Berkeley (United States)
Most of the people on Earth get their fresh water from lakes and rivers. But these only represent 0.007% of the world’s water reserves. With the increase in human population on earth, the demand for fresh water has also increased. Today, two in three people in the world face severe water scarcity for at least one month of the year. Other water sources, such as seawater and wastewater, can be used to meet the growing water needs. But the problem is, these water sources are full of salt and usually contain toxic metals that pollute it.
Scientists and engineers have developed ways to remove salts and toxins from water, a process called desalination. But the existing alternatives are expensive and consume more energy, as these processes involve several stages. Current water purification technology also generates a lot of waste. Some desalination plants waste about half the water they use, with all salts and toxins removed from the contaminated water.
A new type of filter in this technology
I am a PhD student in Chemical and Biomolecular Engineering and am part of a team that recently created a new method of water purification which we hope can make desalination more efficient, reducing the amount of waste in the water. ‘water. and water treatment plants may be smaller. This technology has a new type of filter which can also remove toxic metals while removing salt from the water. Creating an all-in-one filter To create a single filter capable of removing metals and salts.
My colleagues and I first needed a material capable of removing various contaminants, mainly heavy metals, from water. To do this, we turned to smaller, absorbent particles. These mesh particles are designed to selectively separate each contaminant from the water. For example, one type of absorbent particle can only contain mercury. Other types of particles specifically separate only copper, iron, or boron from water. Then I applied these four different types of particles to a thin plastic shell. This created a conventional filter that captures contaminants based on the type of particles I put in the hull.
With a colleague, I put this shell filter in an electrodialysis water purifier. Electrodialysis is a method that uses electricity to suck salts and toxins from water through a membrane and into a separate waste stream. Existing desalination processes to separate this waste – often referred to as brackish or salt water – substance from water can be toxic and expensive. In my team’s modified process, called ion-capture electrodialysis, we hoped that the shell bound to tiny metal-absorbing particles would pick up toxic metals and prevent them from entering the salt water.
In the test, all of the mercury particles were separated from the water.
It will offer three advantages while saving energy: salt and metal will be removed from the water; Toxic metals would be captured in a small membrane that is easily removed – or potentially reused – and the salty waste stream would be free of toxic materials. How effective is ion capture electrodialysis? Our team was successful in making these membranes, so we had to test them. The first test I performed was to use membrane filters with absorbent particles capturing mercury to purify water from three sources – groundwater, brackish water, and industrial wastewater – which contained in the both mercury and salt.
Our team was delighted to see that the membranes separated all the mercury particles from the water with each test. In addition, the membrane was also very effective in removing salt – over 97% was removed with dirty water. After going through our new electrodialysis machine just once, the water was completely drinkable. Importantly, other experiments have shown that no mercury can pass through the filter until almost all of the absorbent particles in the filter are used up. My colleagues and I now needed to see if our ion capture electrodialysis process would work on other common harmful metals.
I tested three membrane filters that contained copper, iron or boron absorbers. Each filter was successful. Each filter captured all of the target pollutants present in the water, while removing over 96% of salts from the water, purifying the water enough to be used. Remaining challenges Our results suggest that our new method of water purification can selectively capture many common contaminants while removing salt from the water. But there are still other technical challenges to explore. First, the mesh absorbent particles that selectively detect the targeted pollutants that my colleagues and I put in the shell are too expensive to fit into mass-produced filters.
Salty sewage will start to seep through the filter
It is possible to place a cheap – but poor quality – absorber in the filter instead, but this can affect the water purification efficiency of the filter. Second, engineers like me have yet to test ion-capture electrodialysis technology at scales greater than those used in the laboratory. Many problems can often arise when transferring new technology from the laboratory to industry. Finally, engineers at water treatment plants will need to find ways to stop the process just before the membrane’s absorbance peaks. Otherwise, toxic pollutants will start to seep through the filter into the salty wastewater.
Engineers could then restart the process after replacing the filter or removing the metals from the filter and collecting them as separate waste. We hope that our work will lead to new methods capable of effectively and efficiently purifying available water sources that are more abundant – but more contaminated – than fresh water. This work is really of great importance. After all, the effects of water scarcity are enormous, both socially and globally.
Adam Uliana, PhD student in chemical and biomolecular engineering, University of California, Berkeley