Design, Building and Performance of a New Photocatalytic Reactor Using TiO₂-Coated Rings Synthesized by Plasma Electrolytic Oxidation

Abstract

An annular UV photocatalytic reactor with recirculation in batch was designed and built. The design considered low construction, simple operation and maintenance costs, availability and durability of the materials used, easy cleaning, and high standards of hygiene and safety. The TiO₂ photocatalysts were synthesized by plasma electrolytic oxidation (PEO) on commercial Ti rings were compared with coatings obtained on Ti plates as a reference, and no influence of the substrate geometry on the morphology, crystallinity, or bandgap of the coatings was observed. The efficiency of the photocatalytic reactor using 10 TiO₂-coated rings was tested by Cr(VI) transformation in the presence of EDTA. The Cr(VI) transformation after 5 h irradiation attained 95%; a rather high photocatalytic activity (62%) was maintained after the third use of the rings without reactivation of the photocatalyst. These coatings synthesized by PEO have not been applied in modular photocatalytic reactors until now.

Keywords

Annular photoreactor / Titanium dioxide / Plasma electrolytic oxidation / Heterogeneous photocatalysis / Hexavalent chromium / Anodic oxidation / Advanced oxidation processes

Acknowledgments

The authors thank Daniel Vega from the XRD Laboratory, Department of Condensed Matter Physics, Comisión Nacional de Energía Atómica, and Enrique San Román’s laboratory at Instituto de Química, Física de Materiales, Medio Ambiente y Energía, Universidad de Buenos Aires (INQUIMAE-UBA) for the DRS. All institutions are in Argentina.

Author Contributions

Conceptualization, H.D.T. and M.L.V.; Methodology, H.D.T. and M.L.V.; Validation, H.D.T., M.L.V., A.E.K., A.N.D., M.I.L.; Formal Analysis, H.D.T.; Investigation, H.D.T., M.L.V., A.E.K. and A.N.D.; Resources, M.L.V. and M.I.L.; Writing—Original Draft Preparation, H.D.T. and M.L.V.; Writing—Review & Editing, H.D.T., M.L.V. and M.I.L.; Visualization, H.D.T.; Supervision, M.L.V. and M.I.L.; Project Administration, M.I.L.; Funding Acquisition, M.L.V.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data is available on request.

Funding

This research was funded by Agencia Nacional de Promoción de Investigación, Desarrollo Tecnológico e Innovación (Agencia I+D+i), grants numbers PICT-2017-2133 and PICT-2017-2494.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References

[1] Zhang L, Dillert R, Bahnemann D, Vormoor M. Photo-induced hydrophilicity and self-cleaning: Models and reality. Energy Environ. Sci. 2012, 5, 7491-7507. doi:10.1039/c2ee03390a.

[2] Yu H, Song L, Hao Y, Lu N, Quan X, Chen S, et al. Fabrication of pilot-scale photocatalytic disinfection device by installing TiO₂ coated helical support into UV annular reactor for strengthening sterilization. Chem. Eng. J. 2016, 283, 1506-1513. doi:10.1016/j.cej.2015.08.042.

[3] Vera ML, Traid HD, Dwojak AN, Rosenberger MR, Schvezov CE. Advances in nanostructured TiO₂ coatings for industrial applications. In Industrial Applications of Nanoparticles—A Prospective Overview, 1st ed.; Litter MI, Ahmad A, Eds.; CRC Press: Boca Raton, FL, USA; Taylor & Francis Group: Oxfordshire, UK, 2023; Volume 1, pp. 228-255.

[4] Fujishima A, Zhang X. Titanium dioxide photocatalysis: Present situation and future approaches. C. R. Chim. 2006, 9, 750-760. doi:10.1016/j.crci.2005.02.055.

[5] Guo Q, Zhou C, Ma Z, Yang X. Fundamentals of TiO₂ Photocatalysis: Concepts, Mechanisms, and Challenges. Adv. Mater. 2019, 31, 1901997. doi:10.1002/adma.201901997.

[6] Armaković SJ, Savanović MM, Armaković S. Titanium Dioxide as the Most Used Photocatalyst for Water Purification: An Overview. Catalysts 2022, 13, 26. doi:10.3390/catal13010026.

[7] Diamanti MV, Ormellese M, Pedeferri M. Application-wise nanostructuring of anodic films on titanium: A review. J. Exp. Nanosci. 2015, 10, 1285-1308. doi:10.1080/17458080.2014.999261.

[8] Sulka GD. Introduction to anodization of metals. In Nanostructured Anodic Metal Oxides:Synthesis and Applications, 1st ed.; Sulka GD, Ed.; Elsevier: Amsterdam, The Netherlands, 2020; Volume 1, pp. 1-34.

[9] Casanova L, Arosio M, Hashemi MT, Pedeferri M, Botton GA, Ormellese M. A nanoscale investigation on the influence of anodization parameters during plasma electrolytic oxidation of titanium by high-resolution electron energy loss spectroscopy. Appl. Surf. Sci. 2021, 570, 151133. doi:10.1016/j.apsusc.2021.151133.

[10] Aliofkhazraei M, Macdonald DD, Matykina E, Parfenov EV, Egorkin VS, Curran JA, et al. Review of plasma electrolytic oxidation of titanium substrates: Mechanism, properties, applications and limitations. Appl. Surf. Sci. Adv. 2021, 5, 100121. doi:10.1016/j.apsadv.2021.100121.

[11] Li G, Ma F, Liu P, Qi S, Li W, Zhang K, et al. Review of micro-arc oxidation of titanium alloys: Mechanism, properties and applications. J. Alloys Compd. 2023, 948, 169773. doi:10.1016/j.jallcom.2023.169773S.

[12] Makurat-Kasprolewicz B, Ossowska A. Recent advances in electrochemically surface treated titanium and its alloys for biomedical applications: A review of anodic and plasma electrolytic oxidation methods. Mater. Today Commun. 2023, 34, 105425. doi:10.1016/j.mtcomm.2023.105425.

[13] Dwojak AN, Vera ML, Traid HD, Rosenberger MR, Schvezov CE, Litter MI. Photocatalytic and mechanical properties of immobilized nanotubular TiO₂ photocatalysts obtained by anodic oxidation: A novel combined analysis. Photochem. Photobiol. Sci. 2022, 21, 1793-1806. doi:10.1007/s43630-022-00257-5.

[14] Manassero A, Satuf ML, Alfano OM. Photocatalytic reactors with suspended and immobilized TiO₂: Comparative efficiency evaluation. Chem. Eng. J. 2017, 326, 29-36. doi:10.1016/j.cej.2017.05.087.

[15] Traid HD, Vera ML, Ares AE, Litter MI. Advances on the synthesis of porous TiO₂ coatings by anodic spark oxidation. Photocatalytic reduction of Cr(VI). Mater. Chem. Phys. 2017, 191, 106-113. doi:10.1016/j.matchemphys.2017.01.034.

[16] Bayati MR, Golestani-Fard F, Moshfegh AZ. The effect of growth parameters on photo-catalytic performance of the MAO-synthesized TiO₂ nano-porous layers. Mater. Chem. Phys. 2010, 120, 582-589. doi:10.1016/j.matchemphys.2009.12.005.

[17] Quintero D, Galvis O, Calderón JA, Castaño JG, Echeverría F. Effect of electrochemical parameters on the formation of anodic films on commercially pure titanium by plasma electrolytic oxidation. Surf. Coat. Technol. 2014, 258, 1223-1231. doi:10.1016/j.surfcoat.2014.06.058.

[18] Pesode P, Barve S. Surface modification of titanium and titanium alloy by plasma electrolytic oxidation process for biomedical applications: A review. Mater. Today Proc. 2021, 46, 594-602. doi:10.1016/j.matpr.2020.11.294.

[19] Traid HD, Vera ML, Litter MI. Total Specific Energy as a New Figure of Merit for the Design of Porous TiO₂ Surfaces Synthesized via Plasma Electrolytic Oxidation. Ind. Eng. Chem. Res. 2023, 62, 7757-7762. doi:10.1021/acs.iecr.3c00386.

[20] Ochiai T, Fujishima A. Design and optimization of photocatalytic water purification reactors. In Photocatalysis and Water Purification, 1st ed.; Pichat P, Ed.; Wiley: Hoboken, NJ, USA, 2013; Volume 1, pp. 361-376.

[21] Ballari MdlM, Satuf ML, Alfano OM. Photocatalytic Reactor Modeling:Application to Advanced Oxidation Processes for Chemical Pollution Abatement. In Heterogeneous Photocatalysis. Topics in Current Chemistry Collections, 1st ed.; Muñoz-Batista M, Navarrete Muñoz A, Luque R, Eds.; Springer: Berlin/Heidelberg, Germany, 2020; Volume 1, pp. 265-301.

[22] Escobedo S, De Lasa H. Photocatalysis for Air Treatment Processes: Current Technologies and Future Applications for the Removal of Organic Pollutants and Viruses. Catalysts 2020, 10, 966. doi:10.3390/catal10090966.

[23] Sundar KP, Kanmani S. Progression of Photocatalytic reactors and it’s comparison: A Review. Chem. Eng. Res. Des. 2020, 154, 135-150. doi:10.1016/j.cherd.2019.11.035.

[24] Binjhade R, Mondal R, Mondal S. Continuous photocatalytic reactor: Critical review on the design and performance. J. Environ. Chem. Eng. 2022, 10, 107746. doi:10.1016/j.jece.2022.107746.

[25] Abd Rahman N, Choong CE, Pichiah S, Nah IW, Kim JR, Oh SE, et al. Recent advances in the TiO₂ based photoreactors for removing contaminants of emerging concern in water. Sep. Purif. Technol. 2023, 304, 122294. doi:10.1016/j.seppur.2022.122294.

[26] Vera ML, Traid HD, Henrikson ER, Ares AE, Litter MI. Heterogeneous photocatalytic Cr(VI) reduction with short and long nanotubular TiO₂ coatings prepared by anodic oxidation. Mater. Res. Bull. 2018, 97, 150-157. doi:10.1016/j.materresbull.2017.08.013.

[27] Meichtry JM, Colbeau-Justin C, Custo G, Litter MI. Preservation of the photocatalytic activity of TiO₂ by EDTA in the reductive transformation of Cr(VI). Studies by Time Resolved Microwave Conductivity. Catal. Today 2014, 224, 236-243. doi:10.1016/j.cattod.2013.10.021.

[28] Tumolo M, Ancona V, De Paola D, Losacco D, Campanale C, Massarelli C, et al. Chromium Pollution in European Water, Sources, Health Risk, and Remediation Strategies: An Overview. Int. J. Environ. Res. Public Health 2020, 17, 5438. doi:10.3390/ijerph17155438.

[29] Litter MI. Last advances on TiO₂-photocatalytic removal of chromium, uranium and arsenic. Curr. Opin. Green Sustain. Chem. 2017, 6, 150-158. doi:10.1016/j.cogsc.2017.04.002.

[30] Kleiman A, Meichtry JM, Xaubet M, Grondona D, Litter MI, Márquez A. Efficiency of cathodic arc-grown N-doped TiO₂ films for the photocatalytic reduction of Cr(VI) under UV-Vis irradiation. J. Phys. D Appl. Phys. 2023, 56, 495303. doi:10.1088/1361-6463/acf7d2.

[31] ASTM B367-22; Standard Specification for Titanium and Titanium Alloy Castings. ASTM International: West Conshohocken, PA, USA, 2022. doi:10.1520/B0367-22.

[32] Traid HD. Síntesis de recubrimientos porosos y nanotubulares de TiO2 anódico aplicados a fotocatálisis heterogénea. PhD Thesis, Applied Science, Universidad Nacional de Misiones, Posadas, Argentina, 2018.

[33] Criado J, Real C. Mechanism of the inhibiting effect of phosphate on the anatase → rutile transformation induced by thermal and mechanical treatment of TiO₂. J. Chem. Soc., Faraday Trans. 1 1983, 79, 2765-2771. doi:10.1039/f19837902765.

[34] Murphy A. Band-gap determination from diffuse reflectance measurements of semiconductor films, and application to photoelectrochemical water-splitting. Sol. Energy Mater. Sol. Cells 2007, 91, 1326-1337. doi:10.1016/j.solmat.2007.05.005.

[35] ASTM D1687-17; Standard Test Methods for Chromium in Water. ASTM International: West Conshohocken, PA, USA, 2017. doi:10.1520/D1687-17.

[36] Zwilling V, Darque-Ceretti E, Boutry-Forveille A, David D, Perrin MY, Aucouturier M. Structure and physicochemistry of anodic oxide films on titanium and TA6V alloy. Surf. Interface Anal. 1999, 27, 629-637. doi:10.1002/(SICI)1096-9918(199907)27:7.

[37] Vera ML. Obtención y caracterización de películas hemocompatibles de TiO2. PhD Thesis, Science and Technology, Instituto Sabato, CNEA-UNSAM, Buenos Aires, Argentina, 2013.

[38] Hanaor DAH, Sorrell CC. Review of the anatase to rutile phase transformation. J. Mater. Sci. 2010, 46, 855-874. doi:10.1007/s10853-010-5113-0.

[39] Dwojak AN, Vera ML, Traid HD, Maydana MF, Litter MI, Schvezov CE. Influence of anodizing variables on Cr(VI) photocatalytic reduction using TiO₂ nanotubes obtained by anodic oxidation. Environ. Nanotechnol. Monit. Manag. 2021, 16, 100537. doi:10.1016/j.enmm.2021.100537.

[40] Weon S, He F, Choi W. Status and challenges in photocatalytic nanotechnology for cleaning air polluted with volatile organic compounds: Visible light utilization and catalyst deactivation. Environ. Sci. Nano 2019, 6, 3185-3214. doi:10.1039/c9en00891h.

[41] Karim AV, Krishnan S, Shriwastav A. An overview of heterogeneous photocatalysis for the degradation of organic compounds: A special emphasis on photocorrosion and reusability. J. Indian Chem. Soc. 2022, 99, 100480. doi:10.1016/j.jics.2022.100480.

[42] Salaeh S, Kovacic M, Kosir D, Kusic H, Stangar UL, Dionysiou DD, et al. Reuse of TiO₂-based catalyst for solar driven water treatment; thermal and chemical reactivation. J. Photochem. Photobiol. A Chem. 2017, 333, 117-129. doi:10.1016/j.jphotochem.2016.10.015.