Thermal and X-ray diffraction investigations of vanadium(V) oxide-alkali persulfate binary systems

Abstract

Thermoanalytieal investigations of the VzO 5-K2S~O 8 system have revevled that, m the presence of excess amounts of VzO~, the initial decomposition temperature is lowered compared to that of the pure salt, An explanation for this lowering is based on the interaction between V2On and the peroxo group of the persulfate ion. The reaction however, is, not unimolecular. The presence of an unknown potassium sulfate complex of V(V) with a catalytic character is indicated by XRD patterns obtained for samples heated up to 410% It has been found that the formation of KzVOs, KV(SO4)2, K~VsO14 and K4VxoOz7 depends on whether V205 or K2SO 4 is present in excess during thermal decomposition.Sharp d-lines for unknown phases are identified. V~Os is found to behave differently towards sodium and potassium persulfates.Compounds such as a-NaVO3, NaVOs, NaV308 and NaV6Oa5 are obtained on thermal analysis of various molar ratios of the V2Os--Na2S2Os system.