Evaluation of the efficiency of odor removal from recycled HDPE using a modified recycling process
A series of recent global and local policymaking processes is promoting or demanding developments in the recycling of post-consumer plastic packaging waste. After successfully clearing most hurdles in the PET bottle sector to promote a successful market launch of the recycled PET products, it is now important to take measures to meet the challenges associated with the recycling of polyolefins such as HDPE. In this respect, the need to further improve recycling technologies is currently prevalent because the quality parameters of the recycled materials do not yet meet the strict industrial requirements. In this context, apart from optical or mechanical properties, there is increasing awareness of odorous contaminants in the recycled products. Therefore, in this study, a modified HDPE recycling method was evaluated for its ability to reduce odors. For the aim of mapping and understanding the odor of recycled HDPE pellets with different residence times in a special decontamination reactor a combinatory sensory and instrumental-olfactometric approach was applied. Furthermore, based on the characterization of the causative odorants by gas chromatography-olfactometry and two-dimensional gas chromatography-mass spectrometry/olfactometry, quantitative determination of selected odorants was carried out over time using stable isotope dilution analysis. With regard to the decontamination efficacy of the evaluated decontamination process, we observed that the decrease in the concentration profiles of the monitored odorants went along with a sensorially relevant overall odor minimization of the recycled HDPE. The results of the study are aiding the adaptation of technological procedures for smell reduction or complete decontamination.