Reminder - POD's met experts are probably just blowing bubbles!...

Reminder - POD's met experts are probably just blowing bubbles! Post #:62756867

Here's some useful background on why POD's ore should involve straightforward andr elatively low cost processing. It just involves blowing bubbles and froth! Lots of froth!

Typical Beneficiation Process of PGMs

Froth flotation is a physico-chemicalprocess whereby mineral particles are separated based on their affinityfor an air environment. Particles with a high affinity for anair environment (hydrophobic) will attach to rising bubbles and float tothe froth phase, thus being separated from the particles that have an affinityfor water molecules (hydrophilic). During flotation, a slurry is fed into anagitated and aerated tank where the separation process takes place,resulting in two products, concentrate and tailings.

Froth flotation began in1905, when Haynes used thetechnique to separate sulphides from gangue using oil [40]. The sulphidemineral particles have different surface properties from those of the gangue,leading to the preferential coating of gangue by oil in Haynes’ work.

Theimmiscibility of oil and water in turn results in the selective flotation ofthe oil-coated sulphide minerals. It is against this foundation thatseveral reagents, which will be discussed in the subsequent sections, have beendeveloped to enhance the selectivity of froth flotation. Factors that influencefroth flotation will be discussed in the subsequent sections; however, at thisjuncture it is important to note that an optimum particle size is required foreffective flotation. Therefore, froth flotation typically follows thecomminution stage, and an example of a flow sheet encompassing bothcomminution and flotation is shown in Figure 1.

Prior to flotation, the run of mine(ROM) feed undergoes closed-circuit milling using a hydrocyclone as aclassifier. The hydrocyclone product (undersize) undergoes variousflotation stages to maximize both grade and recovery.

Recovery is maximized in the rougher stages, whereas grade is maximized inthe cleaner stages. As mentioned above, to create the optimum chemicalconditions for effective separation of particles, flotation reagents areusually added. These reagents are classified as frothers, collectors and regulators.

The flotation reagents help a mineral species to be selectively floated or notfloated. Naturally, certain minerals such as coal, talc, graphite, diamondand molybdenite possess the physico-chemical properties to be separated without theaddition of reagents. Sulphide minerals are rendered hydrophobic by theaddition of xanthate collectors. Because (as mentioned earlier) PGMs tend toexist within base metal sulphide minerals [36], it is therefore possibleto recover PGMs using flotation and to separate them from the non-floatingsilica or chromite gangue.

The interaction of mineral particles with flotation reagents is influenced bythe surface potential (zeta potential). A positive zeta potential attractsanions, and the opposite is true for a negative zetapotential. Forflotation to take place, the surface potential of mineral particles musttherefore be opposite to the charge of the flotation reagents.

The purpose of frothers is to ensure that a stable froth is achieved so that,as much as possible, the minerals attached to the bubbles will be successfullydelivered to the froth phase. Frothers stabilise bubbles by reducing thesurface tension at the air–water interface. Frothers have a hydrophobic chainthat is attracted to the air environment and a hydrophilic head that sits onthe boundary in contact with water. Frothers also help to prevent bubblecoalescence, maintaining a high surface area for particle–bubble contact. Inbiobeneficiation, microorganisms have been reported to work as frothers [5,6,13–16].Collectors increase the tendency of minerals to attach to bubbles. Likefrothers, they are generally heteropolar, having a hydrophobic chain and ahydrophilic head.

Towards the Biobeneficiation of PGMs: Reviewing the Opportunities.Available from: https://www.researchgate.net/publication/357654722_Towards_the_Biobeneficiation_of_PGMs_Reviewing_the_Opportunities