Studies on some fatty acid collectors in the flotation of beach sand minerals of travancore thesis

Abstract

The beach sands of Travancore contain ilmenite, rutile, monazite, zircon, and garnet among others. The present investigations were undertaken not only with a view to find out the effect of some unsaturated and saturated fatty acids in the flotation of these minerals but also to explore the possibilities of developing an all?flotation method for their separation.

In the introduction, which forms the first chapter of this thesis, the beach sand industry in Australia and India is briefly reviewed. An introduction to fatty acid collectors in general and the fatty acids used in this investigation in particular—namely linolenic, linoleic, caprylic, lauric, palmitic, and oleic acids—is given. This is followed by a brief review of the mechanism of flotation.

The chapter dealing with materials and methods includes the preparation of linolenic acid, pre?treatment of the minerals before flotation, and the flotation technique adopted.

Contact curves for flotation and non?flotation of (a) ilmenite, (b) rutile, (c) zircon, (d) monazite, and (e) garnet have been experimentally determined using sodium soaps of linoleic and linolenic acids as collectors and terpineol as the frother. These studies have been made over a wide range of collector concentrations which cover the usual practical reagent concentrations. The pH range of floatability for all the minerals is fairly wide, and the difference in the upper contact curves between ilmenite and the other minerals has revealed the possibility of separation.

The recovery experiments using the soaps of oleic, linoleic, and linolenic acids have shown the superior collecting strength of oleic acid over the other two.

Of the dyes studied, the effect of Congo red has revealed its applicability as a depressant both in the acid and alkaline range. It is concluded that the depressing action of the dye is due to the presence of chelate?forming groups in the molecule of the dye. Of the minerals, ilmenite, rutile, zircon, monazite, and garnet, zircon gives the least value for lower critical pH when sodium chloride is used as the depressant. This is explained as due to the precipitation of the soap from the solution.

In the studies on the flotation of these minerals with sodium soaps of caprylic, lauric, and palmitic acids, it is revealed that the minerals arranged in the increasing order of floatability are ilmenite, rutile, garnet, monazite, and zircon in the case of all three acids. It is also seen that ilmenite is not floatable with low concentrations of the sodium soap of caprylic acid. It is further observed that the pH range of flotation decreases with the number of carbon atoms in the fatty acid molecule.