Investigation of imprinted sol-gel sorbents containing phosphonate ligands

This thesis describes the development of sol-gel materials containing bifunctional phosphonate ligands for the extraction of Sr⁺² and UO₂⁺² ions from solution. Previous techniques developed for removing Sr⁺² and UO₂⁺² ions from aqueous solutions have focused on solvent extraction methods. The extraction technique proposed here utilizes mesoporous sol-gel containing functionalized areas of phosphonate bifunctional compounds of the form ̲≡SiCH₂CH₂CH₂P(O)(OEt)₂, ( ̲≡SiCH₂CH₂CH₂)₂C[P(O)(OEt)₂]₂, and ( ̲≡SiCH₂CH₂CH₂P(O)(OEt)₂)₂(OCH₂CH₂O). By using a solid phase extraction sorbent, organic waste is minimized during the extraction process. The efficiency of Sr⁺² and UO₂⁺² ions extraction by these developed materials was investigated. Studies found that Sr⁺² and UO₂⁺² did not absorb onto the phosphonate ester based ligand sorbents. Imprinted phosphonic acid based sorbents did exhibit high affinities for both Sr⁺² over nonimprinted phosphonic acid based sorbents. These studies also showed no selectivity between Sr⁺² and Ca⁺². As for UO₂⁺², there was no increase in affinity for UO₂⁺² between the imprinted and nonimprinted phosphonic acid based sorbents. However both sorbents showed selectivity between Ca⁺² and UO₂⁺². Finally, the imprinted phosphonic acid sorbents had fast kinetics and could be regenerated in 2.0 M HCI.