Experimental Investigation of the Effect of Ultrasound on Lixiviant Ion Migration in In-Situ Recovery Processing

In-situ recovery can be challenging for application in low-permeability deposits, such as gold- and copper-bearing rocks because of the weak interaction between the mineral and the lixiviant solution. To increase mass transfer in such deposits, we propose the use of ultrasound. Ultrasonic wave emission into a porous solid immersed in liquid can create intense pressure increases and increases in temperature. The high temperature results in increased mass transfer between solid and solution, which for in-situ leaching, can increase the penetration of leaching solution into the solid. A series of experiments have been conducted to monitor the propagation of lixiviant solution through synthetic rock samples. The parameters investigated were ultrasound power, running time and synthetic core sample permeability. The optimum conditions for the maximum migration of lixiviant ions (in these experiments an iodide/tri-iodide model solution) through a synthetic core sample were determined. The migration of lixiviant ions through a synthetic core sample was found to be an order of magnitude higher with the application of ultrasound of 360 W for a running time of 24 h/day (continuous application of ultrasound). Under these conditions and for a test duration of 8 days, the greatest number of ions moved from the source reservoir through a core sample with a permeability of 177 mD to the target reservoir.