Surfactant-Assisted Nuclear Decontamination Process of Solid Substrates in Supercritical CO_2: PC-SAFT Equation of State as a Tool for Modeling the Phase Behavior of Block and Graft PDMS-PEO Amphiphilic Copolymers

摘要

The phase behavior of commercially available PDMS-g-PEO and PDMS-b-PEO surfactants (graft and block type poly (dimethyl siloxane)-poly (ethylene oxide) copolymers) was studied to evaluate their applicability in a supercritical CO_2 (scCO_2) based decontamination process. To this aim, experimental cloud points have been measured in scCO_2 using a classical variable-volume view-cell apparatus. The temperature and pressure ranges were from 298 to 338 K and from 5 to 40 MPa, respectively. The Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was used to model the experimental PDMS-PEO cloud-point curves. The phase behavior of the block copolymers could be described very accurately. A satisfactory description of the graft copolymers was achieved by accounting for the number of the grafted PEO branches. Applying PC-SAFT as a prediction tool, we managed to design an "optimized" surfactant for our needs - i.e. a surfactant with lowest-possible cloud-point pressures and a defined hydrophilic/CO_2-philic balance.