How are silica and iron removed during electrolytic chromium refining?

In the electrolytic refining of chromium, silica and iron are removed through a series of filtration steps during the initial processing of high-carbon ferrochromium.1

• Silica Removal: After the milled ferrochromium is leached with a mixture of sulfuric acid, recycled anolyte, and a chrome alum mother liquor, the resulting slurry is cooled. This cooling process allows silica and other undissolved solids to be separated from the solution via filtration.1
• Iron Removal: Following the removal of silica, the iron in the solution forms crude ferrous ammonium sulfate crystals. These crystals are then filtered out of the mixture, leaving a mother liquor that is further clarified in a filter press before the chromium is precipitated as ammonium chrome alum for use in the electrolytic cell.1