"I think the ability to save water is going to be really big, especially when you're talking about China and other parts of the world," said Mark Orazem a distinguished professor of chemical engineering in UF's Herbert Wertheim College of Engineering.
Mining operations use water for mineral processing, dust suppression and slurry transport. When they're finished with it, the water holds particles of mineral by-products, known as clay effluent which has the consistency of milk. That water is pumped into settling ponds - some are as large as a mile square with a depth of about 40 feet - where the particles can sink to the bottom.
It is a lengthy process because the particles are electrically charged and that charge causes them to repel each other, which keeps them suspended in the water instead of sticking together and sinking to the bottom.
That means mining companies can only re-use the water by skimming a small amount off the top of the ponds. Not only is the particle-filled water useless, the land those settling ponds occupy is a valuable asset that could be used for other purposes.
Prof Orazem's design uses electrodes to allow a continuous feed of clay effluent into a separation system. An electrical potential difference is applied across the electrodes, creating an electric field, which causes the charged particles to move toward the bottom, where they form a wet solid called a cake. In the cake dewatering zone, the particles can't move, so the water is forced to the top.
The cake can then be used to fill the holes created by the mining operation, while the water is now clear enough to be reused to process mined phosphate ore.
"Instead of having the water tied up in these clay settling areas, water is sent back through the process and then reused and reused and reused," Prof Orazem explained.
Prof Orazem's team has created a lab-sized prototype. The next step is to determine how to scale it up to a point where it can work in a real-world mine.
While this concept was designed for Florida phosphate mines, Prof Orazem says it could be used anywhere and would be especially useful in arid North Africa. In Morocco and the Western Sahara, with 85% of the world's phosphate reserves, water is especially in short supply.
