Abstract
Mechanical entrainment of −10 μm gangue particles affects flotation selectivity and dilutes concentrate grade in fine minerals flotation. This study investigated the effect of aggregation/dispersion behaviors of fine hydrophilic particles on their entrainment in batch flotation using quartz and hematite as model minerals. Two structurally similar polysaccharides corn starch and corn dextrin were used as polymer depressants and octadecylamine acetate (ODA) was used as a collector. Batch flotation of fine hematite-quartz mixtures indicated that lower percentages of Fe was recovered into froth using corn starch than corn dextrin; however, similar Fe recoveries in froth were obtained in coarse hematite-quartz mixtures with the two reagents. It was confirmed that the amount of Fe recovery in froth was positively correlated with the proportion of fine hematite in the feed when corn dextrin was used as a depressant. Experimental data collected from batch flotation were fitted to Warren’s models, indicating that the fine hematite was primarily recovered into froth through entrainment rather than true flotation in the presence of high dosage of corn starch or corn dextrin as a depressant (>500 g/t). The surface wettability of mineral particles was studied by micro-flotation and solvent extraction methods. The results showed that the surface hydrophilicity of hematite induced by corn starch or corn dextrin in the presence of ODA was in an identical range. The real-time FBRM measurements coupled with microscope imaging were carried out to monitor particle aggregation/dispersion behaviors in suspension. The results showed that corn starch can aggregate fine hematite and thus reduce their entrainment in batch flotation, while hematite remained dispersed in slurry by corn dextrin and aggravate its entrainment. In addition, a two-stage aggregation process and the formed flocs were observed in FBRM and microscope tests, which provide evidence for the feasibility of the proposed two-stage aggregation/flocculation flotation concept for fine and ultrafine mineral particles.
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