Sustainable and energy efficient leaching of metals by ultrasound controlled cavitation

Purpose and goal
Controlled ultrasound cavitation has the potential to increase both leaching recovery and kinetics and can be utilised on minerals and by-products known to be difficult to leach (scheelite concentrates and speiss). The goal is to modify and optimise a scalable ultrasound cavitation reactor to obtain an energy efficient leaching process at lower temperature and under atmospheric pressure. Important factors are resonance amplification, excitation frequencies, cavitation intensity, temperature, and particle size distribution in the material that is to be leached.

Structure and implementation
The project aims at optimising an ultrasound controlled cavitation reactor. Important factors are to create homogenous slurry of the particle to be leached and the leaching reagents. The excitation signal is adapted to the reactors optimum frequency response and the size of the cavitation bubbles with the particle size distribution of the material that is leached. Optimisation of process parameters as flow, temperature, cavitation intensity and the signals frequency distribution is decisive for an energy efficient leaching. The experimental analysis was performed in four steps.

Results
Results are expected to show that ultrasound controlled cavitation can render a more efficient leaching process provided that the process has been optimised regarding acoustic performance, geometric configuration of the reactor, controlled flow of the slurry and proper adaptation of the process parameters for the material to be leached. The best test result increases the yield by 50% using an electric input power of 100 kWh/kg scheelite concentrate. The results are expected to generate an established cooperation with two industrial partners for implementation on a pilot scale.