Bringing Coarse Particle Flotation To The Masses

Flotation is one of the most industrially significant unit operations in global resource extraction. Before flotation (BF), the vast majority of useful materials, such as metal-bearing minerals, existed in the earth’s crust at such low concentrations that they were un-economical for extraction in significant quantities with available technology. The discovery and rapid adoption of flotation around the turn of the last century led to the global availability of materials at sufficient purity, and in such quantities, that they could be enjoyed by the masses. It has been remarked that the average person today has a higher standard of living than any previous generation in history, and much of this is because of the abundant supply and inexpensive price of metals and materials, such as fertilizer minerals, throughout the world in the after flotation (AF) era. Everywhere, the development of societies and their increasing standard of living is linked to the per capita consumption of these materials, happily forestalling Thomas Malthus’ grim projection that the global population would outstrip earth’s resources some time in the 19th century.

What is flotation?

As an introduction, it is a physico-chemical process whereby air bubbles are contacted with fine particles dispersed as a pulp in water. Under the right conditions, the bubbles will adhere to hydrophobic regions of particles and the buoyancy of the bubbles will lift the hydrophobic particles out of the pulp where they can be recovered separately from the residue. The process is typically repeated in multiple tanks, and for an ore like copper, the metal can be concentrated up to 70 times with recoveries up to 90%, which can then be treated economically by processes such as smelting and refining. Despite the pre-eminence of flotation, there has been relatively little innovation in the basic technology. This is evident by benchmarking flotation with other technologies that were discovered around the same time, such as the automobile or the aeroplane. The most significant achievement over the last 50 yr has been to make flotation tanks bigger, which is important for handling lower ore grades, but is hardly a technological breakthrough.

This is even more disheartening because one of the main shortcomings of conventional flotation has been known for almost one hundred years: the size range for effective flotation of a particle is relatively narrow. If the particle is too small, it is difficult for a bubble to attach, and if a particle is too large, it is easy for the bubble to detach from the particle and drop back into the pulp. In Klassen’s classic text from 1970, “An introduction to the theory of flotation,” he states, “an increase in the upper size limit of floatable particles is of economic significance… If it were possible to float larger particles with high efficiency, then the cost of grinding, filtration, thickening, and drying would be much lower.” Klassen knew that coarse particle flotation (CPF) was the key to radically improving flotation, but nothing was done for another 30 years.

 

This is a preview of an article that was originally published in the May 2025 issue of Global Mining Review.

Subscribe to Global Mining Review for free to read this article in full and many more here.

Read the article online at: https://www.globalminingreview.com/mining/02062025/bringing-coarse-particle-flotation-to-the-masses/