Investigation of Silica Removal from Hematite Concentra of Chador-Malu Flotation Circuit

In Chador-Malu processing plant، reverse flotation is used for dephosphorization of hematite concentrate. Sodium silicate is used as iron depressant and a mixture of Alke and Dirol as collector. The phosphorus content of the concentrate is at an acceptable level (0. 047%) but the silica content is relatively high (3. 5%). The flotation circuit is designed to remove apatite but not silica. Chemical and mineralogical studies of the samples and mass balance of the flotation circuit showed that the silica content of the iron concentrate was mainly in the form of free quartz particles in the size range of minus 45 micron. The main objective of this research was to investigate the possibility of floating silica in the apatite- iron oxide- silica flotation system. Flotation experiments on samples with high silica content، showed that using 800 grams per tones of sodium silicates with silica modulus of 2. 5، at pH of 10، gave better results but the silica contents of iron concentrate (4. 5%) was still high. Addition of Ca++ to the sodium silicate solution، at pH of 11، reduced the silica contents from 4. 5% to 2%، while the iron grade was increased by 1% and the concentrate recovery was reduced by 1%.