Ferrocyanide molybdate, a new inorganic ion exchanger—I: Chemical composition and crystallographic structure

Abstract

The product obtained after precipitation of H 4Fe(CN) 6 with Na 2MoO 4 in HCl solution displays selective ion exchange properties for Cs in acid media. By varying the ratio of the reagents a series of products may be obtained which have similar X-ray spectra. By combination of chemical analysis, density measurements and unit cell determinations two structural models have been found which fit the experimental X-ray data. The first, called “FeMo II”, has the formula {H 4Fe(CN) 6] 5-[MoO 3(H 2O) x ] 12{ and the second, FeMo IV, may be written {[H 4Fe(CN) 6] 4MoO 3(H 2O) x ] 16{. A correlation is given between the chemical constitution of the unit cells, the ion-exchange capacity and the stability range of the products. The molybdenum isopolyacid mostly found in these investigations corresponds to a “Lindqvist” type structure with empirical formula [Mo 6O 6(OH) 16] 8+.