A University of Florida researcher has developed a new method that could dramatically reduce the time it takes to clean up the water left over from phosphate mining operations.
Mark Orazem, a distinguished professor of chemical engineering at the university’s Herbert Wertheim College of Engineering, claims that the new process cuts the treatment time from 25 to 50 years to just two to three hours.
At present, mining wastewater is pumped into huge settling ponds where particles of mineral byproducts slowly sink to the bottom. This takes many years because the particles are electrically charged, causing them to repel each other and keeping them suspended in the water instead of sticking together and sinking to the bottom.
Previous efforts to speed up the process included use of an electric field in the 1990s to separate clay and water in batches, but that concept was deemed uneconomical.
Orazem’s design is different because it allows a continuous feed of clay effluent into a separation system, the University of Florida explained.
“There, upper and lower plates are used as electrodes. 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,” the university said.
Orazem’s team has created a lab-sized prototype and will now work on scaling it up so that it works in a real-world mine.