Engineering What’s in Our Water
Fluoride is a naturally existing ion, like sodium, calcium or magnesium, found in abundance in many environments around the world, including groundwater, oceans and soil. In optimal concentrations, fluoride can strengthen our bones and pearly whites, and since the mid-20th century, it’s been added to drinking water, toothpastes, dental products, and supplements. But too much fluoride can have devastating consequences.
Dangerously high levels of naturally-occurring fluoride can cause fluorosis, a softening of the bones and teeth that leads to discoloration, weaknesses and at the highest levels, malformation and crippling skeletal diseases in children and adults. Globally, tens of millions are at risk in places like Tanzania and India where there is little infrastructure to carefully monitor, treat or filter drinking water sources. Some communities in the U.S. have experienced problems with carefully optimizing their drinking water or keeping fluoride levels stable and safe. Texas, one of the top states for groundwater usage in the country, has seen fluoride contamination in groundwater exponentially increase in recent decades, underscoring a universal question: what’s in our water?
Benny Freeman, Richard B. Curran Centennial Chair of Engineering in the McKetta Department for Chemical Engineering at The University of Texas at Austin, is an expert in polymer membranes for gas and liquid separations. Freeman is also the principal investigator for the Cockrell School of Engineering-led Center for Materials for Water and Energy Systems (M-WET), a multi-university research center taking on some of the most pressing water-related challenges and development of innovative, polymer membrane-based water purification technologies.
Traditional purification processes, such as reverse osmosis, remove virtually all ions from water, including beneficial elements such as sodium, calcium and natural fluoride at healthful concentrations. The resulting “pure” water can be corrosive to metal infrastructure used to distribute water. That’s why the second part of traditional treatment is remineralization. Removing only the harmful ions or calibrated amounts of specific elements is largely beyond the capabilities of current commercial water treatment processes.
Freeman and his research group are at the forefront of inventing a far more effective purification process. Along with longtime colleagues from Australia’s Monash University and CSIRO (Australia’s national science research agency), Freeman’s group is exploring membranes containing MOFs, metal-organic frameworks, with selective ion channels that can be designed at the molecular level to remove targeted elements, inspired by the filtering function of biological cell membranes. In 2018, the group published research demonstrating MOFs ability to efficiently remove lithium from water. Now, they have successfully demonstrated removal of fluoride, achieving biological levels of selectivity. Their research has recently been published in the journal Nature Communications.
This breakthrough in separating ions from water could have a large impact on water purification strategies around the world.
“It’s exciting to think that this development may allow communities around the world to access a toolkit of membranes for removing selected ions from water,” said Freeman.
Associate Professor Matthew Hill, who works in a joint appointment across both Monash University and CSIRO, added that “When further developed, these MOFs have far-reaching potential: defluoridization of water, environmental cleanup, and lithium extraction from water that could revolutionize global energy sourcing, to name just a few.”
“Based on our research, we now have the capability to produce simple and affordable water filters that can be used safely and effectively anywhere in the world,” said Professor Huanting Wang of Monash University. “This is a significant outcome for people in developing countries who lack access to safe, clean drinking water, and for industries who are increasingly seeking ways to reduce the cost of their environmental impact. Our findings also prove we have the capability to determine the most effective filtering material and method to suit a specific material, or a particular industry need.”