Extraction of brominated flame retardants from acrylonitrile butadiene styrene (ABS) using supercritical carbon dioxide

Electrical and electronic equipment, as well as construction materials, commonly contain brominated flame retardants (BFRs), which are harmful to human health and the environment. These additives can cause major issues during disposal or recycling phases and, hence, methods to remove them are highly demanded. This study focuses on removing three BFRs, namely Tetrabromobisphenol A (TBBPA), Decabromodiphenyl Ether (decaBDE), and Hexabromocyclododecane (HBCD) from acrylonitrile butadiene styrene (ABS) plastic using supercritical carbon dioxide (scCO2) extraction. Virgin ABS compounds with known BFR concentrations were prepared by melt extrusion and injection moulding, and the scCO2 extraction parameters, including extractor configuration, extraction time, pressure, temperature, type of co-solvents and physical dimensions of the sample, were optimized. To further remove the BFRs, samples were then cleaned in a pressure extractor with isopropanol (hybrid approach), achieving high BFR removal efficiency. The elemental bromine and BFR concentrations in the samples, both before and after the scCO2 extraction, were examined by X-ray fluorescence (XRF) analysis and mass spectrometry, respectively. In a semi-continuous configuration for the scCO2 extractor at 100 °C and ethanol co-solvent we effectively removed all three BFRs achieving a maximum bromine extraction of 84.3% from ABS-TBBPA samples during 240 min. In the hybrid approach, the extraction increased to 89.4% by treating the samples in the pressure extractor.