Improved flux and anti-fouling performance of a photocatalytic ZnO membrane on porous stainless steel substrate for microalgae harvesting

• Published in: Journal of membrane science 2024-02, Vol.694, p.122405, Article 122405
• Main Authors: Salih, Amar K., Aditya, Lisa, Matar, Fatima, Nghiem, Long D., Ton-That, Cuong
• Format: Article
• Language: English
• Subjects: Algae harvesting; Inorganic microfiltration; Membrane cleaning; Photocatalysis; Self-cleansing; ZnO coating
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2023.122405

Photocatalytic self-cleansing ZnO membranes were developed and used for pre-concentrating microalgae solution prior to harvesting. The inorganic membranes were fabricated via two different methods: (i) direct deposition of ZnO onto a porous stainless steel substrate and (ii) post-growth oxidation of a deposited metallic Zn layer. Systematic surface characterisation revealed a thin layer of homogeneous, crystalline ZnO on the porous membrane. Direct ZnO deposition resulted in a thicker layer with higher UV light absorption capability compared with the post-growth oxidization method. The ZnO coating made the membrane surface highly hydrophilic, resulting in two-fold increase in water permeance compared to the base stainless steel substrate. The high hydrophilicity of the ZnO-coated membrane also led to an increase in the permeate flux of the microalgae solution by up to 100%, making it suitable for microalgae pre-concentration. Upon UV light irradiation, the ZnO membrane demonstrated self-cleansing capability due to the photocatalytic activity of the ZnO coating layer. After 30 min of UV irradiation, the ZnO membrane could achieve 60% permeance recovery after complete fouling. No recovery was observed with the base stainless steel membrane, which was used as the control. [Display omitted] •Photocatalytic self-cleansing membranes developed and used for microalgae harvesting.•Two coating methods successfully applied to stainless steel membranes.•Coating membranes with ZnO led to permeation flux increase by two times.•Photocatalytic cleansing capability using UV light to regenerate fouled membranes.•Membrane coating to tailor its surface chemistry, hydrophobicity and UV absorption.