Ultrasound-Assisted Leaching of Iron from Silicon Diamond-Wire Saw Cutting Waste

Iron removal from silicon powder waste by ultrasound-assisted leaching has been investigated and the leaching conditions optimized to an ultrasonic frequency of 80 kHz, ultrasonic power of 270 W, temperature of 60°C, and sulfuric acid concentration of 12%, achieving an iron removal fraction of 95.24%. The maximum iron removal fraction was obtained after 80 min of leaching without ultrasound, whereas ultrasound-assisted leaching could achieve the same removal fraction after 50 min under the same conditions. The dissolution of iron is a two-step process and follows a homogeneous control model with a second-order rate-controlling step. With the aid of ultrasound, the reaction rate constants k hs increased from 0.0677–0.0995 to 0.0792–0.1914 and from 0.0285–0.1086 to 0.0399–0.1422 in the first and second leaching stage, respectively. This increase of the k hs values further supports the enhancement induced by the application of ultrasound.