JP5016929B2 - Arsenic solution purification method - Google Patents

Description

  The present invention relates to a arsenic liquid purification method for removing mercury or lead present as impurities from an aqueous solution (arsenic liquid) in which arsenic is dissolved at a high concentration.

  In non-ferrous smelting, various smelting intermediates are generated, and there are those that can be various forms of smelting raw materials. Although these smelting intermediates and smelting raw materials contain valuable metals, they contain environmentally undesirable elements such as arsenic. Patent Document 1 discloses a method for separating and recovering arsenic from such an arsenic-containing substance. According to the method of Patent Document 1, since leaching of sulfur is effectively suppressed, it is useful as a technique for treating an arsenic-containing substance in a sulfide form. Patent Document 2 discloses a method of performing aeration in the presence of 1 g / L or more of copper ions when extracting arsenic from an arsenic sulfide-containing material into a copper sulfate-containing aqueous solution.

JP 54-160590 A JP-A-57-160914

  On the other hand, research is being conducted to fix arsenic in arsenic-containing materials generated from industry in the form of a stable bulky crystalline compound, which can be used for disposal and storage. The present applicant has developed a useful technique for synthesizing a scorodite-type iron arsenic compound in which arsenic is hardly eluted from an arsenic-containing solution, and disclosed it in Japanese Patent Application No. 2006-321575. The arsenic liquid obtained by the method of the above patent document can be used for the synthesis of this iron arsenic compound. Further, the present inventors have further studied a method for producing an arsenic solution, and Japanese Patent Application No. 2006-339154 and Japanese Patent Application No. 2006-339156 (hereinafter referred to as “No. May be referred to as “prior application”). When these techniques are combined with the technique such as the above-mentioned Japanese Patent Application No. 2006-321575, an industrially high arsenic treatment process can be constructed.

  However, arsenic-containing substances often contain environmentally undesirable elements such as mercury and lead in addition to arsenic, and mercury and lead are also leached depending on the manufacturing conditions of the arsenic liquid and mixed into the arsenic liquid May be. Then, even if arsenic is fixed in the iron arsenic compound, mercury or lead may be eluted from the compound, which is not a perfect environmental measure.

  The present invention is intended to provide a method for purifying an arsenic solution for greatly reducing the concentration of mercury and lead contained as impurities in the arsenic solution.

  In the present invention, as a method for separating and recovering mercury from the arsenic liquid, the metal sulfide is brought into contact with an arsenic liquid (liquid to be treated) containing mercury as an impurity so that the mercury is contained in the metal sulfide. A method for purifying arsenic liquid recovered as a fraction is provided. Copper sulfide or lead sulfate can be used as the metal sulfide. It is desirable to use a metal sulfide of 30 equivalents or more with respect to the amount of mercury in the liquid to be treated. Here, the arsenic solution is an aqueous solution in which arsenic is dissolved as ions. For example, an arsenic solution containing arsenic at a concentration of 20 g / L or more is a suitable target.

  In the present invention, as a method for separating and recovering lead from the arsenic solution, strontium carbonate is added to the arsenic solution containing lead as an impurity (liquid to be treated) and stirred to thereby obtain a precipitate containing strontium and lead. Provided is a method for purifying an arsenic solution that is produced and recovers lead as a solid. At that time, it is desirable to add 10 equivalents or more of strontium carbonate to the amount of lead in the liquid to be treated. Further, in particular, it is advantageous to reduce the precipitation of arsenic as much as possible by adopting a method in which at least a part of strontium and at least a part of lead are coprecipitated as a sulfate by performing the stirring in the presence of sulfate ions. It is. In this case, it is desirable to add 5 equivalents or more of strontium carbonate to the amount of lead in the liquid to be treated.

  According to the present invention, mercury or lead in an arsenic solution can be efficiently removed by a simple method. The method of the present invention uses an arsenic liquid manufacturing process (for example, the method disclosed in the prior application) for leaching arsenic from an arsenic-containing substance into water, followed by solid-liquid separation. It can be applied and is suitable for industrial implementation. The obtained arsenic solution can be used for the synthesis of a scorodite-type iron arsenic compound in which arsenic is extremely difficult to elute, and the compound is suitable for landfill disposal because there is no fear of mercury or lead eluting. The arsenic solution can also be used for the production of arsenous acid and high-purity arsenic.

A typical flow of the arsenic solution purification method using the present invention is shown in FIGS. FIG. 1 illustrates a case where mercury is separated, and FIG. 2 illustrates a case where lead is separated.
There are various forms of solid materials containing arsenic. Typical examples include those mainly composed of As ₂ S ₃ and sulfides represented by the composition formula of CuS, and those mainly composed of an intermetallic compound of copper and arsenic (such as Cu ₃ As). . However, such an arsenic-containing substance usually contains various elements, and in addition to arsenic, it often contains mercury and lead that are environmentally undesirable.

The inventors have found a method for leaching almost only arsenic from water from such an arsenic-containing substance and disclosed it in the prior application. The technique is based on a simple method in which an oxygen-containing gas is added to a slurry in which an arsenic-containing substance is suspended in water and stirred. The leaching reaction occurring at that time is, for example, the following formula (1) or (2), taking the case of arsenic sulfide As ₂ S ₃ as an example.
As ₂ S ₃ +5 (O) + 3H ₂ O → 2H ₃ AsO ₄ + 3S (1)
As ₂ S ₃ +3 (O) + 3H ₂ O → 2HAsO ₂ + 3S (2)
Further, when the arsenic-containing material as a raw material is mainly composed of an intermetallic compound of copper and arsenic, a method of proceeding the arsenic leaching reaction in the presence of elemental sulfur is suitably employed. The reaction formula is, for example, the following formula (3) when the case of copper arsenide Cu ₃ As is exemplified.
2Cu ₃ As + 6S + 5 (O) + 3H ₂ O → 3CuS + 2H ₃ AsO ₄ (3)

  In order to realize such “water leaching” of arsenic, it is necessary to add an oxidizing agent. However, if the oxidizing action is too strong, copper or mercury may be leached out in a trace amount even though it is desired to keep leaching only with arsenic. In that case, it is preferable that mercury is not leached out as much as possible because mercury is regulated in the order of microgram / L. In that sense, it is suitable to use an oxygen-containing gas as the oxidizing agent. When a means of adding a solid / liquid oxidant is taken, even if the amount of addition is strictly adjusted, there is a high possibility that mercury will be leached if it is excessively added locally.

Here, it is possible in principle to demercurize by a sulfurization reaction using H ₂ S gas, NaSH, or the like, but this is not preferable in the following two points.
1. When mercury is excessively sulfided, it becomes [HgS ₂ ] ²⁻ and remains in the liquid. Although the potential can be controlled to completely remove mercury, it is very difficult to control.
2. The dissolved arsenic will also be sulfided. Since it is a high concentration arsenic solution, NaSH or the like has an excessively strong sulfidation effect for purifying only a very small amount of mercury.

In addition, when “water leaching” is performed, the liquidity becomes acidic. Therefore, although lead is very small, only the solubility of lead sulfate (PbSO ₄ ) is dissolved. In this case, lead becomes a very large impurity in purifying and purifying arsenic. Elements such as lead, tin, and antimony have properties similar to arsenic, and are highly likely to accompany arsenic without being separated, whether crystallized or reduced to metal. In fact, when scorodite-type crystals are precipitated from an arsenic solution containing lead and arsenic is immobilized, lead is eliminated from the solution after the reaction. In other words, lead coprecipitates with arsenic. As a result of the dissolution test for such a scorodite type iron arsenic compound, the amount of lead present in the crystal was very small compared to iron and arsenic, and no lead dissolution was observed. . However, in the future, lead in arsenic may become a problem when an opportunity to dig up the scorodite-type compound from a landfill and recycle it. From this point of view, it is preferable to make an arsenic solution containing as little lead as possible. However, if the solution becomes acidic in the production of the arsenic solution by water leaching, it is very difficult to avoid mixing about 30 mg / L of lead in the arsenic solution.

Hereinafter, a method for separating and recovering mercury and lead from the arsenic solution will be described.
[Separation and recovery of mercury]
According to the study by the inventors, it has been found that a technique of bringing the liquid to be treated into contact with a metal sulfide is extremely effective for separating mercury from the arsenic liquid that is the liquid to be treated. In particular, copper sulfide and lead sulfide can be suitably used as the metal sulfide. In addition, iron sulfide, zinc sulfide, cadmium sulfide, etc. can be used if the mercury is simply removed. However, when iron sulfide or zinc sulfide is used, iron (Fe ²⁺ ) or zinc is leached to some extent in the liquid. Then, although it is desired to separate arsenic from other elements, elements such as iron and zinc are mixed as impurities.

  Zinc and cadmium have a lower ionization tendency than arsenic, so once dissolved in the arsenic solution, when the arsenic solution is used to deposit the arsenic compound, it remains as ions in the solution, so separation is not possible. It is relatively easy. However, iron causes complex phenomena. That is, when iron is dissolved in the arsenic solution, an iron arsenic compound such as scorodite is generated when an oxidizing action is applied. It is not preferable that iron arsenic compounds are produced by air entrained during the purification of mercury and arsenic is precipitated. For this reason, it is better not to use sulfides mainly composed of iron sulfide. However, copper sulfide, lead sulfide, and zinc sulfide may be used as ores. These contain iron as an impurity, but the effect is small because of the small amount.

In order to remove mercury efficiently, it is preferable that the metal sulfide has a fine particle size and is easily dispersed. When using ore, it is important to use it after finely pulverizing it. Further, in order to improve the dispersibility in the liquid, it is advantageous that the specific gravity is small. In that sense, copper sulfide is generally lighter in weight and easier to disperse than lead sulfide. Moreover, the metal sulfide deposited in the liquid generally has a very fine particle diameter and good dispersibility. For example, copper sulfide obtained by depositing hydrogen sulfide, sodium hydrosulfide, sodium sulfide, or the like into a copper sulfate (CuSO ₄ ) solution is excellent in practicality as a sulfide used in the present invention. The amount of metal sulfide used needs to be added in an excessive amount relative to the amount of mercury dissolved in the liquid to be treated. Although approximately 10 equivalents are effective, it is desirable that they be 30 equivalents or more. Although it may seem that it is very much when it is 30 equivalent, since it is 30 equivalent with respect to the mercury concentration which melt | dissolves, it will become a very small addition amount. This is because the amount of mercury actually dissolved is in the order of mg / L (ppm) no matter how much it dissolves.

  In the case of an arsenic solution in which arsenic is leached from an arsenic-containing substance mainly composed of an intermetallic compound of copper and arsenic due to the reaction of the above formula (3), the residue after leaching of arsenic is mostly sulfided. It remains as copper. In such a case, if the mercury concentration in the liquid increases at a certain time during the arsenic leaching process, a portion of the leaching residue (mainly copper sulfide) collected and stored in the previous charge will be leached. The mercury removal according to the present invention can be efficiently performed by returning to step (1). The mercury concentration can be monitored by a method of sampling the liquid from a suitably provided cushion tank or the like, measuring the mercury concentration with, for example, a reduction vapor atomic absorption photometer, and utilizing the result online. It can also be measured by polarography or ICP mass spectrometry.

  Phenomenon is unclear whether the principle of removing mercury in arsenic liquid by metal sulfide is adsorption or whether a substitution reaction of mercury and the metal constituting sulfide occurs. Both may have happened.

  The liquid temperature when the metal sulfide is brought into contact with the arsenic liquid may be in the temperature range from room temperature to about 95 ° C. In the case of mercury, generally, it becomes difficult to go to the precipitation when the temperature becomes high. In that sense, it is preferably 80 ° C. or lower, and more preferably 70 ° C. or lower. However, when the present invention is applied in a process of dissolving arsenic from an arsenic-containing substance, it is not advantageous to make the liquid temperature too low for efficient arsenic dissolution and solid-liquid separation. Therefore, about 50 to 80 ° C. is appropriate.

As a method of bringing the arsenic solution and metal sulfide into contact, stirring and mixing in a container can be mentioned. There is no need for a special large reaction tank, and a leaching tank or a cushion tank can be used. The stirring strength may be such that the metal sulfide can be dispersed in the liquid. 1 kW / m ³ is sufficient. Since the reaction in which mercury is incorporated into the metal sulfide is considered to occur almost instantaneously, it is not necessary to ensure a particularly long reaction time.

  It is preferable to manage the oxidation-reduction potential (ORP) in the direction of decreasing. In the first place, mercury is leached when the oxidizing power is too strong, and at this time, the ORP inevitably becomes higher than the normal state. Although the baseline of ORP slightly changes depending on the pH of the solution, mercury may partially dissolve when the potential exceeds 350 mV to 400 mV at the potential based on the Ag / AgCl electrode. In that case, mercury cannot be removed unless ORP is lowered. It is desirable to watch the ORP before and after the reaction.

  In this way, mercury in the liquid to be treated can be taken into the metal sulfide, and the mercury concentration in the liquid can be greatly reduced. The slurry after the reaction is separated into solid and liquid, and mercury is recovered as a solid content. The solid-liquid separation can be applied to any general filtration means such as a filter press, centrifugal separation, decanter, and belt filter. Equipment and conditions are determined in consideration of filterability, dewaterability, and cleanability. Here, the liquid temperature is preferably as high as possible in order to improve the filterability. However, if it exceeds 70 ° C., the selection of the material of the filtration device is restricted, so care should be taken. For example, when polypropylene is used as a filter plate material for a filter press, the standard one has only heat resistance up to 70 ° C.

  The liquid after the solid-liquid separation is one in which the mercury concentration is significantly reduced while arsenic is dissolved at a high concentration. This has a high utility value as an arsenic solution for fixing arsenic as a scorodite crystal. On the other hand, the solid content separated into solid and liquid contains metal sulfide that has taken in mercury. However, when the present invention is applied using a process of leaching arsenic from arsenic-containing substances into water, Residues remaining after leaching (sulfides and sulfur generated by the above formulas (1) to (3)) are also included. Although such a solid content contains mercury, it is still a valuable substance containing copper and sulfur. For example, in the copper smelting process, it is directly put into a flash smelting furnace and a reflection furnace to make an anode. Can be used to produce and produce sulfuric acid.

[Separation and recovery of lead]
According to the study by the inventors, it has been found that in order to separate lead from the arsenic liquid that is the liquid to be treated, a technique of adding strontium carbonate to the liquid to be treated and stirring and mixing is extremely effective. Barium carbonate has some effect, but strontium carbonate is better. The property of strontium carbonate is not particularly required as long as it has a grade of about 90% or more. In general, the finer the particle size, the better the reactivity seems to be, but it is not so relevant here. Rather, it is more problematic that the strontium carbonate-containing substance aggregates due to moisture and is difficult to disperse in the liquid. Strontium carbonate is generally in the form of a needle-like crystal, but here it is not necessary to be particularly concerned with the shape of the crystal.

  The reaction temperature may be any temperature from room temperature to 95 ° C.

  Strontium carbonate reacts with free sulfate ions in the liquid to become strontium sulfate (celestite). In the process, it coprecipitates with lead sulfate. Lead in the liquid to be treated is separated from the liquid by such a coprecipitation phenomenon. In order to cause such a coprecipitation reaction, it is necessary that some free sulfate ions exist in the liquid.

  However, even in the absence of free sulfate ions, lead can be separated by adding strontium carbonate to the arsenic-containing liquid and stirring. This is because the solubility product of strontium is very low, and even arsenic ions are co-precipitated, that is, strontium arsenate is taken in and precipitated. In this case, arsenic precipitates to some extent, so the precipitation rate of arsenic is slightly higher than when precipitation occurs in the presence of sulfate ions, but lead is largely retained while most of the arsenic remains in the solution. It is possible to precipitate. In order to suppress arsenic precipitation as much as possible, it is desirable to add sulfuric acid to the solution to co-precipitate at least part of strontium and at least part of lead as sulfate. In order to utilize such a coprecipitation reaction, it is desirable to add 1 g / L or more of sulfuric acid. For example, it is more effective to add 5-35 g / L of sulfuric acid.

The following reactions can occur in the liquid.
S + 3 (O) + H ₂ O → H ₂ SO ₄
This reaction tends to occur in the alkaline region. This is because the reaction progresses from left to right as alkali consumes the reaction product sulfuric acid. Conversely, to stop the reaction, sulfuric acid as a reaction product may be added. In this way, S (sulfur) can be recycled. From this point of view, the presence of some sulfuric acid is convenient for leaching only arsenic and not leaching sulfur.

  The amount of strontium carbonate added should be approximately 1.5 equivalents or more with respect to the amount of lead dissolved in the liquid to be treated. The reason why strontium carbonate is added in an excessive amount is that a part of strontium carbonate reacts with free acid containing arsenic present in the arsenic solution and becomes strontium sulfate and the like before it is trapped. It is. In that sense, it is important to rapidly stir and disperse the strontium carbonate to be added in the liquid in order to efficiently remove lead. In order to separate and recover 90% or more of lead dissolved in the liquid as a solid content, the amount of strontium carbonate added is 5 equivalents or more in the case of a liquid to be treated in which sulfate ions are present in an amount of 10 g / L or more in terms of sulfuric acid. Is more preferable, and it is more preferably 7 equivalents or more. When the amount of sulfate ions in the liquid is less than 10 g / L, it is desirable to secure an addition amount of strontium carbonate of 10 equivalents or more, and more preferably 17 equivalents or more.

  When ΔpH = [pH after reaction] − [pH before reaction], ΔpH tends to slightly increase in a range of about 0.2 or less. This is due to neutralization by strontium. ORP also changes somewhat before and after precipitation of lead, and when ΔORP = [ORP after reaction] − [ORP before reaction], ΔORP is approximately in the range of −70 to +5 mV.

  Thus, the lead in the liquid to be treated can be taken into the precipitate, and the lead concentration in the liquid can be greatly reduced. The slurry after the reaction is separated into solid and liquid, and lead is recovered as a solid content. The solid-liquid separation method is the same as that for mercury.

  The post-solution separated after solid-liquid separation is a solution in which the concentration of lead is significantly reduced while arsenic is dissolved at a high concentration. This has a high utility value as an arsenic solution for fixing arsenic as a scorodite crystal. On the other hand, strontium together with lead is present in the solid content separated into solid and liquid, but this solid content can be used for dry copper smelting. That is, slag is generated in dry copper smelting, but strontium contributes as a substitute for the calcium raw material for this slag. In other words, strontium is also effectively used. Also, if the solid content is a substance mainly composed of strontium sulfate, if you want to regenerate strontium carbonate from that substance, isolate only strontium sulfate (may contain some lead) and steam it with coke. Thus, strontium carbonate can be regenerated by dispersing it with water (hot water) and blowing in carbon dioxide gas. Of course, hydrogen sulfide can also be recovered.

Lead is an element with a mysterious effect. Generally, when an object is leached with an acid (such as sulfuric acid), the leaching rate is improved by increasing the acid concentration. In order to leach only arsenic, it is advantageous to adopt a condition in which no acid is added. However, when all other impurities are leached, it is better to add an acid. In that case, excess acid remains in the solution after leaching. This acid is very disturbing to subsequent processing. In general, neutralization is performed using an alkali or alkaline earth, but if it is alkaline, the salt concentration is increased by neutralization, and if it is alkaline earth, gypsum is generated more than necessary. However, lead can be successfully used as a recyclable raw material by lead smelting. Therefore, it is possible to use the Pb raw material well for adjusting the acid concentration.
The basic reaction formula is as follows.
PbO + H ₂ SO ₄ = PbSO ₄ + H ₂ O
PbSO ₄ is usually recycled to metal lead by dry smelting.
Recycling called the CX process can also be considered for hydrometallurgy.
PbSO ₄ + Na ₂ CO ₃ (a) = PbCO ₃ + Na ₂ SO ₄ (a)
Here, (a) means that it is dissolved in water.
PbCO ₃ = PbO + CO ₂
Na ₂ SO ₄ is recovered by concentrated crystallization.
Thus, the acid concentration can be adjusted by making good use of PbO and PbSO ₄ .

  As described above, the separation of mercury and the separation of lead have been described. However, when it is desired to separate and recover both mercury and lead from the arsenic solution, the above-described methods may be sequentially performed. Either may be carried out first, and after carrying out sequentially in one container, the solid-liquid separation can be completed once.

<< Creation of liquid A to be treated >>
700 g of a solid arsenic-containing substance having the composition shown in Table 1 was taken on a dry basis. In addition, 3500 mL of water was weighed. The arsenic-containing substance and water were placed in a 5 L autoclave, and a stirring blade (two-stage paddle blade) and an insertion gas pipe leading to the liquid phase were set and sealed. The stirring blade was rotated at 1000 rpm, and the temperature was raised to 65 ° C. while vigorously stirring the liquid. In order to eliminate the inert gas (derived from the initial air) as much as possible in the gas phase part, the valve leading to the gas phase part is temporarily opened at 65 ° C., and the internal gas until the gauge pressure becomes zero. Kicked out. Thereafter, the container was again sealed and oxygen gas having a purity of 99% was blown into the liquid phase part of the container while maintaining the temperature at 65 ° C. The pressure rises because the reaction is in a sealed container. Oxygen was blown in while adjusting the oxygen gas introduction valve so that the oxygen partial pressure in the gas phase was maintained at about 0.2 MPa. In this state, stirring was continued for 4 hours. The slurry after completion of the stirring operation was subjected to solid-liquid separation with a pressure filter. Solid-liquid separation was performed using a 1 μm PTFE membrane filter at a pressure of 0.4 MPa.

To the filtered solution, mercury chloride HgCl ₂ , a special grade reagent (manufactured by Wako Pure Chemical Industries, Ltd.) was added with the aim of achieving a mercury concentration of about 100 mg / L, and the solution A (mercury) was dissolved by stirring and dissolving. An arsenic solution containing And the pH of the to-be-processed liquid A, ORP (Ag / AgCl electrode reference | standard) measurement, and a composition analysis were performed.

  The composition analysis was carried out by ICP analysis after dissolving with hydrochloric acid as follows. That is, 2 mL of the liquid was collected with a whole pipette, put into a 100 mL volumetric flask, 8 mL of a special grade hydrochloric acid (33% grade) was added, and then diluted to 100 mL with water. At this time, no precipitate was generated, and the measurement was performed by ICP as it was. When the analysis sensitivity of ICP was exceeded, it was further diluted 10 to 200 times and ICP analysis was performed. Mercury was also analyzed by ICP. Table 2 shows the analysis results of the liquid A to be treated. Normally, in the leaching by oxygen pressurization at 0.2 MPa, mercury is leached only at about 5 μg / L. Here, 112 mg / L of 22400 times is obtained by supplying mercury with a reagent. The target of about 100 mg / L was 112 mg / L because of handling errors such as the amount of reagent added.

<< Comparative Example 1 >>
500 mL of the liquid A to be treated was collected and stirred with a three-padded paddle made of PTFE. A PTFE plate (10 mm width) was inserted as a baffle plate. The stirring rotation speed was relatively weak at 200 rpm. The temperature of the liquid was adjusted to 55 ° C. 0.200 g of lead sulfide PbS of a special grade reagent (manufactured by Wako Pure Chemical Industries, Ltd.) corresponding to 3 equivalents of mercury in the solution was weighed and slowly added to the above solution. This 0.200 g is calculated from (112 / 200.59) × (207.19 + 32) × 3 (equivalent) × 0.5 (L) = 200 mg. Stirring was continued for 15 minutes while maintaining the liquid temperature at 55 ° C. Thereafter, solid-liquid separation was performed. Solid-liquid separation was performed using a 1 μm PTFE membrane filter at a pressure of 0.4 MPa. About the post-filtration liquid after filtration, after measuring pH and ORP, a part was fractionated and ICP analysis was performed. The analysis method is the same as the method performed for the liquid A to be processed.
The analysis results of the rear solution are shown in Table 3, and the removal rate (precipitation rate) of each element calculated from these analysis results and the analysis results of the liquid to be treated is shown in Table 4 (Example 1 and Comparative Example below) 2, the same in Example 2).

Example 1
The same operation as in Comparative Example 1 was performed. However, 2.000 g of lead sulfide PbS was weighed and added so as to be 30 equivalents to mercury. Other conditions are the same as in Comparative Example 1.

<< Comparative Example 2 >>
The same operation as in Comparative Example 1 was performed. However, instead of lead sulfide PbS, 0.080 g of copper sulfide CuS, a special grade reagent (manufactured by Wako Pure Chemical Industries, Ltd.) corresponding to 3 equivalents of mercury in the liquid was weighed and added slowly. Other conditions are the same as in Comparative Example 1. The above 0.080 g is calculated from (112 / 200.59) × (63.546 + 32) × 3 (equivalent) × 0.5 (L) = 80 mg.

Example 2
The same operation as in Comparative Example 2 was performed. However, 0.800 g of copper sulfide CuS was weighed and added so as to be 30 equivalents to mercury. Other conditions are the same as in Comparative Example 2.

From Comparative Example 1, Example 1, Comparative Example 2, and Example 2, the following can be said.
Mercury can be separated and recovered as a solid from an arsenic-containing liquid containing mercury by sulfides such as PbS and CuS. At that time, arsenic can be kept in the liquid. The ability of CuS to purify mercury is superior to PbS. However, if the amount of sulfide added is too small, the removal of mercury from the arsenic solution will be insufficient.

<< Creation of liquid B to be treated >>
In the preparation of the liquid A to be processed, the liquid B to be processed was prepared by performing the above-described method except that mercury chloride HgCl ₂ was not added. In comparison with the liquid to be treated A, there was no change in the composition analysis result of the liquid. Table 5 shows the analysis result of the liquid B to be treated.

Example 3
500 mL of the liquid B to be treated was collected and stirred with a three-padded PTFE paddle. A PTFE plate (10 mm width) was inserted as a baffle plate. The stirring rotation speed was relatively weak at 200 rpm. The temperature of the liquid was adjusted to 55 ° C. 23.0 mg of strontium carbonate SrCO ₃ (purity 97%, average particle size of about 1 μm, specific surface area of about 5 m ² / g), manufactured by Solvay, was weighed on a precision balance and handled on a medicine wrapping paper. Slowly added. The equivalent value of 23.0 mg of this strontium carbonate added to the lead content of 37 mg / L in the liquid is 23.0 (mg) × 0.97 / (87.62 + 12.01 + 3 × 16) / (37 (mg ) /207.19) /0.5 (L) = 1.69 equivalents. Stirring was continued for 15 minutes while maintaining the liquid temperature at 55 ° C. Thereafter, solid-liquid separation was performed. Solid-liquid separation was performed using a 1 μm PTFE membrane filter at a pressure of 0.4 MPa. About the post-filtration liquid after filtration, after measuring pH and ORP, a part was fractionated and ICP analysis was performed. The analysis method is the same as the method performed for the liquid A to be processed.
The analysis results of the rear solution are shown in Table 6, and the removal rates (precipitation rates) of each element calculated from these analysis results and the analysis results of the liquid to be treated are shown in Table 7 (in Examples 4 to 6 below) the same).

Example 4
The same operation as in Example 3 was performed. However, the amount of strontium carbonate added was 105.0 mg. The equivalent value of the addition amount of 105.0 mg of this strontium carbonate with respect to the lead content of 37 mg / L in the liquid is 105.0 (mg) × 0.97 / (87.62 + 12.01 + 3 × 16) / (37 (mg ) /207.19) /0.5 (L) = 7.73 equivalents. Other conditions are the same as those in Example 3.

Example 5
The same operation as in Example 3 was performed. However, the amount of strontium carbonate added was 269.0 mg. The equivalent value of the addition amount of 269.0 mg of strontium carbonate with respect to the lead content of 37 mg / L in the liquid is 269.0 (mg) × 0.97 / (87.62 + 12.01 + 3 × 16) / (37 (mg ) /207.19) /0.5 (L) = 19.79 equivalents. Other conditions are the same as those in Example 3.

Example 6
The same operation as in Example 3 was performed. However, the amount of strontium carbonate added was 679.0 mg. The equivalent value of the addition amount of 679.0 mg of this strontium carbonate to the lead content of 37 mg / L in the liquid is 679.0 (mg) × 0.97 / (87.62 + 12.01 + 3 × 16) / (37 (mg ) /207.19) /0.5 (L) = 49.96 equivalents. Other conditions are the same as those in Example 3.

The following can be said from Examples 3-6.
When strontium carbonate is added to an arsenic-containing liquid in which lead is dissolved, lead in the liquid can be separated and recovered as a solid without adding new sulfuric acid as a free acid. At this time, although it is very slight, pH rises and ORP falls. Most of the arsenic present in the liquid remains in the liquid, but since no acid such as sulfuric acid is added, strontium arsenate is formed and slightly precipitated. Most of the lead dissolved in the liquid co-precipitates along with this precipitation reaction, and becomes solid matter accompanying strontium arsenate. Although no free acid is added, 90% or more of lead dissolved in the arsenic solution can be removed by adding about 17 equivalents or more of strontium carbonate with respect to lead.

<< Creation of liquid C to be treated >>
The above-mentioned to-be-processed liquid B was created, and the to-be-processed liquid C was created by adding the concentrated sulfuric acid of the quantity corresponding to the sulfuric acid density | concentration of 10 g / L further to the liquid using the Pasteur pipette. Although the pH and ORP slightly shifted in comparison with the liquid to be treated B, the composition analysis result of the liquid did not change (except for the increase in sulfur accompanying the addition of sulfuric acid). Strictly speaking, the volume should have increased by about 5 mL (ie, 10 g / specific gravity of 1.84) with respect to 1000 mL, but the volume change is small at 0.5%, so there is a variation in the composition analysis value. It is presumed that it was not. Table 8 shows the analysis result of the liquid C to be treated.

<< Examples 7 to 10 >>
In Examples 7 to 10, operations similar to those in Examples 3 to 6 were performed, respectively, except that the liquid C to be treated was targeted.
Table 9 shows the analysis results of the rear solution, and Table 10 shows the removal rate (precipitation rate) of each element calculated from these analysis results and the analysis result of the liquid to be treated.

The following can be said from Examples 7 to 10.
When strontium carbonate is added to an arsenic-containing liquid in which lead is dissolved in the presence of sulfate ions, the equivalent amount of strontium carbonate is reduced compared to the case where sulfate ions are not added, and lead in the liquid is efficiently separated as a solid content.・ Can be collected. This is considered to be due to the effect of coprecipitation of at least part of strontium and at least part of lead as sulfate (coprecipitation reaction of lead accompanying precipitation of strontium sulfate).

<< Creation of liquid D to be treated >>
The above-mentioned to-be-processed liquid B was created, and the to-be-processed liquid D was created by adding the concentrated sulfuric acid of the quantity corresponding to the sulfuric acid density | concentration of 30 g / L to the liquid using the Pasteur pipette. Although the pH and ORP slightly shifted in comparison with the liquid to be treated B, the composition analysis result of the liquid did not change (except for the increase in sulfur accompanying the addition of sulfuric acid). Strictly speaking, the volume should have increased by about 15 mL (ie, 30 g / specific gravity of 1.84) with respect to 1000 mL, but the change in volume is as small as 1.5%, so there is a variation in the composition analysis value. It is presumed that it was not. Table 11 shows the analysis result of the liquid D to be treated.

<< Examples 11 to 14 >>
In Examples 11 to 14, operations similar to those in Examples 3 to 6 were performed except that the liquid D to be treated was targeted.
Table 12 shows the analysis results of the rear solution, and Table 13 shows the removal rate (precipitation rate) of each element calculated from these analysis results and the analysis result of the liquid to be treated.

The following can be said from Examples 11-14.
The arsenic removal rate (precipitation rate) was significantly reduced by increasing the amount of sulfate ions present compared to Examples 7-10. This is presumably because the presence of sufficient sulfate ions in the liquid caused most of the strontium to precipitate as strontium sulfate, and the reaction that arsenic combined with strontium did not occur so much. Moreover, as in Examples 7 to 10, lead in the liquid can be efficiently separated and recovered as a solid content.

The figure which showed the typical flow about the purification | cleaning method of the arsenic liquid which isolate | separates mercury using this invention. The figure which showed the typical flow about the purification method of the arsenic liquid which isolate | separates lead using this invention.

Claims (8)

  A method for purifying an arsenic solution in which mercury is contained in the metal sulfide and recovered as a solid content by bringing the metal sulfide into contact with an arsenic solution (treatment liquid) containing mercury as an impurity.   The method for purifying arsenic liquid according to claim 1, wherein copper sulfide is used as the metal sulfide.   The method for purifying arsenic liquid according to claim 1, wherein lead sulfide is used as the metal sulfide.   The method for purifying an arsenic solution according to any one of claims 1 to 3, wherein 30 equivalents or more of metal sulfide is used with respect to the amount of mercury in the liquid to be treated.   A method for purifying an arsenic solution in which strontium carbonate is added to an arsenic solution (liquid to be treated) as an impurity and stirred to produce a precipitate containing strontium and lead, and the lead is recovered as a solid content.   The method for purifying an arsenic solution according to claim 5, wherein at least a part of strontium and at least a part of lead are coprecipitated as a sulfate by performing the stirring in the presence of sulfate ions.   The method for purifying an arsenic solution according to claim 5, wherein 10 equivalents or more of strontium carbonate is added to the amount of lead in the liquid to be treated.   The method for purifying arsenic liquid according to claim 6, wherein 5 equivalents or more of strontium carbonate is added to the amount of lead in the liquid to be treated.

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