Froth Flotation. Why is it still so intensively researched?

Try explaining nuclear fusion or a car's SatNav to a non-scientist. It's not easy. But explaining the principle of froth flotation is not too difficult- you add chemicals to a mixture of ground ore particles and water, which makes the valuable particles 'greasy' and thus water repellent. You then blow air through the mixture, and the greasy mineral particles stick to the air bubbles and can be skimmed off and separated from the waste.

Simple! So why does this apparently fairly simple process, which was patented over a century ago, attract some of the finest scientific minds in the minerals industry and contribute to a major portion of the peer-reviewed papers published each year in mineral processing journals?

This posting is prompted in part by that of 27th March, and also by an email from Dr. Stephen Grano, of the Universityof Adelaide, Australia, one of my most respected Minerals Engineering reviewers.

Stephen writes: I think a lot of scientists dabble with flotation in their career because it has elements of hydrodynamics, surface chemistry, plant design, froths, etc for a three phase system with mobile gas/liquid interface. So it lends itself to research. But I sometimes wonder where we have got with all the research. The fact is that nowadays a plant metallurgist should be getting >90% recovery and should consider their own position if they are not, with all the tools (QEM-SCAN etc) that are common place. Thirty years ago that was not the case. Thirty years ago people suspected that pyrite in a copper concentrate was activated by Cu ions - now they have proof. But what to do about it...in a plan? I believe that the next step changes will come from new sensors which will be able to measure liberation on-line and surface chemistry on-line. If I were a company, I would not be putting my money into standard surface chemistry research any more. They need sensors in the plant. They know the mechanisms now. The trouble with current sensors like x-ray probes is that it is only a bulk assay and not a measure of liberation. So we are at 90% recovery but can we maintain that for all ores and at lowest possible cost? That means we need to maximise throughput for recovery which means floating coarse composite particles of low liberation. That is another area for research. Do we need more review articles on copper activation and oxidation, and water effects? Do we need more papers trying to increase fine particle recovery by hydrodynamics as it is possible to recover these particles given enough time? We know a lot of that already. One of these days, either next year or in 10 years time or longer, someone will have to say "this is the same as what was published in 1985 or whatever". What I am concerned about is papers that purport to be different but in reality are very derivative or that are pseudo fundamental and justified as being fundamental but in fact don't shed any new light on the matter. I am afraid to say that there are so many now doing flotation that the research has been somewhat commoditised in my view. It may be that more rigorous reviews are required. I get the impression that some researchers think that if it was not in the last 5 years it has not been done. Yet the fundamental questions remain unsolved and continue to be unsolved.

These are provocative words from Stephen, which I hope will promote some serious debate both here and on LinkedIn. Is part of the answer to my eponymous question, as Stephen implies, regurgitation - are journals publishing work similar to that carried out in the past, but now lost in the mists of time? Are we to some extent going round in circles?

I have a feeling that this might be partly true, and is evidenced by the plethora of flotation papers churned out each year at international meetings.

But there is more to it than this. I have argued before about the importance of flotation, indeed that it has my vote for being the most important technological development of the 20th century (6th June 2011). Originally developed to concentrate sulphide minerals, it is now ubiquitous in the minerals industry, treating oxidised ores, oxides, non-metallics and coal. Miners have always 'cherry picked', treating the richest and easiest ores available, such that today the available ores are often low grade and very difficult to treat, and many modern industries demand metals which were virtually unheard of 20 years ago, such as indium, lithium, germanium and neodymium. Intensive research is therefore needed to keep pace with this increasing pressure on the minerals industry.

Today's civilisation is dependent on a plentiful supply of the so- called 'base metals' such as copper, zinc, lead and nickel. Without prior concentration of the valuable minerals in the ore, extraction of the metals from these minerals would be hopelessly uneconomic, effectively making these base metals 'precious metals'. The wealth of information on the flotation of these ores is vast, but even so intensive research on sulphide mineral flotation continues, in the quest for more effective and environmentally friendly reagents, improved circuits and machines, and better ways to control and optimise the process. Base metal mines treat huge tonnages and very small improvements in recovery can lead to huge gains.

In November the world's leading flotation scientists and engineers will meet in Cape Town for Flotation '13, MEI's largest conference. Papers will be presented on the state of the art in flotation technology and the meeting will provide the opportunity for young researchers to network with the major players in this field. The deadline for abstract submission is the end of June and I look forward to receiving papers on cutting edge technology, hoping also that authors make use of the wealth of information stored in the archives over the past 100 years.