Effects of Water Chemistry on Hematite Selective Flocculation and Dispersion

The only industrially proven method for the beneficiation of fine-grained (<25 mu m) hematite ores is selective flocculation and dispersion desliming followed by reverse cationic flotation. This process is reliant upon both water chemistry and proper reagent selection and dosing for effective separation of the hematite from gangue minerals. This study was performed to assess the effects of water chemistry on the beneficiation process in a pilot-scale deslime thickener. Grade versus recovery curves were constructed at varying water chemistries. In each set of experiments the concentration of one water chemistry parameter was varied while all others were held constant. The varied parameters included pH, sodium concentration and calcium concentration. The optimal pH for the separation of hematite from silica was found to be around 10.5. This was hypothesized to be due to a maximization in starch selective adsorption. Minimization in the sodium concentration showed increases in both the grade and the recovery of iron. Minimization in the calcium concentration showed increases in the grade of iron but losses in the recovery of iron. This study showed that the most effective way at increasing both the grade and recovery of the process was to optimize the pH and minimize the sodium concentrations.