Selective Removal of Colorants from Plastic Packaging via Bio-Based Solvent Extraction

Packaging accounts for nearly 40% of global plastic waste, and additives such as colorants significantly hinder recycling by degrading polymer properties and reducing the value of recyclates. Developing efficient strategies for selective colorant removal is therefore essential to improve the sustainability and economic viability of plastic recycling processes.

This work evaluates a solid–liquid extraction approach using bio-based solvents for the selective removal of colorants from polyethylene (PE) and polyethylene terephthalate (PET) packaging waste. High decolorization efficiencies were achieved for both low-density polyethylene (LDPE) and PET, with complete colorant removal observed in specific polymer–solvent systems. Polymer characterization by Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) confirmed that the treatment preserved the chemical structure and thermal properties of the materials. In addition, the extracted colorants could be readily separated from the solvent by filtration, enabling solvent reuse and pigment recovery without additional purification steps.

These findings demonstrate that bio-based solvent extraction is a technically viable and efficient strategy for the selective removal of colorants from plastic packaging waste. By improving the quality and recyclability of treated polymers, this approach can contribute to more sustainable and higher-value mechanical recycling processes.

Acknowledgments: This work was developed within the scope of the project CICECO–Aveiro Institute of Materials, UID/50011 & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020), financed by national funds through the FCT/MCTES (PIDDAC). This work is funded by national funds through FCT – Fundação para a Ciência e a Tecnologia, I.P., under the project GREEN-PATH (Ref. 2023.15169.PEX, DOI 10.54499/2023.15169.PEX). AMF acknowledge FCT for the research contract CEECIND/00361/2022 (DOI 10.54499/2022.00361.CEECIND/CP1720/CT0020).