Chelating collectors

The use of chelating solvent extractants such as the hydroxyoximes for the flotation of oxidized copper ores has been reported 8 9 unfortunately, although laboratory tests have shown that the use of chelating collectors has potential, they are not yet in widespread commercial use. 

A number of attempts have been made to understand the mechanism of the adsorption of chelates on oxide minerals. For instance, IR spectroscopic studies10 have indicated the presence of a basic monosalicylaldoximate copper complex as well as the bis-salicylaldoximate complex on the surface of malachite (basic copper carbonate) treated with salicylaldoxime. However, other workers4 have shown that the copper chelate is partitioned between the surface and dispersed within the solution, and that a dissolution-precipitation process is responsible for the formation of the chelate. Research into the chemistry of the interaction of chelating collectors with mineral surfaces is still in its infancy, and it can be expected that future developments will depend on a better understanding of the surface coordination chemistry involved. 

It has been shown that the combined use of 8-hydroxyquinoline, a chelating collector, and amyl xanthate can yield good flotation of chrysocolla at pH 7-10 (Mukai and Waka-matsu, 1975). 

The so-called chelating collectors, such as hydroxamic acids, continue to be studied by flotation specialists. The flotation selectivity of minerals partly soluble in the flotation pulp has been studied, at bench scale, in [159]. It has been shown that optimum results are achieved, when the mineral to be floated is the most soluble in the system and the chelate formed with the cation on the surface is most stable. 

For any adsubble method, if the material to be removed (termed the colligend) is not itself surface-active, a suitable surfactant (termed the collector) may be added to unite with it and attach or adsorb it to the bubble surface so that it may be removed (Sebba, Ion Flotation, Elsevier, New York, 1962). The union between colligend and collector may be by chelation or other complex formation. Alternatively, a charged colhgend may be removed through its attraction toward a collector of opposite charge. 

During oxide lead flotation, the choice of collector is rather limited to xanthates, which are used in operating plants. Dithiophosphates and mercaptans are used as secondary collectors. This is due to the fact that natural ores contain a variety of floatable gangues, for which the anionic flotation process is not applicable. The use of chelating agents as flotation collectors for oxide lead flotation have been extensively examined [5,6], Oximes/fuel oil... 

Supported electrodes. The mixture of catalyst and charcoal is poured into the space between two mechanically rigid walls, with asbestos paper as support and a graphite felt or metal sheet as current collector. No binder is necessary. With such electrodes, both liquid and gaseous working materials can be studied. For the experiments with dissolved fuels described in Section 4.2, we used modified electrodes of this type 6 mg chelate was mixed with 6 mg soot and poured between two graphite felt discs. 

Chelating agents that can form insoluble, hydrophobic chelates on the surface of minerals are potential collectors for the selective flotation of minerals.3 4 As early as 1927, Vivian5 reported the use of cupferron, a well-known analytical reagent, as a collector for the flotation of cassiterite (Sn02). Since then, there have been a number of reports on the use of chelating agents in flotation. 

These collectors are effective only under oxidizing conditions, and it is generally accepted that the species that confers hydrophobicity on the mineral surface is either a chemisorbed metal thio compound or the oxidized form of the collector, dithiolate. The amounts of each species formed will depend on the relative stabilities of the metal—sulfur and sulfur—sulfur bonds. The formation of four-membered chelate rings is also possible with soft metal ions such as copper(I) because the largely covalent character of the bond in this instance is able to overcome the strain within the ring by extensive electron delocalization. This could account for the >artial selectivity of some of these reagents for the copper minerals, which has been put to good use in the sequential flotation of copjrer, lead and zinc from complex sulfide ores. ... 

As early as in the beginning of this century, chelating agents have been used as collectors in the flotation. For example, cupferron was used for flotation of oxidized copper minerals and 8-hydroxy quinoline for wolframite and lead-zinc minerals. Recently, chelating agents have been used as depressants by Schubert, Avotins and Nagaraj for the separation of fluorite from gangue minerals and molibdenite from copper sulfide minerals, respectively [3,13]. 

Immobilized Metal Affinity Chromatography. The buffers used in the initial His-tag purification are detailed in Table II. The 50 mL lysate is loaded onto a 1 mL NP -charged HiTrap Chelating HP column (Amersham Pharmacia, Cat. 17-0408-01) nsing the AKTA FPLC system with Frac-950 fraction collector (Amersham Pharmacia). The pnrification scheme is detailed in Table III. The His-tagged Sec23/24 complex should elute at an Imidizole concentration aronnd 150 mM with a typical chromatogram and resultant western blot of fractions shown in Fig. 2. 

Nagaraj, D. R., and Somasundaran, P. 1981. Chelating agents as collectors in flotation Oximes-copper minerals systems. Min. Eng. 33 1351. 

Natarajan, R., and Nirdosh, I. 2008. Quantitative structure-activity relationship (QSAR) approach for the selection of chelating mineral collectors. Min. Eng. 21 1038. 

Uses Asphalt antistripping agent emulsifier ore flotation collector chelating agent corrosion/scale inhibitor curing agent for epoxy resins and urethanes flocculant wet str. paper resins... 

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