(672e) Extraction and Simulated Moving Bed Methods for Efficient Recovery of High-Purity Polycarbonates and Flame Retardants from Polymer Wastes

More than one million tons of polycarbonates and 500,000 tons of flame retardants from waste electrical and electronic equipment are consigned to landfills at an increasing rate of 3-5% per year. Recycling the polymer and flame retardants from the waste should have a major environmental impact. Pure solvents cannot selectively extract polycarbonates from mixtures of polymers with similar properties. In this study, selective mixed-solvents are found using guidelines from Hansen solubility parameters, gradient polymer elution chromatography, and solubility tests. A room-temperature extraction process using two mixed solvents sequentially is developed to recover polycarbonates with high yield (>95%). The recovered polycarbonates have similar purity and molecular weight distribution as virgin polycarbonates. A side stream of the extraction process contains two major flame retardants. A size-exclusion simulated moving bed process (SEC-SMB) is developed to recover high purity (>99%) flame retardants with high yield (>99%). The SEC-SMB is over an order of magnitude more efficient than conventional SEC processes. Fast startup methods are developed to reduce the SMB start-up time by more than 18 fold. The estimated cost of recovery is less than 30% of the purchase cost for polycarbonates and flame retardants. This method would potentially reduce raw materials from petroleum, use 84% less energy, reduce emission by 1-6 tons CO_­2­ per ton polymer, and reduce polymer accumulation in landfills and associated environmental hazards. A combination of mixed-solvent extraction and SEC-SMB can be economical for recovering other polymers and small molecules from polymer wastes.