I'm a postgraduate student and I'm currently researching ammonia nitrogen degradation through photocatalysis.
The following experiment parameters are :
1. 200W Xe Lamp
2. 200mL aqueous ammonia nitrogen(NH4Cl) solution
3. 5ppm(mg/L) ammonia nitrogen concentration
4. 0.5g/L photocatalyst
5. 35cm distance between reaction chamber and light source
6. Continuous maintain the solution pH at 8.1(average sea water pH)
7. 30mins dark adsorption
8. 30mins interval to take out 2.5mL sample
And using modified indophenol blue method to determine the concentration of ammonia nitrogen :
1. 0.05g Sodium nitroprusside(SNP) in 10mL deionized water (5g/L)
2. 1.11g phenol(PhOH) in 10mL 95% Ethanol(EtOH) (111g/L)
3. 1M NaOH
4. 2g trisodium citrate and 0.1g sodium hydroxide in 10mL deionized water, then adding 5mL Sodium Hypochlorite Pentahydrate (oxidizing Solution)
The combination of modified indophenol blue method is :
2.5mL sample, 0.1mL NaOH, 0.2mL PhOH, 0.2mL SNP, 0.3mL Oxidizing Solution
The samples already covered with plastic wrap to ensure no gaseous state of ammonia will dissolve in mixed solution, but the result still having unsteady concentration of ammonia during photocatalysis.
Can anyone know which part did I made a mistake?
Unfortunately, I am not familiar with several aspects of your work (photocatalysis, the analytical method), so my comments may be of limited value. However, I note that at pH 8.1 a relevant percentage of the total ammonium + ammonia N would be in the NH3 form. Dissolved NH3 does not readily volatilize from water (H-bonding) but of course as the temperature rises, more would be emitted. So 2 questions. How much does the temperature rise from the 200 W bulb at 35 cm? Is the reactor sufficiently sealed to prevent ammonia gas escape? In any case, good luck with your work!
- Peter
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