Comparative Evaluation of Natural and Synthetic Flocculants on Selective Metal Recovery from Low-Grade Iron Ore Slimes

Iron ore washing plants generate slimes in significant volumes, which need to be treated for meeting the raw material demand as well as environmental mitigation. Selective flocculation, an emerging fines beneficiation route, has been chosen for the upgradation of Barsua iron ore slimes. Characterization studies revealed that the sample consists of 52.6% Fe, 3.8% SiO2, 7.4% Al2O3 and 6.7% LOI with hematite and goethite as the major iron-bearing minerals, intricately associated with quartz and kaolinite. Twin objectives of this study are: first to evaluate the selectivity of the polymer reagents for the desired mineral from the ore assemblage. Flocculation efficiency of starch and polyacrylamide (PAM) has been investigated. PAM has been found to be a better flocculant than starch for iron oxide minerals owing to the presence of chelating group in PAM structure, which is primarily responsible for advanced selective adsorption and formation of stable metal complexes. Second objective is adoption of factorial experimental design to assess the effects of process variables such as pH, pulp density and flocculant dosage on the selective flocculation of slimes. Process performance has been optimized to identify main and interactional effects using ANOVA statistical models. Successful upgradation has been envisaged with a Fe grade of 65.90% and recovery of 91.04% at optimized conditions of pH: 9, pulp density: 20% and flocculant dosage: 45 ppm, with a separation efficiency of 69.59%.