Sorbents with non-covalently immobilized β-diketones for preconcentration of rare earth elements

A comparison of the efficiency of sorbents obtained by different methods of non-covalent immobilization of β-diketones on some low-polar matrices with respect to extraction of rare earth elements (REEs) was carried out. It was shown that sorbents containing reagent amounts of 1-8mmol/g can be obtained by sorption of reagents on low-polar matrices from aqueous and aqueous-organic solutions, and the value for the maximum capacity of the sorbent correlates with the specific surface of the matrix. Similar sorbents were also prepared by impregnating the matrix with reagent. It was found out that, under the chosen conditions, sorbents modified by extracting reagent from the aqueous solutions are more stable and extract lanthanum with higher distribution coefficients than those obtained by impregnation. We have found conditions for quantitative extraction of REEs from seawater in the proposed preconcentration systems (pH 4.0, minicolumn dimensions 2×10mm, v=4ml/min). It was shown that all REE may be quantitatively recovered in both ways: on modified sorbents and as complexes with reagents on unmodified matrices. We have proposed a sorbent for lanthanum preconcentration from large volumes of water samples (500ml). The sorbent is stable in dynamic conditions and is based on hyper cross-linked polystyrene modified with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (PMBP). Desorption could be carried out with 1-2M HNO₃. REEs were determined by ICP-MS, LODs achieved were in ng/l range.