Thermal analysis of binding of iodinated contrast agents to TiO sub(2)

• Published in: Journal of thermal analysis and calorimetry 2014-06, Vol.116 (3), p.1521-1526
• Main Authors: Annarapu, Shashidhar, Nee, Matthew J
• Format: Article
• Language: English
• Subjects: Contrast agents; Drinking water; Oxidation; Photocatalysis; Reagents; Sewage; Thermal analysis; Titanium dioxide
• ISSN: 1388-6150; 1572-8943
• DOI: 10.1007/s10973-014-3756-9

Iodinated contrast agents such as iohexol and diatrizoate are pharmaceutical compounds of emerging concern in sewage and drinking water. These are resistant to removal through conventional water treatment processes. Photocatalytic degradation (PD) of these compounds over titanium dioxide has been suggested as a possible technique for the removal of iohexol and diatrizoate from sewage water. Several studies have evaluated these compounds, finding that the two do not respond in the same way to the presence of photocatalyst, which could imply that direct oxidation by surface electron holes is a major route for one compound but not the other. It is necessary that analytes adsorb to the photocatalyst for this oxidation to occur. We employ thermogravimetric analysis to characterize desorption of these analytes from two different forms of titanium dioxide. Compared to pure analyte and pure photocatalyst, additional peaks are seen near 700 degree C when the contrast agents are adsorbed to titanium dioxide. This implies that direct oxidation by electron holes is not a primary factor in the PD of iodinated contrast agents. We evaluate the effects of analyte concentration and titanium dioxide crystal structure on these results to address the general applicability of our approach.