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

Washington Orlando Meneses Quelal,Borja Velázquez-Martí,Andrés Ferrer Gisbert

doi:10.1007/s11356-021-15611-w

Washington Orlando Meneses Quelal, Borja Velázquez-Martí + Show 1 more

Open Access

https://doi.org/10.1007/s11356-021-15611-w

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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.

Highlights

Plastics have become a crucial part of our lifestyles as they are highly functional, hygienic, lightweight, and inexpensive (Pol and Thiyagarajan 2010; Pol and Thiyagarajan 2010)
For an 11–12% w/v NaCl concentration, most PS (80.3%) floated to the surface, while acrylonitrile butadiene styrene (ABS), PA, and PC sank to the bottom
For a 40% NaCl w/v concentration, most of Separation of the virgin polymer mixture with C2H5OH high density polyethylene (HDPE)+PP fraction is previously separated with water and ethyl alcohol into individual polymers of PP and HDPE (Fig. 6)

Summary

Introduction

Plastics have become a crucial part of our lifestyles as they are highly functional, hygienic, lightweight, and inexpensive (Pol and Thiyagarajan 2010; Pol and Thiyagarajan 2010). According to Mancheno et al (2016), the highest amount of plastics adding up worldwide is made from polycarbonate (PC), polystyrene (PS), Responsible Editor: Ta Yeong Wu. the problem is that all the plastics generated end up as waste causing negative effects on the environment (Huysman et al 2017). Most plastics take hundreds of years to disintegrate when they are dumped in a landfill. The increasing amount of plastic waste is exerting great pressure on the limited space of landfills (Takoungsakdakun and Pongstabodee 2007) causing improper management negatively affecting the environment (Aljerf 2016). In correspondence with the continuous growth of post-consumer plastic waste and the Environ Sci Pollut Res inadequate management of these, there is a special interest in continuing to search for efficient, economic, and environmental alternatives to better manage plastic waste (Bing et al 2016)

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