**3. Conclusion**

Strictly speaking, contaminant treatment can be defined as the complete degradation or mineralization of the contaminants. However, the photocatalytic degradation is suitable for treating hazardous organic pollutants. Generally, biological treatment is the most economical treatment option and the most compatible with the environment when feasible. Though the feasibility of adopting the photocatalytic oxidation is much explored they are not adopted practically, due to the problem of surplus power needed for generation of UV radiation. But in the present years ferrite doped titanium dioxide (TiO2) addresses this issue and, it also enhances the reusability of the catalyst. Hence it could be an ideal treatment to transform the bio-persistent compounds for an effective treatment system with sustainability. They also address the green technology, by utilizing sunlight as their source of excitation. This could be further eliminates or reduces the production of sludge's, a secondary pollutant. In near future the practise of biological methods could be replaced by the heterogeneous oxidation process. Such replacement will lead pathway to a green technology for the sustainable development.

#### **4. Acknowledgement**

The authors are grateful to IPPP, Department of Civil Engineering and Faculty of Engineering University of Malaya for their grant (RG091/10SUS) and moral support respectively.

### **5. References**


In the present scenario, the major difficulty regarding the doped TiO2 photocatalyst is the possible loss of photoactivity due to recycling of photocatalyst and long-term storage. It is believed that the efficiency of the metal-doped TiO2 under visible light wholly depends on the synthesizing and doping method adopted. In some cases, such doped photocatalysts showed zero activity under visible light or considerably lower activity in the ultraviolet spectral range compared to the non-doped TiO2 because of high carrier recombination rates through the metal ion levels. The problem is that the non-metal-doped TiO2 catalyst has very low photoactivity under visible light compared to that under UV light (Zaleska, 2008).TiO2 with visible light absorption can be employed to purify and disinfect the water and make it more suitable for consumption. Beside these limitations the major edge of the photocatalytic oxidation process over other process is because it's an only green and

Strictly speaking, contaminant treatment can be defined as the complete degradation or mineralization of the contaminants. However, the photocatalytic degradation is suitable for treating hazardous organic pollutants. Generally, biological treatment is the most economical treatment option and the most compatible with the environment when feasible. Though the feasibility of adopting the photocatalytic oxidation is much explored they are not adopted practically, due to the problem of surplus power needed for generation of UV radiation. But in the present years ferrite doped titanium dioxide (TiO2) addresses this issue and, it also enhances the reusability of the catalyst. Hence it could be an ideal treatment to transform the bio-persistent compounds for an effective treatment system with sustainability. They also address the green technology, by utilizing sunlight as their source of excitation. This could be further eliminates or reduces the production of sludge's, a secondary pollutant. In near future the practise of biological methods could be replaced by the heterogeneous oxidation process. Such replacement will lead pathway to a green

The authors are grateful to IPPP, Department of Civil Engineering and Faculty of Engineering

Ahmed, S., Rasul, M., Martens, W., Brown, R., & Hashib, M. (2010). Heterogeneous

Alnaizy, R. & Akgerman, A. (2000). Advanced oxidation of phenolic compounds. *Advances* 

Al-Rasheed, R., & Cardin, D. (2003). Photocatalytic degradation of humic acid in saline

Al-Rasheed, R., & Cardin, D. (2003). Photocatalytic degradation of humic acid in saline

photocatalytic degradation of phenols in wastewater: A review on current status

waters. Part 1, Artificial seawater: Influence of TiO2, temperature, pH, and air-flow.

waters. Part 2, Effect of various photocatalytic materials. *Applied Catalysis A:General,* 

University of Malaya for their grant (RG091/10SUS) and moral support respectively.

and developments. *Desalination,* 261, pp. 3-18

*in Environmental Research,* 4,pp. 233-244

*Aldrich. Chemosphere,* 51, pp. 925-933

sustainable process towards waste treatment.

technology for the sustainable development.

**4. Acknowledgement** 

246, pp. 39-48

**5. References** 

**3. Conclusion** 


Heterogeneous Photocatalytic Oxidation an Effective Tool for Wastewater Treatment – A Review 235

Malato, S., Fernández-Ibáñez, P., Maldonado, M., Blanco, J., & Gernjak, J. (2009).

Matsunaga, T., Tomoda R., Nakajima T. & Wake H., (1985). Photoelectrochemical

Matthews, R. (1990). Purification of water with near-UV illuminated suspensions of titanium

Matthews, R. (1993). Photocatalysis in water purification: Possibilities, problems and

Matthews, R.W., Abdullah,M.,& Low, G. K.C. (1990). Photocatalytic oxidation for total

Michael, R., Scot, T., Wonyong, C., & Detlef, W. (1995). Environmental application of

Mills, A., & Hunte, S. (1997). An overview of semiconductor photocatalysis. *Journal of* 

Mills, A., Belghazi, A., & Rodman, D. (1996). Bromate removal from drinking water by

Minero, C., Maurino, V., & Pelizzetti, E. (1997). Photocatalytic transformations of hydrocarbons at the sea water/air interface under solar radiation. *Marine Chemistry,* 58, pp. 361-372 Motheo, A., & Pinhedo, L. (2000). Electrochemical degradation of humic acid. *Science of The* 

Narayana, R. L., M, M., Aziz, A., & Saravanan, P. (2011). Photocatalytic decolourization of

Obernosterer, I., & Herndl, G. (2000). Differences in the optical and biological reactivity of

coastal marine environments. *Limnology and Oceanography,* 45, pp. 1120-1129 Ohno, T., Sarukawa, K., Tokieda, K., & Matsumura, M. (2001). Morphology of a TiO2

Ollis, D., Pelizzetti, E., & Serpone, N. (1991). Photocatalyzed destruction of water contaminants. *Environmental Science and Technology,* 25, pp. 1522-1529 Peyton, G. & Glaze, W. (1988). Destruction of pollutants in water with ozone in combination

Pirkanniemi, K. & Sillanpaa, M. (2002). Heterogeneous water phase catalysis as an environmental application: A review, *Chemosphere*, 48, pp. 1047-1060 Rajeshwar, K. & Ibanez, J.G.(1995). Electrochemical aspects of photocatalysis: application to

Rajeshwar, K. & Ibanez, J.G. (1997). *Environmental Electrochemistry: Fundamentals and* 

Rajeshwar, K., Chenthamarakshan, C., Goeringer, S., & Djukic, M. (2001). Titania-based

environmental remediation. *Pre Applied Chemistry 73*, 12, pp. 1849-1860

*Applications in Pollution Abatement*, Academic Press, San Diego

basic green dye by pure and Fe, Co doped TiO2 under sunlight illumination.

the humic and non-humic dissolved organic carbon component in two contrasting

photocatalyst (Degussa, P-25) consisting of anatase and rutile crystalline phases.

with ultraviolet radiation. 3. Photolysis of aqueous ozone. *Environmental Science and* 

detoxification and disinfection scenarios. *Journal of Chemical Education,* 72, pp. 1044-

heterogeneous photocatalysis. Materials, mechanistic issues, and implications on

organic carbon analysis. *Analytica Chimica Acta,* 223, pp. 171-179

semicondutor photocatalysis. *Chemical Reviews,* 95, pp. 69-96

*Photochemistry and Photobiology A: Chemistry,* 108, 1, pp. 1-35

semiconductor photocatalysis. *Water Research,* 30, pp. 1973-1978

overview and trends. *Catalysis Today,* 147, pp. 1-59

dioxide. *Water Research,* 24, pp. 653-660

*Total Environment,* 256, pp. 67-76

*Journal of Catalysis,* 203, pp. 82-86

*Technology,* 229,pp.761-767

1049

*Desalination,* 269, pp. 249-253

*Letters*, 29, 211-214

Amsterdam

Decontamination and disinfection of water by solar photocatalysis: Recent

sterilization of microbial cells by semiconductor powders, *FEMS Microbiology* 

prospects. In D. Ollis, H. AL-Ekabi, D. Ollis, & H. AL-Ekabi (Eds.), *Photocatalytic Purification and Treatment of Water and Air,* pp. 121-139, Elsevier Science,


Gaffney, J., Marley, N., & Clark, S. (1996). Humic and fulvic acids and organic colloidal

Glaze, W., Lay, Y. & Kang, J. (1995). Advanced oxidation processes. A kinetic model forthe

Goslich, R., Dillert, R., & Bahnemann, D. (1997). Solar water treatment: principles and

Guittonneau, S., Glaze, W., Duguet, J. & Wable, O. (1991). Characterization of natural waters

Han, F., Kambala, V., Srinivasan, M., Rajarathman, D., & Naidu, R. (2009). Tailored titanium

Herrmann, J. (1999). Heterogeneous photocatalysis: fundamentals and applications to the removal of various types aqueous pollutants. *Catalysis Today,* 53, pp. 115-129 Herrmann, J., Duchamp, C., Karkmaz, M., Hoai, B., Lachheb, H., & Puzenat, E. G. (2007).

Hilgendorff, M., Hilgendorff, M., & Bahnemann, D. (1993). Reductive photocatalytic

Hoffmann, M., Martin, S., Choi, W., & Bahnemann, W. (1995). Environmental applications of

Huang, A. C., Spiess, F.-J., Suib, S., Obee, T., Hay, S., & J.D., F. (1999). Photocatalytic degradation of triethylamine on titanium dioxide thin films. *Journal of Catalysis,* 188, pp. 40-47 Joanna, G., Maciej, H., & Antoni, W. (2000). Photocatalytic decompstion of oil in water.

Kawai, T., & Sakata, T. (1980). Conversion of carbohydrate into hydrogen fuel by a

Kidak, R. & Ince, N.H. (2006). Ultrasonic destruction of phenol and substituted phenols: A review of current research. *Ultrasonics Sonochemistry,* 13,pp.195–199 Legrini, O., Oliveros, E. & Braun, A.M. (1993). Photochemical processes for water treatment.

Leyva, E., Moctezuma, E., Ruiz, M.G., & Torez-Martínez, L. (1998). Photo degradation of

Lindner, M., Bahnemann, D., Hirthe, B., & Griebler, W. (1995). Solar water detoxification:

Linsebigler, A., Lu, G., & Yates, J. (1995). Photocatalysis on surfaces: Principles, mechanisms,

MacCarthy, P. (2001). The principles of humic substances. *Soil Science,* 166, pp. 738-751

phenol and 4-chlorophenol by BaO-LiO2-TiO2 catalysts. *Catalysis Today*, 40, pp. 367-

Novel TiO2 powders as highly active photocatalysts. *Solar Engineering, 1 ASME*, pp.

semiconductor photocatalysis. *Chemical Reviews,* 95, 1, pp. 69-96

environmental role. *Washington: Amer. Chemical. Soc.*, pp. 2-16

treatment: A review. *Applied Catalysis A: General,* 359, pp. 25-40

reactors. *Water Science and Technology,* 35, pp. 137-148

priority substances. *Catalysis Today,* 101, pp. 230-210

photocatalytic process. *Nature,* 286, pp. 74-476

and selected results. *Chemical Reviews,* 95, pp. 735-758

*World Congress*, Zürich, Switzerland

*Materials,* 146, pp. 624-629

*Water Research,* 34, pp. 1638-1644

*Chemical Reviews*, 93,pp. 671- 698

376

399- 408

34,pp. 2314-2323

material in the environment, in: Humic and fulvic acids: isolation, structure, and

oxidation of 1,2-dibromo-3-chloropropane in water by the combination of hydrogen peroxide and UV radiation. *Industrial and Engineering Chemistry Research,*

for potential to oxidize organic pollutants with ozone *Proceedings of 10th Ozone* 

dioxide photocatalysts for the degradation of organic dyes in wastewater

Environmental green chemistry as defined by photocatalysis. *Journal of Hazardous* 

elimination of tetrachloromethane on platinized titanium dioxide in aqueous suspension. In M. Tomkiewicz, R. Haynes, H. Yoneyama, & Y. Hori (Ed.), *Environmental Aspects of Electrochemistry and Photoelectrochemistry, Proceedings of Electrochemical Society* (pp. 112-121). Pennington: The Electrochemical Society Hincapié, M., Maldonado, M.I., Oller, I., Gernjak, W., Sánchez-Pérez, J.A., Ballesteros, M.M.,

& Malato, S. (2005). Solar photocatalytic degradation and detoxification of EU


**Part 3** 

**Water Resources Planning and Management** 

