The photodegradation experiment materials included RhB, catalyst (catalyst does not include carbon or carbon compounds), crystallizing dish, and magnetic stirrer. After 2 hours of irradiation, the RhB is decolorized by the catalyst, and the RhB dye color changes from pink to transparent (do not observe any pink on the catalyst). The mixture included Catalyst and RhB centrifuged for 10 min to remove the catalyst. The irradiated RhB and not irradiated RhB were filled into glass vials for TOC analysis. However, the results could not be accepted. The not irradiated RhB TOC concentration is large than the TOC of irradiated RhB. Wondering if any professor could give suggestions or comments.
Hello Dr. Yurii V Geletii; thanks for your questions. I thought RhB could not be reacted under light to volatile CO2. If only RhB were under irradiation, the TOC volume does not change too much. However, when adding catalysts into the RhB solution, the CO2 concentration will increase since the RhB was decomposed by photocatalytic reaction (the catalyst reacts with water and oxygen to produce active species). And the expected results were that the RhB would be oxidized/reduced to CO2 after adding the catalyst under lights. The TOC analyzer will measure the concentration of organic carbon in RhB. But, in actual, the TOC concentration increased after irradiation.
Do you have a control experiment with catalyst irradiated in absence of Rhodamine B?
Hello Dr. Andersen, yes, I did the control experiments. There are two groups including DI water, DI water+catalyst. The DI water after exposed to the air under irradiation, the TOC concentration increase from 0.12 to 4.3 ppm. The DI water + catalyst, the TOC increased from 0.15 to 2.5 ppm. All instruments I used were glass products. And rinse them very clearly. The TOC analyzer used 21% phosphoric acid, and the acid volume is 0.2 mL.@Henrik Rasmus Andersen
hello ...
thank you for question ....
I think that the RhB is decolorized by the catalyst in present of uv radiation to formation decomposed organic compounds(colorless) which may be react with excess of catalyst in present of ray to formation another organic compounds ...
may be can see it by using GC-MASS spectroscopy before and after photodegradation.
Fay Yu, how much of the increase in TOC is explained by the background increase?
Mohammed Masood I cannot see how your mechanism explain the TOC increase. How do you get more organic carbon atoms in solution?
Hello Mohammed ,Masood
Sorry for the delayed response. The experiments currently don't have any additional questions. The reason behind the issue was the evaporation of some water in the organic dye. As a result, the final solution lost a significant amount of water, leading to an increase in the final TOC.
best regards
Hello Dr. Henrik Rasmus Andersen,
thanks for your reply. The experiments were finished in June. Currently, I don't have any questions. The reason behind the issue was the evaporation of some water in the organic dye. During three hours, the experiment was performed under light, the light makes heat. As a result, the final solution lost a significant amount of water, increasing the final TOC. Sorry for the delayed response.
Best regards.
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