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Photocatalytic Properties of Heat-treated Carbon Nitride to Reduce Cyanide Pollutant from Aqueous Solution

Mahtabpour, Hossein | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53880 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Sadrnezhad, Khatiboleslam
  7. Abstract:
  8. Cyanide ion is one of the materials used in various industries related to metallurgy, the release of which in the environment causes water, air and soil pollution. Numerous researchers have used different methods to remove this pollutant from the environment. Comparing these methods with each other, photocatalytic processes have attracted a lot of attention due to the use of sunlight as a sustainable energy source, good efficiency, low cost, etc. Therefore, in the present study, first the heat-treated graphite carbon-nitride photocatalyst was synthesized and then characterized by X-ray diffraction (XRD) tests, infrared spectroscopy (FT-IR), scattered reflectance spectroscopy (DRS), photoluminescence (PL), specific surface area estimation (BET) and field emission scanning electron microscopy (FE-SEM) imaging were characterized and compared with graphitic carbon-nitride without heat treatment. The results of these tests showed that the photocatalytic properties of heat-treated carbon nitride improved compared to the initial graphitic carbon nitride. Then, the effect of process parameters such as initial cyanide concentration, photocatalyst concentration, time and acidity of the test medium, on the photocatalytic removal efficiency of this contaminant from aqueous solution (alkaline deionized water with different pHs) was studied and modeled by central composite design response surface method. The model adapted to the data was statistically and practically evaluated. The modeling results showed that among the selected variables, decrease in initial cyanide concentration, increase in acidity and increase in time had the greatest effect on increasing process efficiency by 5.57%, 46.1% and 31.22%, respectively. Also, among the quadratic variables, increasing the quadratic power of acidity and increasing interaction between time-acidity were associated with the greatest effect on increasing the yield (compared to other quadratic variables) by 7.06% and 4.92%, respectively. The obtained model also showed 95% agreement in the fit of the test data and 85.3% in the prediction of the results. By optimizing the test conditions (cyanide concentration equal to 20 mg/L, photocatalyst concentration equal to 0.5 g/L, time 9 hours and pH equal to 13), the photocatalyst used is able to remove 44% of water-soluble cyanide. Practical verification of the model has also shown that it has the ability to accurately predict the results with very little error. Also, the results of additional tests showed that its structural stability was maintained after performing the cyanide removal test for 7 hours in ultraviolet light. Finally, kinetic studies showed that the process of photocatalytic removal of cyanide follows a quadratic equation of velocity with a velocity constant of 0.004 h-1
  9. Keywords:
  10. Cyanide ; Emission Reduction ; Design of Experiments Method(DOE) ; Photocatalyst ; Carbon Nitride Photocatalyst

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