TiO2 coating procedures

There are various methods available to coat TiO2 onto the surface of the membrane. I will explain briefly some of them, and the method I used.

Ion assisted deposition
This method was used for coating on super-hydrophobic porous teflon membrane. The author stated that the coating of TiO2 by the chemical wet process such as a sol-gel method is very difficult. The method involved acceleration voltage, temperature, and oxygen. Heated at 523 K.

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TiO2-UV batch for UF fractionation

The result of my experiment employing TiO2-UV was not satisfying. In terms of flux, TiO2-UV membrane showed severe decline after 30, 60, and around 90 minutes. Not only that, the rejection of membrane coated by TiO2 under UV exposure was lower than naked membrane. This probably due to smaller molecule as a result of the breaking caused by photocatalysis process. After certain minutes, it is possible that TiO2-UV react with the HA, braking bonds within HA molecules, the molecules become smaller, thus it will penetrate the pore of TiO2-UV, so the DOC will be much higher than naked membrane. How about flux? my logic says if the rejection is lower, so the flux should be better as flux and rejection usually work on the opposite way. If the flux better, usually rejection worse, vice versa.

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TiO2-UV performance

First stage of experiment has been accomplished. The result was not satisfying. I used 50, 15 and 1 kD. In terms of flux and accumulated flux, TiO2-UV displayed lower result compare to just naked membrane. Although for 50 kD and 15 kD initial flux were higher than naked membrane, but after around 30-100 minutes, they showed severe decline for flux. This also applied for 1 kD TiO2-UV membrane. I do not think that permeability plays a big role on this, since the permeability of all membranes were similar, there were not significant difference. This also proves that TiO2 does not affect the structure of the membrane.

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Seems TiO2+UV do not have effect toward HA removal

I almost finished my current short term goal. I did some tests, using membrane 50 kD, 15 kD. For both, I used same comparison, one using TiO2 coating plus UV, the other one without them, just naked membrane. Seems that percentage removal of TOC between TiO2+UV membrane and just naked membrane, better for naked membrane. Wow.. I keep wondering why..

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