Selective flotation separation of bastnaesite and parisite from fluorite by carboxymethyl chitosan depressant

In rare earth flotation, the separation of bastnaesite and parisite from fluorite is challenging by the similarity of their surface properties and solubility. This study utilized carboxymethyl chitosan (CTS) as a green organic inhibitor for the flotation separation of bastnaesite and parisite from fluorite. The inhibitory effect and mechanism of CTS on fluorite were studied through flotation tests and modern detection methods. The flotation tests results indicate that CTS can effectively inhibit fluorite under the conditions: CTS concentration of 20 mg/L, octyl hydroxamic acid (OHA) concentration of 1×10 –4 mol/L, and at pH 9.8, whereas it only slightly affects the flotation recovery of bastnaesite and parisite. The mechanism analysis results indicate that CTS selectively adsorbs on fluorite surface and reduces the contact angle from 27.25° to 20.38°, while significantly delaying the adhesion process of bubbles on the fluorite surface and reducing its ultimate adhesion angle. CTS undergoes strong chemical adsorption on the surface of fluorite, hindering the subsequent adsorption of OHA, but has weak adsorption on the rare earth minerals. CTS chelates with Ca 2+ on the fluorite surface through its –COO – molecule, forming a hydrophilic Ca(COOR) adsorption cover on the fluorite surface to increase its steric hindrance and inhibit fluorite flotation. Therefore, CTS can be used as a green, environmentally friendly, and highly selective inhibitor to achieve efficient flotation separation of bastnaesite and parisite from fluorite.