Separation of virgin plastic polymers and post-consumer mixed plastic waste by sinking-flotation technique

Abstract

The main objective of this research is to separate virgin polymers (PA, PC, PP, HDPE; PS, and ABS) and post-consumer plastic waste from municipal solid waste (MSW) using the sinking-flotation technique. Separation was carried out on a pilot scale in an 800-l useful volume container with 160 rpm agitation for one hour. Tap water, ethanol solutions, and sodium chloride at different concentrations were used as densification medium. Virgin polymers were separated into two groups: low-density (HDPE and PP) and high-density polymers groups (PS, ABS, PA, and PC). Polymers whose density was less than that of the medium solution floated to the surface, while those whose density was greater than those of the medium solution sank to the bottom. The experimental results showed that complete separation of HDPE from PP achieved 23% ethanol v/v, whereas high-density polymers separated up to 40% w/v sodium chloride. Polymer recovery ranged from 70 to 99.70%. In post-consumer recycled plastic waste, fractions of 29.6% polyolefins, 37.54% PS, 11% ABS, 8% PA, 12% PC PET, and PVC were obtained. Finally, cast plates were made of the post-consumer waste to properly identify the polymer type present in the separated fractions.

Recent Studies and Technologies in the Separation of Polyvinyl Chloride for Resources Recycling: A Systematic Review

“…According to relevant research compiled in this systematic review, many gravity separation methods have been extensively investigated and employed for PVC recycling. These techniques include sink-float separation [27], hydrocyclone with suspension media [28,29], hydraulic separator [30], and jig separation [31,32], and they vary in terms of equipment requirements, operational parameters, and applications as summarized in Table 1.…”

“…The sink float separation technique was developed and has been employed as a method of separation based on varying the density of the aqueous media utilized during the density-based process. According to Quelal et al [27], multiple separation steps were needed with different media density (i.e., 1.000, 1.090, 1.100, and 1.175 g/cm 3 ) to separate post-consumer plastics including PVC, polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), and acrylonitrile butadiene styrene (ABS). These authors reported an approximately 84.6% recovery of each plastic using sodium hydroxide (NaOH) and tap water as an aqueous media for separation.…”

Recovery of Plastics from WEEE through Green Sink–Float Treatment

“…Bill et al, 2022 [ 17 ] used solutions prepared with demineralised water and magnesium sulfate (MgSO 4 ) at different concentrations for sorting different plastic polymers. In the study by Meneses Quelal et al [ 18 ] the separation efficiency of plastics in aqueous solutions to which ethanol (C 2 H 6 O) and sodium chloride (NaCl) were added at different concentrations was evaluated, obtaining recovery rates ranging from 70% to 99.70% for virgin plastics.…”

Practicality of physical recycling method for waste polymer composites exampled via high density polyethylene/automobile shredder residue composites

“…9,10 Cleaner utilization of ASR is still of great challenges and significance. 11 Sorting and chemical recycling are generally considered the preferred methods, including foam flotation, 12 solvent separation, 13 gasification technology 14 and so forth. However, ASR is too complex to be sorted thoroughly, making it only possible for single or partial components such as metals, polyvinyl chloride.…”