Chemical recycling of Polyethene terephthalate as a sustainable binder in soil stabilization

ABSTRACT: As a form of white pollution, polyethene terephthalate (PET) waste imposes a significant burden on the environment and stabilizing weak soils can be considered one of the geotechnical solutions to recycle this waste. Bis(hydroxyethyl) terephthalate (BHET) is the main product produced by the glycolysis of PET waste. In this study, BHET polymer was dissolved in sodium hydroxide (NaOH) solutions to produce three different concentrations of BHET (5, 10, 20 g/L) to produce disodium terephthalate salt (Na2TP) and ethylene glycol (EG). The prepared solutions were mixed with Sand Bentonite Mixture (SBM) to enhance their physical and mechanical characteristics for landfill application. The maximum dry density values of the compacted SBM are increased whereas, optimum moisture content values are decreased with BHET-NaOH solution treatment. The values of unconfined compressive strength and elastic stiffness increased due to denser soil arrangement and enhancement in stress transfer due to Na2TP crystals at particle contact points. The Scanning electron microscopy revealed Na2TP crystals precipitated and coated on Sand as well as clay surfaces. The weight percentage obtained from Energy-dispersive X-ray spectroscopy supports the close resemblance of Na2TP crystals and Na-bentonite. The findings of this paper are extremely important and serve as a foundation for the applications of PET waste in large-scale geotechnical projects.