Enhanced iron recovery from magnetic separation of ultrafine specularite through polymer-bridging flocculation: A study of flocculation performance and mechanism

Abstract

The refractory low-grade iron ores are generally ground to fine particles in beneficiation, and the conventional magnetic separation process has difficulties in sufficiently recovering ultrafine Fe-bearing minerals, resulting in the loss of Fe to the tailings. In this study, the polymer-bridging flocculation performance of cross-linked starch (CLS), carboxymethyl starch (CMS), and sodium alginate (SA) on ultrafine specularite were explored by flocculation-magnetic separation and flocculation-sedimentation tests. The characteristics of specularite flocs and flocculation mechanism of three polymeric agents on specularite were researched with microscopic observation, laser particle measurement, zeta potential test, and FTIR analysis. The results showed that the flocculation of ultrafine specularite with CLS, CMS and SA increased the iron concentrate yield by 12.50%, 6.40% and 18.74% under optimal conditions. The CLS and CMS performed excellent selectivity for specularite, while SA exhibited poor selectivity due to its flocculation behavior on quartz. After the addition of CLS, CMS and SA, the ultrafine specularite was flocculated significantly, with the content of particles smaller than 20 μm reduced from 82.68% to 67.72%, 68.92% and 45.23%, correspondingly. The flocculation mechanism confirmed that the interactions of three flocculants with specularite included hydrogen bonding, chemisorption of carboxyl and hydroxyl groups, while neither CLS nor CMS interacted with quartz except for the hydrogen bonding adsorption of SA on the quartz surface.