Solid-phase extractive preconcentration and separation of lanthanum(III) and cerium(III) using a polymer-supported chelating calix [4] arene resin

Abstract

In the present paper, solid-phase extractive preconcentration and separation of lanthanum(III) and cerium(III) using calix[4]arene-o-vanillinsemicarbazone immobilized on a polymeric matrix, a Merrifield peptide resin, is proposed. The diamino derivative of calix[4]arene was first diazotized and coupled with o-vanillinsemicarbazone to obtain a new "upper-rim" functionalized calix[4]arene-o-vanillinsemicarbazone. It was then covalently linked to the Merrifield peptide resin and characterized by FT-IR and elemental analysis. Quantitative studies were carried out by spectrophotometry and ICP-AES with a relative standard deviation of 1.7%. Various physicochemical parameters like pH, concentration of eluting agents, flow rate, total sorption capacity, metal-ligand stoichiometry, exchange kinetics, preconcentration factor, distribution coefficient, breakthrough capacity, resin stability, and effect of electrolytes and associated metal ions have been studied. The uptake and stripping of these metal ions on the resin was fast, indicating a better accessibility of La(III) and Ce(III) towards the chelating sites. Detection limits corresponded to three times the standard deviation of the blank (3σB) and amounted to 3.05 and 6.86 µg/L, along with preconcentration factors of 153 and 133 for La(III) and Ce(III), respectively. The robustness of the procedure is demonstrated by the recoveries obtained (>97.5%) for La(III) and Ce(III) in the presence of several cations and anions. The proposed method was satisfactorily applied to the separation of La(III) and Ce(III) from each other and also from U(VI) and Th(IV) by sequential acidic elution and varying pH. The validity of the method was tested by analyzing these metal ions in monazite sand and standard geological materials.