Surface interactions and locked cycle flotation of novel collectors on bastnäsite ore

Abstract

Flotation of a bastnäsite containing ore with novel collectors was investigated using locked cycle froth flotation. Previous research into the flotation of bastnäsite ore simply considered single stage flotation and while this is a good place to start the testing of novel collectors, it is not representative of the conditions employed in a full-scale flotation plant. This study investigates both salicylhydroxamic acid (collector 2) and n,2-hydrocyclohexanecarboxamide (collector 5) in locked cycle flotation and contact angle studies and includes a comparative economic assessment comparing the two novel collectors listed above to the fatty acid flotation previously used at Mountain Pass in California. Locked cycle flotation allows for the simulation of continuous flotation processes using bench scale flotation equipment. This allows the collectors to be tested in conditions that more closely match the conditions that would be found in flotation plants in industry. Locked cycle flotation with collector 2 returned rare earth oxide grades between 58.5% and 66.9% and recovery between 42.8% and 74.7% while rejecting 78% of the calcite. Locked cycle flotation with collector 5 returned rare earth oxide grades between 13.2% and 13.8% with recoveries between 26.6% and 41.3% while rejecting 9% of the calcite. The rejection of calcite is an important consideration because it affects the downstream reagent consumption in the leaching step of the rare earth element processing. Locked cycle flotation showed a large disparity in performance between collector 2 and collector 5. This disparity was investigated using contact angle studies. Performing contact angle test work allows for comparisons to be made regarding the applied hydrophobicity of a collector to the surface of a mineral.