Tce Today
Chis Taylor
Applying electrical potential attracts solid waste.
CLEANING wastewater from mining operations takes on average, 25-50y to complete, but a new method shortens the cleaning time to 2–3 hours.
Chemical engineers from the US’ University of Florida (UF) have developed a method that allows a continuous feed of clay effluent – water with mineral by-product particles – to flow into a separation system, where the plates on the top and bottom are used as electrodes.
Standard cleaning processes are lengthy because the particles are electrically charged. This means they repel each other, which keeps them suspended in the water instead of binding and sinking. By applying an electrical potential across the electrodes and creating an electric field, the team were able overcome the repelling nature of the particles by creating an attractive force at the positive electrode.
The charged clay particles to move toward the bottom, where they form a solid called a “cake”, leaving water to flow to the top for separation.
The cake residue can also be useful in filling the holes created by the mining operation, while the water is now clear enough to be reused to process mined phosphate ore.
Mark Orazem, professor of chemical engineering at UF said, “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.”
Mining operations use water for mineral processing, dust suppression and slurry transport. After the process, companies can re-use the water skimmed off the top. The useless clay effluent occupies 241 km2 of land space in Florida alone that would be valuable for other purposes.
Orazem said the team’s next step will be to scale up the prototype to where it can be used in an operating mine. He believes the technology would be especially useful in Morocco and the Western Sahara, where 85% of the world’s phosphate reserves reside, with limited water supplies for heavy mining.
“Recycling water is going to be critically important. In Florida, it’s an issue. In the desert, it’s going to be a major issue,” Orazem added.
