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

The uptake of cesium, strontium and europium from dilute nitric acid s olutions by a poly(sodium acrylate-acrylic acid) PAA hydrogel has been investigated. pH variations are consistent with cation exchange proce sses: -COO-, Na+/H+, -COO-, Na+/M(m+) (M(m+) = Cs+ and Sr2+) and -COOH /Eu3+. Saturation of the gel is achieved For metal/carboxylate ratios R = 0.5. The swelling ratios of gels loaded with metal cations are tho se of uncharged, shrunk gels (Sr, Eu) or of charged, swollen gels (Cs) in agreement with the formation of uncharged (-COO)(2) Sr, (-COO)(2)E uX (X = NO3 or OH) type complexes and (-COO-, Cs+) ion pairs. The meta l cations are extracted in the gels following the order of their affin ities with carboxylic groups Eu3+ > Sr2+ > Cs+. An increase of the ion ic strength of the metal aqueous solution up to 0.5M NaNO3 leads to sl ightly decrease the europium uptake by the PAA hydrogel, but O.1M NaNO 3 is sufficient to prevent the Sr and Cs extractions.