Classifying – separating – and assorting solids – Fluid suspension – Liquid
Patent
1994-07-15
1996-04-09
Lithgow, Thomas M.
Classifying, separating, and assorting solids
Fluid suspension
Liquid
252 61, B03D 1012, B03D 102, B03D 106
Patent
active
055053106
DESCRIPTION:
BRIEF SUMMARY
This invention concerns the use of 2-mercapto-benzoxazole derivatives as collectors for the selective flotation of metal ores, as well as the related flotation process. More particularly, this invention relates to the selective flotation of those ores which are substantially in form of sulphides, to separate materials containing copper, zinc and silver.
As known in the art, flotation techniques use the selective activity of some special reagents on the various mineral components in order to separate one of said components or to provide an enrichment of the product in one of such components. The reagents employed for this purpose are commonly referred to as flotation "collectors", or "collecting agents" (or "collection agents").
The known or used collectors of the existing art are classified in two main classes, depending upon their ionic or nonionic nature. The use of non-ionic oily or neutral collectors is generally restricted to the flotation of non polar minerals, whilst the ionic collectors are used for all the other ore types. The ionic collectors are absorbed on the ore surface through an essentially chemical bond.
The conventional collectors suitable for the sulphide mineral flotation are mercaptan-based (i.e. thiol type) compounds and, among them, xanthates are the most widespread. However, such agents are effective on the whole sulphide class, without showing any specific selectivity within the said class.
While in most cases this property does not involve any problem, in some specific cases the composition of the ore to be treated is such that the use of modifying compounds is needed to make the collecting activity more specific.
Actually, the ore could contain a number of different commercially valuable sulphides forming an intimate admixture with each other and with the gangue, and each one of said sulphides could be present in such amount as to justify its recovery. For example, this occurs with complex sulphide ores consisting of intimate associations of chalcopyrite (CuFeS.sub.2), sphalerite (ZnS) and galena (PbS) into a pyrite matrix, which associations could also contain a valuable amount of silver and, in some cases, of gold.
The use of modifiers often causes strong problems without giving the desired results, particularly when treating ores of a complex composition, whose surface features are not sufficiently defined.
It is clear from the foregoing that the use of collectors capable of bonding given sulphides in a selective way with respect to other sulphides would be highly recommended in some cases. The use of such collectors would limit the inclusion of undesired materials, thus resulting in higher recoveries of the desired metal(s), at higher concentrations.
According to this invention, it has been found that a class of mercapto-benzoxazole compounds shows superior selectivity in sulphide mineral flotation, thus affording effective separation between minerals of this category.
Compounds generically belonging to the class of mercapto-benzoxazoles are known, and are proposed as collecting agents in U.S. Pat. No. 1,801,318. The latter, however, does not suggest that the compounds disclosed may be active on some kinds of sulphides only, while being inactive on the others.
Compounds having some analogy with the compounds of this invention, specifically some mercapto-benzothiazole derivatives, are disclosed in Italian patent 1,181,890 (corresponding, e.g., to DE-A-3 613 277) as used in the selective flotation of lead and zinc ores. Such disclosure generically refers to both oxide and sulphide ores and evidences the ability of mercapto-benzothiazoles to separate lead ores, such as galena (PbS),from zinc ores,such as sphalerite (ZnS),by selectively floating the former with respect to the latter. To this regard it should be noted that, according to the known art, zinc can be floated only when previously activated by treatment with copper sulphate, in order to enrich the ore particle surface in copper salts.
However, the mercapto-benzothiazole-based collectors showed a comparable effectiveness
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patent: 1780000 (1930-10-01), Bolton
patent: 1801318 (1931-04-01), Moses et al.
patent: 4511464 (1985-04-01), Bergman
patent: 4724072 (1988-02-01), Bornengo
patent: 4851037 (1989-07-01), Bornengo
patent: 5120432 (1992-06-01), Bornengo
Alesse Vittorio
Bergamini Fabrizio
Bornengo Giorgio
Marabini Anna
Consiglio Nazionale Delle Ricerche
Lithgow Thomas M.
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