Investigation on the Selective Depression of a Low Molecular Weight Carboxylated Starch on the Flotation of Forsterite and Ilmenite

Selective depressant plays an important role in mineral flotation. In this work, a low molecular weight carboxylated starch (LMWCS) was prepared as the selective depress ant for the separation of forsterite and ilmenite by flotation. Flotation behaviors and adsorption mechanisms were investigated using micro-flotation experiment, zeta potential, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and quartz crystal microbalance with dissipation (QCM-D). Compared to the conventional natural starch, the LMWCS has stronger depression on the flotation of forsterite. The XPS analysis proved that the LMWCS was adsorbed onto the Ti active site of ilmenite surface by weak hydrogen bond and onto the Al active site of the forsterite surface by strong chemisorption. The AFM and QCM-D analysis showed that the adsorption layer density of the LMWCS on the forsterite surface is higher than that of ilmenite. Therefore, the LMWCS is an effective and promising depressant for the forsterite flotation