ABSTRACT
In a great majority of separation and/or preconcentration processes a solid sorbent is brought into contact with a liquid or a gas phase with the aim of retaining some solutes on or in the solid sorbent phase. This chapter focuses on polyurethane foam sorbents, the most typical representative of the quasi-spherical membrane-shaped solid sorbents. Polyurethane foams are the most widely used cellular plastics in separations chemistry. The general principle for preparing cellular plastics is the dispersion of the gas phase in a liquid to obtain liquid foam which will then be solidified to a solid cellular plastic. The main methods for uniform dispersion of the gas bubbles are chemical, physical, or mechanical. A wide variety of cellular plastics may be made by mixing microspheres with the liquid polymer which on solidification gives rise to a cellular product without direct polymer/gas interaction.
