7. Conclusion
In the present study, titanium dioxide particles were produced using sol-gel method under the influence of pulsed electric field. The aim was to study the visible light irradiation in photocatalysis processes when the sol-gel method of TiO2 nanocrystals were affected by pulsed electric field. It was expected that specific surface area, calcination temperature and pH had influence on the photocatalytic activities of produced crystals.
Different pulse frequencies and treatment times were used to investigate the influence of PEF. The pulsed electric field experiments were carried out with three different between specific surface area and frequency of the pulsed electric field nor between specific surface area and the treatment time of pulsed electric field. With short treatment time and low frequency of pulsed electric field treatment, the specific surface area could be increased from 29 m2/g (PEF 50 Hz 12 minutes) to 34 m2/g (PEF 963 Hz 12 minutes). Comparing the TiO2 particles which were made in previous study by Mäkinen with pulsed electric field via sol-gel method, the specific surface area was also increased. It increased from 21 m2/g (PEF 50 Hz 12 minutes) to 39 m2/g (PEF 949 Hz 12 minutes). When the time of pulsed electric field treatment was longer, the specific surface area did not change significantly. It was from 32.87 m2/g (PEF 50 Hz 24 minutes) to 32.23 m2/g (PEF 963 Hz 24 minutes). Thus for the TiO2 particles made in previous study by Mäkinen it decreased from 46 m2/g (PEF 50 Hz 24 minutes) to 23 m2/g (PEF 949 Hz 24 minutes). This is notable because specific surface area is one of the key factors that determine the photocatalytic performance of a
photocatalyst. Based on the experimental results, it could be seen that degradation rates of the oxalic acid and formic acid were faster with high specific surface area under the visible light irradiation, especially for formic acid.
According to the experimental results, it was also noticed that the calcination temperature in the sol-gel process has a significant effect on photocatalytic performance. From low temperature (400 °C) to high temperature (500 °C), the specific surface area of TiO2 precipitated decreased from 41 m2/g to 25 m2/g. The results for degradation rate of oxalic acid and formic acid are different. After 4 hours irradiating the concentration of oxalic acid with the samples calcined at 400 °C and 500 °C were 42.49 ppm and 43.21 ppm, respectively. So the degradation rate of oxalic acid calcined with lower temperature (400 °C) was faster than the sample obtained at higher calcination temperature (500 °C). But for the concentration of formic acid, with 400˚C calcination was 4.51ppm and 500˚C calcination was 4.18 ppm. So the degradation rate was opposite with oxalic acid. The higher calcination temperature (500 ˚C) was faster than low calcination temperature (400 ˚C).
Produced particles were used as photocatalysts for the degradation of oxalic acid and formic acid under the visible light irradiation. Degradation rate of oxalic acid and formic acid was chosen to be the indicator of photocatalytic performance. The photocatalytic activities of samples produced by the sol-gel method were also compared to photocatalytic activities of the TiO2 particles made in previous study at the same conditions. Moreover, the photocatalytic activity of commercial TiO2 was also carried out to make a reference for comparison.
For oxalic acid, results from the photocatalytic experiments show that pulsed electric field did have an effect on the photocatalytic activity of TiO2 particles. By using pulsed electric field via sol-gel method to made TiO2 particles, under the visible light treatment to degraded oxalic acid. The degradation rate of oxalic acid with the sample
made in current study was not obvious compared with the sample made in previous study. In the current study, the fastest degradation was obtained using 294 Hz 24 minutes (38.89 ppm) treatment, the second fastest was gotten with the sample 50 Hz 24 minutes (39.61 ppm). Moreover the degradation rate for TiO2 particles which made by previous study was much more active. Low frequency long treatment time (PEF 50 Hz 24 minutes) or high frequency short time treatment time (949 Hz 12minutes) was appropriate to produce TiO2 particles which have higher photocatalytic activity under visible light. Specific surface area was higher for samples precipitated with either low frequency long time or high frequency short time.
The degradation rate of formic acid was generally higher for samples that were produced under the influence of pulsed electric field. TiO2 particles were more active for formic acid than oxalic acid under the visible light. According to the results of TiO2 particles made using pulsed electric field via sol-gel method both in current and previous studies, the best condition was obtained by high frequency short time (PEF 963 Hz, 12 min), and the second one with the lowest frequency and longer time (PEF 50 Hz, 24 min). The higher photocatalytic activities of samples that were produced under the influence of pulsed electric field are attributed to larger specific surface areas, especially for formic acid degradation. Moreover, there was one more sample (50 Hz 24 minutes) which was prepared without adjusting pH. The result of degradation was not satisfactory compared to the sample when pH was adjusted.
Four different TiO2 particles with concentration of Cu (0 %, 5 %, 9 % and 13 %) were tested under the visible light irradiation to investigate the photocatalytic activities of formic acid. Results show that without Cu doped TiO2 particles had the highest degradation rate of formic acid compared with copper doped TiO2 samples. Moreover, the degradation rate decreased with the increase of the content of copper in TiO2
samples. Thus copper doped TiO2 particles are not suitable for the degradation of formic acid.
For both oxalic acid and formic acid the commercial TiO2 powder had higher photocatalytic activities compared to the samples that were produced in the current work. It can be explained that the commercial TiO2 has the highest specific surface area which is 45 m2/g. The specific surface areas of samples produced with sol-gel method were in the range of 16 – 40 m2/g. Based on the literature, the commercial TiO2 is a mixture of rutile and anatase crystallites. Crystallite mixtures can have an effect and thus increase photocatalytic activity. Therefore, the commercial TiO2
particles are more active since it has higher specific surface area [75].
Further studies may focus on investigations on the effect of pulsed electric field on TiO2 crystal structures via sol-gel method since different polymorphs have different effects on photocatalytic activities of pollutants.
8. References:
[1] Pelizzetti, E., Serpone, N. 1986. Homogeneous and Heterogeneous Photocatalysis, D. Reidel Publishing Company, Dordrecht,
[2] Serpone, N., Pelizzetti, E. 1989. Photocatalysis—Fundamentals and Applications, John Wiley & Sons, New York.
[3] Kamat, P.V. 1993. Photochemistry of nonreactive and reactive (semiconductor) surfaces. Chemical. Review, vol. 93, pp. 267.
[4] Elvers, B., Hawkings, S. 1996, Ullmann's Encyclopedia of Industrial Chemistry.
5th ed., vol. 27, Weinheim: Wiley-VCH.
[5]Mikhaylin, S., Nikonenko, V., Pourcelly, G. & Bazinet, L. 2014. Intensification of demineralization process and decrease in scaling by application of pulsed electric field with short pulse/pause conditions. Journal of Membrane Science，vol. 468, pp.
[6] Mäkinen, S. 2014. Pulsed electric field assisted sol-gel preparation of TiO2
particles and their photocatalytic properties, Master’s thesis, LUT.
[7] Hashimoto, K., Irie, H. 2005. TiO2 photocatalysis: a historical overview and future prospects, Japanese Journal of Applied Physics. pp. 8269-8285
[8] Yin, W., Chen, S., Gong, X., Yan. 2010. Effective band gap narrowing of anatase TiO2 by strain along a soft crystal direction. Applied Physics Letters, vol. 96, pp.
221-223
[9] Fujishima, A, Honda, K. 1972. “Electrochemical photolysis of water at a semiconductor electrode, International Journal of Photoenergy, vol. 238 pp. 37-38.
[10] Zhang, H., Banfield, J.F. 2000. Understanding polymorphic phase transformation behavior during growth of nanocrystalline aggregates: Insights from TiO2. Geochemical, vol. 104 pp.3481–3487.
[11] Ranade, M.R., Navrotsky, A., Zhang, H.Z., Banfield, J.F., Elder, S.H., Zaban, A., Borse, P.H., Kulkarni, S.K., Doran, G.S., Whitfield, H.J. 2002. Energetics of nanocrystalline TiO2. Proceedings of the National Academy of Sciences of the United States of America, vol.99, pp.6476–6481.
[12] Shklover, V., Nazeeruddin, M.K., Zakeeruddin, S.M., Barbe, C., Kay, A., Haibach, T., Steurer, W., Hermann, R., Nissen, H.U., Grätzel, M. 1997. Structure of nanocrystalline TiO2 powders and precursor to their highly efficient photosensitizer, Chemistry of Materials，vol. 9 pp.430–439.
[13] Burnside, S.D., Shklover, V., Barbe, C., Comte, P., Arendse, F., Brooks, K., Grätzel, M. 1998. Self-Organization of TiO2 Nanoparticles in Thin Films Chemistry of Materials，vol. 10 pp.2419–2425.
[14] Fujishima, A., Zhang, X., Donald, A. 2008. TiO2 photocatalysis and related surface phenomena. Water Research, vol. 21, pp.515-582
[15] Ramamoorthy, M., Vanderbilt, D., King-Smith, R.D. 1994. First-principles calculations of the energetics of stoichiometric TiO2 surfaces. Physical Review B，vol.
49 pp. 721-727
[16] Hengerer, R., Bolliger, B., Erbudak, M., Grätzel, M. 2000. Structure and stability of anatase TiO2 and surface. Electronic Refereed Journal Article, vol.460, pp.162–
169.
[17] Liang, Y., Gan, S., Chambers, S.A., Altman, E.I. 2001. Surface structure of anatase TiO2 (001): reconstruction, atomic steps, and domains. Physical Review B, vol.
63 pp. 235-242
[18] Ruziicka, N., Herman, G.S., Boatner, L.A., Diebold, U. 2003. Structure and properties of the anatase polymorph of titanium dioxide. Master’s thesis, Tulane University
[19] Beltran, A., Gracia, L., Andres, J. 2006. Density functional theory study of the brookite surfaces and phase transitions between natural titanium polymorphs. The Journal of Physical Chemistry B, vol.110, pp. 23417–23423.
[20] Dubrovnik, L.S., Dubrovinskaia, N.A., Swamy V., Muscat J., Harrison N.M., Ahuja R., Holm B., Johansson B. 2001. The hardest known oxide, Nature, vol.410, pp.
653–654.
[21] Mattesini M., de Almeida J.S., Dubrovinsky, L., Dubrovinskaia, N., Johansson, B., Ahuja, R. 2004. Cubic TiO2 as a potential light absorber in solar-energy conversion Physical Review B, vol.70, pp.115101-9.
[22] Andersson, S., Magnéli, A. 1956. Diskrete titanoxydphasem TiO2. Naturwissenschaften, vol. 43, pp. 495–496.
[23] Bursill, L.A., Hyde, B.G. 1972. Crystallographic shear in the higher titanium oxides, structure, texture, mechanisms, and thermodynamic. Program. Solid State Chemical, vol. 7, pp. 177–253.
[24] Le Page, Y., Strobel, P. 1983. Structural chemistry of magnetic phases TiO2. Solid State Chemistry, vol. 47, pp. 6–15.
[25] Le Page, Y., Strobel, P. 1982. Crystallographic shear in higher titanium oxides Solid State Chemistry, vol. 44, pp. 273–281.
[26] Goodenough J.B. 1960. The chemical structure of solids, Physical Review, vol.
117, pp. 1442.
[27] Marezio, M., Gauzzi, A., Licci, F., Gilioli, E. 2000. Superconductivity Physica, C, vol. 338, pp. 1–8.
[28] Legrini, O., Oliveros, E., Braun, A.M. 1993. Photochemical processes for water treatment. Chemical Reviews, vol. l93, pp. 671-698
[29] Ollis, D.F., Pelizzetti, E., Serpone, N. 1989. Photocatalysis-Fundamentals and Applications, Wiley, New York, pp. 603
[30] Turchi, C.S., Ollis, D. 1990. Photocatalytic degradation of organic water contaminants: mechanisms involving hydroxyl radical attack. Journal of catalysis, vol.
122, pp. 178.
[31] Sun, L., Bolton, J.R. 1996. Determination of quantum yield for the photochemical generation of hydroxyl radicals in TiO2 suspensions. Journal of Physical Chemistry, vol. 100, pp. 4127.
[32] Bard, A.J. 1974. Encyclopedia of Electrochemistry, Marcel Dekker, New York, pp. 191.
[33] Draganic, Z.D., Draganic, I.G., Kosanic, M.M. 1964. Radiation chemistry of oxalate solutions in the presence of Oxygen over a wide range of acidities. Journal of Physical Chemistry, vol. 68, pp. 2085.
[34] DraganicÂ, Z.D., Kosanic, M.M., Nenadovic, M.T. 1967. On the products formed in the combustion of explosives, Physical Chemistry, vol. 71, pp. 2390.
[35] Frank, S.N., Bard, A.J., Am, J. 1977. Heterogeneous photocatalyst oxidation of cyanide ion in aqueous solutions at titanium dioxide powder. Journal of the American Chemical Society, vol. 9, pp. 303.
[36] Hoffmann, M.R., Martin, S.T., Choi, W., Bahnemann, D.W. 1995.
Environmental application of semiconductor photocatalysis. Chemical Review, vol.95 pp.69.
[37] Fujishima, A., Rao, T.N., Tryk, D.A. 2000. Titanium dioxide photocatalysis.
Photochemistry Review, vol.1 pp.1.
[38] Hongo, B. 2000. Titanium dioxide photocatalysis. Journal of Photochemistry and Photobiology C: Photochemistry Reviews, vol. 1 pp.1–21.
[39] Fujishima, A., Hashimoto, K., Watanabe, T. 1999. TiO2 Photocatalysis:
Fundamentals and Applications, BKC, Tokyo.
[40] Sopyan, I., Marasawa, S., Hashimoto, K., Fujishima, A. 1994. Highly efficient TiO2 film photocatalyst, degradation of gaseous Acetaldehyde. Chemical. Review, vol.
23 pp. 723.
[41] Negishi, N., Iyoda, T., Hashimoto, K., Fujishima, A. 1995. Preparation of transparent TiO2 thin film photocatalyst and its photocatalytic activity.
Photochemistry Review, vol. 24 pp. 841.
[42] Sopyan, I., Watanabe, M., Marasawa, S., Hashimoto, K., Fujishima, A. 1996. An efficient TiO2 thin-film photocatalyst: Photocatalytic properties in gas phase acetaldehyde degradation Photochemistry Review, vol. 25, pp. 69.
[43] Matsubara, H., Takasa, M., Koyama, S., K., Hashimoto, Fujishima A. 1995.
Preparation and its photocatalytic activity under weak UV light illumination.
Chemical. Review, vol. 24, pp. 767.
[44] Sopyan, I., Watanabe, M., Marasawa, S., Hashimoto, K., Fujishima A. 1996.
Environmental issues in the electronics industries. Chemical. Review, vol. 9, pp. 79.
[45] Carp, O., Huisman, C.L, Reller, A. 2004. Photoinduced reactivity of titanium dioxide, Progress. Solid State Chemistry, vol. 32, pp. 33.
[46] Herrmann, J.M. 1999. Heterogeneous photocatalysis: fundamentals and applications to the removal of various types of aqueous pollutants, Catalysis Today, vol.53, pp. 115.
[47] Zhao, J., Yang, X. 2003. Photocatalytic oxidation for indoor air purification: a literature review, Building and Environment, vol. 38, pp. 645.
[48] Dung, N.T., Khoa, N.V., Herrmann, J.M. 2005. Photocatalytic degradation of reactive dye in aqueous TiO2 suspension under UV-visible light, International Journal of Photoenergy, vol. 7, pp. 11.
[49] Ibrahim, G., Abdul, A. 2008. Heterogeneous photocatalytic degradation of organic contaminants over titanium over titanium dioxide: a review of fundamentals, progress and problems. Photochemistry Reviews, vol.9, pp.1-12
[50] Hoffmann, M.R., Martin, S.T., Choi, W., Bahnemann, D.W. 1995.
Environmental application of semiconductor photocatalysis. Chemical Review, vol. 95, pp. 69.
[51] Serpone, N., Lawless, D., Disdier, J., Herrmann, J.M. 1994. Synthesis properties and application of oxide nanomaterials. The Journal of Physical Chemistry, vol. 10, pp. 643.
[52] Takeuchi, M., Yamashita, H., Matsuoka, M., Anpo, M., Hirao, T., Itoh, N., Iwamoto N. 2000. Photocatalytic decomposition of NO under visible light irradiation on the Cr-ion-implanted TiO2 thin film photocatalyst. Chemical Engineering Journal, vol. 129, pp.135.
[53] Kazuhito, H., Hiroshi, I., Akira, F. 2005. Photocatalysis: a historical overview and future prospects, Japanese Journal of Applied Physics, vol. 44, pp. 8269–8285.
[54] Curco, D., Gimenez, J., Addardak, A., Cervera-March, S., Esplugas, S. 2002.
Effects of radiation absorption and catalyst concentration on the photocatalytic degradation of pollutants. Catalysis Today, vol.76, pp.177.
[55] Abu Tariq, M., Faisal, M., Muneera, M., Bahnemann, D. 2007. Photochemical reactions of a few selected pesticide derivatives and other priority organic pollutants in aqueous suspensions of titanium dioxide, Journal of Molecular Catalysis, vol. 265, pp. 231.
[56] Guillard, C., Lachheb, H., Houas, A., Ksibi, M., Elaloui, E., Herrmann, J.M.
2003. Influence of chemical structure of dyes of pH and of inorganic salts on their photocatalytic degradation by TiO2 comparison of the efficiency of powder and supported TiO2, Journal of Photochemistry and Photobiology A, vol. 158, pp. 27.
[57] Krysa, J., Keppert, M., Jirkovsky, J. Stengl, V., Subrt, J. 2004. Fabrication of Sm- and Mn-doped lead titanate ceramic powder and ceramics by sol–gel methods.
Original Material Chemistry and Physics, vol. 86, pp.83-87.
[58] Saquib, M., Muneer, M. 2003. TiO2 mediated photocatalytic degradation of a triphenylmethane dye (gentian violet), in aqueous suspensions. Dyes Pigments, vol.
56 pp. 37-49
[59] Chun, H., Yizhong, W., Hongxiao, T. 2000. Destruction of phenol aqueous solution by photocatalysis or direct photolysis. Chemosphere, vol.41, pp. 1205.
[60] Haque, M.M., Muneer, M. 2007. Retracted: simple, selective and sensitive spectrophotometri determination of fenitrothion using novel chromogenic reagent.
Journal of Hazardous Materials, vol.145, pp. 51.
[61] Michael, D., James, R. Allen, J. 2002. Electrochemical investigation of the energetics of particulate titanium dioxide photocatalysts. The Journal of Physical Chemistry B, vol. 13, pp.4086-4093
[62] Jager, H. 2011. Process performance analysis of pulsed electric field (PEF) food application. Master thesis, Prozesswissenschanften der Technischen Universitat Berlin.
[63] Zou, Z.G., Ye, J.H., Sayama, K., Arakawa, H. 2001. A new type of water splitting system composed of two different of TiO2 photocatysts. Nature, vol. 414, pp.
625.
[64] Qin, B., Gustavo, V. 1998. Inactivating microorganisms using a pulsed field continuous treatment system. IEEE Transactions on Industry Applications, vol. 34, pp.
43-50
[65] Maged, E.A., Mohamed, H. Amer, E. 2012. Pulsed electric fields for food processing technology, structure and function of food engineering. The International Journal of Science and Technology, vol. 3, pp. 275-306
[66] Du¨kkanci, M., Gunduz, G. 2006. Ultrasonic degradation of oxalic acid in aqueous solutions, Ultrasonics Sonochemistry, vol.13 pp.517.
[67] McMurray, T. A., Byrne, J. A., Dunlop, P. S. M., Winkelman, J. G. M., Eggins, B. R., McAdams, E. T. 2004. Intrinsic kinetics of photocatalytic oxidation of formic and oxalic acid on immobilized TiO2 films. Applied Catalysis A: General, vol. 262, pp. 105.
[68] Kosanic, M. M., 1998. Photocatalytic degradation of oxalic acid over TiO2 power.
Journal of Photochemistry and Photobiology A: Chemistry, vol. 119 pp. 119-122
[69] Salmimies, R. 2010. Typical precipitate calcium oxalate with heavy waters, Master’s thesis, LUT.
[70] Candal, R.J. Zeltner, W.A., Anderson, M.A. 2000. Effects of pH and applied potential on photocurrent and oxidation rate of saline solutions of formic acid in a photoelectrocatalytic reactor. Environmental Sciences Technology, vol.34, pp. 3443.
[71] Kim, D.H., Anderson, M.A. 1996. Solution factors affecting the photocatalytic and photoelectrocatalytic degradation of formic acid using supported TiO2 thin films, Journal of Photochemistry and Photobiology. A: Chemistry, vol.94, pp. 221.
[72]. He, C., Li, X., Xiong, Y., Zhu, X., Liu, S. 2005. The enhanced PC and PEC oxidation of formic acid in aqueous solution using a Cu–TiO2/ITO film. Chemosphere, vol. 58, issue. 4, pp. 381-389.
[73]. Turki, A., Guillard, C., Dappozze, F., Berhault, G., Ksibi, Z., Kochkar, H. 2014, Design of TiO2 nanomaterials for the photodegradation of formic acid – Adsorption isotherms and kinetics study. Journal of Photochemistry and Photobiology A:
Chemistry, vol. 279, pp. 8-16.
[74] McMurry, J. E., Fay, R. C. 2008. Chemistry (Fifth edition). Pearson Education, Inc., USA, pp. 88-90
[75] Hurum, D. C., Agrios, A. G., Gray, K. A. 2003. Explaining the enhanced photocatalytic activity of Degussa P25 mixed-phase TiO2 using EPR. Journal of Physical Chemistry B, vol.107, pp. 4545-4549.
APPENDIX I, 1
Figure A1.1. BET surface area report. Pulsed electric field at 50 Hz for 12 min.
APPENDIX I, 2
Figure A1.2. BET adsorption isotherm. Pulsed electric field at 50 Hz for 12 min
APPENDIX I, 3
Figure A1.3. BET surface area report. Pulsed electric field at 50 Hz for 24 min.
APPENDIX I, 4
Figure A1.4. BET adsorption isotherm. Pulsed electric field at 50 Hz for 24 min
APPENDIX I, 5
Figure A1.5. BET surface area report. Pulsed electric field at 294 Hz for 12 min
APPENDIX I, 6
Figure A1.6. BET adsorption isotherm. Pulsed electric field at 294 Hz for 12 min
APPENDIX I, 7
Figure A1.7. BET surface area report. Pulsed electric field at 294 Hz for 24 min.
APPENDIX I, 8
Figure A1.8. BET adsorption isotherm. Pulsed electric field at 294 Hz for 24 min
APPENDIX I, 9
Figure A1.9. BET surface area report. Pulsed electric field at 963 Hz for 12 min.
APPENDIX I, 10
Figure A1.10. BET adsorption isotherm. Pulsed electric field at 963 Hz for 12 min
APPENDIX I, 11
Figure A1.11. BET surface area report. Pulsed electric field at 963 Hz for 24 min.
APPENDIX I, 12
Figure A1.12. BET adsorption isotherm. Pulsed electric field at 963 Hz for 24 min
APPENDIX I, 13
Figure A1.13. BET surface area report. No pulsed electric field treatment
APPENDIX I, 14
Figure A1.14. BET adsorption isotherm. No pulsed electric field treatment
APPENDIX I, 15
Figure A1.15. BET surface area report. Pulsed electric field at 963 Hz for 12 min with 400 ˚C calcination.
APPENDIX I, 16
Figure A1.16. BET adsorption isotherm. Pulsed electric field at 963 Hz for 12 min with 400 ˚C calcination.
APPENDIX I, 17
Figure A1.17. BET surface area report. Pulsed electric field at 963 Hz for 12 min.
with 500 ˚C calcination.
APPENDIX I, 18
Figure A1.18. BET adsorption isotherm. Pulsed electric field at 963 Hz for 12 min with 500 ˚C calcination.
APPENDIX II, 1
Table A2.1. The concentrations of formic acid after visible light irradiation. Samples were made by previous study using pulsed electric field at 50Hz for 12 min (Row 8-12).
APPENDIX II, 2
Table A2.2. The concentrations of formic acid after visible light irradiation. Samples were made by previous study using pulsed electric field at 50Hz 24 min (Row 8-12), 294Hz 12 min (Row 21-25) and 949Hz 12min (Row 27-31). Samples were made by current study using pulsed electric field at 294Hz 12min (Row 21-25) and 963Hz 12min (Row 35-39).
APPENDIX II, 3
Table A2.3. The concentrations of formic acid after visible light irradiation Samples were made by previous study using pulsed electric field at 50Hz 24 min (Row 8-12).
Samples were made by current study using pulsed electric field at 50Hz 24min (Row 14-18).
APPENDIX II, 4
Table A2.4. The concentrations of formic acid after visible light irradiation. Samples were made by previous study using pulsed electric field at 949Hz 24 min (Row8-12) and without PEF treatment (Row 14-18).
APPENDIX II, 5
Table A2.5. The concentrations of formic acid after visible light irradiation.
Commercial Samples and the samples were made by current study without PEF treatment.
APPENDIX II, 6
Table A2.6. The concentrations of formic acid after visible light irradiation. Samples were made by current study using pulsed electric field at 50Hz 12 min (Row 8-12) and 294Hz 24min (Row 14-18).
APPENDIX II, 7
Table A2.7. The concentrations of formic acid after visible light irradiation. Samples were made by current study using pulsed electric field at 949Hz 24 min (Row 8-12) and 963Hz 12min with 400 ˚C calcination (Row 14-18).
APPENDIX II, 8
Table A2.8. The concentrations of formic acid after visible light irradiation. Samples were made by current study using pulsed electric field at 963Hz 12min with 500 ˚C calcination (Row 8-12).
APPENDIX II, 9
Table A2.9. The concentrations of formic acid after visible light irradiation. Took 100mg previous study made samples using pulsed electric field at 50Hz 24min (Row
APPENDIX II, 10
Table A2.10. The concentrations of formic acid after visible light irradiation. The samples doped 13% Cu (Row 8-12) and 963Hz 12min with 400 ˚C calcination (Row 14-18)
APPENDIX II, 11
Table A2.11. The concentrations of formic acid after visible light irradiation. 100mg commercial samples (Row 11-15) and the samples without Cu doped (Row 17-21).
APPENDIX II, 12
Table A2.12. The concentrations of formic acid after visible light irradiation. The samples doped 5 % Cu (Row 8-12) and 9 % Cu (Row 14-20).