Flotation collophane from high-iron phosphate ore by using sodium ligninsulfonate as depressant

The contamination of iron emanating from limonite in phosphate concentrates has been a problem in phosphate ore processing. This study explored froth flotation to remove limonite away from collophane using sodium ligninsulfonate as depressant. It was observed that sodium ligninsulfonate displayed a good depression effect toward limonite but had little depression effect on collophane flotation. Additionally, the contact angle, zeta potential, and isotherm adsorption tests were performed to investigate the interaction mechanism of sodium ligninsulfonate on collophane and limonite minerals. It was found that the adsorption density of sodium ligninsulfonate onto limonite surface is higher than that onto collophane surface. The results of thermodynamic calculation indicated that sodium ligninsulfonate chemically adsorbed on limonite surface in alkaline condition, while a weak physical adsorption happened between sodium ligninsulfonate and collophane.