Effect of molten salts on the structure, morphology and electrical conductivity of PET-derived carbon nanostructures

Abstract

The effective disposal and/or utilization of polyethylene terephthalate ((C10H8O4)n, PET) waste plastics are currently global problems that need to be addressed urgently. The current research examines the molten salt-based thermal treatment of PET waste, as a new approach to tackle this challenge. The effect of various molten salts, comprising KCl, MgCl2, ZnCl2, NaCl, KF and NaF on the structural and morphological evolution of PET upon heating in air to 1300 °C is investigated. PET is transformed into carbon materials with different characteristics, including graphene-like nanosheets and porous nanostructures, with different electrical conductivity values, depending on the type of salt employed. The melting and evaporation points, as well as the cation size of the salt, are found to have a significant influence on the morphology and the crystallization level of the carbon products, based on which the characteristics of PET-derived carbons are regulated. Accordingly, the crystallinity and graphitization degree of the carbon materials obtained in NaF, KF and NaCl are found to be considerably greater than those obtained in ZnCl2, MgCl2 and KCl. The possible mechanism involved in the conversion of PET into carbon nanostructures in the molten salt environment is discussed. The results obtained provide insights into molten salt conversion of PET into carbon materials with different properties for various applications.