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Deodorization efficiency per odor compound as a function of the octanol-water partition coefficient (log P ow ) after washing with water (indicated in blue), NaOH + CTAB (indicated in red), and ethyl acetate (indicated in green): (a) for PE bottles and PE films; (b) for PP bottles and PP trays; (c) for PET bottles and PET trays; and (d) for PS trays. Linear regression lines are shown in corresponding colors. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)
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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 efficien...
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Context 1
... importance of polarity is more systematically illustrated in Fig. 5, showing the deodorization efficiencies of the analyzed odor compounds as a function of their log P ow value for the different packaging types. It can be observed that the influence of polarity is most pronounced when packages are washed with water, as the slope of the linear regression line fitted to the experimental data points ...
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... slopes of the linear fits can be decreased by adding a surfactant (indicated in red in Fig. 5). Generally, the decrease in removal efficiencies of the odorous compounds having a log P ow of zero and for the odorous compounds with a log P ow of 10 is only around 20%, whereas with water, this will be around 50%. Fig. 5 also shows that by using an organic solvent, such as ethyl acetate, the effect of the polarity of the odorous ...
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... slopes of the linear fits can be decreased by adding a surfactant (indicated in red in Fig. 5). Generally, the decrease in removal efficiencies of the odorous compounds having a log P ow of zero and for the odorous compounds with a log P ow of 10 is only around 20%, whereas with water, this will be around 50%. Fig. 5 also shows that by using an organic solvent, such as ethyl acetate, the effect of the polarity of the odorous constituents can almost be neglected, as the slope of the linear fit is almost zero (indicated in green in Fig. 5). This was already reported for plastic films (Roosen et al., 2020a), but is now, for the first time, confirmed ...
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... of zero and for the odorous compounds with a log P ow of 10 is only around 20%, whereas with water, this will be around 50%. Fig. 5 also shows that by using an organic solvent, such as ethyl acetate, the effect of the polarity of the odorous constituents can almost be neglected, as the slope of the linear fit is almost zero (indicated in green in Fig. 5). This was already reported for plastic films (Roosen et al., 2020a), but is now, for the first time, confirmed for other packaging types as ...
Citations
... 8 Recycled plastics can have an unpleasant odor, which makes them unsuitable for use in production lines. [10][11][12][13][14] Research indicates that the unpleasant odor of recycled plastic materials may be due to different factors, such as: thermal and environmental degradation (humidity and temperature) of the polymer, additives, contact with other substances, improper storage of the container etc. 15,16 Odor can be a limiting factor, which means that in some cases its most suitable use is for outdoor applications such as: benches, planters and litter garbage cans etc. ...
In recent years, the production and consumption of plastics has increased. This growth in production has resulted in an increasing amount of plastic waste, which is a global problem. Among plastics, high density polyethylene (HDPE) is one of the most widely used polymers in the packaging industry, so its waste is used in the recycling process. One of the main disadvantages of accepting recycled HDPE in production processes is its odour, which makes it impossible to use in production lines. The aim of this work is to reduce and/or eliminate the odours present in the HDPE samples selected for recycling through the use of sepiolites. FTIR analysis of the HDPE samples sent for recycling showed the presence of small amounts of polypropylene (PP), (PET), flexible polyurethane, dirt and adhesives, which could be the cause of the bad odour. Washing the sample showed a decrease in odour, probably due to the removal of dirt and other products that can lead to the degradation of the plastics responsible for the odour. The characterisation of the mixture of sepiolites and HDPE aims to analyse the mechanical and thermal stability of the sample. Not only can pre-washing lead to odour reduction, but also extrusion and injection processes at elevated temperatures can lead to the removal of volatile or semi-volatile compounds. Sensory analysis showed a reduction in odour in HDPE samples with sepiolites, particularly with 15% Pensil sepiolite, to the detriment of mechanical stability. At lower concentrations of sepiolite, the results are good from a sensory, mechanical and thermal point of view, which could mean an industrial application in the manufacture of benches, flower pots, etc.
... For both types of PCR, we found that increasing the percentage of recycled plastic included in the packaging, i.e., increasing the concentration of the odorous material, had a negative effect on the judgment of the products. This finding is in agreement with previous studies aiming to characterize and minimize odorants in PCR, reporting PCR odor as one of the main barriers to consumers' acceptability [27][28][29][30][31]. Ruokamo et al. [88] surveyed Finnish consumers and found that they would be more willing to accept visual irregularities (color and surface) in products made from recycled plastic rather than odor. ...
... Indeed, we found that increasing the percentage of PCR for the creamy bottles did not affect the perceived odor intensity, but it significantly increased for the 50% and 100% of the grey PCR. Efficiency measures of odor removal in the deodorization processes of PCR plastic are usually operationalized in terms of reduced perceived odor intensity [24,[29][30][31]. However, the effect of odor intensity is not always so straightforward. ...
This study investigates consumers’ acceptance and perceptions of post-consumer recycled (PCR) plastic packaging with an off-odor, and the effect of a sustainability claim thereupon. We utilized a mixed design to examine the influence of the percentage of PCR, packaging color, and the presence of a sustainability claim on consumer perceptions. Participants were presented with vignettes describing a scenario involving the purchase of shampoo bottles with or without a sustainability claim and asked to smell and rate the odor qualities of the bottles, as well as their acceptability and willingness to buy. The study found a main effect of the percentage of PCR and color on acceptability and willingness to buy and a main effect of the percentage of PCR on the perceived odor properties. However, the presence of a sustainability claim did not significantly affect consumer perceptions. The findings provide valuable insights for stakeholders in the sustainable production and consumption sector and offer recommendations for future research to further explore the impact of sustainability claims in shaping consumer acceptance of sustainable packaging with suboptimal sensory properties.
... Analysis of gas chromatography and mass spectrometry data demonstrates the efficacy of different washing media in eliminating odors from different polymers, as proposed by Roosen et al. [28]. This shows how effective certain washing mediums are at removing odors. ...
In the current scenario, a green product is designed to have a minimal impact on the environment as it is made from recycled materials. In the highly energy-intensive industry, green production has a significant influence on business sustainability. The intelligent environment around us created an unavoidable problem, because of the uncontrolled growth in waste materials like plastic and electrical trash. Both seriously endanger the environment, wildlife, and human health, trash has an impact on societal structures and financial systems in future generations. Industrial and domestic plastic wastes, which are dumped in landfills or the environment, are mostly made of polyethylene (PE) polymers. These wastes’ polymeric nature makes them difficult for microorganisms to degrade. Incorporating biological and chemical processes together is facilitated by pyrolysis and the biodegradation of alkenes to achieve the maximum biodegradation of PE plastics, as proposed in this study, to reduce plastic waste. This research outcome demonstrates that the Waste plastic recycling plant dataset is taken to show the decomposition of high-density PE plastic to simpler alkene with microbial-assisted degradation of alkene to biomass through bacterial communities. Communities of microbes from three different environments inoculating at three nutrient levels are monitored for their ability to degrade model alkenes (with several carbon atoms) within 5 days. There is Plenty of evidence indicating that the nutritional content significantly influences the rates at which hydrocarbons are broken down. These findings imply that the microorganisms required for alkene breakdown are present in a wide range of ambient microbial communities and are significantly chosen under optimized environments such as nutrient enrichment.
... The removal efficiency of each heteroatom component was calculated by comparing the ratio of relative peak areas before and after adsorption, as per Eq. (2) [41]. ...
... Cabanes et al. [24] employed an advanced decontamination approach utilizing hot water to eliminate odors, but they reported insufficient deodorization efficiency in the case of polyethylene. Demets et al. [25] and Roosen et al. [26] explored various approaches for dehalogenating plastic waste using an industrial water-based and ethyl acetate washing process. The results showed a significant decrease of over 70 % in volatile organic compounds. ...
... The fibers were subsequently switched in the inlet of the GCapparatus coupled with a mass-selective detector. The VOC compounds were identified using a modified NIOSH method described in [25,26]. ...
Most research into the treats of plastic wastes have concentrated mainly on single-exposure pathways or products. These practices fail to acknowledge that the complications of carbon particles from engines are produced not only by diesel but by any plastic oils due to the vast amount of contaminants. With the potential to significantly weaken the impact of contaminants, the present study investigates the effects of dehalogenation and catalytic pyrolysis on plastic waste, as well as the risks associated with plastic oil blends on diesel engine. Different types of washing were conducted to effectively dehalogenate plastic waste. After pretreatment, odor compounds were analyzed using GC–MS. Subsequently, various types of pretreated plastic samples underwent catalytic pyrolysis with a 5:1 ratio of HDPE to Al2O3⋅2SiO2⋅2H2O. Differences in physico-chemical properties and hydrocarbon compounds of oils were determined. Experiments were performed using different fuel blends in a diesel engine under steady-state conditions, and their effects on combustion, emissions, morphology, and size particles were analyzed. The results show that sample B exhibited a lower toxicity level of 1,3-butadiene compared to other samples, while acetone and terpenes represented the second and third-highest emission levels in flakes, respectively. Sample C started to degrade at low temperatures (<300 ◦C) due to carbon addition from ethyl acetate solvent into the tertiary carbon chain of the flakes. DAP3 fuel achieved a higher reaction due to its degree of unsaturation and lower viscosity, resulting in the formation of smaller fuel droplets at high injection pressure and heat release rate (HRR). Higher emission levels were observed by DAP1 and D100, exceeding the Euro 5/6 standard limits. However, DAP3 fuel resulted in an average reduction of ~17.14% and 21.86% in CO and smoke emissions, respectively, accompanied by a slight decrease in NOx and HC levels. Conversely, there were inconsistencies in the emission results observed with DAP2. Compared to D100, both DAP1 and DAP2 exhibited a significant accumulation and coarse particles in the PM10 forms at a peak of ~83 nm. Whereas the DAP3 showed a smaller mobility Dp with a low nucleation particle peak, which was prone to absorb the unburned HC soot and later change to accumulation mode particles.
... The solvent used is specific to the target polymer for dissolution, meaning the technology can also be used as a selective method for recycling parts of a multicomponent product such as multilayers [48]. The second option is a type of non-aqueous washing, typically employing chemicals such as solvents to have an additional effect on the pretreatment, for instance de-inking, de-lamination [48] or increased de-odourization [49,50]. Current European standardization [37] differentiates mechanical and chemical recycling by whether the process is "significantly changing the chemical structure of the material". ...
... Since a high cleaning effect was already reached in this study under condition B (55 °C and 1 wt.% NaOH), and washing with a detergent is also reported to be able to reduce the volatile organic compound (VOC) content in the recyclate from post-consumer plastic waste [99], incorporating a surfactant The de-inking mechanism can be revised as follows: ...
... Since a high cleaning effect was already reached in this study under condition B (55 • C and 1 wt.% NaOH), and washing with a detergent is also reported to be able to reduce the volatile organic compound (VOC) content in the recyclate from post-consumer plastic waste [99], incorporating a surfactant washing process may improve the quality of flexible polyolefin recyclates from post-consumer sources with lower energy consumption. The integration of the de-inking process into existing recycling plants, either by directly adding surfactants to the current washing unit or installing an additional hot-washing unit, should be further explored. ...
One of the major applications (40% in Europe) of plastic is packaging, which is often printed to display required information and to deliver an attractive aesthetic for marketing purposes. However, printing ink can cause contamination in the mechanical recycling process. To mitigate this issue, the use of surfactants in an alkaline washing process, known as de-inking, has been employed to remove printing ink and improve the quality of recyclates. Despite the existence of this technology, there are currently no data linking the de-inking efficiency with typical printing ink compositions. Additionally, it is necessary to investigate the de-inking process under the process parameters of existing recycling plants, including temperature, NaOH concentration, and retention time. This study aims to evaluate the performance of commonly used printing inks with different compositions under various washing scenarios for plastic recycling in conjunction with different de-inking detergents containing surfactants or mixtures of surfactants. The results indicate that the pigments applied to the ink have no significant effect on the de-inking process, except for carbon black (PBk 7). Nitrocellulose (NC) binder systems exhibit high de-inkability (over 95%) under the condition of 55 °C and 1 wt.% NaOH. However, crosslinked binder systems can impede the de-inking effect, whether used as a binder system or as an overprint varnish (OPV). The de-inking process requires heating to 55 °C with 1 wt.% NaOH to achieve a substantial effect. Based on the findings in this work, breaking the Van der Waals forces, hydrogen bonds, and covalent bonds between the printing ink and plastic film is an essential step to achieve the de-inking effect. Further research is needed to understand the interaction between surfactants and printing inks, enabling the development of de-inkable printing inks and high-performance surfactants that allow for de-inking with less energy consumption. The surfactant and NaOH have a synergistic effect in cleaning the printing ink. NaOH provides a negative surface charge for the adsorption of the cationic head of the surfactant and can hydrolyze the covalent bonds at higher concentrations (>2 wt.%).
... A main hurdle is the presence of undesired compounds that are present in recycled products (Eriksen et al., 2018;Horodytska et al., 2020). For example, the presence of volatile organic compounds (VOCs) and, consequently, unpleasant smell of reprocessed plastics is still a huge issue and one of the main reasons why large volumes of recycled plastic can currently not be used for many applications (Roosen et al., 2022a). ...
... It is indicated that water is able to remove the more polar compounds from plastic films, but that the more apolar compounds are removed for less than 50% . Such compounds are often chemically categorized as alkanes, aromatics, and terpenes, among others (Roosen et al., 2022a). For these more apolar compounds, at least a detergent should be added, which is able to form micelles and, hence, stabilize the VOCs in the water medium (Roosen et al., 2022a). ...
... Such compounds are often chemically categorized as alkanes, aromatics, and terpenes, among others (Roosen et al., 2022a). For these more apolar compounds, at least a detergent should be added, which is able to form micelles and, hence, stabilize the VOCs in the water medium (Roosen et al., 2022a). In previous studies, VOCs were mainly analyzed in sorted plastic waste 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.
... Important uses of GC also include the determination of trace levels of monomers, the monitoring of residual polymerization initiators and/or catalysts, the quantification of additives, and the evaluation of their degradation products [33]. Additional degradation products can also be evaluated together with odorous components [34]. ...
One convenient strategy to reduce environmental impact and pollution involves the reuse and revalorization of waste produced by modern society. Nowadays, global plastic production has reached 367 million tons per year and because of their durable nature, their recycling is fundamental for the achievement of the circular economy objective. In closing the loop of plastics, advanced recycling, i.e., the breakdown of plastics into their building blocks and their transformation into valuable secondary raw materials, is a promising management option for post-consumer plastic waste. The most valuable product from advanced recycling is a fluid hydrocarbon stream (or pyrolysis oil) which represents the feedstock for further refinement and processing into new plastics. In this context, gas chromatography is currently playing an important role since it is being used to study the pyrolysis oils, as well as any organic contaminants, and it can be considered a high-resolution separation technique, able to provide the molecular composition of such complex samples. This information significantly helps to tailor the pyrolysis process to produce high-quality feedstocks. In addition, the detection of contaminants (i.e., heteroatom-containing compounds) is crucial to avoid catalytic deterioration and to implement and design further purification processes. The current review highlights the importance of molecular characterization of waste stream products, and particularly the pyrolysis oils obtained from waste plastics. An overview of relevant applications published recently will be provided, and the potential of comprehensive two-dimensional gas chromatography, which represents the natural evolution of gas chromatography into a higher-resolution technique, will be underlined.
... Sorting, separation and other pre-treatment methods, which are also performed in mechanical recycling will not be discussed in detail, neither will surface treatment techniques such as de-inking. The interested reader is herewith referred to the respective specialized literature [34,[41][42][43][44][45][46][47][48]. The most important waste pre-treatment techniques for thermochemical recycling are dehalogenation and the removal of residues and additives prior to pyrolysis to produce a feedstock more suitable for petrochemical processes. ...
Advanced plastic waste recycling via pyrolysis and subsequent steam cracking of pyrolysis oils has the potential to partly close the cycle between the petrochemical production of plastics and current end-of-life waste management (i.e., downcycling, incineration, landfilling). However, the greatest obstacle is the complex composition of real plastic waste and their contamination with numerous additives and residues. Consequently, the lower quality of pyrolysis products compared to fossil feedstocks needs to be drastically improved by universally applicable upgrading and decontamination techniques. Techniques range from waste pre-treatment to reduce the halogen and additive contents, via in-situ techniques applied during pyrolysis to post-treatment techniques to purify the obtained pyrolysis oils using hydrotreatment, filtration or adsorption. Incorporated into a petrochemical cluster, high-quality petrochemical feedstocks can be produced from plastic waste, which, combined with electrification, could lead to a CO2 emission reduction of >90% compared to incineration as the current mostly used disposal method.
