We used the commercial chlorpyrifos (liquid). The conditions were 4 ppm of chlorpyrifos (200ml of solution), 0.1 g of catalyst (doped-TiO2), duration time (4 hours), light source (xenon lamp).
At first, we assumed the maximum wavelength around 266 nm as showed in the spectrum at 0 min. Then, we predicted that would show the decrease of absorbance from 0 min to 4 hours, indicating the photodegradation of chlorpyrifos occurs. Based on the spectrum, it showed the decrease at 30 min but increased back after 1 hour and created another peak. Is it indicates the intermediate product was formed? Do you have any opinions on this result? I'm really appreciated your help and thanks in advance.
Hi Nurul.
I hope you are doing great.
To answer your question, I am gonna suppose you only use UV-Vis spectroscopy to follow the absorbance profiles after the treatment. If that is the case, you have to consider that due to the photocatalytic activity of the system, chlorpyrifos is being degraded (most likely oxidized) and thus subproducts are formed in the system. Since you are not separating them before the analysis, the Uv-Vis spectra you are obtaining consists on the contribution of all, the initial Chlorpyrifos and the by-products.
I might say that the decrease on the peak around 230 nm might suggest the degradation of the N-containing aromatic ring (that wavelength is associated with pi-pi* transitions) without the abstraction of N. The formation of the peak around 290 nm might suggest the formation of molecule with a higher n-pi* transition.
I would recommend you to separate the sub-products with for instance HPLC before quantifying the pollutant concentration.
Hi Nurul,
As asked Fabio, you should make some prelimilary analysis as photolysis to make sure that photodegradation occur and the there contribution on the photodegradation activity.
You can cheick out on the librery some by-products of Chlorpyrifos, and use HPLC or LCM-MS to evaluate quantities of by-products.
as concern mineralization, you should us COT analysis.
Best Regards
- Badges
- Science topic