Understanding the surface chemical factors affecting flotation and recovery of rare earth element containing minerals.

The Research Project was a colaborative was partially funded by NSERC as part of the Engage Program and looked at understanding factors involved in 2 aspects of the flotation process: 1) the surface chemistry factors related to the flotation (or not) of rare metal/REE minerals and 2) surface chemical factors promoting the inclusion of gangue phases, in the flotation concentrate.

The first problem involves the discrimination of the rare metal/REE minerals to various streams in the flotation process. For flotation the process involves the creation of a hydrophobic surface through the adsorption of selective collectors. There is speculation that poor recovery of REE bearing minerals may be related to collector adsorption blockage in response to: surface oxidation, (commonly controlled by mineral chemistry) and/or gangue slimes adsorption.

The second problem relates to the inadvertent flotation/recovery of the gangue mineral biotite. From a flotation perspective, the pertinent questions for problem 2 are: i) is flotation in response to collector adsorption, ii) is the material naturally floating, and iii) is the surface rendered hydrophobic by a series of reagents added during the process.

Understanding of the factors operating on the surface of these minerals will potentially provide opportunities for modifying the flotation regime, promoting improved selectivity and discrimination of the value and non-added value minerals to selective streams.

Avalon Rare Metals Inc. is a Canadian mineral exploration and development company whose primary focus is on the production of rare metals and minerals. The 100%-owned Nechalacho Deposit, N.W.T. is one of the largest undeveloped rare earth element (REE) resources in the world. The deposit is notable as it hosts a significant enrichment of heavy rare earth elements (HREE; Eu,Tb,Dy) highly valuable for their applications in green energy technology and high tech applications. The REE’s and other rare metals are contained within a number of mineral phases including oxides, phosphates, carbonates and silicates. Their separation from the remainder of the host rocks will be accomplished by flotation and gravity separation. Flotation of value-added mineral species is a complex process, controlled by many factors such as surface charge, collector properties and surface chemical reactions resulting from the interaction with various other minerals and components in the system [1-3]. The complexity of the separation process is further compounded by the fact that many of the unwanted minerals (gangue phases) have similar surface properties to the REE minerals. The inclusion of gangue minerals in the flotation product results in grade reduction and significant problems in down stream recovery operations. The net effect is to increase costs associated with final commodity recovery and a corresponding reduction in profitability.

Research Project

This NSERC Engage grant will look at understanding factors involved in 2 aspects of the flotation process: 1) the surface chemistry factors related to the flotation (or not) of rare metal/REE minerals and 2) surface chemical factors promoting the inclusion of gangue phases, specifically biotite, in the flotation concentrate.

The first problem involves the discrimination of the rare metal/REE minerals to various streams in the flotation process. For flotation the process involves the creation of a hydrophobic surface through the adsorption of selective collectors. There is speculation that poor recovery of REE bearing minerals may be related to collector adsorption blockage in response to: surface oxidation, (commonly controlled by mineral chemistry) and/or gangue slimes adsorption.

The second problem relates to the inadvertent flotation/recovery of the gangue mineral biotite. From a flotation perspective, the pertinent questions for problem 2 are: i) is flotation in response to collector adsorption, ii) is the material naturally floating, and iii) is the surface rendered hydrophobic by a series of reagents added during the process.

Understanding of the factors operating on the surface of these minerals will potentially provide opportunities for modifying the flotation regime, promoting improved selectivity and discrimination of the value and non-added value minerals to selective streams.

Key Words: Flotation, Rare Earth Elements, REE, surface analysis, TOF-SIMS, XPS.

A NSERC-Avalon Rare Metals Sponsored Project; EGP428456-11

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