Structural investigation of titanyl sulfate dihydrate and intermediates formed during thermal decomposition

Titanyl sulfate dihydrate (TiOSO4.2H2O) is one possible intermediate formed during the production of titanium dioxide, a commonly used pigment whose production is worth more than a billion dollars worldwide each year. Due to the crystal habit of TiOSO4.2H2O the pumping and separation steps of industrial processes are made extremely difficult. To understand the conditions which lead to the formation of TiOSO4.2H2O, there is a need to examine its solid state structure and what influences its atomic arrangement. This study aimed to define the solid state structure of TiOSO4.2H2O via an indirect, retrospective method, investigating thermal phase changes and intermediate structures formed during decomposition. Related compounds (TiOSO4.H2O and TiO(OH)2) were also investigated to aid the structural identification of TiOSO4.2H2O. Using techniques such as TGA, High Temperature-XRD, High Temperature-FTIR and SEM two structures for TiOSO4.2H2O were proposed. The structures are variations of one another, exhibiting bidentate and binuclear sulfate bonding as well as hydrogen bonding between the sulfate ion and adjacent water molecule. A mechanism by which TiOSO4.2H2O thermally decomposes is also proposed. The custom built in-situ High Temperature FTIR cell used in this study could reach temperatures of 1100oC. Such high temperature FTIR has not been reported previously. It is hoped that results from this study will stimulate further interest in this area and eventually lead to conclusive structure analysis and improved industrial processes.