Use of an interactive carbohydrate polymer phenomenon for the separation of polyoxometalates

Keggin type polyoxometalates (POMs) have been proposed as agents for improving the feasibility of oxygen bleaching technique used in producing cellulose fibre in the wood pulping industry. To investigate the possible interactions between carbohydrate polymers and POMs, several different POM anions were eluted through a column containing dextran chromatography gel (Sephadex G-50). Solutions of KCl (0.05 and 0.10 mol/l) and NaCl (0.10 mol/l) were used as eluents. The elution volumes (Ve) of all the POMs tested were found to be greater than the Ve of the internal standard, glycine. The Ve of the POMs increased along with increasing electrolyte concentration. When eluted with 0.10 mol/l KCl solution, the Ve were greater than the respective values of the same POMs eluted with 0.10 mol/l NaCl solution. These facts suggest that POM and the Sephadex gel form complexes, and that the tendency for this to take place depends on the type and concentration of cations present in the system. The method described in this paper may be useful in analysing and purifying mixtures of POMs.