KR810002044B1 - Process of hydrometallurgical treatment for eliminating impurities from a solution containing dissolved metals - Google Patents

Abstract

The method of hydrometallurgical treatment for eliminating metal impurities from zinc sulphate containing Fe+++ is characterized by adding a silicate to the zinc sulphate to form a silicic acid, and then mixing a neutralizing base to it to make pH values between 1.5 and 4.5 and to precipitate metal impurities with the residue of solid state, consisted mainly of ferro silicate.

Description

Wet metallurgical treatment to remove impurities from a solution containing dissolved metals.

1 is a first block diagram specifically illustrating a method according to the invention,

FIG. 2 is a block diagram specifically illustrated by modifying one of the methods of the present invention described in FIG.

The present invention relates to a wet metallurgical treatment for removing metal impurities from a solution in which the metals to be extracted are dissolved and included, in particular, a method for removing iron impurities from a zinc sulfate solution.

In the wet metallurgical process, there are three main industrial methods for the selective removal of iron in the form of residues that are easily filterable and therefore filterable in zinc sulphate effluents from the corrosives of oxidized zinc or ie roasted zinc ores. There is a way.

This residue is originally made of jarosite, goethite or hematite by relevant methods.

However, this method is problematic in general because these residues are not industrially or industrially worthless, and even storage issues are urgent from the point of view of environmental pollution, and also maintain the required flow rates and durations. To do this requires expensive and hand-held machinery.

One of the main objectives of the present invention is to contain impurities which are to be removed and to produce residues which can be used directly as raw materials for industrial use or in the manufacture of industrial products such as construction tools without any further treatment. It is to provide a simple way.

Residues obtained by the process of the invention can be used as stacks or as aggregates used in cement or concrete.

Other details and features of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings and in the specific embodiments which do not limit the scope of the invention.

Like reference numerals in the accompanying drawings indicate the same or similar components.

Generally, the present invention relates to a wet metallurgical treatment for removing metal impurities from a solution in which metals to be extracted in a metal form are dissolved.

In particular, the present invention relates to a method for removing metal impurities, in particular iron, from a solution of zinc sulfate by electrolysis to extract zinc into the metal state. The solution used here is usually obtained by eroding residues of oxidized zinc ores, especially zinc oxide, which is discharged by leaching zinc ores with sulfuric acid.

The method according to the present invention adds silicate or zinc silicate, such as alkaline earth metal, to the solution described above to form dissolved silicate, so that metal impurities precipitate between pH 1.5-4.5, which can be filtered well and easily washed. It is characterized by the formation of silicate residues.

If zinc silicate is used, first maintain the pH of the solution below 1.5 so that the zinc silicate dissolves quickly, then add alkaline earth metal silicate (preferably calcium silicate or lime) to maintain the pH at 1.5-4.5 It was precipitated to form a solid silicate residue consisting mainly of iron silicate.

In the same case, an oxidized zinc ore can also be used to maintain the pH below 1.5. The formation of silicic acid is accomplished by the addition of alkaline earth metal silicates and when the pH is maintained between 1.5 and 4.5 to allow the impurities described above to precipitate. The solid silicate residues described are formed, which can be done by adding sufficient basic silicates or lime.

In other cases, only alkaline earth metal silicates may be used, especially when calcium silicates are used.

Because such silicates are sufficiently dissolved between pH 1.5-4.5, precipitation of the ions to be removed occurs after these silicates are dissolved.

The actual amount of silica dissolved in this solution always remains extremely reduced. This is because solid silicate residues form when the silicate dissolves and reacts instantly with iron or other possible metal ions to be removed and remains between pH 1.5-4.5. The preferred range for the precipitation to form in solution is in the range of pH 2.5-3.

In order to prevent excess dissolved silica coming after precipitation, it is advisable that the amount of silicate added does not exceed the stoechiometrical amount for the impurities to be removed.

Figure 1 illustrates in detail a specific embodiment of the process according to the invention, ie the various steps necessary for extracting zinc from oxidized zinc ores.

This method consists of depositing zinc metal on the cathode by electrolysis of zinc sulfate obtained by corrosion of the ore (1) with sulfuric acid (2) called "return acid". Not shown in the drawings.

The corrosives described above can be made in one or two stages as is known.

Even in the case of making the corrosive in one step, an excess of ore is used so that it can be used until corrosion does not occur in the neutral medium as illustrated in FIG.

The solution (3) containing zinc sulfate isolated according to (II) was purified and sent to the above-mentioned electrolysis step, while the remaining residue separated from it (ie 200-400 g / l solid phase) was purified. The residue (4), which has a concentration and is commonly called “neutral residue”, was corroded with a more concentrated acid to dissolve the zinc ferromagnetics at temperatures typically 85-95 ° C.

Corrosion of such neutral residues with acids can occur using one or more counterflow steps.

Figure 1 illustrates two stage corrosion.

In (III), the neutral residue (4) is corroded using more concentrated acid (10) and circulating acid (2), and then in (IV), so that iron is dissolved in solution (5) and concentration is high. After separation into a residue (6), the residue was corroded again with about 98 acids (7) and circulating acid (2), which were more concentrated than those used in the previous step. After filtering in VI), the filtered material was treated with washing water (8) to obtain noble metals and lead-rich solid residues (9) which may be present in the ore (1).

Part 10 of the filtrate, the more concentrated acid formed in (VI), is recycled to (III) for use in corrosion, while the remaining filtrate is diluted with wash water (8) and solution (5) so that the acidity is H _256. SO ₄ per 1ℓ 5-250g that is possible if the H ₂ SO ₄ 1ℓ per 30-60g, most preferably by the present invention is liquid (11) made of 30-45g per H ₂ SO ₄ 1ℓ is the pH at (ⅶ) The oxidized zinc ore 12 was neutralized until less than 1.5, that is, between 0.5 and 1.5.

The solution was decanted in (iii) to separate the residue (13) and returned to (III) to corrode the neutral residue in order to solubilize the zinc ferromagnetic material as needed.

In addition, a sufficient amount (15) of basic silicate, such as calcium silicate, or slag, is added to the acidic solution (14) prepared by decanting in (iii), while maintaining a pH of 1.5-4.5 and 2.5-3 as much as possible. Thus, in the present invention, dissolved silica soil in the silicic acid state was formed in (i) to precipitate the silicate residues containing impurities, especially iron. Fe ⁺⁺⁺ which may be present in the solution when this precipitation takes place in an oxidizing medium, for example by introducing an oxidizing medium, for example air or oxygen 16 or by adding an oxidant 17 such as HnO ₂ as necessary. After oxidation, Fe ⁺⁺ also precipitates.

Corrosion time in (iii) is generally about 1-4 hours, depending on the presence of Fe ⁺⁺ ions.

The reaction product formed in (iii) was filtered in (x) and treated with washing water (19), followed by filtration in (x), whereby the concentrated product (18) was concentrated in (x). In (20) and (XI), the filtrate 21 and the solution 3 diluted with the wash water 19 are combined to proceed to the electrolysis step to extract zinc.

Steps to follow in (iii) may be omitted in many cases. This is because the concentration of the solid phase is generally relatively high.

Therefore, the reaction mixture formed in (iii) can be filtered directly.

The filtrate (22) formed in (XI) is a solid silicate residue containing all impurities to be removed from the zinc sulphate solution to be sent to the electrolysis step, so the substance is usually antimony or arsenic present in zinc ore. , Impurities such as aluminum, tin and germanium, especially iron.

FIG. 2 shows one variation of the specific embodiment illustrated in FIG. 1, which is the fact that the corrosion step described above is achieved without separating the residue produced from the neutralization step. This is different from the method illustrated in.

In this variant, the basic silicates of alkaline earth metals, i.e. calcium silicates, such as slack, or silicate zinc oxides made of slack, zinc oxide or lime as necessary to precipitate impurities in steps (iii) and (iii) described above It is recommended to use and after the solid silicate residues are formed, it is separated in the same manner as illustrated in FIG.

Several experiments have been described below, which have been carried out to determine the chemical reaction conditions for carrying out the process according to the invention.

Example 1

No leaching of leach (300 ml) and slack (29 g) containing 10 g / l Fe, 150 g / l Zn and 5.4 g / l Mg but no other impurities. It was added to the reactor containing the leach solution (100ml).

The reactants were added regularly to maintain the pH above 5 during the reaction.

The reaction mixture was stirred with a helix (helix), a spiral stirrer at 70-80 degrees Celsius, and the warm mixture was filtered under vacuum.

The composition of the filtrate is as follows; Zn, 149.8 g / l; Mg, 7 g / l; Al, 0.05 g / l; Fe, 0.7 g / l.

Example 2

A leachate containing 10g of Fe, 150g of Zn, 8.4g of Mg, and a small amount of Cu (300ml), and a slack (26g) containing no iron but with the same content of other impurities (100ml ) Was added to the reactor containing.

During the reaction, the reactants were mixed regularly to maintain the pH above 1.5, and air was injected to maintain the oxidizing conditions.

The composition of the filtrate obtained by stirring the whole reactant at 70-80 degrees Celsius and then filtering the warm reaction mixture in vacuum.

Zn, 149.8 g / l; Mg, 8.3 g / l; Al, 0.1 g / l.

Example 3

A leachate (300 mL) and slack (26 g) containing 10 g of Fe, 150 g of Zn, and 11.4 g of Mg were placed in a reactor containing leachate (100 mL) containing no iron but the same impurities. During which the reaction was added regularly to maintain a pH of at least 1.5 during the reaction.

After slightly adding an organic or inorganic oxidizing agent, the reaction medium was stirred with helix at 70-80 degrees Celsius. The composition of the filtrate obtained by filtering this warm mixture in vacuum is as follows.

Zn, 149.8 g / l; Mg, 10.4 g / l; Al, 0.2 g / l.

In these three embodiments, the following conclusions can be drawn.

Practically all iron, ie bivalent iron, as well as trivalent rail can be removed.

The concentration of -Mg is kept below a certain threshold.

As one practical industrial embodiment of the process according to the invention based on the block diagrams of FIGS. 1 and 2, the following examples were made.

The roasted zinc ore (measured at 15.5 tonnes per hour) with the following analyses was contacted in (I) with circulating acid (2) (79 cubic meters per hour) with a concentration of 176 g / l H ₂ SO ₄ .

Zn Fe Pb Al ₂ O ₃

60% 9% 1.77% 0.249%

The thickened residue containing the zinc ferromagnetic substance having a concentration of 400 g / l solid phase obtained in (II) was corroded by hot acid at (90) to (95) in (III) and (VI) Recycled acid (10) and circulating acid (2), which form most of the filtrate obtained by filtration, were added to obtain an average acidity of about 30 g / l.

Part of the ferromagnetic material was removed, and the concentrated residue (6) was introduced from (V) by introducing a circulating acid (2) and clean sulfuric acid (7) concentrated to about 98% (per ml) Reprocessed at a rate of 100-500 g).

This corroded residue 9 contains substantially all of the lead and precious metals present in the treated ore while substantially all of the zinc is removed.

A portion 11 of the filtrate is diluted with wash water 8 and added to the decanted solution 5 to produce an acidic solution containing about 30-40 g / l of H ₂ SO ₄ .

In addition to zinc, this solution, which contains a high concentration of dissolved iron and other metals that are harmful to electrolysis, is suitable for precipitating iron and other harmful metals while substantially maintaining all zinc in the solution. Will be processed.

Calcium silicate (12), (15) is added to this solution to maintain the pH at 1.5-4.5 based on the second variant shown in FIG. 2, and if necessary, other basic substances such as lime are also added. In order to further promote the evaporation of the solution, the amount of dissolved CaSO ₄ is reduced by injecting the oxidant 16 and the oxidizing air 17.

The precipitation reaction of F ⁺⁺⁺ is so fast that it is virtually complete after 1 hour. However, it is desirable to extend the reaction time in (i) to about 4 hours in order to oxidize F ⁺⁺ which may be generated from sulfur contained in ore and slack.

In fact, the oxidation of Fe ⁺⁺ to Fe ⁺⁺⁺ occurs relatively slowly.

The pH of the solution obtained at the end of the precipitation of iron should be similar to the pH of the solution (at I) obtained in the leachate, so that it can be used directly in the purification step prior to entering the electrolysis step.

Since the pH of the solution to be filtered in (XI) is a relatively low acidity of about 3-4, less expensive materials can be used than previously known purification methods, and the efficiency of zinc extraction is about 99.5%.

It was found that the silicates obtained in this way are very well filtered and can be thoroughly backwashed.

These residues are not only very stable and unprofitable materials but also have features that can be used by the present invention as starting materials for producing aggregates or building blocks in cement and also as materials used for stacking.

This residue has also been found to be particularly active in the cement industry due to the fact that it contains iron in a form that can be easily handled on an industrial scale. Furthermore, before inserting into the furnace a product containing gypsum produced by neutralizing the sulfuric acid slack in the acidic solution and silica, alumina, etc., which are mainly released from the slag but also partially released from the treated solution. It is an additive to the starting materials that are used after insertion, but is especially useful for cement applications.

The present invention therefore also contemplates any industry which is capable of consuming the product formed by the above-mentioned methods without filtration or drying and the product containing the aforementioned components as well as useful applications of the product, in particular in the field of cement. The application in It has also been observed that the magnesium solution in the solution to be subjected to zinc electrolysis as has been obtained so far in the experiments described above can be reduced by coprecipitation with silicate derivatives, in particular iron silicate.

As already mentioned earlier, silicic acid concentrated in the medium is always at very low concentrations and is substantially constant during the precipitation process.

Since the reactivity of alkaline earth metal silicates, especially slack, is very high, it is not necessary to react by the batch method by changing pH conditions.

The silicic acid thus produced is immediately precipitated by iron and transferred to the electrolysis step along with other harmful metals such as magnesium, as mentioned previously.

Advancing the first neutralization step with oxidized or silicified zinc ore until the pH reaches about 1.5 further enhances the advantages of the process.

If zinc oxide was used, the quality of the final silicate residues is much lower.

In addition, the introduction of zinc silicate in the first stage is a very practical method for extracting zinc from ores that are difficult to treat by methods specially prepared for silicate ores.

In fact it has been found that the dissolution reaction of zinc silicate can be completed quickly and the residue thus formed can be filtered really well, unless the pH of the medium exceeds 1.5 or more, and generally not so with higher pH solutions. As an example, when the solution contains aluminum, it tends to precipitate in the form of silicon-alumina on the surface of the zinc silicate particles at pH about 3 and also inhibits the dissolution reaction of the zinc silicate particles. It has therefore been found that on industrial scale it is not possible to use zinc silicate in place of silicates of alkaline earth metals to precipitate metal impurities in solution without substantially reducing the reaction rate and zinc yield at pH above 1.5.

This problem does not exist when using a slag having a high content of calcium silicate. This silicate is highly reactive between pH 1.4-4.5.

It should also be noted that the present invention is not limited to the purification of zinc sulfate solution flowing out of the leachate of zinc ores or the modifications described above.

Therefore, many other wet metallurgy methods can precipitate harmful impurities, such as silicate residues, according to more variations of the process of the present invention than have been clearly described so far.

The acidic conditions for the precipitation of the silicate residues depend on the type of impurities to be removed and the type of metals to be extracted by electrolysis or the type of acid released or another extraction process to obtain selective sorting.

As illustrated in the accompanying drawings, several steps of modifications to the methods can be divided into two or more than two steps, for example, after the formation of silicic acid by first adding a basic material such as a basic silicate. It may be the case of corrosion in (i), which allows the separation of basic materials that are not completely corroded in this slack, and secondly, for example, the addition of excess lime to the oxidizing medium in order to precipitate iron to the maximum. .

Some of the advantages of the process according to the invention compared to some conventional steps prior to the process according to the invention include the treatment of residues from the leaching of zinc ore, in which a relatively large amount of SO ₄ It should be noted that the outflow of ions controls the amount of sulfuric acid in the overall reaction and makes it possible to obtain concentrated solutions by diluting the concentrated acid and by virtue of the heat generated during corrosion.

As a result of the foregoing description of the process according to the invention, the process according to the invention is particularly useful for purifying a solution containing iron to be removed.

The present invention is based on the fact that iron plays an important role in the chemical and precipitation phenomena occurring in solution. Therefore, after dissolving the siliceous zinc ore at a pH of 1.5 or less, the precipitation mechanism of the method of removing silica from the siliceous zinc ore by precipitating the dissolved silica by raising the pH of the solution to 1.5 or more while maintaining a relatively high temperature. It is quite different from the method according to the invention.

In this case, while the silica is solidified by the polymerization reaction, iron silicate is formed in the method according to the present invention even if the high temperature is not set as a whole condition.

It is important to note throughout the unexpected important fact that when the magnesium content in the solution to be purified exceeds some threshold, some of this magnesium co-precipitates with the formed iron silicate. In such a method, the presence of magnesium in lime used at elevated pH above 1.5 does not have any particular drawbacks.

In some cases according to the present invention, if the content of magnesium or silicate in the ore is relatively high, it forms a sufficient amount of iron silicate which is necessary to obtain a well filtered and well washed residue and the other impurities present in the solution are sufficient. In order to be co-precipitated, it may be useful to raise the pH of the above-mentioned solution to above 1.5 and then add a certain amount of iron ions to the solution.

The amount of iron added should be substantially stoichiometric, preferably with respect to dissolved silica, dissolved or dissolved in solution.

Claims (1)

In the wet metallurgical treatment for removing metal impurities from a zinc sulfate solution containing Fe ⁺⁺⁺ ions, silicate is added to a zinc sulfate solution to dissolve it to form silicic acid, and then neutralized base to pH 1.5-4.5. A wet metallurgical treatment for removing metal impurities from a zinc sulphate solution containing Fe ⁺⁺⁺ ions, wherein the metal impurities are precipitated as a solid residue mainly composed of iron silicate.

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