Abstract
Temperature-swing adsorption (TSA) is one of the promising application fields of temperature-sensitive gels. In TSA, both the adsorption and desorption are carried out only by shifting temperature within a few degrees across the phase transition temperature of gel. Among the various gels, photocross-linked temperature-sensitive gels are the most promising for practical applications because of their higher mechanical strength. The objective of the present study is to clarify the adsorption characteristics of TSA from kinetic point of view.Temperature-sensitive ENT-DEAA gels were polymerized with a photo-crosslinkable prepolymer ENT-3400 and temperature-sensitive diethylacrylamide (DEAA) monomer. The effects of gel size on swelling-shrinking behavior were investigated first. The equilibrated swelling ratio did not depend on gel size. The swelling and shrinking rates were analyzed based on first-order reaction kinetics. The swelling rate was almost constant with gel sizes up to about 0.4 mm, and decreased with further increase in gel size. In the shrinking process, on the other hand, the rate decreased with further increase in gel size.The effects of gel size on adsorption and desorption rates were also investigated using nonionic surfactant Triton X-102 and phenol as an adsorbate. The equilibrated adsorbed amount did not depend on gel size. Both the adsorption and desorption rates decreased with increasing gel size. The dependency of adsorption rates decreased with increasing gel size. The dependency of desorption rate on gel size was larger than that of adsorption rate. These dependencies on gel size were discussed from practical point of view.
