Using pectin to separate talc and molybdenite through the surface modification with Cu 2+ : Applications and mechanism

Organic depressants have low selectivity in separating molybdenite and talc because their metal sites lack activity for organics chemisorption. In this study, surface modification by copper sulfate was used to induce the differential adsorption of pectin onto molybdenite and talc surfaces for enhanced flotation separation. Contact-angle experiments, scanning electron microscopy, adsorption measurements, time-of-flight secondary-ion mass spectrometry, and X-ray photoelectron spectroscopy analyses were conducted to reveal the interaction mechanism. Results illustrated that molybdenite and talc could not be separated using pectin alone, while molybdenite was selectively depressed after surface modification by copper sulfate and this effect was strengthened under alkaline conditions. Metal sites (Mg, Si and Mo) of talc and molybdenite themselves were unable to react with pectin, whereas Cu + would deposit and further function as active site for pectin chemisorption after surface modification. However, the quantity of deposited Cu sites dropped on talc surface and increased on molybdenite surface with increased pH, and the Mo atoms of molybdenite crystal were activated to take part in pectin chemisorption. Therefore, more pectin was adhered on molybdenite surface, which imparted molybdenite stronger wettability. Herein, surface-modification through metal ions can enable the differential adsorption of organic depressants and enhance the flotation separation of minerals.