Extraction of polybrominated diphenyl ethers contained in waste high impact polystyrene by supercritical carbon dioxide

A new recycling process for the supercritical CO2 (sc-CO2) extraction of polybrominated diphenyl ethers from waste high impact polystyrene (HIPS) was developed in this paper. HIPS was first dissolved in d-limonene. The remaining decabromo diphenyl ether (decaBDE) particles in solution were then removed by centrifugation, and the PBDEs in the centrifugate solution were further extracted by sc-CO2. The influence of temperature and pressure, the volume ratio of sc-CO2 to plastic solution, and the concentration of decaBDE in the solution on the separating efficiency were investigated. The decaBDE particles in 20 % of the HIPS solution can be removed by centrifugation at a speed of 10,000 r/min at 30 A degrees C. The suitable sc-CO2 fluid conditions were 65 A degrees C and 20 MPa, and the optimum volume ratio of the sc-CO2 to the HIPS solution was 2:1. More than 97 % of the PBDEs were successfully removed, and the concentration of PBDE residues in the recycled HIPS was reduced to lower than 0.1 % (dry) by this recycling process.