Potentiometric titrations of chemically immobilised humic acid and salicylic acid and their uptake of Eu(III) as a function of pH and ionic strength

Potentiometric titrations of chemically immobilised humic acid (CBHA) and salicylic acid (CBSA), have been performed for comparison with titrations of silica gel which is the material upon which the acids were immobilized. The results for the CBHA show a sensitivity to ionic strength effects while results for the CBSA and silica gel showed an insensitivity to changes in ionic strength. The chemically immobilized materials lost some organic carbon while in solution and whereas the amount of dissolved organic carbon (DOC) was constant with respect to pH changes for the CBHA, a pH dependence was observed for the DOC in the case of CBSA. Eu(III) uptake is highly enhanced (relative to uptake by silica gel) in the case of CBSA, especially at low pH values (5), and slightly enhanced after pH of 7. In the case of CBHA, there is a slight enhancement of Eu(III) uptake both at pH values below and after pH of 7. For all solids, this uptake was insensitive to ionic strength changes.