A new process to clean mine tailings water, which cuts the process from years to hours, has been discovered.
A University of Florida researcher has uncovered a way to process mining effluent water that has been used in minerals processing, dust suppression, slurry transport, and general tailings.
So far the technology is focused on phosphate mines mines in Florida, according to University of Florida, however there will be application for it on a wider scale.
Mark Orazem, a professor of chemical engineering in UF's Herbert Wertheim College of Engineering where the discovery was made, explained that typically after phosphate miners finish with processing water, the water itself holds particles of mineral byproducts, known as clay effluent.
“It looks like a solid, but if you throw a stone into it, it'll splash," Orazem said.
When this water is pumped into settling ponds it takes some time to actually ‘settle’ as the particles are electrically charged, sothe particles' like charge causes them to repel each other, keeping them suspended instead of clumping and falling to the pond floor.
“That means mining companies can re-use the water only a bit at a time — the part skimmed off the top; 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,” the University explained.
While a process was developed in the 1990s using an electric field to separate clay and water in batches, it was uneconomical at the time.
Orazem’s design is different because it allows a continuous feed of clay effluent into a separation system.
Upper and lower plates are used as electrodes, where an electrical potential difference is applied across the electrodes, creating an electric field, which causes the charged particles to move toward the bottom of the pond 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 backfill voids created during mining, while the water is now clear enough to be reused in processing.
“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,” Orazem said.