Applied_Spectroscopy_Practica_01_01 - 26

2
14
Applied Spectroscopy Practica
Figure 1. Schematic representation of the main steps in the Polystyvert-patented16 dissolution/precipitation PS-recycling process; Cy and
H are used as the solvent and antisolvent, respectively.
environmental impact in terms of CO2 emissions.12 Some
key challenges include solvent management, the reduction
of the solvent volume used for purification, and the energetic
cost associated with drying the recycled resin.
This paper focuses on the optimization of a versatile recycling
process of dissolution/precipitation for polystyrene (PS),
developed by Polystyvert Inc.16 As illustrated in Fig. 1, the
first step consists of the dissolution of contaminated PS materials
coming from various streams such as construction, food,
electronics, etc. The " green " solvent used in this process is
p-cymene (Cy), which is a fragrant compound derived from
the essential oil of pine. Once the PS is solubilized, a first filtration
removes the macroscopic solid contaminants such as
other plastics, paper, etc. After a possible purification step17
used to remove fine insoluble impurities such as pigments or
lime, the PS is selectively precipitated using heptane (H) as an
antisolvent. The obtained precipitated PS " paste, " which consists
of PS swollen by the solvents, is then washed with H in
order to extract both the residual Cy and the soluble impurities.
After a devolatilization step, the PS is extruded to
obtain recycled PS pellets that can be directly used, while
the contaminated solvents are purified by distillation for
reuse purpose.
As a result, knowing the amounts of Cy, H, and PS at different
strategic points is essential to optimize the recycling
process. For example, when washing the PS paste with H,
it is necessary to remove as much Cy as possible to reduce
the energy consumption and duration of the devolatilization

Applied_Spectroscopy_Practica_01_01

Table of Contents for the Digital Edition of Applied_Spectroscopy_Practica_01_01