Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing single metal
Reissue Patent
1999-07-22
2001-07-03
Phasge, Arun S. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing single metal
C205S574000, C205S602000, C205S604000, C205S606000, C205S607000, C423S027000, C423S036000
Reissue Patent
active
RE037251
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the hydrometallurgical treatment of metal ores or concentrates. In particular, it relates to the extraction of metals from ores in the presence of halogen ions, such as chloride ions. It also relates to the extraction of nickel and cobalt from laterite ores.
BACKGROUND OF THE INVENTION
Hydrometallurgical treatment of copper sulphide ores, such as chalcopyrite (CuFeS
2
), is problematical because the severe conditions required in a pressure oxidation step for the effective leaching of copper from these ores results in oxidation of the sulphide in the ore to sulphate, resulting in the generation of large amounts of acid which requires expensive neutralization. Attempts have been made to render the sulphide concentrate leachable under relatively milder conditions under which the sulphide would only be oxidized to elemental sulphur and not all the way through to sulphate. These attempts include the pretreatment of the concentrate prior to the pressure oxidation step to render the sulphide concentrate more readily leachable, and the leaching of the concentrate in the presence of chloride ions, such as described in U.S. Pat. No. 4,039,406. In this process, the copper values in the concentrate are transformed into a solid basic copper sulphate from which the copper values must then be subsequently recovered, as described in U.S. Pat. No. 4,338,168. In the process described in U.S. Pat. No. 4,039,406 a significant amount (20-30%) of sulphide in the ore or concentrate is still oxidized to sulphate, resulting in greater oxygen demand during the pressure leach and the generation of sulphuric acid. This is particularly unfavourable for low grade concentrates, where the S/Cu ratio is high.
The present invention provides a process for the hydrometallurgical extraction of copper and other metals in the presence of halogen ions, such as chloride and bromide in solution.
SUMMARY OF THE INVENTION
According to the invention, there is provided a process for the extraction of metal from a sulphide ore or concentrate, comprising the steps of subjecting the ore or concentrate to pressure oxidation in the presence of oxygen and an acidic chloride solution to obtain a resulting pressure oxidation filtrate and an insoluble basic metal sulphate salt, characterized in that the pressure oxidation is conducted in the presence of a source of bisulphate or sulphate ions which is selected from the group consisting of sulphuric acid and a metal sulphate which hydrolyzes in the acidic solution and wherein the amount of the source of bisulphate or sulphate ions which is added contains at least the stoichiometric amount of sulphate or bisulphate ions required to produce the basic metal sulphate salt less the amount of sulphate generated in situ in the pressure oxidation.
According to one particular embodiment of the invention, the process further comprises the steps of recycling the pressure oxidation filtrate to the pressure oxidation step; leaching the basic metal sulphate salt produced by the pressure oxidation in a second leaching with an acidic sulphate solution to dissolve the basic metal salt to produce a leach liquor containing metal sulphate in solution and a resulting solid residue; separating the leach liquor from the solid residue; subjecting the leach liquor to a solvent extraction process to produce metal concentrate solution and a raffinate; and recycling the raffinate to the second leaching step. In this embodiment, the pressure oxidation may be carried out at a temperature of from about 115° C. to about 175° C. The pressure oxidation may further be carried out under an oxygen partial pressure of from about 50 psig (345 kPa) to about 250 psig (1725 kPa).
Also according to the invention, there is provided a process for the extraction of a non-cuprous metal from a metal ore or concentrate, comprising the step of subjecting the ore or concentrate to pressure oxidation in the presence of oxygen and an acidic solution containing halogen ions and a source of bisulphate or sulphate ions to form a solution of said non-cuprous metal, wherein said source of bisulphate or sulphate ions is selected from the group consisting of sulphuric acid and a metal sulphate which hydrolizes in said acidic solution. In this specification, M represents the metal being extracted, such as copper, zinc, nickel or cobalt.
The halogen concentration in the pressure oxidation filtrate, which is recycled to the pressure oxidation step, is preferably maintained in the range of from about 8 g/L to about 20 g/L, preferably about 11 g/L to about 14 g/L, and more preferably at about 12 g/L.
Reference is made to the use of chloride in the specification. However, it will be appreciated that the chloride could be substituted with bromide, if desired.
The term “non-cuprous metal” as used herein refers to a metal other than copper.
The second leaching is preferably effected at a pH in the range of from about 1.3 to about 2.2. It has been found that this maximizes the solution of base metal and minimizes the solution of iron. More preferably, the second leaching is effected in a pH range of from about 1.6 to about 1.9.
The second leaching may be carried out at a temperature of from about 20° C. to about 70° C., preferably, from about 35° C. to about 45° C.
For the second leaching, residence times of up to one hour or less, such as 15 to 20 minutes, have been found to be adequate.
The raffinate may be split into a first portion comprising about two-thirds of the raffinate and a second portion comprising about one-third of the raffinate and the first portion may be recycled to the second leaching and the second portion may be subjected to a secondary solvent extraction to produce a secondary lixiviant and a secondary raffinate. The secondary lixiviant may be used as extractant in the solvent extraction of the leach liquor.
In another embodiment of the invention, the pressure oxidation is carried out at a predetermined molar ratio of H
30
/M, where H
+
represents the hydrogen ions in the acidic chloride solution and M represents the metal in the ore or concentrate, so that the pressure oxidation filtrate contains a first portion of the metal in the ore or concentrate and the basic metal salt contains a second portion of the metal in the ore or concentrate and further comprising the steps of separating the pressure oxidation filtrate and the basic metal salt; leaching the basic metal salt in a second leaching step with an acidic sulphate solution to dissolve the metal salt to produce a second metal solution and a solid residue; and subjecting the pressure oxidation filtrate and the second metal solution to solvent extraction to produce concentrated metal solution for electrowinning of metal therefrom.
The invention also extends to copper, zinc, nickel and cobalt whenever produced by the process according to the invention.
Further objects and advantages of the invention will become apparent from the description of preferred embodiments of the invention below.
REFERENCES:
patent: 4008076 (1977-02-01), Junghauss et al.
patent: 4971662 (1990-11-01), Sawyer et al.
patent: 5431788 (1995-07-01), Jones
patent: 3392127 (1991-10-01), None
Subramanian et al., “Oxygen Pressure Leaching of Fe-Ni-Cu Sulfide Concentrates at 110° C.—Effect of Low Chloride Addition”, Hydrometallurgy Section, Jan. 5, 1976, pp. 117-125.
Cominco Engineering Services Ltd.
Oliff & Berridg,e PLC
Phasge Arun S,.
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