Nanoporous manganese oxides as environmental protective materials-effect of Ca and Mg on metals sorption.

The selectivity of nanoporous manganese oxides for some alkali and transition metals over calcium and magnesium was studied. Two tunnel-structured oxides (OMS-1 and OMS-2) were synthesized by means of a hydrothermal route. Competitive uptake of metals and acid was studied using batch kinetic measurements at different metal ion concentrations. The experimental data were correlated with a dynamic model. The results show that the studied OMS materials selectively adsorb Cu, Ni and Cd in the presence of Ca and Mg. It was also found that the exchange rates were reasonably high due to the small particle dimensions. Both materials are stable in the studied conditions and their maximum Cu uptake capacity was 0.9-1.3 mmol/g. The results indicate that both materials have potential for environmental applications involving the uptake of harmful metal ions.

Co-eluent effect in partition chromatography. Rhamnose-xylose separation with strong and weak cation-exchangers in aqueous ethanol.

The effect of ethanol in aqueous eluent on the chromatographic separation was studied at 298 K. Two sugars, L-rhamnose and D-xylose, were separated by using strong and weak cation-exchangers as a stationary phase. The ionic form of the resins was Na+ or Ca2+. The separations were carried out with sugar feed concentrations up to 35 wt% and with both low (about 1%) and high (about 10%) feed volume to bed volume ratios. The separation of the sugars was improved by adding ethanol into the eluent. The separation was also significantly enhanced when the weak cation-exchangers with the greatest affinity for water were used instead of strong cation-exchangers as a separation medium for the sugars having different hydrophilicities. The experimental data were successfully explained with a rate-based column model, which accounted for the volume changes of the stationary phase. A thermodynamic sorption model was utilized in column calculations.