Flotation chemistry of boron minerals

Boron minerals exhibit an array of solubilities depending upon the cations in the lattice structure. A classification of semisoluble (colemanite and ulexite) and soluble salts (borax) may be appropriate as each group of minerals behaves differently in flotation. While borax has to be concentrated from its saturated brine, colemanite can be recovered by conventional flotation as other semisoluble salt-type minerals. A common problem encountered in both classes of boron minerals is the presence of significant amounts of clay minerals, which adversely affect flotation recoveries in the form of slime coatings. Flotation is typically accomplished by means of both anionic and cationic collectors. Pure boron and clay minerals and their mixtures have therefore been subjected to a series of microflotation, electrokinetic, adsorption, and atomic force microscopy studies with cationic and anionic collectors. The effect of mono- and multivalent ions in the absence and presence of clay is presented to elucidate their effect as activators in certain pH regions. Flotation chemistry studies on the interaction of boron minerals with anionic and cationic surfactants over the last 10 years together with new findings are reviewed to illustrate the role of electrostatic interactions even in saturated brine solutions. (C) 2002 Elsevier Science (USA).