Waste into resources: lengthening the life of membranes that create clean water from wastewater
Professor Tao He is Chair of Membrane Material and Separation Technology at the Shanghai Advanced Research Institute, Chinese Academy of Sciences. A Leaders in Innovation Fellowships (LIF) alumnus, he is an expert in water membranes that create clean water from wastewater. He proved that membranes can be 'slippery' and designed a new surface structure to increase membrane life-span.
We interviewed Tao on his research, successes, and learnings from LIF:
What is the focus of your research?
My expertise is in developing membranes to get pure water from any kind of water. I look at four different water sources: underground, surface, municipal waste, and industrial wastewater.
What sets your membranes apart?
One of my innovations is in using heat rather than electricity, which is commonly used in other membrane filters. Heat is more accessible and environmentally-friendly – you can get waste heat from industry, or from solar power in off-grid areas.
You heat up the water until it evaporates, and the vapour permeates across the hydrophobic membrane – which is basically a piece of paper with lots of pores.
We also designed a new membrane surface structure. We put these small ‘pillars’ on top of the membrane surface, which create a lot of air space. Particles normally attach to solid surfaces, so with a surface of mainly air, there is nowhere for the particles to stick.
Commercial membranes often become ‘fouled’ or saturated with the crystals found in saline solutions (usually containing up to about 26% sodium chloride). In lab experiments, our membrane stays clean even with water containing up to 40% sodium chloride. This means it has a much longer life time than typical membranes.
Why did you start working on water membranes?
I was educated as a chemical engineer in China. During a trip to an ammonia production plant, I found that a very complicated process was used to separate nitrogen from air to produce ammonia. I asked myself why not create a gas separation membrane to get rid of oxygen, and feed pure nitrogen directly into the production.
However, gas membranes represent a marginal share of the membrane market, compared to water. In my graduate study, I moved into water membranes. Water sounds simple, but it is very complicated. Until today there are no foul-proof membranes for water treatment, you still have to clean them with chemicals.
Water is fun and challenging!
What did you learn from the LIF programme?
After LIF I realised how difficult it is to make and sell products – you’re always looking for money to survive and it’s difficult to promote your technology to investors. But I’m surviving now!
The training changed my ideas about my work, and where I bring value to the team. I learned that I’m a technical person, not a sales person. I can’t do everything, so it’s better to use my time on and effort on research, and find people who can do sales and promotion better than me. I learned about the importance of collaborating with people who have different ways of thinking.
Through LIF I also learned about other opportunities, such as the Newton Advanced Research Fellowship I was awarded by the Royal Society.
Are you in touch with anyone from LIF?
I meet for dinner sometimes with some of the Chinese cohort. I’ve also been collaborating with one of my cohort, Wei Wang, on lithium battery separators. But after two years, I’ve realised that this might be purely scientific research, without commercial potential.
I like pure scientific research and discovery, but after you publish so many papers, you wonder what comes from them. I want to put my limited resources into something that will give us a better future. LIF really changed my mindset on this – I think everybody had the same feeling.
What are you working on now?
I’m working with Glasgow University on the Newton Fellowship project. We’re planning to build a small prototype showing that our membrane can be used to clean surface water in remote areas using solar energy.
As of January 2019, I also have funding from the National Science Foundation in China. We’re working in a consortium of groups from the BRICS countries (Brazil, Russia, India, China, South Africa) on different applications of turning waste into resources. Each government supports their country’s group, but we’re working together.
Wastewater can contain a lot of precious metals and nutrients. In China for example, we have geothermal water containing lithium. Using our membrane technology, we can extract pure water and lithium, and there is plenty of heat for the process as the water is at 70-80 degrees Celsius.
With our technology, people in these areas can now have access to clean water, and industry can use the lithium.
What has been your biggest success since LIF?
I’m very proud of a theory we recently published in the journal Water Research.
We discovered how hydrophobic surfaces can be anti-fouling, because they are slippery – and so the contaminants in the water pass over and don’t get stuck. Although the theory was first introduced over 200 years ago, by a French researcher, Claude-Louis Navier, we were the first to clearly demonstrate that membrane surfaces are indeed slippery. I am happy that the scientific world today is less conservative than before, and so our discovery was accepted quickly.
The question now is how to sustain the slipperiness.
I’m also proud to be a co-editor of the journal Desalination, it’s a highly-respected journal in my research area. Perhaps this achievement is indirectly related to my learnings from LIF.
And any areas for improvement?
I’m disappointed that I haven’t managed to commercialise any products at large scale yet. Four years ago, I was very ambitious – I thought I’d have a product out within two years.
As scientists, we’re always looking for new things, but people don’t like new things! You have to make something really disruptive that replaces the existing tech. Otherwise, you need to gradually change people’s attitudes, make them understand your tech and slowly get it into the market. It’s difficult and slow, and you have to be extremely lucky and persistent.
I have one product which is close to market. I’m collaborating with a friend who uses tubular membranes to filter wastewater from power plants. We’ve spent two years trying to improve the membrane resistance, and I think we’ve almost solved it - I hope within two years we can have a more resistant tubular membrane in the market.