| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2005: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2004: ¥2,400,000 (Direct Cost: ¥2,400,000)
|
|---|
| Research Abstract |
The hydration numbers of anions were determined on two strongly basic anion exchange resins (tetramethylammonium- and hydroxyethyltrimethylammonium-types, hereafter referred to as SBA1 and SBA2) and one weakly basic anion exchange resin (trimethylamino-type, hereafter referred to as WBA), which were dried in the air at a relative humidity of 35% at 298 K. The anions on SBA1 had increasing hydration numbers with a decrease in Gibbs hydration energy (ΔG_<hyd>) in water, with a limiting hydration number of 3 observed in the range of ΔG_<hyd><-400 kJ mol^<-1>. The selectivity coefficient of the anions accordingly decreased with the decrease in ΔG_<hyd>, to a limiting value of 10^<-1> in the range of ΔG_<hyd><-400 kJ mol^<-1>. The anions on WBA were more dehydrated than those on SBA1. The remarkably smaller hydration numbers of H_2P0_<4^->,F^-, and HCOO^- on WBA are ascribed to the hydrogen bonding between the H atom on the protonated amine group and the negatively charged basic sites on the anions. There were, however, no significant differences between the selectivity coefficients of such anions on WBA and those on SBA1. In contrast, only H_2P0_<4^-> was extremely dehydrated on SBA2 and SBA3 with an increase in selectivity coefficient. The PM3 calculation suggested the hydrogen bonding between the H atom on the hydroxyethyl group and the O atom of H_2PO_<4^->. The hydrogen bonding which occurs at a different site from the electrostatic attraction sites is effective to enhance the dehydration and adsorption of hydrophilic polyatomic anions. The hydration states of the anions on SBA1 may well simulate those of the anions distributed in benzene together with counter cations.
|
