CA1070504A - Method for removing arsenic from copper electrolytic solutions or the like - Google Patents
Method for removing arsenic from copper electrolytic solutions or the likeInfo
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- CA1070504A CA1070504A CA243,923A CA243923A CA1070504A CA 1070504 A CA1070504 A CA 1070504A CA 243923 A CA243923 A CA 243923A CA 1070504 A CA1070504 A CA 1070504A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B15/00—Obtaining copper
- C22B15/0063—Hydrometallurgy
- C22B15/0084—Treating solutions
- C22B15/0089—Treating solutions by chemical methods
- C22B15/0093—Treating solutions by chemical methods by gases, e.g. hydrogen or hydrogen sulfide
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D11/00—Solvent extraction
- B01D11/04—Solvent extraction of solutions which are liquid
- B01D11/0492—Applications, solvents used
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G28/00—Compounds of arsenic
- C01G28/001—Preparation involving a solvent-solvent extraction, an adsorption or an ion-exchange
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
- C22B3/38—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds containing phosphorus
- C22B3/384—Pentavalent phosphorus oxyacids, esters thereof
- C22B3/3846—Phosphoric acid, e.g. (O)P(OH)3
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
- C22B3/40—Mixtures
- C22B3/409—Mixtures at least one compound being an organo-metallic compound
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
- C25C1/12—Electrolytic production, recovery or refining of metals by electrolysis of solutions of copper
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Metallurgy (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Electrochemistry (AREA)
- Electrolytic Production Of Metals (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method for removing arsenic present in a solution with copper which comprises bringing the solution into contact with an organic phase containing tributyl phosphate to thereby extract arsenic present in said solution into the organic phase.
A method for removing arsenic present in a solution with copper which comprises bringing the solution into contact with an organic phase containing tributyl phosphate to thereby extract arsenic present in said solution into the organic phase.
Description
" 1070504 ___________________________ Field of the Invention This invention relates to a hydrometallurgical method which comprises removing arsenic from an arsenic-containing solution, such solutions typically resulting from industrial processes for the production of copper are most commonly en-countered in a copper electrolyzing process or from a process for purifying a copper electrolytic solution (hereinafter referred to as "a copper electrolytic solution and the like"), such as a copper electrolytic solution, a solution resulting from the concentration of the liquid effluent resulting from the electrolysis of a copper electrolytic solution until arsenic is a~out to precipitate (to be referred to as a "decopperized electrolytic solution"), or a solution resulting from the de-copperizing electrolysis of the above-mentioned solution until arsenic is about to electrodeposit. More specifically, it relates to a method for extracting arsenic using an organic solv~nt which comprises bringing the above copper electrolytic solution and the like into contact with an organic phase to transfer arsenic into the organic phase.
Description of the Prior Art Some arsenic is présent in ore materials processed in non-ferrous metallurgy, especially in copper ores. Most of the arsenic encountered in copper refining is recovered as dust from smelting, for example, in a flash smelting furnace, or from a copper-making process, for example, in a converter or a refining furnace, and recycled. However, a part of the arsenic is accumulated in a waste sulfuric acid solution resulting from a gas washing step at the time of collecting sulfur dioxide.
,~o70S04 1 Still another part of the arsenic is accumulated in a copper electrolytic solution and the like in a copper electrolyzing step. Accordingly, arsenic accumulates within the copper-refining system unless the arsenic is removed from the system.
In order to remove arsenic from a copper electrolytic solution and the like, a decopperizing electrolysis has typically been used as a purifying step to remove arsenic in the form of an electrolytic slime together with the copper. In decopperizing electrolysis performed to remove arsenic from a copper electro-lytic solution and the like or a solution resulting from theconcentration of an electrolytic solution containing arsenic until arsenic is about to precipitate (to be referred to as a decopperized electrolytic solution), it is difficult to separate arsenic from copper, especially when it is considered that the arsenic is generally recycled to an earlier step (e.g., to a converter or refining furnace) in the form of a mixed slime of copper and arsenic for further utilization of the copper. Such a method cannot be viewed as a basic procedure to remove arsenic.
In addition, in later stages of decopperizing electrolysis, toxic gases such as arsine (AsH3) are generated, and high costs are needed to render the arsine harmless. -At the same time, the current efficiency is reduced since the copper concentration decreases. The process, hence, becomes inefficient.
Another known method involves removing arsenic as a sulfide. When arsenic is removed by adding hydrogen sulfide gas to a copper electrolytic solution or to a decopperizing electrolytic solution for the purpose of purification, the efficiency of the reaction of the hydrogen sulfide is low, and, at the same time, co-precipitation of copper cannot be avoided.
Accordingly, an extra step is ncessary to separate copper and ~070504 1 arsenic from a mixed precipitate of arsenic sulfide and copper sulfide.
The above processes can be summarized as follows.
Assuming the first operational step is a copper electrolysis, the starting material is, of course, a copper electrolytic solution. Following copper electrolysis, a major portion of the copper has usually been removed from the copper electrolytic solution by the electrolysis. The "spent" copper electrolytic solution is usually divided into two portions, a major portion thereof is recycled for the formation of additional copper electrolytic solution and a minor portion is concentrated, whereby arsenic can be eliminated by concentration and CuSO4 nH20 removed to provide a decopperized electrolytic solution. The decopperized electrolytic solution is commonly subjected to decopperizing electrolysis, providing substantial proportions of Cu and a decopperized solution. The decopperized solution can be subjected to dearsenizing electrolysis, if desired, and the product thereof recycled along with the major portion of the "spent" copper electrolytic solution to form additional copper electrolytic solution-On the other hand, for a smelting process, typicallycrude copper is intially fed to a flash smelting furnace in mat form. The product of the flash smelting furnace is copper sulfide which is typically forwarded to a converter (copper-ma~ing processing) which results in obtaining of crude copper.
The output of the converter is forwarded to a refining furnace wherein some Cu and other materials such as Zn are removed and recycled to the flash smelting furnace and waste products such as SO2 are removed by washing. The product of the refining furnace is formed into a semi-crude copper anode, and subjected to copper electrolysis, arsenic being present therein.
'1070504 1 SU~RY OF THE INVENTION
________________________ We have now found that by bringing a copper electrolytic solution and the like into contact with an organic solvent phase containing tributyl phosphate, arsenic in the electrolytic solu-tion or the like can be selectively extracted into the organic phase.
According to this invention, there is thus provided a method for removing arsenic from a copper electrolytic solution and the like which comprises bringing the copper electrolytic solution and the like into contact with an organic solvent phase containing tributyl phosphate to thereby extract arsenic present in said solution into the organic solvent phase.
DETAILED DESCRIPTION OF THE INVENTION
_____________________________________ The present invention is thus directed to the removal of arRenic from a copper electrolytic solution and the like by a liquid-liquid extraction method instead of resorting to con-ventional methods involving the addition of hydrogen sulfide gas or decopperizing electrolysis.
The copper electrolytic solution and the like treated in accordance with the present invention typically comprises at least copper ions, arsenic ions and sulfuric acid. On a typical commercial scale, copper ions are present in an amount above about 30 g/Q, arsenic ions in an amount a~ove about 1 g/Q and sulfuric acid (as ~2S04; hereafter the same) in an amount above about lSO g/Q. Other conventional components may be present, of course, for ~xample, nickel ions in an amount a~ove about 1 g/Q are typically encountered in copper electrolytic solutions and the like on an industrial scale.
1 It will be apparent to one skilled in the art that copper electrolytic solutio~ and the like, e.g., decopperized electrolytic solutions and decopperized solutions, are not limited in any special fashion, and that such solutions can have various compositions depending upon the exact industrial scheme which is involved. However, as with any process inven-tion, it is possible to describe certain solutions which are commonly, but notinvariably, encountered in the art, and these are set forth below to assist one skilled in the art in under-standing the general environment of the present invention; the description which follows regarding various solutions is not to be construed as limitative, however.
One co~monly encountered copper electrolytic solution comprises from about 30 to about 60 g/Q of Cu, from about 150 to about 250 g/Q H2SO4, from about 1 to about 7 g/Q As, and typically, minor portions of Sb (on the order of about 0.1 to about 0.7 g/Q) and Ni in an amount of about 1 to about 20 g/Q.
Typica~y decopperized electrolytic solutions resulting therefrom contains Cu in an amount of from about 15 to about 30 g/Q, H2SO4 in an amount of from about 200 to 350 g/Q and As in an amount of from about 3 to about 10 g/~, with conventionally Sb being present in an amount of about 0.2 to about 1.0 g/Q and Ni being present in an amount of about 1 to about 30 g/Q.
A decopperized solution, on the other hand, with results from the decopperizing electrolysis of such a decopperized electrolytic solution will typically contain about 0.01 to about 5 g/Q copper, about 270 to about 600 g/R H2SO4 and about 3 to about 10 g/Q As, with Sb and Ni conventionally being present in amounts on the order of about 0.2 to about 1.0 g/Q and about 1 to about 30 g/Q, respectively.
1 The tributyl phosphate (TBP for short) used as an extracting reagent in the present invention has the structure [CH3 (CH2) 30] 3P=O. TBP is generally used in a suitable organic solvent since it has a specific gravity close to that of water and a high viscosity.
The organic solvent which essentially serves as a diluent may, for example, be a hydrocarbon, especially kerosene (a (C12-C15)paraffin).
The extent of dilution is arbitrary, but generally, 10 TBP is diluted so that it is contained in a proportion of about 50 to about 75% by volume in the resulting organic phase. When TBP is diluted so that the resulting organic phase contains a larger amount of TBP, the specific gravity and the viscosity of the organic phase increase, and after contact with the aqueous phase the organic phase and the aqueous phase tend to form an emulsion. When the dilution is performed so that the resulting organic phase contains too small of an amount of TBP, i.e.j substantially less than about 50% by volume, phase separability is good, but the amount of arsenic extracted during each contact decreases and the efficiency becomes low.
Sometimes good phase separation is obtained by adding a higher alcohol, such as 2-ethylhexanol, dodecyl alcohol, etc., to the organic phase, in an amount of about 5% by volume or less.
The higher alcohol has the effect of preventing the separation of the organic phase into two phases which often occurs when the concentration of arsenic in the organic phase increases, and ensures extraction with good efficiency.
The contacting of the organic phase with the aqueous solution phase is effected in any conventional manner, most preferably merely by mixing the two phases with stirring. When 1 ideal mixing is carried out, the contact time is sufficiently 5 to 10 seconds, but in actual operations the contact time is preferably about 30 seconds.
There is no particular limit on the temperature of the extraction system, but there is a tendency that arsenic is easier to extract into the organic phase as the temperature is lower, e.g., the temperature is preferably about 10 to about 20 C.
The volume ratio of the organic phase to the aqueous phase (to be referred to as the "0/A ratio") at the time of con-tact is not restricted in any particular manner. However, thereis a tendency that the arsenic content of the aqueous phase after extraction decreases with increasing 0/A ratios. Based on the preceeding discussion, it is believed that one skilled in the art will easily be able to determine optimum ~/A ratios for any particular processing sequence. As a general guideline, an 0/A
ratio on the order of about 1:1 will typically be most preferred from an industrial scale operational viewpoint.
When an organic phase containing TBP is used, arsenic can be extracted from a copper electrolytic solution or the like without being affected by other metal elements such as Sb, Cu, Ni, etc. present therein. However, the sulfuric acid concentra-tion of the aqueous phase affects arsenic extraction and there is a tendency that the results of the extraction become better as the sulfuric acid concentration is increased, e.g., to about 300 to 400 g/Q. The organic phase containing TBP, however, tends to extract sulfuric acid to some extent, and as the sulfuric acid concentration of the a~ueous phase treated is increased, the amount of sulfuric acid extracted becomes higher.
~he industrial operation of the extracting method of this invention can be performed by a batch extraction or a con-tinuous extraction, i.e., a counter-current extraction in multi-1 stages, the optimum number of stages being established in accord-ance with conventional chemical engineering techniques. In order to extract arsenic with good efficiency, counter-current extrac-tion in multi-stages is most preferred. The extracting apparatus can be freely selected from those in general industrial use, for example, a mixer settler, a rotary disc contacter, a pulse column, or a centrifugal extractor.
If desired, a stripping can be performed to remove -arsenic from the organic phase. The aqueous phase that can be used for such a stripping may, for example, be an alkaline solution such as an aqueous solution of sodium hydroxide, an aqueous solution of sodium carbonate or an aqueous ammonia solu-tion, but water is most suitable as it is readily available. By contacting such an aqueous phase with the organic phase containing arsenic, it is possible to strip the arsenic into the aqueous ~ !
phase. As a result of stripping, the organic phase is regenerated, and it can be recycled to the extracting operation. While not to be construed as limitative, industrial scale operation is typically carried out using an alkali solution in an amount of about 1.2 to about 1.5 times the equivalent of the arsenic and sulfuric acid present (molar equivalents; moles of alkali per mole of arsenic and sulfuric acid).
The optimum contact ratio of the organic phase to the aqueous phase in the above stripping procedure is determined utilizing conventional chemical engineering principles; on an industrial scale, the contact ratio will generally be about 3:1 to ahout 10:1, with more preferred operation occurring when the contact ratio is about 5:1. The time of stripping is primarily decided upon by the total ~olumes of the aqueous phase and the organic phase, and the concentrations thereof, but on an ~070504 1 industrial scale using systems as are commonly encountered stripping is successfully carried out for about 30 seconds at a temperature of from about 20 to about 30C.
The arsenic can be recovered from the aqueous solution after stripping in a simple manner by reducing, i.e., by blowing sulfur dioxide into the aqueous solution, prior to or after concentrating the aqueous solution, to crystallize out the arsenic as arsenic trioxide. In order to increase the rate of recovery of the arsenic trioxide, it is preferred to blow sulfur dioxide into the aqueous solution to thereby reduce the arsenic in the aqueous solution into the trivalent state. The optimum ratio of sulfur dioxide to the aqueous solution can be det~rmined utilizing conventional chemical engineering principles, but, generally speaking, sulfur dioxide is blown into the aqueous solution in an amount of from about 2 to about 10 times the equivalent of the arsenic in the solution (molar equivalents) at slightly above atmospheric pressure for about 10 to about 30 mlnutes. The temperature is optionally selected, and typically the temperature is just the inherent temperature of the aqueous solution as it is received from the preceeding process step.
By the method of this invention as described above, arsenic can be removed from a copper electrolytic solution and the like, and the removed arsenic can be recovered in the form of arsenic trioxide, for example.
Another method for recovery of the arsenic from the a~ueous solution after stripping is to precipitate arsenic trisulfide by adding a sulfiding agent such as hydrogen sulfide, sodium sulfide or sodium hydrogen sulfide to the system.
The main purpose of the present invention is to extract arsenic from a copper electrolytic solution or the like with TBP
g _ 1 at good efficiency. The invention can also be applied to other sulfuric acid aqueous solutions containing arsenic. However, when the arsenic acid is contained in the trivalent state, for example, in the case of a waste sulfuric acid solution in a gas washing process of a sulfuric acid plant, the efficiency of the extraction in accordance with this invention has been found to be reduced. A copper electrolytic solution or the like is characterized in that arsenic is present in a proportion of about 50 wt% or more in a higher valency state other than the trivalent state, i.e., in the pentavalent state.
Since hydrogen sulfide gas is not used in the method of this invention, pollution and offensive odors can be pre-vented. Since the result of extracting arsenic is better as the sulfuric acid concentration is higher, arsenic can be removed at good efficiency even from a copper electrolytic solution, a solution before decopperizing electrolysis, or a solution subjected to decopperizing electrolysis, all of which have a high sulfuric acid concentration, e.g., about 320 to about 390 g/Q.
When the method of this invention is applied to a copper electrolytic solution and the like, the organic phase containing TBP selectively extracts arsenic and some sulfuric acid, and does not extract copper, nickel, antimony, and chlorine, etc., con-tained in the copper electrolytic solution and the like extent.
Accordingly, it is possible to separate arsenic from other elements, especially copper. So, no arsenic-copper separation step is required.
While toxic gases are generated in a conventional de-copperizing electrolysis, the working environment can be markedly improved ~y the present invention. This is a substantial ad-vantage in actual operations.
1 The following Examples illustrate the present invention in qreater detail without limiting the same. All examples were conducted at atmospheric pressure and at normal room temperature, unless otherwise indicated. It is to be specifically noted that the pressure of operation is not of importance to the present invention and typically atmospheric pressure will be used.
Nothing would prohibit the use of sub- or super-atmospheric pressures, but little is to be gained in the sense of process efficiency by going to such more complicated systems.
Example l In this example, arsenic was extracted from a copper electrolytic solution obtained from a copper electrolysis plant and a decopperizing electrolytic solution by batch-wise operation.
lO0 cc of each of these solutions and lO0 cc of a kerosene-TBP phase containing 50~ by volume TBP were placed in a separating funnel, shaken at room temperature using a shaker for 5 minutes, and then allowed to stand to permit the mi~;ture to separate into two phases. The concentrations of the components in the aqueous phase were analyzed, and the results are shown in Table l.
Table l Components Analysis of aqueous phase (g/liter) As Sb Cu -2 Starting Copper electrolytic solution (before 5.18 0.52 46.8 215 extraction) Finishing Copper electrolytic solution (after 4.53 0.52 26.3 348 30 extraction) ~070504 1 Table 1 Continued ComponentsAnalysis of aqueous phase (g/liter) AsSb Cu Starting Solution before de-copperizing electrolysis 8.10 0.72 26.3 348 (before extraction) Finishing Solution before de-copperizing electrolysis 5.24 0.72 26.3 329 (after extraction) Example 2 4.09 liters of a solution obtained by cooling a copper electrolytic solution obtained from a copper electrolysis plant to room temperature and then filtering the same (aqueous phase), to remove the deposited Sb2O5, Sb2O3 As2O5 and 9.64 liters of kerosene containing 50% by volume TBP and 5% by weight of 2-ethylhexanol (organic phase) were prepared, and subjected to a con~inuous extraction.
The apparatus used for the extraction was a rotary disc contacter having an inner diameter of 50 mm, a column length of 600 mm and containing 22 partition walls and rotary discs. The flow rate of the organic phase was 121 cc/min., and the flow rate of the filtered copper electrolytic solution was 51 cc/min.
The extraction was carried out at room temperature for 80 minutes while the discs were rotated at a speed of about 500 rpm.
Further, a continuous stripping was performed using 9.66 liters of the organic phase into which arsenic had been extracted, and 8.28 liters of water. The same rotary disc contacter as above was used for the stripping. The flow rate of the organic phase was 60 cc/min., and the flow rate of the aqueous phase was 52 cc/min. The stripping was carried out fcr ~070504 1 160 minutes at room temperature while rotating the discs at a speed of 400 rpm.
The results of these tests are shown in Table 2.
Table 2 Copper Electrolytic Solution Organic Solvent Before Before Extraction Extraction 4.09 Q 9.64 Q
Cu 46.8 g/Q
H2SO4 236 g/Q (965 g) As 4.72 g/Q (19.3 g) Sb 0.52 g/Q
Extraction Solution After Extraction Organic Solvent After Extraction 4.07 Q 9.66 Q
Cu 46.9 g/Q Cu Trace H2SO4 223 g/Q (908 g) H2SO4 5.9 g/Q (57 g) As 2.18 g/Q (8.9 g) As 1.08 g/Q (10.4 g) Sb 0.52 g/Q Sb Trace Stripping Water 8.28 Q
Water (aqueous phase) Organic Solvent After Stripping After Stripping 8.30 Q 9.64 Q
Cu Trace Cu Trace H2SO4 6-9 g/Q(57 g) H2SO4 <0.01 g/Q
As 1.25 g/Q (10.4 g) As <0.01 g/Q
Sb Trace Sb Trace Example 3 A continuous extraction was performed using 5.0 liters of a copper electrolytic solution obtained from a copper electro-lysis plant before decopperizing electrolysis (aqueous phase) and 11.2 liters of kerosene containing 50~ by volume of TBP and 1 5% by volume of 2-ethylhexanol (organic phase). The same apparatus as was used in Example 2 was used for the extraction.
The flow rate of the organic phase was 112 cc/min., and the flow rate of the aqueous phase was 50 cc/min. The extracting was performed at room temperature for 100 minutes while rotating the discs at a speed of about 500 rpm.
A continuous stripping was carried out using 11.5 liters of the organic phase into which arsenic had been extracted and 10.9 liters of water. The same apparatus as was used in the t stripping of Example 2 was used. The flow rate of the organic phase was 58 cc/min., and the flow rate of the aqueous phase was 55 cc/min. The extraction was carried out at room temperature for 200 minutes while rotating the discs at a speed of about 400 rpm.
The results are shown in Table 3.
Table 3 Copper Electrolytic Solution Organic Solvent Before Before Extraction Extraction , . __ . .
5.0 Q 11.2 Q
Cu 26.8 g/Q
H2SO4 348 g/Q
As 7.8 g/Q (39.0 g) Sb 0.72 gJQ
Extraction Organic Solvent Solution After Extraction - After Extractlon 4 7 Q 11.5 Q
Cu 28.1 g/Q Cu Trace H2SO4 325 g/Q ~2SO4 16 g~
As 0.55 g/Q (2.59 g) As 3.17 g/Q (36.41 g) Sb 0.75 g/Q Sb Trace 1 Table 3 continued Stripping Water 10.9 Q
Water (aqueous phase) Organic Solvent After Stripping After Stripping 11.2 Q 11.2 Q
Cu Trace Cu Trace H2S04 16.4 g/Q H2S04 <0.01 g/Q
As 3.25 g/Q (36.41 g) As <0.01 g/Q
Sb Trace Sb Trace One liter of the extract resulting from the stripping was heated to boiling and concentrated to 107 cc. Thereafter, the concentrated extract was cooled to room temperature while blowing about 8Q of sulfur dioxide thereinto for 15 minutes to crystallize out 2.5 g of arsenic trioxide crystals. The crystals after being washed with water contained 75.6% of As.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one s~illed in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
Description of the Prior Art Some arsenic is présent in ore materials processed in non-ferrous metallurgy, especially in copper ores. Most of the arsenic encountered in copper refining is recovered as dust from smelting, for example, in a flash smelting furnace, or from a copper-making process, for example, in a converter or a refining furnace, and recycled. However, a part of the arsenic is accumulated in a waste sulfuric acid solution resulting from a gas washing step at the time of collecting sulfur dioxide.
,~o70S04 1 Still another part of the arsenic is accumulated in a copper electrolytic solution and the like in a copper electrolyzing step. Accordingly, arsenic accumulates within the copper-refining system unless the arsenic is removed from the system.
In order to remove arsenic from a copper electrolytic solution and the like, a decopperizing electrolysis has typically been used as a purifying step to remove arsenic in the form of an electrolytic slime together with the copper. In decopperizing electrolysis performed to remove arsenic from a copper electro-lytic solution and the like or a solution resulting from theconcentration of an electrolytic solution containing arsenic until arsenic is about to precipitate (to be referred to as a decopperized electrolytic solution), it is difficult to separate arsenic from copper, especially when it is considered that the arsenic is generally recycled to an earlier step (e.g., to a converter or refining furnace) in the form of a mixed slime of copper and arsenic for further utilization of the copper. Such a method cannot be viewed as a basic procedure to remove arsenic.
In addition, in later stages of decopperizing electrolysis, toxic gases such as arsine (AsH3) are generated, and high costs are needed to render the arsine harmless. -At the same time, the current efficiency is reduced since the copper concentration decreases. The process, hence, becomes inefficient.
Another known method involves removing arsenic as a sulfide. When arsenic is removed by adding hydrogen sulfide gas to a copper electrolytic solution or to a decopperizing electrolytic solution for the purpose of purification, the efficiency of the reaction of the hydrogen sulfide is low, and, at the same time, co-precipitation of copper cannot be avoided.
Accordingly, an extra step is ncessary to separate copper and ~070504 1 arsenic from a mixed precipitate of arsenic sulfide and copper sulfide.
The above processes can be summarized as follows.
Assuming the first operational step is a copper electrolysis, the starting material is, of course, a copper electrolytic solution. Following copper electrolysis, a major portion of the copper has usually been removed from the copper electrolytic solution by the electrolysis. The "spent" copper electrolytic solution is usually divided into two portions, a major portion thereof is recycled for the formation of additional copper electrolytic solution and a minor portion is concentrated, whereby arsenic can be eliminated by concentration and CuSO4 nH20 removed to provide a decopperized electrolytic solution. The decopperized electrolytic solution is commonly subjected to decopperizing electrolysis, providing substantial proportions of Cu and a decopperized solution. The decopperized solution can be subjected to dearsenizing electrolysis, if desired, and the product thereof recycled along with the major portion of the "spent" copper electrolytic solution to form additional copper electrolytic solution-On the other hand, for a smelting process, typicallycrude copper is intially fed to a flash smelting furnace in mat form. The product of the flash smelting furnace is copper sulfide which is typically forwarded to a converter (copper-ma~ing processing) which results in obtaining of crude copper.
The output of the converter is forwarded to a refining furnace wherein some Cu and other materials such as Zn are removed and recycled to the flash smelting furnace and waste products such as SO2 are removed by washing. The product of the refining furnace is formed into a semi-crude copper anode, and subjected to copper electrolysis, arsenic being present therein.
'1070504 1 SU~RY OF THE INVENTION
________________________ We have now found that by bringing a copper electrolytic solution and the like into contact with an organic solvent phase containing tributyl phosphate, arsenic in the electrolytic solu-tion or the like can be selectively extracted into the organic phase.
According to this invention, there is thus provided a method for removing arsenic from a copper electrolytic solution and the like which comprises bringing the copper electrolytic solution and the like into contact with an organic solvent phase containing tributyl phosphate to thereby extract arsenic present in said solution into the organic solvent phase.
DETAILED DESCRIPTION OF THE INVENTION
_____________________________________ The present invention is thus directed to the removal of arRenic from a copper electrolytic solution and the like by a liquid-liquid extraction method instead of resorting to con-ventional methods involving the addition of hydrogen sulfide gas or decopperizing electrolysis.
The copper electrolytic solution and the like treated in accordance with the present invention typically comprises at least copper ions, arsenic ions and sulfuric acid. On a typical commercial scale, copper ions are present in an amount above about 30 g/Q, arsenic ions in an amount a~ove about 1 g/Q and sulfuric acid (as ~2S04; hereafter the same) in an amount above about lSO g/Q. Other conventional components may be present, of course, for ~xample, nickel ions in an amount a~ove about 1 g/Q are typically encountered in copper electrolytic solutions and the like on an industrial scale.
1 It will be apparent to one skilled in the art that copper electrolytic solutio~ and the like, e.g., decopperized electrolytic solutions and decopperized solutions, are not limited in any special fashion, and that such solutions can have various compositions depending upon the exact industrial scheme which is involved. However, as with any process inven-tion, it is possible to describe certain solutions which are commonly, but notinvariably, encountered in the art, and these are set forth below to assist one skilled in the art in under-standing the general environment of the present invention; the description which follows regarding various solutions is not to be construed as limitative, however.
One co~monly encountered copper electrolytic solution comprises from about 30 to about 60 g/Q of Cu, from about 150 to about 250 g/Q H2SO4, from about 1 to about 7 g/Q As, and typically, minor portions of Sb (on the order of about 0.1 to about 0.7 g/Q) and Ni in an amount of about 1 to about 20 g/Q.
Typica~y decopperized electrolytic solutions resulting therefrom contains Cu in an amount of from about 15 to about 30 g/Q, H2SO4 in an amount of from about 200 to 350 g/Q and As in an amount of from about 3 to about 10 g/~, with conventionally Sb being present in an amount of about 0.2 to about 1.0 g/Q and Ni being present in an amount of about 1 to about 30 g/Q.
A decopperized solution, on the other hand, with results from the decopperizing electrolysis of such a decopperized electrolytic solution will typically contain about 0.01 to about 5 g/Q copper, about 270 to about 600 g/R H2SO4 and about 3 to about 10 g/Q As, with Sb and Ni conventionally being present in amounts on the order of about 0.2 to about 1.0 g/Q and about 1 to about 30 g/Q, respectively.
1 The tributyl phosphate (TBP for short) used as an extracting reagent in the present invention has the structure [CH3 (CH2) 30] 3P=O. TBP is generally used in a suitable organic solvent since it has a specific gravity close to that of water and a high viscosity.
The organic solvent which essentially serves as a diluent may, for example, be a hydrocarbon, especially kerosene (a (C12-C15)paraffin).
The extent of dilution is arbitrary, but generally, 10 TBP is diluted so that it is contained in a proportion of about 50 to about 75% by volume in the resulting organic phase. When TBP is diluted so that the resulting organic phase contains a larger amount of TBP, the specific gravity and the viscosity of the organic phase increase, and after contact with the aqueous phase the organic phase and the aqueous phase tend to form an emulsion. When the dilution is performed so that the resulting organic phase contains too small of an amount of TBP, i.e.j substantially less than about 50% by volume, phase separability is good, but the amount of arsenic extracted during each contact decreases and the efficiency becomes low.
Sometimes good phase separation is obtained by adding a higher alcohol, such as 2-ethylhexanol, dodecyl alcohol, etc., to the organic phase, in an amount of about 5% by volume or less.
The higher alcohol has the effect of preventing the separation of the organic phase into two phases which often occurs when the concentration of arsenic in the organic phase increases, and ensures extraction with good efficiency.
The contacting of the organic phase with the aqueous solution phase is effected in any conventional manner, most preferably merely by mixing the two phases with stirring. When 1 ideal mixing is carried out, the contact time is sufficiently 5 to 10 seconds, but in actual operations the contact time is preferably about 30 seconds.
There is no particular limit on the temperature of the extraction system, but there is a tendency that arsenic is easier to extract into the organic phase as the temperature is lower, e.g., the temperature is preferably about 10 to about 20 C.
The volume ratio of the organic phase to the aqueous phase (to be referred to as the "0/A ratio") at the time of con-tact is not restricted in any particular manner. However, thereis a tendency that the arsenic content of the aqueous phase after extraction decreases with increasing 0/A ratios. Based on the preceeding discussion, it is believed that one skilled in the art will easily be able to determine optimum ~/A ratios for any particular processing sequence. As a general guideline, an 0/A
ratio on the order of about 1:1 will typically be most preferred from an industrial scale operational viewpoint.
When an organic phase containing TBP is used, arsenic can be extracted from a copper electrolytic solution or the like without being affected by other metal elements such as Sb, Cu, Ni, etc. present therein. However, the sulfuric acid concentra-tion of the aqueous phase affects arsenic extraction and there is a tendency that the results of the extraction become better as the sulfuric acid concentration is increased, e.g., to about 300 to 400 g/Q. The organic phase containing TBP, however, tends to extract sulfuric acid to some extent, and as the sulfuric acid concentration of the a~ueous phase treated is increased, the amount of sulfuric acid extracted becomes higher.
~he industrial operation of the extracting method of this invention can be performed by a batch extraction or a con-tinuous extraction, i.e., a counter-current extraction in multi-1 stages, the optimum number of stages being established in accord-ance with conventional chemical engineering techniques. In order to extract arsenic with good efficiency, counter-current extrac-tion in multi-stages is most preferred. The extracting apparatus can be freely selected from those in general industrial use, for example, a mixer settler, a rotary disc contacter, a pulse column, or a centrifugal extractor.
If desired, a stripping can be performed to remove -arsenic from the organic phase. The aqueous phase that can be used for such a stripping may, for example, be an alkaline solution such as an aqueous solution of sodium hydroxide, an aqueous solution of sodium carbonate or an aqueous ammonia solu-tion, but water is most suitable as it is readily available. By contacting such an aqueous phase with the organic phase containing arsenic, it is possible to strip the arsenic into the aqueous ~ !
phase. As a result of stripping, the organic phase is regenerated, and it can be recycled to the extracting operation. While not to be construed as limitative, industrial scale operation is typically carried out using an alkali solution in an amount of about 1.2 to about 1.5 times the equivalent of the arsenic and sulfuric acid present (molar equivalents; moles of alkali per mole of arsenic and sulfuric acid).
The optimum contact ratio of the organic phase to the aqueous phase in the above stripping procedure is determined utilizing conventional chemical engineering principles; on an industrial scale, the contact ratio will generally be about 3:1 to ahout 10:1, with more preferred operation occurring when the contact ratio is about 5:1. The time of stripping is primarily decided upon by the total ~olumes of the aqueous phase and the organic phase, and the concentrations thereof, but on an ~070504 1 industrial scale using systems as are commonly encountered stripping is successfully carried out for about 30 seconds at a temperature of from about 20 to about 30C.
The arsenic can be recovered from the aqueous solution after stripping in a simple manner by reducing, i.e., by blowing sulfur dioxide into the aqueous solution, prior to or after concentrating the aqueous solution, to crystallize out the arsenic as arsenic trioxide. In order to increase the rate of recovery of the arsenic trioxide, it is preferred to blow sulfur dioxide into the aqueous solution to thereby reduce the arsenic in the aqueous solution into the trivalent state. The optimum ratio of sulfur dioxide to the aqueous solution can be det~rmined utilizing conventional chemical engineering principles, but, generally speaking, sulfur dioxide is blown into the aqueous solution in an amount of from about 2 to about 10 times the equivalent of the arsenic in the solution (molar equivalents) at slightly above atmospheric pressure for about 10 to about 30 mlnutes. The temperature is optionally selected, and typically the temperature is just the inherent temperature of the aqueous solution as it is received from the preceeding process step.
By the method of this invention as described above, arsenic can be removed from a copper electrolytic solution and the like, and the removed arsenic can be recovered in the form of arsenic trioxide, for example.
Another method for recovery of the arsenic from the a~ueous solution after stripping is to precipitate arsenic trisulfide by adding a sulfiding agent such as hydrogen sulfide, sodium sulfide or sodium hydrogen sulfide to the system.
The main purpose of the present invention is to extract arsenic from a copper electrolytic solution or the like with TBP
g _ 1 at good efficiency. The invention can also be applied to other sulfuric acid aqueous solutions containing arsenic. However, when the arsenic acid is contained in the trivalent state, for example, in the case of a waste sulfuric acid solution in a gas washing process of a sulfuric acid plant, the efficiency of the extraction in accordance with this invention has been found to be reduced. A copper electrolytic solution or the like is characterized in that arsenic is present in a proportion of about 50 wt% or more in a higher valency state other than the trivalent state, i.e., in the pentavalent state.
Since hydrogen sulfide gas is not used in the method of this invention, pollution and offensive odors can be pre-vented. Since the result of extracting arsenic is better as the sulfuric acid concentration is higher, arsenic can be removed at good efficiency even from a copper electrolytic solution, a solution before decopperizing electrolysis, or a solution subjected to decopperizing electrolysis, all of which have a high sulfuric acid concentration, e.g., about 320 to about 390 g/Q.
When the method of this invention is applied to a copper electrolytic solution and the like, the organic phase containing TBP selectively extracts arsenic and some sulfuric acid, and does not extract copper, nickel, antimony, and chlorine, etc., con-tained in the copper electrolytic solution and the like extent.
Accordingly, it is possible to separate arsenic from other elements, especially copper. So, no arsenic-copper separation step is required.
While toxic gases are generated in a conventional de-copperizing electrolysis, the working environment can be markedly improved ~y the present invention. This is a substantial ad-vantage in actual operations.
1 The following Examples illustrate the present invention in qreater detail without limiting the same. All examples were conducted at atmospheric pressure and at normal room temperature, unless otherwise indicated. It is to be specifically noted that the pressure of operation is not of importance to the present invention and typically atmospheric pressure will be used.
Nothing would prohibit the use of sub- or super-atmospheric pressures, but little is to be gained in the sense of process efficiency by going to such more complicated systems.
Example l In this example, arsenic was extracted from a copper electrolytic solution obtained from a copper electrolysis plant and a decopperizing electrolytic solution by batch-wise operation.
lO0 cc of each of these solutions and lO0 cc of a kerosene-TBP phase containing 50~ by volume TBP were placed in a separating funnel, shaken at room temperature using a shaker for 5 minutes, and then allowed to stand to permit the mi~;ture to separate into two phases. The concentrations of the components in the aqueous phase were analyzed, and the results are shown in Table l.
Table l Components Analysis of aqueous phase (g/liter) As Sb Cu -2 Starting Copper electrolytic solution (before 5.18 0.52 46.8 215 extraction) Finishing Copper electrolytic solution (after 4.53 0.52 26.3 348 30 extraction) ~070504 1 Table 1 Continued ComponentsAnalysis of aqueous phase (g/liter) AsSb Cu Starting Solution before de-copperizing electrolysis 8.10 0.72 26.3 348 (before extraction) Finishing Solution before de-copperizing electrolysis 5.24 0.72 26.3 329 (after extraction) Example 2 4.09 liters of a solution obtained by cooling a copper electrolytic solution obtained from a copper electrolysis plant to room temperature and then filtering the same (aqueous phase), to remove the deposited Sb2O5, Sb2O3 As2O5 and 9.64 liters of kerosene containing 50% by volume TBP and 5% by weight of 2-ethylhexanol (organic phase) were prepared, and subjected to a con~inuous extraction.
The apparatus used for the extraction was a rotary disc contacter having an inner diameter of 50 mm, a column length of 600 mm and containing 22 partition walls and rotary discs. The flow rate of the organic phase was 121 cc/min., and the flow rate of the filtered copper electrolytic solution was 51 cc/min.
The extraction was carried out at room temperature for 80 minutes while the discs were rotated at a speed of about 500 rpm.
Further, a continuous stripping was performed using 9.66 liters of the organic phase into which arsenic had been extracted, and 8.28 liters of water. The same rotary disc contacter as above was used for the stripping. The flow rate of the organic phase was 60 cc/min., and the flow rate of the aqueous phase was 52 cc/min. The stripping was carried out fcr ~070504 1 160 minutes at room temperature while rotating the discs at a speed of 400 rpm.
The results of these tests are shown in Table 2.
Table 2 Copper Electrolytic Solution Organic Solvent Before Before Extraction Extraction 4.09 Q 9.64 Q
Cu 46.8 g/Q
H2SO4 236 g/Q (965 g) As 4.72 g/Q (19.3 g) Sb 0.52 g/Q
Extraction Solution After Extraction Organic Solvent After Extraction 4.07 Q 9.66 Q
Cu 46.9 g/Q Cu Trace H2SO4 223 g/Q (908 g) H2SO4 5.9 g/Q (57 g) As 2.18 g/Q (8.9 g) As 1.08 g/Q (10.4 g) Sb 0.52 g/Q Sb Trace Stripping Water 8.28 Q
Water (aqueous phase) Organic Solvent After Stripping After Stripping 8.30 Q 9.64 Q
Cu Trace Cu Trace H2SO4 6-9 g/Q(57 g) H2SO4 <0.01 g/Q
As 1.25 g/Q (10.4 g) As <0.01 g/Q
Sb Trace Sb Trace Example 3 A continuous extraction was performed using 5.0 liters of a copper electrolytic solution obtained from a copper electro-lysis plant before decopperizing electrolysis (aqueous phase) and 11.2 liters of kerosene containing 50~ by volume of TBP and 1 5% by volume of 2-ethylhexanol (organic phase). The same apparatus as was used in Example 2 was used for the extraction.
The flow rate of the organic phase was 112 cc/min., and the flow rate of the aqueous phase was 50 cc/min. The extracting was performed at room temperature for 100 minutes while rotating the discs at a speed of about 500 rpm.
A continuous stripping was carried out using 11.5 liters of the organic phase into which arsenic had been extracted and 10.9 liters of water. The same apparatus as was used in the t stripping of Example 2 was used. The flow rate of the organic phase was 58 cc/min., and the flow rate of the aqueous phase was 55 cc/min. The extraction was carried out at room temperature for 200 minutes while rotating the discs at a speed of about 400 rpm.
The results are shown in Table 3.
Table 3 Copper Electrolytic Solution Organic Solvent Before Before Extraction Extraction , . __ . .
5.0 Q 11.2 Q
Cu 26.8 g/Q
H2SO4 348 g/Q
As 7.8 g/Q (39.0 g) Sb 0.72 gJQ
Extraction Organic Solvent Solution After Extraction - After Extractlon 4 7 Q 11.5 Q
Cu 28.1 g/Q Cu Trace H2SO4 325 g/Q ~2SO4 16 g~
As 0.55 g/Q (2.59 g) As 3.17 g/Q (36.41 g) Sb 0.75 g/Q Sb Trace 1 Table 3 continued Stripping Water 10.9 Q
Water (aqueous phase) Organic Solvent After Stripping After Stripping 11.2 Q 11.2 Q
Cu Trace Cu Trace H2S04 16.4 g/Q H2S04 <0.01 g/Q
As 3.25 g/Q (36.41 g) As <0.01 g/Q
Sb Trace Sb Trace One liter of the extract resulting from the stripping was heated to boiling and concentrated to 107 cc. Thereafter, the concentrated extract was cooled to room temperature while blowing about 8Q of sulfur dioxide thereinto for 15 minutes to crystallize out 2.5 g of arsenic trioxide crystals. The crystals after being washed with water contained 75.6% of As.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one s~illed in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
Claims (13)
1. A method for removing arsenic present in a solution with copper which comprises bringing the solution into contact with an organic phase containing tributyl phosphate to thereby extract arsenic present in said solution into the organic phase.
2. The method of claim 1 wherein the organic phase having arsenic extracted thereinto is further contacted with water or an alkaline aqueous solution to strip the arsenic into the aqueous phase.
3. The method of claim 1 wherein said organic phase as an extractant contains about 50% to about 75% by volume of tributyl phosphate.
4. The method of claim 1 wherein said organic phase as an extractant further contains a higher alcohol which is 2-ethyl hexanol or dodecyl alcohol.
5. The method of claim 4 wherein the higher alcohol is present in an amount of about 5% by volume or less.
6. The method of claim 2, wherein said organic phase as an extractant contains about 50% to about 75% by volume of tributyl phosphate.
7. The method of claim 2, wherein said organic phase as an extractant further contains a higher alcohol which is 2-ethylhexanol or dodecyl alcochol.
8. The method of claim 7, wherein the higher alcohol is present in an amount of about 5% by volume or less.
9. The method of claim 2, further comprising concentrating the aqueous phase to recover the arsenic.
10. The method of claim 9 wherein sulfurous acid gas is blown into the water or the alkaline aqueous solution prior to or after concentrating the aqueous phase.
11. The method of claim 2, further comprising adding a sulfiding agent to the aqueous phase after stripping to preci-pitate the arsenic in a form of arsenic trisulfide.
12. The method of claim 11, wherein said sulfiding agent is hydrogen sulfide, sodium sulfide or sodium hydrogen sulfide.
13. The method of claim 2 wherein the alkaline aqueous solution is an aqueous solution of sodium hydroxide or sodium carbonate, or an aqueous ammonia solution.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1681275A JPS551354B2 (en) | 1975-02-12 | 1975-02-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070504A true CA1070504A (en) | 1980-01-29 |
Family
ID=11926560
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA243,923A Expired CA1070504A (en) | 1975-02-12 | 1976-01-16 | Method for removing arsenic from copper electrolytic solutions or the like |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS551354B2 (en) |
| CA (1) | CA1070504A (en) |
| DE (1) | DE2603874B2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4115512A (en) * | 1976-12-03 | 1978-09-19 | Noranda Mines Limited | Method for removing arsenic from copper and/or nickel bearing aqueous acidic solutions by solvent extraction |
| EP0106118B1 (en) * | 1982-10-19 | 1986-06-11 | Austria Metall Aktiengesellschaft | Process for removing arsenic from a copper-bearing electrolyte |
| IT1194304B (en) * | 1983-07-07 | 1988-09-14 | Samim Soc Azionaria Minero Met | PROCEDURE FOR THE SEPARATION OF ARSENIC FROM ACID SOLUTIONS THAT CONTAIN IT |
| IT1187725B (en) * | 1985-08-01 | 1987-12-23 | Eniricerche Spa | PROCEDURE FOR THE SEPARATION OF ARSENIC FROM ACID SOLUTIONS THAT CONTAIN IT |
| DE3725611A1 (en) * | 1987-08-01 | 1989-02-09 | Henkel Kgaa | METHOD FOR THE JOINT SEPARATION OF STONE ELEMENTS FROM VALUE METAL ELECTROLYTE SOLUTIONS |
| DE4204994A1 (en) * | 1992-02-19 | 1993-08-26 | Henkel Kgaa | METHOD FOR SEPARATING INTERFERENCE ELEMENTS FROM VALUE METAL SOLUTIONS |
-
1975
- 1975-02-12 JP JP1681275A patent/JPS551354B2/ja not_active Expired
-
1976
- 1976-01-16 CA CA243,923A patent/CA1070504A/en not_active Expired
- 1976-02-02 DE DE19762603874 patent/DE2603874B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| JPS551354B2 (en) | 1980-01-12 |
| DE2603874A1 (en) | 1976-08-26 |
| JPS5191821A (en) | 1976-08-12 |
| DE2603874B2 (en) | 1977-06-16 |
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