Decontamination of solid substrates using supercritical carbon dioxide-Application with trade hydrocarbonated surfactants

摘要

The phase behavior of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)triblock copolymers(PEO-PPO-PEO Pluronics)in liquid and supercritical carbon dioxide has been studied by cloud point measurements.It shows that such trade hydrocarbonated surfactants are fairly soluble(0.1 wt.%)in carbon dioxide in relatively mild conditions of temperature and pressure(T<65 deg C,P<30 MPa).An empirical model based on the molecular weight of the copolymer has been proposed to predict the pressure-temperature phase diagram for a series of Pluronics(10 wt.% of ethylene oxide).Furthermore,the water/CO2 interfacial tension has been measured to investigate the interactions between water and the polar moieties of the surfactants(PEO blocks and hydroxyl end-groups)as well as the interactions between CO2 and the"CO2-philic"moiety of the surfactants(PPO block).An interfacial saturation concentration was evidenced and it was shown to depend on the temperature at a given pressure.The cloud point curves and interfacial tension data are fully consistent with a change in the affinity of the surfactant for CO2 versus pressure and temperature.A correlation between CO2-philic characteristics and surface active properties of the copolymers is given.