Abstract
Porous metal membranes have recently received increasing attention, and significant progress has been made in their preparation and characterisation. This progress has stimulated research in their applications in a number of key industries including wastewater treatment, dairy processing, wineries, and biofuel purification. This review examines recent significant progress in porous metal membranes including novel fabrication concepts and applications that have been reported in open literature or obtained in our laboratories. The advantages and disadvantages of the different membrane fabrication methods were presented in light of improving the properties of current membrane materials for targeted applications. Sintering of particles is one of the main approaches that has been used for the fabrication of commercial porous metal membranes, and it has great advantages for the fabrication of hollow fibre metal membranes. However, sintering processes usually result in large pores (e.g., >1 µm). So far, porous metal membranes have been mainly used for the filtration of liquids to remove the solid particles. For porous metal membranes to be more widely used across a number of separation applications, particularly for water applications, further work needs to focus on the development of smaller pore (e.g., sub-micron) metal membranes and the significant reduction of capital and maintenance costs.
Highlights
Membrane-based processes have become increasingly attractive due to their ability to reliably remove contaminants, their affordability, and the increasing prominence of energy and water issues necessitating efficient treatment of waste effluents
Three different flat macroporous metal (ASI 316L stainless steel) membranes were evaluated in their study, and the results revealed that higher air velocity and higher temperature of the feed solution resulted in greater water evaporation flux
These results showed that the processes using catalytic metal membranes seemed promising for both denitrification and catalytic oxidation of aromatic components in water, operating costs were high as the catalysts are made from noble metals (e.g., Pt, Pd), and they need to be replaced once they have lost their catalytic activity
Summary
Membrane-based processes have become increasingly attractive due to their ability to reliably remove contaminants, their affordability, and the increasing prominence of energy and water issues necessitating efficient treatment of waste effluents. Inorganic membrane materials cost more than organic polymeric membrane materials, they offer some advantages such as temperature stability, resistance towards solvents, narrow pore size distribution, and the opportunity for more sterilisation options [2] They can be widely used for the chemical and pharmaceutical industry and for many water applications, for high temperature, extreme pH, abrasive environments, and high-pressure processes that preclude the use of existing polymeric membranes. Metal membranes offer some advantages over the polymeric membranes for these applications because the modules can be cleaned by high pressure back-flushing, reducing the use and influence of cleaning chemicals [9] Another advantage of using metal membranes in food processing is their stability during steam sterilisation [9]. Novel fabrication techniques that were recently investigated for potentially producing nanoscale porous metal membranes and future research directions will be discussed
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