Superconducting High Gradient Magnetic Separation of Titanium and Chromium Compounds for Recycling Rare Metals in the Incinerated Ash

In order to recover Ti and Cr compounds from the incinerated bottom ash, the wet high gradient magnetic separation (HGMS) was investigated by using a superconducting magnet. To separate Ti and Cr from Fe particles, it is necessary to weaken the magnetic force, which is acting on Ti and Cr particles. At first, basic tests using a pure sample of Ti or Cr compound were performed in order to minimize the amount of captured fraction of Ti and Cr compounds. As a result, the minimum amount of captured fraction of each compound was obtained by varying the magnetic susceptibility of the fluid. As for Ti compound (TiO2, CaTiO3), iron tri-chloride and manganese sulfate were used to change the magnetic susceptibility. Likewise, as for Cr compound (Cr2O3), water based magnetic fluid was used. By applying the condition, which gives the minimum captured fraction, to a mixture sample of Ti (or Cr) and Fe compounds, Ti and Cr compounds were efficiently recovered as nonmagnetic products.Furthermore, the conditions obtained from basic tests were applied to the bottom ash from an industrial waste incinerator, which has a high content of TiO2. As a result of wet HGMS after leaching ash with HCl, the TiO2 grade was increased from 10wt% to 28wt%, whereas the TiO2 recovery reached 64 wt%.