Abstract
BACKGROUND: The presence of certain polybrominated flame retardants in electrical and electronic equipment plastics can make recycling of the raw materials difficult. We have investigated the use of ionic liquids to selectively remove these harmful components and a series of imidazolium‐ and pyridinium‐based ionic liquids have been prepared in a microwave reactor. Microwave synthesis is rapid and the products obtained are identical to those obtained by conventional synthetic methods.
RESULTS: The solubilities of the flame retardants decabromodiphenyl ether (deca‐BDE), antimony trioxide and high‐impact polystyrene (HIPS) in the ionic liquids, identified 1‐hexylpyridinium bromide as the most suitable for solid–liquid and liquid–liquid extraction, for the selective recovery of materials from the plastic composite. Optimum extraction of deca‐BDE and antimony trioxide was achieved by liquid–liquid extraction from an 8% solution of HIPS in ethyl acetate, with a reaction time of 10 min at 77 °C. The percentages of deca‐BDE and Sb~2~O~3~ extracted are 92.7% and 99.9%, respectively. The chain length of the polymer is not degraded by the extraction process, giving a residue that can be recycled.
CONCLUSIONS The results show that ionic liquids can be designed to achieve selective material recovery from composites. Copyright © 2008 Society of Chemical Industry