Is it possible that semiconductor nanomaterial composite showing more adsorption (removal of pollutant in the absence of light) than photocatalytic activity (removal of pollutant in the presence of light)? What could be the possible mechanism for that?
& can we compare these two processes?
A mechanism might be that the absorption of light causes a (metastable) reconstruction which is unfavorable for your catalytic process. If the catalytic activity goes up again in the dark, maybe the reconstruction is reversible.
That doesn't mean it's true in your case, actually finding out what's happening in such a case may be hard work.
Yes, this is possible, especially if the pollutant is a dye. If you chose a dye as pollutant, than you might resolve the adsorption issue by choosing another dye: if you chose methylene blue (cationic dye), than choosing methyl orange (anionic dye) could result in lower adsorption rate.
István Székely i understood your point.
But if in case zeta potential of semiconductor material and the pollutant is negative and the removal in the absence of light is 95% and removal in the presence of light 98%, then is it possible that other forces of attraction are working there? How that could be explained?
Kuljit Kaur did you carry out photolysis experiments for the pollutant (in absence of semiconductor, only exposure to light)? Could be that the pollutant is highly unstable, or the initial concentration is very low.
Another possibility could be, that your semiconductor in aqueous suspension is slightly unstable thus protonating the suspension, and decreasing its pH value (this can be easily ruled out by preparing a suspension containing distilled water and the semiconductor, and by measuring the suspensions' pH for 1-2 hours).
Dear Székely István, I haven't done that yet. I'll try both experiments to check for these possibilities and will let you know if these are the factors affecting my results or if there is something else. Thank you so much.
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