Surface and chemical properties of chlorite in relation to its flotation and depression

Abstract

The chlorite group of minerals exhibit a wide range of surface charging properties in aqueous suspensions. A systematic review of the literature as it relates to the flotation, depression and surface properties of chlorite and related minerals was undertaken, with a view to using this information to help develop suitable reagent schemes which might allow the selective removal of chlorite from sulphide and oxide flotation systems. The surface charge on chlorite mineral particles originates from permanent charges on basal planes of the crystallites and pH dependent (amphoteric) charge on crystallite edges, typical of clay minerals. The net charge on chlorite particles depends upon the edge/face plane ratio (crystallite size), the solution pH and the presence of specifically adsorbing ions (principally Ca 2z ). Both cationic and anionic surfactants (collectors) are observed to adsorb on chlorite particles, over a wide range of pH conditions. This apparently contradictory behaviour is most likely due to the dual modes of surface charging and the effects of cation substitution into the chlorite lattice. In the case of anionic collectors, some specific (chemical) adsorption energy may also contribute to the adsorption properties. Chlorite depressants used in oxide and sulphide flotation are typical of those used for other silicate minerals. The most common of these depressants are sodium silicate (Na 2 SiO 3 ), carboxymethylcellulose and fluoro compounds (hydrogen fluoride and sodium hexafluorosilicate). There have been no studies of the effects of the chlorite surface charging properties upon depressant selection, although it appears likely that the edge/face plane ratio will strongly influence the depressant adsorption behaviour.

The Effect of Sodium Alginate on Chlorite and Serpentine in Chalcopyrite Flotation

“…However, these two phyllosilicates have different crystal structures and surface properties and further affect flotation in different ways. Chlorite is a 2:1 phyllosilicate with an interlayer brucite-like sheet containing Mg, Al, and Fe octahedrally coordinated [13]. After the liberation, there are broken bonds of the brucite-like sheet, which cause staggered charged surfaces.…”

“…The depression of chlorite is achieved by increasing its surface hydrophilic ability, thus reducing its floatability. The depressants primarily include sodium silicate, hydrogen fluoride, tripolyphosphate, and a variety of other polysaccharides [13]. For serpentine, however, the depression is principally achieved by creating electrical repulsion or steric hindrance to disperse serpentine from valuable particles' surfaces.…”

Surface Properties and Floatability Comparison of Aegirite and Specularite by Density Functional Theory Study and Experiment

“…They also found that starch was not a selective depressant for magnetite in the process of the reverse cationic flotation of iron ores when iron-containing silicates as amphiboles are present in the flotation system [8]. Carboxymethyl cellulose, an effective depressant for iron oxide, was also found to be a depressant for chlorite [14].The novel high-efficiency depressants or collectors are considered to be an effective method to solve the unsatisfactory separation problems [15,16]. These depressants and collectors are targeted for making a sufficient hydrophilic and hydrophobic state of the mineral and gangue surface, respectively.…”

“…They also found that starch was not a selective depressant for magnetite in the process of the reverse cationic flotation of iron ores when iron-containing silicates as amphiboles are present in the flotation system [8]. Carboxymethyl cellulose, an effective depressant for iron oxide, was also found to be a depressant for chlorite [14].…”

The Effect of New Modified Fatty Acid (CY-23) Collector on Chlorite/Hematite Separation

“…Chlorite distributes in nature widely and is one of the most common minerals in sedimentary, low-grade metamorphic, and hydrothermal metamorphic rocks [1][2][3]. Reports of the separation of chlorite and other minerals are often seen [4][5][6][7].…”