hello every body
i had synthesised titanium dioxide with sol gel method following this experimental protocol .
i add titanium tetraisopropoxide dropwise to HCl solution (concentration 1mol/L) in report of Ti/H+ equal to 4. under high stirring conditions 500rpm and ambiante temperature for three hours.
after some days a white precipitate is formed and i separated it by centrifugation, and i dried at 110°C for three hours. after drying the powder is grounded with a mortar then the powder is calcined for 3 hours at 450°C.
I performed photocatalytic tests trying to degrade rhodamine B (20ppm with a ratio of 1g of TiO2 / 1L of pollutant). the results are negative.
the XRD analysis showed that the catalyst has a rutile phase (2theta = 27.4) and the anatase phase is completely absent.
why I can't obtain anatase phase and an active TiO2. According to the literature, the obtained TiO2 phase depends directly on the calcination temperature. the rutile must be present at more than 600 to 700°C.
is there any problem on experimental protocol, pollutant model,...etc
thank you very much
Phase change should be more sensitive with temperature control. So....please verify in which temperature your phase has been changed.
Anatase-rutile transition usually occurs in the between range 400 – 1200°C ,two phases may be exists within this range. Phase transform may depends on the preparation method, purity , concentration of precursor , particle size and supporting materials. Also heating rate may be another influencing factor. In general, rutile is highly stable structure than anatase and it is obtained after annealing of anatase at more than 600°C.
Anatase to rutile transformation depend upon your synthesize protocol. Increase in water ratio promotes A to R phase Transformation. Please find this DOI and read the paper. pubs.acs.org/doi/abs/10.1021/jp904358g.
They got anatase phase even at 700 degree C with lower water ratio. Increase in water ratio promotes A to R Transformation. I think in your case you may used higher water ratio. You please decrease your water content and increase the HCL concentration. That ll be fine.
Well Regards,
Divya Arumugam
Hi there,
I strongly agree with Prof. Hassan. You should know that the change between the phases is controlled by the temperature degree as well the kind of precursor .
Regards,
Thank your every body
Thé precursor is very known and many many articles have get anatase form with this precursor.
The rate of heat is 5 degrees per minute until 450 degree for three hours.
You said it depends on experimental protocol, what exactly influence the catalyst in my protocol....please give me sources.
Have nice day
Anatase to rutile transformation depends on many factors: the preparation method, purity, concentration of the precursor and particle size. Of course, you need to carefully control the temperature of the furnace. please try this temperature
hello
1) Mr hassan koohestani i said that the temperature of furnace is well controlled and is 450°C for three hours (5°C/minute until 450°C and in this level it take 3 hours).
2) Anatase to rutile transformation depends on many factors : what factor exactly in this protocol, i can't change all factors it is impossible....please give me sources. .......
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