What are the best methods for separating minerals in ultrafine particles?

Exactly ... but then we are on an AI generated topic. It almost feels like playing chess against a computer in 1986 :) ... what was that move again? Spiral concentrators or shaking tables can hardly be considered "enhanced" gravity separators. Shaking tables do not generate centrifugal forces. Shear flows increasing the settling velocities of UFP??? Seriously?

Being able to find a single universal solution for all the problems (often conflicting) would be great; however, it's more practical to segregate conflicting problem groups and address them separately. At present, separation is often practised in three groups: Coarse, intermediate and fines. Segregating UFP from the fines and then processing them separately can be one approach. In the case of coal, solid-solid separation of UFP is not so much of a problem as recovery from solid- liquid separation is.

Centrifuge force [Hydro-cyclone] A hydrocyclone is a high-throughput gravity separation device used for separating slurry particles based on particle weight. For example, particles of similar size but different specific gravity, or particles of different size but identical specific gravity. Hydro-cyclone Separates particles using the generated centrifugal forces. This centrifugal force is generated because the liquid enters the cyclone tangentially at high speed and is accelerated by a conical middle section. This helps to create a liquid vortex in the cyclone.

For gravity separation between 10 and 5 microns the old Bartles-Mozley separator can often be effective, otherwise there's not too many options.

Based on my experience, separating minerals in ultrafine particles can be a challenging task due to the small size of the particles and their similar physical and chemical properties. These following methods can be used: 1. Froth Flotation 2. Gravity Separation 3. Magnetic Separation 4. Electrostatic Separation 5. Hydrocyclones and Cyclonic Separation: 6. Gravitational Settling and Sedimentation 7. Chemical and Leaching Methods 8. Nano-filtration and Ultrafiltration

Magnetic methods may be preffered depending on the mineral, however, they have drawbacks. They need fine grinding of the ore, which increases the cost and energy use. They also work only for highly magnetic minerals, such as magnetite. Other minerals need more advanced techniques. For example, iron ore processing may need magnetic separation to remove iron impurities from the ore. However, if the ore has high sulfur content, it may also need flotation separation to remove the sulfide minerals, such as pyrite. Flotation separation is versatile and adaptable, but it is complex and requires a lot of reagents and water.

Also if you need a dry method for separating particles with Ultra Fine sizes you can utilise a [Turbo Air Classifier] installed just after the finest [Screen shaker] you can afford. The classifier wheel is able to achieve tip speeds up to 120 meters/second. Superfine powders in the range of down to D97 = 2 μm Ultrafine classification at high throughputs..

In my experience there is a temptation to isolate the -10 microns stream and treat it separately. You actually get better recoveries if you do not separate out the -10 microns fraction. For ferromagnetic minerals like magnetite, the finer particles are recovered by magnetic floculation. The finer particles are attracted to the coarser particles. For paramagnetic minerals like hematite, the finer particles tend to ??piggy back ??onto the coarser particles which causes an increase in magnetic susceptibility and thus improving the chance of recovery. When using WLIMS and WHIMS make sure you decrease throughput and increase magnetic gradient to enhance recovery of UFPs.

They can also be fairly expensive, and should only be used when the density is very similar between ore and waste. They do have the benefit of being compact, and thus easily portable.

Wet high intensity magnetic separators (WHIMS) can be effective at ultra-fine sizes but mineralogy an magnetic susceptibility are important considerations.

Remember to ask, “will it work in my backyard?” What works in a large laboratory in a modern city may not be as easy to operate 1,000km from any power source, and even generators need fuel. Then there is also a need to have a technician on site.

Chemicals have to be transported, so be prepared for accidents enroute to the site, or in the mixing shed. Also environmental regulations are getting ever stricter. Rather look at local ecological solutions where these exist. If you plan to use acid have a large limestone deposit close by, and if you do check it isn’t home to rare bats, primitive cave art, or other considerations.

A chemical separation process will usually apply where the product involves a change of state i.e leaching an oxide to produce a sulphate, or as part of a purification process. Be prepared to spend time on S/L separation as many of the products are difficult to thicken, wash and filter.

When considering the separation of UFPs it all starts with mineralogy. You have to know what minerals you are dealing with and you need to understand the differences in physical properties and the differences in response to chemical attack. Only then can you start looking at options for separating the UFPs that you are dealing with.

One of the biggest issues I have faced is being asked why this multimillion project isn’t working, and being TOLD to fix it! For some reason metallurgists and geologists seem to be the bottom rung on the planning team without the authority to abort unwise projects. Remember to always beware of the power of fools in a large group.

Several methods can be used to separate minerals in ultrafine particles depending on the physical properties of the minerals such as colour, density etc. Froth flotation involves using surfactants to attach air bubbles to the surface of the particles taking advantage of the minerals’ different physicochemical surface properties such as wettability. Magnetic separation can be used to separate magnetic minerals from non-magnetic ones by taking advantage of differing degrees of attraction exerted on various minerals by magnetic fields. Electrostatic separation uses an electrical charge to separate particles based on their polarity differences. DMS is a gravity method that uses a liquid to separate particles based on their density.

Membrane technologies have had great success- Reverse Osmosis to Ultrafiltration. Great example is Canamea mine in Mexico, they extended mine life by treatment of mine water to recover further ore and supplement the demonising UG orebody. The white paper- Membranes and mine water- waste or revenue stream explains this in detail for those interested

At the end of the day it is going to come down to cost. Many methods currently being considered for UFP extraction cost more than the product can be sold for. Any process that requires the use of consumables to work will need an audit of cost to determine if it's even worth considering. For precious metals and certain high demand products like lithium or cobalt, more complex and expensive methods are worthy of consideration, but adding a delivery bill for chemicals to process food grade limestone products used in things like toothpaste probably isn't going to be profitable.