Iranian Water Research Journal

Iranian Water Research Journal

Evaluation of the efficiency of TiO2 coating on steel substrates in the removal of E. coli using the photocatalytic method

Document Type : Original Article

Author
Akram Seifi
Department of Water Science & Engineering, Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran
10.22034/IWRJ.2025.15044.2649
Abstract
Introduction:
By growing the population and expanding industries, the need for sustainable and efficient wastewater treatment methods has become increasingly urgent. Among the different technologies, advanced photocatalytic oxidation is a promising technology, gaining attention for its ability to disinfect water and wastewater with minimal formation of harmful by-products. This study explored the use of titanium dioxide (TiO2) nanoparticles for photocatalytic disinfection of water contaminated with Escherichia coli (E. coli), focusing on using different stainless-steel substrates to enhance disinfection performance. The primary objective was to identify optimal conditions for achieving maximum bacterial removal efficiency while ensuring the stability and reusability of the coated substrates.
Materials and Methods:
In this research, TiO2 nanoparticles were deposited on various stainless-steel substrates, including the inner surface of stainless-steel pipes, brushed stainless-steel sheets, and stainless-steel meshes. The TiO2 nanoparticles were coated at different dosages (5, 10, 15, and 35 mg/cm²) on surfaces, and their performance was evaluated under UV light (6 W) for a residence time of 90 minutes. The brushed stainless-steel sheet was coated using physical vapor deposition (PVD), providing a durable and uniform TiO2 layer. In contrast, stainless-steel meshes and the inner surfaces of stainless-steel pipes were coated using solution-based methods by brushing, followed by heat treatment to stabilize the coating. To assess the effectiveness of these coatings, laboratory experiments were conducted using ultrapure water contaminated with E. coli at an initial concentration of approximately 10⁹ CFU/ml. The photocatalytic disinfection process was carried out in a reactor equipped with a UV light source (6 W). Samples were collected at intervals (2, 5, 10, 20, 30, 60, and 90 minutes), and bacterial concentrations were determined using standard agar plate culture methods. Disinfection efficiency was calculated based on the bacterial log reduction and removal percentages of E. coli. The pseudo-first-order kinetic model was applied to analyze the disinfection data, and reaction rate constants (k) were determined to assess the effectiveness of different coatings. In addition, statistical analyses, including the Mann-Whitney U test and Kruskal-Wallis test, were employed to evaluate differences in performance between various coating conditions.

Result and Discussion:
The study revealed that TiO2 coatings on the inner surfaces of stainless-steel pipes achieved the highest bacterial removal efficiencies, reaching 99.99% disinfection within 20 minutes at dosages of 35 mg/cm² and 5 mg/cm². However, the coatings on stainless-steel pipes exhibited stability issues, as TiO2 particles gradually shedd over time, which could reduce their long-term effectiveness. In contrast, stainless-steel mesh coated with TiO2 nanoparticles at a dosage of 10 mg/cm², combined with UV irradiation, achieved a removal efficiency of 99.96% within 30 minutes. This configuration demonstrated a balance between high efficiency and stability, making it a reliable choice for sustained applications. Furthermore, the stainless-steel mesh showed better resistance to particle shedding compared with the inner surfaces of the pipes. The disinfection process was effectively described by the pseudo-first-order kinetic model, as indicated by high correlation coefficients (R²). The highest reaction rate constants (k) were observed for coatings on stainless-steel pipes (35 mg/cm²) and stainless-steel meshes (10 mg/cm²). Statistical analyses revealed no significant differences in disinfection efficiency between these two configurations. This result suggested that stainless-steel mesh coated with 10 mg/cm² dosages of TiO2 offers an equally effective and more stable alternative. The findings established the critical role of nanoparticle dosage in determining the performance of photocatalytic systems. The findings from this research provided valuable insights into the design and optimization of sustainable water treatment technologies that align with global efforts to address water scarcity and pollution challenges. Currently, numerous water treatment plants worldwide are equipped with UV lamps that use ultraviolet light for water disinfection. However, studies have shown that relying solely on UV light can lead to the production of smaller-than-average colony phenotypes in surviving bacteria, which can pose a serious health risk. Therefore, the industrial-scale application of TiO2 nanoparticles as a sustainable and effective disinfection method in water treatment should be considered. However, challenges such as costs, nanoparticle stability, and the need for advanced technologies to separate and recover photocatalysts must still be addressed. Therefore, it is recommended to investigate the durability and reusability of TiO2 coatings under continuous operation, to evaluate the effectiveness of alternative light sources, including solar or energy-efficient LEDs, to reduce operational costs, to extend the findings to pilot-scale studies to assess the feasibility of implementing TiO2-based photocatalytic systems in industrial water treatment facilities, and to examine the potential environmental risks associated with TiO2 nanoparticle shedding and develop strategies for nanoparticle recovery and reuse.
Keywords
Nanomaterial immobilization
Stainless-steel mesh
Disinfection
Coating
Pseudo-first-order kinetic model
1.     Amanighadim, A., Dorraji, M. and Lotfihayayee, K., 2017. Investigation on TiO2 nanophotocatalysts performance in simultaneous removal of humic acid and biological contaminants (E. coli) from contaminated water under UV light irradiation. Applied Chemistry Today, 12(44), pp. 55-68. [In Persian]
 
2.     Chen, Y., Huang, W., He, D., Situ, Y. and Huang, H., 2014. Construction of heterostructured g-C3N4/Ag/TiO2 microspheres with enhanced photocatalysis performance under visible-light irradiation. ACS Applied Materials & Interfaces, 6(16), pp. 14405-14414.
 
3.     De Vietro, N., Tursi, A., Beneduci, A., Chidichimo, F., Milella, A., Fracassi, F. and Chidichimo, G., 2019. Photocatalytic inactivation of Escherichia coli bacteria in water using low pressure plasma deposited TiO2 cellulose fabric. Photochemical & Photobiological Sciences, 18, pp. 2248-2258.
 
4.     Garoma, T., Umamaheshwar, S.K. and Mumper, A., 2010. Removal of sulfadiazine, sulfamethizole, sulfamethoxazole, and sulfathiazole from aqueous solution by ozonation. Chemosphere, 79(8), pp. 814-820.
 
5.     He, J., Cheng, J. and Lo, I.M., 2021. Green photocatalytic disinfection of real sewage: efficiency evaluation and toxicity assessment of eco-friendly TiO2-based magnetic photocatalyst under solar light. Water Research, 190, p. 116705.
 
6.     Ho, N., Gamage, J.D. and Zhang, Z.J., 2010. Photocatalytic degradation of eriochrome black dye in a rotating corrugated drum photocatalytic reactor. International Journal of Chemical Reactor Engineering, 8(1).
 
7.     Hosseini, F., Assadi, A.A., Nguyen-Tri, P., Ali, I. and Rtimi, S., 2022. Titanium-based photocatalytic coatings for bacterial disinfection: The shift from suspended powders to catalytic interfaces. Surfaces and Interfaces, 32, p. 102078.
 
8.     Hrudey, S.E. and Charrois, J.W., eds. 2012. Disinfection by-products and human health. IWA Publishing, London.
 
9.     Isopencu, G., Eftimie, M., Melinescu, A., Dancila, A.M. and Mares, M., 2022. Recycling of glass waste by deposition of TiO2 for the intensification of the photocatalytic effect in the purification of wastewater. Coatings, 12(11), p. 1794.
 
10. Jiao, Y., 2020. UV/Photocatalyst based photoreactor design for water treatment. Doctoral Dissertation. Laurentian University of Sudbury.
 
11. Jiao, Y., Shang, H., and Scott, J. A., 2021. A UVC based advanced photooxidation reactor design for remote households and communities not connected to a municipal drinking water system. Journal of Environmental Chemical Engineering, 9(3), p. 105162.
 
12. Kışla, D., Gökmen, G.G., Evrendilek, G.A., Akan, T., Vlčko, T., Kulawik, P. and Ozogul, F., 2023. Recent developments in antimicrobial surface coatings: Various deposition techniques with nanosized particles, their application and environmental concerns. Trends in Food Science & Technology, 135, pp. 144-172.
 
13. Marugán, J., van Grieken, R., Pablos, C., Satuf, M.L., Cassano, A.E. and Alfano, O.M., 2015. Kinetic modelling of Escherichia coli inactivation in a photocatalytic wall reactor. Catalysis Today, 240, pp. 9-15
 
14. Mecha, A.C., Onyango, M.S., Ochieng, A. and Momba, M.N.B., 2019. UV and solar photocatalytic disinfection of municipal wastewater: inactivation, reactivation and regrowth of bacterial pathogens. International Journal of Environmental Science and Technology, 16(7), pp. 3687-3696.
 
15. Ochiai, T., Masuko, K., Tago, S., Nakano, R., Nakata, K., Hara, M. and Fujishima, A., 2013. Synergistic water-treatment reactors using a TiO2-modified Ti-mesh filter. Water, 5(3), pp. 1101-1115.
 
16. Pablos, C., Marugan, J., van Grieken, R. and Serrano, E., 2013. Emerging micropollutant oxidation during disinfection processes using UV-C, UV-C/H2O2, UV-A/TiO2 and
UV-A/TiO2/H2O2. Water Research, 47(3), pp. 1237-1245.
 
17. Pajandi, S., 2012. Evaluation of removal efficiency of trihalomethanes (THMs) from water using titanium dioxide (TiO2) based on nano photocatalysis. Master's thesis, Water and Wastewater Engineering. [In Persian]
 
18. Rincón, A.G. and Pulgarin, C., 2007. Absence of E. coli regrowth after Fe3+ and TiO2 solar photoassisted disinfection of water in CPC solar photoreactor. Catalysis Today, 124(3-4), pp. 204-214.
 
19. Robertson, J.M., Robertson, P.K. and Lawton, L.A., 2005. A comparison of the effectiveness of TiO2 photocatalysis and UVA photolysis for the destruction of three pathogenic micro-organisms. Journal of Photochemistry and Photobiology A: Chemistry, 175(1), pp. 51-56.
 
20. Saravanan, A., Kumar, P.S., Jeevanantham, S., Karishma, S. and Kiruthika, A.R., 2021. Photocatalytic disinfection of micro-organisms: Mechanisms and applications. Environmental Technology & Innovation, 24, p. 101909.
 
21. Tabatabaei, S.H. and Najafi, P., 2009. Effects of irrigation with treated municipal wastewater on soil properties in arid and semi-arid regions. Irrigation and Drainage, 58(5), pp. 551-560.
 
22. Van Grieken, R., Marugán, J., Sordo, C. and Pablos, C., 2009. Comparison of the photocatalytic disinfection of E. coli suspensions in slurry, wall and fixed-bed reactors. Catalysis Today, 144(1-2), pp. 48-54.
 
23. Von Gunten, U., 2018. Oxidation processes in water treatment: are we on track?. Environmental Science & Technology, 52(9), pp.5062-5075.
 
24. Wang, L., Wu, W., Xie, X., Chen, H., Lin, J. and Dionysiou, D.D., 2018. Removing Escherichia coli from water using zinc oxide-coated zeolite. Water Research, 141, pp. 145-151.
 
25. Wongaree, M., Bootwong, A., Choo-In, S., and Sato, S., 2022. Photocatalytic reactor design and its application in real wastewater treatment using TiO2 coated on the stainless-steel mesh. Environmental Science and Pollution Research, 29(30), pp. 46293-46305.
 
26. Zazouli, M.A., Ahanjan, M., Kor, Y., Eslamifar, M., Hosseini, M. and Yousefi, M., 2015. Water disinfection using photocatalytic process with titanium dioxide nanoparticles. Journal of Mazandaran University of Medical Sciences, 24(122), pp. 227-238. [In Persian]
 
27. Zhang, C., Li, Y., Shuai, D., Shen, Y. and Wang, D., 2019. Progress and challenges in photocatalytic disinfection of waterborne viruses: a review to fill current knowledge gaps. Chemical Engineering Journal, 355, pp. 399-415.
 
28. Zhao, Y. Huang, G., An, C., Huang, J., Xin, X., Chen, X. and Song, P., 2020. Removal of Escherichia coli from water using functionalized porous ceramic disk filter coated with Fe/TiO2 nano-composites. Journal of Water Process Engineering, 33, p. 101013.
 

  • Receive Date 12 December 2024
  • Accept Date 06 February 2025
  • Publish Date 21 March 2025