Kinetics of thorium-polyelectrolyte interaction

The rate constants for thorium dissociation from humic acid, PMA (polymaleic acid) and PMVEMA (poly[-methylvinylether/maleic acid]) were measured in the pH range of 4.20 to 5.94. The rate of thorium dissociation from these polyelectrolytes was determined by measuring the rate at which thorium was complexed with an exchange ligand. Arsenazo III was employed as the exchange ligand and its complexation of thorium was monitored by visible spectroscopy. The dissociation of thorium from these polyelectrolytes occurred by several first order pathways. These pathways fit into two categories based on their dependence on pH, temperature and the amount of time thorium was in contact with the polyelectrolyte prior to dissociation. Less than 6 +/- 1 KJ/mole activation entropy was found for the first category of thorium dissociation. Between 20 +/- 2 and 30 +/- 2 KJ/mole activation energy and from -200 +/- 20 to -250 +/- 20 joule/mole-K0 activation entropy was found for the second category of thorium dissociation