UPTAKE OF CESIUM, STRONTIUM AND EUROPIUM BY A POLY(SODIUM ACRYLATE-ACRYLIC ACID) HYDROGEL

摘要

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 Sir~(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, 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/U NaNO, leads to slightly decrease the europium uptake by the PAA hydrogel, but 0.1M NaNO_3 is sufficient to prevent the Sr and Cs extractions.