Active transport of Selective Metal Ions by Thermo-Sensitive Polymer Gel

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With the aim of developing polymeric gels sensitive to external stimuli and able to reversibly adsorb and release divalent ions, co-polymer gels (pNIPA/MA) of N-isopropylacrylamide and methacrylic acid monomers were prepared. Cu, Co, Ni, and Pb ions were used for target divalent ions. The gels shows in a strong affinity to target ions at 45 ℃, deswelling state, but the affinity is diminishes at the swelling state, 25 ℃. The pNIPA/MA gel adsorbed Cu, Co, Ni ions at the deswelling state, and released the metal ions at the swelling state. Therefore, Cu ion was transported from higher temperature liquid (45 ℃) to lower temperature liquid (25 ℃) against gradient of Cu ion concentration. It is possible that the pNIPA/MA gel removed Cu ion less than 1 ppm at 45 ℃, and concentrated that to more than 100 times at 25 ℃. For development of separation speed, acceleration of thermal responsibility was also investigated on pNIPA gel. The pNIPA gel prepared in a hydrophobic tubing as a matrix, PTFE or silicone, deswelled faster than that prepared in a hydrophilic tubing. The hydrophobic matrix was suitable for preparation of the fast-responsive pNIPA gel. The kinetic parameters of deswelling were also investigated in the presence of sugars as hydrophilic probes. Furthermore, another type of thermo-sensitive gel having an upper critical solution temperature was investigated by using N-acetylacrylamide. The gels shows considerable change of volume by changing of temperature in water-alcohol system.