A Study of the Hydration and Dehydration of Vanadyl Arsenate by X-ray Diffraction Analysis, Infrared and Raman Spectroscopy

✍ Scribed by Ludvík Beneš; Klára Melánová; Vítězslav Zima; Miroslava Trchová; Eva Uhlířová; Pavel Matějka

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 314 KB
• Volume: 2000
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/(sici)1099-0682(200005)2000:5<895::aid-ejic895>3.0.co;2-#

✦ Synopsis

The course of the intercalation and deintercalation of water molecules in vanadyl arsenate has been studied by X-ray diffraction analysis and by infrared and Raman spectroscopies. The formation of VOAsO 4 hydrates at ambient temperature has been found to depend on relative humidity (r.h.): VOAsO 4 ⋅ 5 H 2 O (basal spacing c = 10.48 A ˚) is formed at r.h. above 76%, VOAsO 4 ⋅ 3 H 2 O (c = 8.03 A ˚) at 43-76% r.h., VOAsO 4 ⋅ 2 H 2 O (c = 7.33 A ˚) at 11-43% r.h.; dehydrated VOAsO 4 (c = 4.18 A ˚) exists near 0% r.h. Like the thermal dehydration of VOPO 4 ⋅ 2 H 2 O, the thermal dehydration of VOAsO 4 ⋅ 3 H 2 O proceeds in a stepwise manner so that the dihydrate and monohydrate are formed en route to the anhydrous compound. The arsenate monohydrate is gradually dehydrated over a broad temperature range. The broad diffraction lines observed can be explained in terms of the exist-