Oily wastewater treatment by photocatalytic membranes: a review

ABSTRACT

Oily wastewaters are among the most challenging to treat in conventional treatment plants. They have been produced in increasing amounts in a wide range of compositions, which may lead to serious environmental and population health issues if not properly treated. Membrane separation processes have emerged as a promising alternative for efficient treatment of effluents. Nevertheless, membrane fouling is a critical drawback. This is especially true when used with oily wastewater due to the sticky nature of oil molecules. Photocatalytic membranes (PMs) with antifouling properties have been developed aiming the process intensification. When photocatalytic surfaces are irradiated by a suitable light source they generate oxidative radicals, which can react and degrade foulants and other compounds. Oily wastewaters possess unique properties compared to other types of effluents, and photocatalysis and membrane separation process performances depend on a complex range of parameters. Thus, this review presents and discusses research efforts to develop antifouling PMs for treating oily wastewater, including the parameters that influence membrane separation and photocatalytic processes. The main features sought for these membranes, including the degradation of foulants during filtration under irradiation, self-cleaning capability, hydrophilicity, and reduction of fouling layer density are comprehensively revised. Finally, although is not possible to compare directly the efficiency and performance of PMs to treat oily wastewater due to differences on the experimental protocol, different operating conditions, initial concentrations of target contaminants, light sources and configuration of PMs, the self-cleaning properties and antifouling effects achieved by this technology are highly promisor.

GRAPHICAL ABSTRACT

KEYWORDS:

• Photocatalysis
• microfiltration
• self-cleaning membrane
• antifouling membrane
• oil filtration

Acknowledgements

Sections 3–5 of this work are derived from Chapter 2 of the first author's PhD thesis at the Federal University of Santa Catarina [23].

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author, L.L. Coelho, upon reasonable request.

Additional information

Funding

This research was supported by the Brazilian Coordination for the Improvement of Higher Education Personnel (CAPES) (Project number 88881.142487/2017-01); National Council for Scientific and Technological Development (CNPq – Brazil) (Project number 405.223/2018-8, and INCT MIDAS).

Notes on contributors

Leticya Lais Coelho

Dr. Leticya Lais Coelho is graduated (2015) and holds Master (2017) and Doctorate (2022) degrees in Chemical Engineering from the Federal University of Santa Catarina, with a sandwich period in the University of Bremen (Germany) and fellowship with the Metropolitan University of Manchester (UK). During her master, she worked on the development of photocatalysts, and her PhD was pursued on the development of antifouling photocatalytic ceramic membranes for the treatment of oily effluents and degradation of pharmaceuticals. She has experience in environmental chemical engineering and materials engineering, with an emphasis on developing new products in photocatalysis and membrane separation processes, photocatalytic membranes, microfiltration, tape casting phase inversion, TiO₂, and water and effluent treatment.

Michaela Wilhelm

Dr. Michaela Wilhelm is a Chemist and holds PhD in Inorganic Chemistry from the Carl-von-Ossietzky University of Oldenburg, Germany. Since 2002, she has been teaching and researching in the field of sol-gel materials and Polymer derived Ceramics (PDC). She currently works as Senior Scientist and head of the PDC subgroup in the Advanced Ceramic Group of the Department of Production Engineering at the University of Bremen, Germany. Her research focuses on the development of highly porous, multi-functional ceramics and hybrid materials derived from organic-inorganic polymers like polysiloxanes and polycarbosilanes for application in separation or energy conversion technologies as well as catalysis. Particular attention is paid to the hierarchically ordering of the porosity to ensure an optimized mass transport of liquids or gases as well as adjusted surface characteristics of the multifunctional compounds to increase the interaction of the surrounding media with the surfaces. Dr. Wilhelm published more than 80 papers in international journals and presented about 50 papers on conferences; [email protected]

Dachamir Hotza

Prof. Dr.-Ing. Dachamir Hotza is graduated in Chemical Engineering (1988) and holds a Master's degree in Mechanical Engineering (1991) from the Federal University of Santa Catarina (UFSC). His Ph.D. was obtained in Materials Engineering (1996) from the Technische Universität Hamburg Harburg (TUHH), Germany. He is a Full Professor (2014) at the Federal University of Santa Catarina, where he belongs to the Research Group on Converging and Enabling Technologies (G-TECH). He currently coordinates the Laboratory for the Processing of Ceramics (PROCER) and the Interdisciplinary Laboratory for the Development of Nanostructures (LINDEN) at UFSC. He has experience in Chemical Technology and Materials Engineering, focusing on processing, sustainability and nanotechnology.

Regina de Fátima Peralta Muniz Moreira

Prof. Regina de Fátima Peralta Muniz Moreira is a full professor in the Department of ChemicalEngineering and Food Engineering at the Federal University of Santa Catarinasince 1983 and is a supervisor of the Energy and Environment Laboratory at UFSC.She has published more than 187 articles in international journals, 7 book chapters and 7 patents, and more than 260 articles published in proceedings.She concluded the supervision of 67 dissertations and 35 PhD thesis in the graduate program in Chemical Engineering of the Federal University of Santa Catarina. She coordinated several national and international cooperation projects. Prof Regina has a wide experience in the treatment of water and wastewater focused in the following subjects: treatment of physical and chemical effluents, Advanced Oxidation Processes, Photocatalysis and Environmental catalysis. Her papers have more than 4600 citations and h index =41 (Scopus).