Depletion of the protective aluminum hydroxide coating in TiO₂-based sunscreens by swimming pool water ingredients

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• 作者：Jurate Virkutyte^a ; Souhail R. Al-Abed^b ; ^{al-abed.souhail@epa.gov} ; Dionysios D. Dionysiou^c
• 关键词：Sunscreen lotion ; Nanosized TiO2 ; Swimming pool water ; Al(OH)3 layer
• 刊名：Chemical Engineering Journal
• 出版年：2012
• 期刊代码：16_13858947
• 类别：ce
• 出版时间：15 May, 2012
• 卷：191
• 期：Complete
• 页码：95-103
• 文件大小：1487 K

摘要

In sunscreen lotion (SSL) formulations, titanium dioxide (nTiO₂) nanoparticles are coated with an Al(OH)₃ layer to shield against the harmful effects of hydroxyl radicals (OH), superoxide anion radicals (O₂^{鈭?/sup>), and other reactive oxygen species (ROS) (e.g. H₂O₂) generated when TiO₂ nanoparticles are exposed to UV radiation. Therefore, it is crucial to ensure their structural stability in the environment where the protective layer may be compromised and adverse health and environmental effects can occur. The main focal point of our work was to research the stability of the Al(OH)₃ layer in swimming pool water. Thus 2 g L鈭? of SSL was subjected to treatment with swimming pool water (SPW) containing from 0.2 to 7 ppm chlorine (HOCl/OCl鈭?/sup>) concentrations. The changes in the protective coating of TiO₂ nanoparticles were analyzed using several X-ray based microscopic techniques in addition to Fourier transform infrared spectroscopy (FTIR) and Zeta potential measurements. Results indicated that an increase in chlorine concentration in SPW significantly affected the integrity of the Al(OH)₃ protective layer and increased zeta potential from 鈭?4 mV to nearly 鈭? mV, rendering rather unstable TiO₂ nanoparticles. The highest redistribution of Al (At%) from 鈭? to as high as 15.6 was achieved when SSL was subjected to 3.5 and 7 ppm of chlorine in SPW. Results strongly suggest that water chemistry influences the characteristics of TiO₂ in sunscreen environment.}