Recycling of Bulk Polyamide 6 by Dissolution-Precipitation in CaCl<sub>2</sub>-EtOH-H<sub>2</sub>O Mixtures
To address the problems of virgin plastic production from fossil resources and the growing amount of plastic waste, a rapid transition to a circular economy is being pursued. The separation of mixed plastics into pure fractions is of paramount importance for promoting recycling and preventing downcy...
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2025-01-01
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| author | Ruben Goldhahn Ann-Joelle Minor Liisa Rihko-Struckmann Siew-Wan Ohl Patricia Pfeiffer Claus-Dieter Ohl Kai Sundmacher |
| author_facet | Ruben Goldhahn Ann-Joelle Minor Liisa Rihko-Struckmann Siew-Wan Ohl Patricia Pfeiffer Claus-Dieter Ohl Kai Sundmacher |
| author_sort | Ruben Goldhahn |
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| description | To address the problems of virgin plastic production from fossil resources and the growing amount of plastic waste, a rapid transition to a circular economy is being pursued. The separation of mixed plastics into pure fractions is of paramount importance for promoting recycling and preventing downcycling. In this study, experimental parameters were determined for the selective bulk dissolution of polyamide 6 (PA 6) filaments (1.75 mm diameter, 1 cm length) in CaCl<sub>2</sub>-EtOH-H<sub>2</sub>O mixtures (CEW) at 75 °C. These parameters included the energy supply mode, dissolution time, CEW composition and CEW:PA mass ratio. Compared with energy supply by microwaves, energy supply by ultrasound improved the yield of dissolved and recovered PA 6 after 5 h from 31% to 52%. In total, the yield of PA 6 after 3 h of bulk dissolution increased from 18% to 69% when the energy supply mode was changed from microwave to ultrasound and the H<sub>2</sub>O:EtOH molar ratio of CEW was increased from 0.40 to 1.33 while maintaining an optimal CEW:PA mass ratio of 8.5. Additionally, master plot analysis suggested that dissolution under microwave energy supply followed a contracting cylinder model, whereas dissolution under ultrasonic energy supply aligned with a 2D diffusion or third-order kinetic model. Microscopic observations suggested that, in the case of ultrasonic energy supply, oscillating bubbles on the particle surface enhanced the dissolution rate of PA 6 filaments in CEW. |
| format | Article |
| id | doaj-art-f1fde661b36747f5adb4f4572d678564 |
| institution | OA Journals |
| issn | 2313-4321 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | MDPI AG |
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| series | Recycling |
| spelling | doaj-art-f1fde661b36747f5adb4f4572d6785642025-08-20T02:03:32ZengMDPI AGRecycling2313-43212025-01-01101510.3390/recycling10010005Recycling of Bulk Polyamide 6 by Dissolution-Precipitation in CaCl<sub>2</sub>-EtOH-H<sub>2</sub>O MixturesRuben Goldhahn0Ann-Joelle Minor1Liisa Rihko-Struckmann2Siew-Wan Ohl3Patricia Pfeiffer4Claus-Dieter Ohl5Kai Sundmacher6Max Planck Institute for Dynamics of Complex Technical Systems, Department of Process Systems Engineering, Sandtorstraße 1, 39106 Magdeburg, GermanyMax Planck Institute for Dynamics of Complex Technical Systems, Department of Process Systems Engineering, Sandtorstraße 1, 39106 Magdeburg, GermanyMax Planck Institute for Dynamics of Complex Technical Systems, Department of Process Systems Engineering, Sandtorstraße 1, 39106 Magdeburg, GermanyInstitute of Physics, Faculty of Natural Sciences, Otto-von-Guericke University, Universitätsplatz 2, 39106 Magdeburg, GermanyInstitute of Physics, Faculty of Natural Sciences, Otto-von-Guericke University, Universitätsplatz 2, 39106 Magdeburg, GermanyInstitute of Physics, Faculty of Natural Sciences, Otto-von-Guericke University, Universitätsplatz 2, 39106 Magdeburg, GermanyMax Planck Institute for Dynamics of Complex Technical Systems, Department of Process Systems Engineering, Sandtorstraße 1, 39106 Magdeburg, GermanyTo address the problems of virgin plastic production from fossil resources and the growing amount of plastic waste, a rapid transition to a circular economy is being pursued. The separation of mixed plastics into pure fractions is of paramount importance for promoting recycling and preventing downcycling. In this study, experimental parameters were determined for the selective bulk dissolution of polyamide 6 (PA 6) filaments (1.75 mm diameter, 1 cm length) in CaCl<sub>2</sub>-EtOH-H<sub>2</sub>O mixtures (CEW) at 75 °C. These parameters included the energy supply mode, dissolution time, CEW composition and CEW:PA mass ratio. Compared with energy supply by microwaves, energy supply by ultrasound improved the yield of dissolved and recovered PA 6 after 5 h from 31% to 52%. In total, the yield of PA 6 after 3 h of bulk dissolution increased from 18% to 69% when the energy supply mode was changed from microwave to ultrasound and the H<sub>2</sub>O:EtOH molar ratio of CEW was increased from 0.40 to 1.33 while maintaining an optimal CEW:PA mass ratio of 8.5. Additionally, master plot analysis suggested that dissolution under microwave energy supply followed a contracting cylinder model, whereas dissolution under ultrasonic energy supply aligned with a 2D diffusion or third-order kinetic model. Microscopic observations suggested that, in the case of ultrasonic energy supply, oscillating bubbles on the particle surface enhanced the dissolution rate of PA 6 filaments in CEW.https://www.mdpi.com/2313-4321/10/1/5circular economypolymer recyclingpolyamide 6dissolution-reprecipitationprocess intensification |
| spellingShingle | Ruben Goldhahn Ann-Joelle Minor Liisa Rihko-Struckmann Siew-Wan Ohl Patricia Pfeiffer Claus-Dieter Ohl Kai Sundmacher Recycling of Bulk Polyamide 6 by Dissolution-Precipitation in CaCl<sub>2</sub>-EtOH-H<sub>2</sub>O Mixtures Recycling circular economy polymer recycling polyamide 6 dissolution-reprecipitation process intensification |
| title | Recycling of Bulk Polyamide 6 by Dissolution-Precipitation in CaCl<sub>2</sub>-EtOH-H<sub>2</sub>O Mixtures |
| title_full | Recycling of Bulk Polyamide 6 by Dissolution-Precipitation in CaCl<sub>2</sub>-EtOH-H<sub>2</sub>O Mixtures |
| title_fullStr | Recycling of Bulk Polyamide 6 by Dissolution-Precipitation in CaCl<sub>2</sub>-EtOH-H<sub>2</sub>O Mixtures |
| title_full_unstemmed | Recycling of Bulk Polyamide 6 by Dissolution-Precipitation in CaCl<sub>2</sub>-EtOH-H<sub>2</sub>O Mixtures |
| title_short | Recycling of Bulk Polyamide 6 by Dissolution-Precipitation in CaCl<sub>2</sub>-EtOH-H<sub>2</sub>O Mixtures |
| title_sort | recycling of bulk polyamide 6 by dissolution precipitation in cacl sub 2 sub etoh h sub 2 sub o mixtures |
| topic | circular economy polymer recycling polyamide 6 dissolution-reprecipitation process intensification |
| url | https://www.mdpi.com/2313-4321/10/1/5 |
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