Improved Photodegradation of Organic Contaminants Using Nano-TiO2 and TiO2 -SiO2 Deposited on Portland Cement Concrete Blocks.

The photocatalytic activity of TiO2 nanoparticles (nano-TiO2 ) and its hybrid with SiO2 (nano-TiO2 -SiO2 ) for degradation of some organic dyes on cementitious materials was studied in this work. Nanohybrid photocatalysts were prepared using an inorganic sol-gel precursor and then characterized using XRD, SEM and UV-Vis. The grain sizes were estimated by Scherrer's equation to be around 10 nm. Then, a thin layer was applied to Portland cement concrete (PCC) blocks by dipping them into nano-TiO2 and nano-TiO2 -SiO2 solution. The efficiency of coated PCC blocks for the photocatalytic decomposition of two dyes, Malachite Green oxalate (MG) and Methylene Blue (MB), was examined under UV and visible irradiation and then monitored by the chemical oxygen demand tests. The results showed that more than 80% and 92% of MG and MB were decomposed under UV-Vis irradiation using blocks coated with nano-TiO2 -SiO2 . TiO2 /PCC and TiO2 -SiO2 /PCC blocks showed a significant ability to oxidize dyes under visible and UV lights and TiO2 -SiO2 /PCC blocks require less time for dye degradation. Based on these results, coated blocks have increased photocatalytic activity which can make them commercially accessible photocatalysts.