salam
during photocatalytic tests of titanium dioxide with rhodamine6G (20ppm, 50mL) with 0.05g of catalysts.
The solution is left in dark for 30min and the first sample is taken. And then the solution is put in UV lamp and then I took the samples every 30 minute. The samples are centrifuged and passed in UV-VIS to measure concentration.
The results are very strange, the concentrations are decreased untill 4ppm in the absorption test and then increase untill 15ppm in photocatalitic phase.
Is there any problem in taking this samples or in centrifugation? This problem makes me crazy. I don't now if the problem is in the catalyst.
Thanks
I think that the problem is not catalyst . You can prepare different concentrations of solution (rhodamine6G ) to detect if the problem is instrument or experiment operation.
I have tried this solution R6G with zinc oxide and the results are normal, the concentration decrease with time.
Dear Sidali,
I have few comments.
I think it is better to allow continuous stirring when you are doing the experiment (both under dark and Light) ,
Please keep the sample under dark for one hour and take the measurement to confirm adsorption - desorption is established
How about the particle size of TiO2, if the size is very small, centrifuging at the rpm you used might not effective. Unless all the TiO2 particles are not removed form the sample the result will not reliable due to scattering effect.
dear soorya
what you recomand for separating catalyst from R6G solution in simple ????
Dear Sidalli,
I am sorry for the delay response.
It is good way to introduce TiO2 coated grass piece or you may coat the TiO2 inside the reaction vessel itself.
Another important point is to observe the pH of the reaction medium before and after the reaction. If the PH is varying you have to consider to keep the PH constant through out the course of reaction. the point is some dyes change or intensify the colour with the pH. (Specially increasing the pH) on the otherhand, TiO2 has a Isoelectric Point (PI) of 5.8. below which TiO2 is positively charged and above the PI the TiO2 is negatively charged. At the PI it remain uncharged. depending on the pH, the TiO2 may dissolved and come in to the solvent. that may effect to complicate removal of TiO2 from the solvent.
Thank you.
dear soorya
the oprating parameters like pH, temperature, initial concentrations of both of catalyst and R6G and speed of rotation are keeped canstant during UV irradiation. i think preleving 3mL of simple not affect those concentrations.
i have trayed with TiO2 degussa p25 and i have no degrdation of pollutant during 2.5 hours of radiation.
Thank you
Dear Sidali,
Please read this paper which will help you to carry out your research.
http://www.sciencedirect.com/science/article/pii/S1319610310000815
Thank you.
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