates and in all time conditions. A relative increase in the DE with the increase in process time, particularly for PET and to some extent for PLA, was seen. For PP, no significant impact of time and temperature was observed under the conditions tested. The DE of volatile surrogates was higher than that of semi-volatiles. Results indicate that the scCO₂ treatment did not affect the physical and sensorial properties, nor the overall migration of PP, although it contributes to a considerable reduction in extractable n < C24 alkanes.

CONCLUSIONS

Results indicate that scCO₂ can be used to decontaminate post-consumption PP beverage cups with higher DEs than those for PET and PLA, applying mild processing conditions. © 2022 Society of Chemical Industry.

Synthetic Lubricants Derived from Plastic Waste and their Tribological Performance

The energy efficiency, mechanical durability, and environmental compatibility of all moving machine components rely heavily on advanced lubricants for smooth and safe operation. Herein an alternative family of high-quality liquid (HQL) lubricants was derived by the catalytic conversion of pre- and post-consumer polyolefin waste. The plastic-derived lubricants performed comparably to synthetic base oils such as polyalphaolefins (PAOs), both with a wear scar volume (WSV) of 7.5×10^-5  mm^-3 . HQLs also performed superior to petroleum-based lubricants such as Group III mineral oil with a WSV of 1.7×10^-4  mm^-3 , showcasing a 44 % reduction in wear. Furthermore, a synergistic reduction in friction and wear was observed when combining the upcycled plastic lubricant with synthetic oils. Life cycle and techno-economic analyses also showed this process to be energetically efficient and economically feasible. This novel technology offers a cost-effective opportunity to reduce the harmful environmental impact of plastic waste on our planet and to save energy through reduction of friction and wear-related degradations in transportation applications akin to synthetic oils.

Brominated flame retardants extraction from waste electrical and electronic equipment-derived ABS using supercritical carbon dioxide

Persistent organic pollutants such as brominated flame retardants represent a major problem in the end-of-life of polymer materials. This study investigates the extraction of brominated flame retardants (BFR) from real waste electrical and electronic equipment (WEEE) using supercritical carbon dioxide (sc-CO₂). Sc-CO₂ is a non-toxic solvent which possesses intermediate properties between liquids and gases which confer it high diffusivity and solubility. A batch of WEEE-derived acrylonitrile-butadienestyrene (ABS) was first characterized to determine its bromine and BFR composition which was found to be four times higher than the regulation limit set in 2019. Then, different parameters of the sc-CO₂ process such as temperature, pressure, granulometry and the use of a co-solvent were studied to estimate the effect of each one on the BFR extraction efficiency. With the view to determine the recyclability of the treated polymer, the impact of the extraction process on the polymer material was also studied by Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Size Exclusion Chromatography (SEC). The extraction process performed on <500 µm particle size sample at 40 °C and 500 bars during 6 h and using ethanol as a co-solvent allowed to remove 43.5 ± 0.9% of bromine, which was the maximum extraction rate obtained. Sc-CO₂ extraction was found to be an efficient technique to remove tetrabromobisphenol A (TBBPA) but the tested conditions did not allow to remove enough polybromodiphenylethers (PBDE) to satisfy the regulation. Sc-CO₂ process seems to be a promising pre-treatment method prior to mechanical recycling as no degradation effect on the polymer matrix was observed.

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

While the annual European demand for polyolefins is 25 million tonnes, only 3 million tonnes of recycled polyolefins find their place in the market, despite collecting 15 million tonnes of post-consumer polyolefins every year. Brand owners of care products are showing their interest in using post-consumer recycled plastics for their packaging. However, there is a general concern in using these materials, as recycled polymers can contain unwanted substances that may expose the consumer to health risks or make the packaging unattractive. Accordingly, the presence of these contaminants narrows the market opportunity of recycled plastics to applications with low-quality requirements and in which the product is not in direct contact with the consumer. Though mechanical recycling is the most widespread solution presents limitations in terms of decontamination, as only superficial substances are removed. Thereby, the volatile organic compounds (VOCs) migrated to the polymer matrix remain inside. Consequently, there is a need to find a solution to purify recycled plastics and increase their market share. This study focuses on removing VOCs from post-consumer recycled HDPE through two innovative methods applied for the first time in this field, steam stripping and polyethylene glycol (PEG) extraction. The methodology implemented to analyze the volatile organic compounds in HDPE was HS-SPME-GC/MS. Both methods showed a decrease above 70% in the VOCs content compared to extrusion-degassing. Moreover, these were compared to hot air stripping, a new technology developed at an industrial scale for the removal of VOCs. As a result, steam stripping improved efficiency in reducing the overall VOCs compared to hot air stripping. The PEG extraction method lowered the volatile polar compounds further than using hot air stripping. Additionally, none of these technologies modified the HDPE melting flow index.

Beyond Mechanical Recycling: Giving New Life to Plastic Waste

Increasing the stream of recycled plastic necessitates an approach beyond the traditional recycling via melting and re-extrusion. Various chemical recycling processes have great potential to enhance recycling rates. In this Review, a summary of the various chemical recycling routes and assessment via life-cycle analysis is complemented by an extensive list of processes developed by companies active in chemical recycling. We show that each of the currently available processes is applicable for specific plastic waste streams. Thus, only a combination of different technologies can address the plastic waste problem. Research should focus on more realistic, more contaminated and mixed waste streams, while collection and sorting infrastructure will need to be improved, that is, by stricter regulation. This Review aims to inspire both science and innovation for the production of higher value and quality products from plastic recycling suitable for reuse or valorization to create the necessary economic and environmental push for a circular economy.

Solvent-based separation and recycling of waste plastics: A review

Since the creation of first man-made plastic, the global production and consumption of plastics have been continuously increasing. However, because plastic materials are durable and very slow to degrade, they become waste with high staying power. The over-consumption, disposal, and littering of plastics result in pollution, thus causing serious environmental consequences. To date, only a fraction of waste plastics is reused and recycled. In fact, recycling plastics remains a great challenge because of technical challenges and relatively insufficient profits, especially in mixed plastics. This review focuses on an environmentally friendly and potentially profitable method for plastics separation and recovery and solvents extraction. It includes the dissolution/reprecipitation method and supercritical fluid extraction, which produce high-quality recovered plastics comparable to virgin materials. These methods are summarized and discussed taking mass-produced plastics (PS, PC, Polyolefins, PET, ABS, and PVC) as examples. To exploit the method, the quality and efficiency of solvent extraction are elaborated. By eliminating these technical challenges, the solvent extraction method is becoming more promising and sustainable for plastic issues and polymer markets.

Natural antioxidants: sources, extraction and application in food systems

Purpose

The study aims to describe the main classes of antioxidants existing in fruit, beverages, vegetables and herbs and the different extraction and application of antioxidants in food. Oxidative degradation of lipids, especially induced by reactive oxygen species, leads to quality deterioration of foods and cosmetics and could have harmful effects on health. A major challenge is to develop tools to assess the antioxidant capacity and real efficacy of these molecules. Recently, many review papers regarding antioxidants from different sources and different extraction and quantification procedures have been published. However, none of them has all the information regarding antioxidants (sources, extraction and application in food).

Design/methodology/approach

This paper tries to take a different perspective on antioxidants for the new researcher involved in this field.

Findings

Antioxidants from fruit, vegetables and beverages play an important role in human health, for example, preventing cancer and cardiovascular diseases and lowering the incidence of different diseases. A number of plant products act as scavengers of free radical species and so have been classified as antioxidants. Antioxidants are an important group of food additives that have the ability to protect against detrimental change of oxidizable nutrients and consequently they extend shelf-life of foods.

Research limitations/implications

Most of the antioxidants present in foods are phenolic and polyphenolic compounds, but their efficacy in food for the prevention of oxidation or in the body for dealing with oxidative stress and its consequences depends on different factors.

Originality/value

This study collected the last finding in the field of sources and applications of natural antioxidants.

Antioxidants: Characterization, natural sources, extraction and analysis

Recently many review papers regarding antioxidants from different sources and different extraction and quantification procedures have been published. However none of them has all the information regarding antioxidants (chemistry, sources, extraction and quantification). This article tries to take a different perspective on antioxidants for the new researcher involved in this field. Antioxidants from fruit, vegetables and beverages play an important role in human health, for example preventing cancer and cardiovascular diseases, and lowering the incidence of different diseases. In this paper the main classes of antioxidants are presented: vitamins, carotenoids and polyphenols. Recently, many analytical methodologies involving diverse instrumental techniques have been developed for the extraction, separation, identification and quantification of these compounds. Antioxidants have been quantified by different researchers using one or more of these methods: in vivo, in vitro, electrochemical, chemiluminescent, electron spin resonance, chromatography, capillary electrophoresis, nuclear magnetic resonance, near infrared spectroscopy and mass spectrometry methods.