Mixed plastics flotation

Plastic-Plastic Separation Both dry and wet processes can be used to separate one plastic from another in a recycling operation. The most common wet separation methods are based on differences in density between particles of different plastics [1, 2, 10, 49], Density is a bulk property of the plastic. Unfortunately, many factors beyond polymer type affect density. Plastic particles can also show differences in surface properties. Plastic-plastic separation methods based on surface property differences include triboelectric separation [75] (a dry process) and froth flotation [75] (a wet process). Density-based and surface-property-based methods for separating a stream of mixed plastics are covered in the following sections. 

Examples of mixed post-consumer plastic waste by the combination of a three-stage sink-float method and selective flotation have been presented. The appropriate conditions, e.g., wetting agents, frother, depressant, and pH condition, are of importance (122). 

S. Pongstabodee, N. Kunachitpimol, and S. Damronglerd, Combination of three-stage sink-float method and selective flotation technique for separation of mixed post-consumer plastic waste, Waste Manage. (Oxford), 28(3) 475—483,2008. 

Takoungsakdakun, T., Pongstabodee, S., 2007. Separation of mixed post-consumer PET-POM-PVC plastic waste using selective flotation. Separation Purification Technology 54 (2), 248-252. 

Pomykala JA Jr., Jody BJ, Daniels EJ. Thermoplastic separation and recovery for various mixed scrap plastics by the argonne developed froth flotation technology. Global plastics envi-romnental conference proceedings 2007. 

By the flotation method, a light and a heavy fractions were separated from urban plastic wastes in an industrial plant. In Table 2, Mix 5 corresponds to the light fraction, whose composition was estimated by thermal analysis Mix 6 is a blend of virgin HDPE with 25 wt% of the heavy fraction. 

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