AMASiNG will pave the road for new membrane markets in China

Clean water is a major challenge all over the world with an estimated 750 million people lacking access to clean water. Effective membranes for water filtration are essential in many applications where drinking water is produced by desalination; polluted water is filtrated and cleaned for environmental purposes; and to make already “clean” water even cleaner for use in the production of, e.g., medical products.

The secret behind cleaning water with membranes lies in their structure and surface properties: It takes much less effort to filter out a worn out boot from wastewater than removing undesired bacteria or particles.

DTU Energy at the Technical University of Denmark has decades of experience with research in advanced ceramic materials and processing techniques for obtaining a desired structure of the final component. Until now, DTU Energy has primarily used this know-how for production of multilayer structures for state-of-the-art devices for energy conversion and storage. Now DTU Energy and the Danish company LiqTech International A/S, a specialist in air and water filtration, have joined in a project to exploit their strong competences for developing new possibilities in water membranes for biopharma and food & beverage industries in China.

“LiqTech have existing and functional membranes that are excellent, but we aim to improve the membranes for new application areas and markets”, senior researcher Michela Della Negra, project manager at DTU Energy, says.

In a new two-year project called “Ceramic high-flux microfiltration membrane” (AMASiNG) the two partners will explore new ways of obtaining an optimal porosity in the final product. They will test how the properties of raw materials and different processing procedures can affect the filtration performance.

The membranes in the project are made of silicon carbide (SiC), which have a number of environmental advantages when used in biopharma and food & beverage:

• Longer lifetime and therefore less waste generation;
• Membranes can tolerate high temperature steam cleaning, which can eliminate the use of cleaning chemicals;
• High filtration area per volume of carrier substrate;
• Very hydrophilic therefore they allow high water flux and resist fouling.

To purify as an example antibiotics, the cellular components must be effectively separated from the fermentation broth, letting only the pure antibiotics flow through the membrane.

"We need to refine the microstructure to adapt the membranes for new uses. This will result in a refined ultrafiltration membrane, "says development engineer at LiqTech Jan Hoffmann Jørgensen. Michela Della Negra from DTU continues:

“You need to have a very precise cutoff, which means having control over the particles that are rejected by the membrane and those that can pass through it. For this purpose, it is not enough to control the pore size, but you have to know also the surface chemistry and the electrical potential of your membrane, as certain materials can enhance small particle rejection due to electrostatic effects”, Michela Della Negra explains.

A very simple example is comparing membrane filtration to pouring water over either sand or medium-sized stones. The water drains differently due to different grain size, i.e. pore-size, but if the surface charge of the ‘sand’ is altered or removed during the production of the membrane, the “sand” can clump together and form “stone”-like particles, opening channels between them, thus leading to lower effectivity of the membranes.

To avoid this problem occurring, the researchers at DTU aim for smaller particles and lower pore-size. It might require working with ceramic nano-suspensions but it takes very complex chemistry to get there.

“We are looking at the sedimentation speed and electrostatic repulsion in the colloidal suspensions used for making the coating. They give us indications about the pore size in the membrane”, Michela Della Negra says.

The partners will be working in close contact to each other, since each variable during material processing (from milling of the inorganic powder, to shaping and sintering) can potentially affect the characteristics of the final product. Optimization in one step might require adjustments in another; therefore the final product quality is critically dependent on a broad and deep overview on the entire production route.