Flotation '21: Day 2 update

Tuesday 9th November

Since the development of xanthates in the early 20th century, flotation reagents have been developed to treat virtually every known ore type, and there is a bewildering array. Reagent chemistry has adapted to treat increasingly lower grade and refractory deposits and the range of flotation is being extended via these new and enhanced reagents into the treatment of wastes, high-tech metals and rare earths, all contributing to the goal of the circular economy and today's 25 presentations looked at developments in reagents for sulphide and non-sulphide minerals.

There were 8 papers in the morning session on reagents for sulphide ores, dealing with the differential flotation of pyrite and arsenopyrite; the flotation behavior of enargite and chalcopyrite in sodium sulphite solution; the study of thionocarbamate and amyl xanthate collector adsorption on covellite and pyrite surfaces; and the impact of reagents on carbon management strategies in sulphide plants. The latter was presented by Dr Tarun Bhambhani, of conference sponsor Solvay Mineral Processing Chemicals, USA, who is seen 2nd right in the Solvay booth at Flotation '19.

Apart from conventional sulphide mineral reagents, there were some new developments. Selective flotation of copper and molybdenum, especially chalcopyrite and molybdenite is a continuing problem since the current NaHS process requires a closed system flotation plant because of hydrogen sulfide emission in acidic conditions. Dr. Hajime Miki, of Kyushu University, Japan, discussed recent developments for alternative additives to NaHS such as redox reagents.

The use of green and renewable chemicals represents an interesting approach to improve the sustainability and environmental friendliness of mining operations. Xanthates are a class of industrially used collectors which are produced from fossil raw materials and whose decomposition byproducts represent an environmental risk. Therefore, alternative collector chemistries should be found to reduce the environmental impact of flotation processes and avoid complex water cleaning systems. Dr. Robert Hartmann of Aalto University, Finland, described a study on the flotation of chalcopyrite using a cellulose-based collector, with promising results, and Edgar Shach of the Technical University Freiberg, Germany, introduced investigations on the working mechanism of the nitrile based sulfide collector Tecflote®, a new group of collectors for sulphide flotation. 

The biggest challenge in flotation has always been the selective concentration of non-sulphide minerals, and the list of such minerals continues to grow, 17 presentations being made in the very long afternoon session, where many innovations in reagent chemistry were introduced.

Dr. Wonder Chimonyo, of The University of Queensland, opened the session by examining the potential of new peptides as biocompatible alternatives to amine collectors in iron ore flotation, where they are conventionally used to float siliceous gangue minerals including quartz. The use of amines, however, produces major challenges such as high frothing propensity, toxicity and low selectivity.

Feliciana Ludovici, of the University of Oulu, Finland, also introduced new reagents for quartz flotation, cellulose- based chemicals, alternatives to traditional petroleum-based chemicals which pose a risk for the environment and human health. Dr Ted Nuorivaara, of Aalto University, Finland, also showed how utilising cellulose-based polymer-surfactant mixtures as frothers can improve the flotation recovery of Cu from flash smelting slags. 

Dr. Yan Foucaud, of Université de Lorraine, France, explained why the extraction of monazite from tailings is challenging, considering its low concentration and the presence of gangue minerals that behave similarly throughout flotation. His group has developed a new monazite flotation route using lanthanum ions to promote the adsorption of fatty acids onto monazite surfaces.

Dr Panagiotis Angelopoulos, of National Technical University of Athens, also looked at the development of novel green chemicals from renewable resources to overcome inherent problems arising from the use of classical collectors. In the study presented, the potential of substituting conventional collectors with lignin nanoparticles to produce apatite concentrate from low grade ore with considerable La and Ce content was investigated.

High grade phosphate deposits are increasingly rare nowadays, making the industry rely on more challenging carbonate-rich phosphate ores. The gangue minerals contained in this type of ore, notably calcite and dolomite, have similar surface properties rendering them hard to separate from apatite as the main phosphate mineral by flotation. Prof Lev Filippov of the Université de Lorraine described the evaluation of the performance of non-ionic reagents such as ethoxylated and branched fatty alcohols in the flotation of phosphate ore to enhance selectivity.

Dr Natalija Schwarzmayr, of conference sponsor Nouryon Surface Chemistry AB, Sweden, looked at phosphate esters as boosters in the direct flotation of apatite, while Manar Derhy, of the Mohammed VI Polytechnic University and Cadi Ayyad University, Morocco, described a different approach, using bio-based collectors for the selective flotation of phosphate ores: Flaxseed, Nigella, and Olive oils.

Nouryon at Flotation '19

There is a growing interest in microbes and their biological products (bioreagents) as reagents due to their adaptability, selectivity, and flexibility, and Yvonne Perocillo, of the Helmholtz-Institut Freiberg, Germany, looked at the potential for poly-γ-glutamic acid (PGA) and Marinobactins (MBS) as bioflotation reagents, PGA as a depressant in semisoluble salt type mineral systems in the case of calcite as a gangue in scheelite flotation and MBS as a chelating type collector in oxide flotation such as hematite.

Nahid Molaei of the University of Toronto also showed how bioreagents have potential in flotation, commercially available biopolymers having been successful in the treatment of clays in flotation, decreasing environmental problems that occur by using inorganic and organic reagents.

It has been a very long and interesting day with 3 short breaks, which included a networking session where we try to create the random meetings over a cup of coffee at a conference. Delegates who opted to take part were placed at random into a group of 3 participants for 5 minutes, after which they were moved to another group. No substitute for the real thing of course, but it would be good to have feedback from those who took part in this.

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@barrywills