Pretreatment of Plastic Waste: Removal of Colorants from HDPE Using Biosolvents

abstract

Plastics recycling remains a challenge due to the relatively low quality of the recycled material, since most of the developed recycling processes cannot deal with the additives present in the plastic matrix, so the recycled products end up in lower-grade applications. The application of volatile organic solvents for additives removal is the preferred choice. In this study, pretreatment of plastic packaging waste to remove additives using biosolvents was investigated. The plastic waste used was high-density polyethylene (HDPE) with blue and orange colorants (pigment and/or dye). The first step was to identify the type of colorants present in the HDPE, and we found that both plastics presented only one colorant that was actually a pigment. Then, limonene, a renewable solvent, was used to solubilize HDPE. After HDPE dissolution, a wide range of alcohols (mono-, di-, and tri-alcohols) was evaluated as antisolvents in order to selectively precipitate the polymer and maximize its purity. The use of limonene as solvent for plastic dissolution, in combination with poly-alcohols with an intermediate alkyl chain length and a large number of hydroxyl (OH) groups, was found to work best as an antisolvent (1,2,3-propanetriol and 1,2,4-butanetriol), leading to a removal of up to 94% and 100% of the blue and orange pigments, respectively. Finally, three cycles of extraction were carried out, proving the capability of the solvent and antisolvent to be recovered and reused, ensuring the economic viability and sustainability of the process. This pretreatment provides a secondary source of raw materials and revenue for the recycling process, which may lead to an increase in the quality of recycled polymers, contributing to the development of an economical and sustainable recycling process.

keywords

EXTRACTION; SOLVENT; CRYSTALLINITY; POLYMERS

subject category

Biochemistry & Molecular Biology; Chemistry

authors

Ferreira, AM; Sucena, I; Otero, V; Angelin, EM; Melo, MJ; Coutinho, JAP

Groups

G4 - Renewable Materials and Circular Economy

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

European network of FURan based chemicals and materials FOR a Sustainable development (FUR4Sustain)

acknowledgements

This work was developed within the scope of the projects CICECO-Aveiro Institute of Materials, UIDB/50011/2020 and UIDP/50011/2020 financed by national funds through the FC/MCTES, and, when appropriate, cofinanced by FEDER under the PT2020 Partnership Agreement. This publication is supported by COST Action FUR4Sustain- European network of FURan based chemicals and materials FOR a Sustainable development, CA18220, supported by COST (European Cooperation in Science and Technology). FCT/MCTES is also acknowledged for funding 2020.00647.CEECIND (Vanessa Otero), and Research Unit LAQV-REQUIMTE (UIDB/50006/2020; UIDP/50006/2020).