Solid phase extraction of cesium from aqueous solution using sol-gel encapsulated cobalt hexacyanoferrate

The synthesis and evaluation of silica sol-gels doped with cobalt hexacyanoferrate (CoHCF) for solid phase extraction of Cs+ from aqueous solution is described. The CoHCF is formed by first introducing K4Fe(CN)(6) (HCF) into the sol-gel and subsequently contacting the porous solid to a solution containing Co2+. Generally, sols contain alcohol as a co-solvent, which limits the solubility of HCF. Inclusion of generation-4 polyamidoamine (G4-PAMAM) dendrimer in the sol-gel increases the level of HCF and, in turn, the CoHCF. The uptake capacity of this composite was 0.43+/-0.01 mmol Cs+ g(-1). A second approach to increasing the level of HCF silica is to exclude alcohol from the sol and use ultrasound to obtain a homogeneous suspension; HCF concentrations up to 0.17 M in the sol were thereby achieved. After gelation and reaction with Co2+, the resulting composite had a capacity of 0.61+/-0.01 mmol Cs+ g(-1). With 0.5 mM Cs+ as the sample, the presence of either 0.5-100 mM Na+ or 10 mM Ca2+ did not change that value at the 95% confidence level.