Probably should start a thread on POD metallurgy but at the same time it may be better to develop this thread as it has a good headline.
Building on original interactions with our now departed POD'er@PetrStiff concerned about major capex requirements, recent very useful insights from experienced PGM tech Keith Goode thanks to @HomeBrand and in the absence of info from POD, here's some useful background on why POD's ore should involve straightforward and relatively low cost processing. It just involves blowing bubbles and froth! Lots of froth!
That's it from me for a while. DD updated. Sit and wait.TypicalBeneficiation Process of PGMs
Frothflotation is a physico-chemical process whereby mineral particles are separated based on theiraffinity for an air environment. Particles with a high affinity for an air environment(hydrophobic) will attach to rising bubbles and float to the froth phase, thusbeing separated from the particles that have an affinity for water molecules (hydrophilic).Duringflotation, a slurry is fed into an agitated and aerated tank where the separation process takes place,resulting in two products, concentrate and tailings.
Frothflotation began in 1905, when Haynes used the technique to separate sulphidesfrom gangue using oil [40]. The sulphide mineral particles have differentsurface propertiesfrom those of the gangue, leading to the preferential coating of gangue by oilin Haynes’ work. The immiscibility of oil and water in turn results in theselective flotation of the oil-coated sulphide minerals. It is against thisfoundation that several reagents, which will be discussed in the subsequentsections, have been developed to enhance the selectivity of froth flotation.Factors that influence froth flotation will be discussed in the subsequent sections; however, atthis juncture it is important to note that an optimum particle size is required for effective flotation. Therefore, froth flotation typically follows the comminution stage, and an exampleof a flow sheet encompassing both comminution and flotation is shown in Figure1.
Priorto flotation, the runoff mine (ROM) feed undergoes closed-circuitmilling using a hydrocyclone as a classifier. The hydrocyclone product(undersize) undergoes various flotation stages tomaximize both grade and recovery.
Recovery is maximized in the rougher stages,whereas grade is maximized in the cleaner stages. As mentioned above, tocreate the optimum chemical conditions for effective separation of particles,flotation reagents are usually added. These reagents are classified asfrothers, collectors and regulators. The flotation reagents help a mineralspecies to be selectively floated or not floated. Naturally, certain mineralssuch as coal, talc, graphite, diamond and molybdenite possess the physico-chemicalproperties to be separated without the addition of reagents. Sulphide mineralsare rendered hydrophobic by the addition of xanthate collectors. Because (asmentioned earlier) PGMs tend to exist within base metal sulphide minerals [36], it istherefore possible to recover PGMs using flotation and to separate them fromthe non-floating silica or chromite gangue.
The interaction ofmineral particles with flotation reagents is influenced by the surfacepotential (zeta potential). A positive zeta potential attracts anions, and theopposite is true for a negative zetapotential. For flotation to take place, the surface potential of mineral particles must therefore be opposite to thecharge 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 successfully delivered to the froth phase. Frothers stabilise bubbles by reducing the surface tension at the air–water interface. Frothers have a hydrophobic chain that is attracted to the air environment and a hydrophilic head that sits on the boundary in contact with water. Frothers also help to prevent bubble coalescence, maintaining a high surface area for particle–bubble contact. In biobeneficiation, microorganisms have been reported to work as frothers [5,6,13–16]. Collectors increase the tendency of minerals to attach to bubbles. Like frothers, they are generally heteropolar, having a hydrophobic chain and a hydrophilic 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
