Uptake of cesium, strontium and europium by a poly(sodium acrylate-acrylic acid) hydrogel

Abstract

The uptake of cesium, strontium and europium from dilute nitric acid solutions by a poly(sodium acrylate-acrylic acid) PAA hydrogel has been investigated. pH variations are consistent with cation exchange processes: COO −, Na + H + , COO −, Na + M m+ ( M m+ = Cs + and Sr 2+) and COOH Eu 3+ . Saturation of the gel is achieved for metal/carboxylate ratios R = 0.5. The swelling ratios of gels loaded with metal cations are those of uncharged, shrunk gels (Sr, Eu) or of charged, swollen gels (Cs) in agreement with the formation of uncharged (COO) 2Sr, (COO) 2EuX (X = NO 3 or OH) type complexes and (COO −, Cs +) ion pairs. The metal cations are extracted in the gels following the order of their affinities with carboxylic groups Eu 3+ > Sr 2+ > Cs +. An increase of the ionic strength of the metal aqueous solution up to 0.5 M NaNO 3 leads to slightly decrease the europium uptake by the PAA hydrogel, but 0.1 M NaNO 3 is sufficient to prevent the Sr and Cs extractions.