JP2008196039A - Method of removing fluorine from processing liquid used in wet zinc smelting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently adsorb and remove fluorine so that fluorine does not accumulate in liquid when using zinc-containing matters such as crude zinc oxide containing fluorine in a wet zinc smelting process. <P>SOLUTION: The problem can be solved by making fluorine ions and ferric ions to co-exist in a sulfuric acid solution, neutralized the solution to produce iron precipitate and removing the fluorine through adsorption to and coprecipitation with the iron precipitate. In order to make the most of the capacity of elemental iron as a fluorine adsorbent, the fluorine-adsorbing iron precipitate is redissolved and used as an iron raw material for adsorbing fluorine for a plurality of times. By utilizing undissolved residues produced in the zinc smelting process as an iron raw material serving as an adsorbent and using fluorine-containing crude zinc oxide etc. as a neutralizer, the purpose can be accomplished through only the operations generally conducted in the wet zinc smelting process, i.e. dissolving, neutralization and solid-liquid separation, without requiring a large capital investment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of removing fluorine from a process liquid for wet zinc smelting.

  In a general wet zinc smelting process, zinc sulfide ore is roasted to oxidize and desulfurize zinc sulfide, which is the main component, to obtain a sinter containing zinc oxide as the main component. Then, this sinter is brought into contact with an electrolytic tail solution to dissolve and leach zinc. The electrolytic tail solution used here is a sulfuric acid acidic solution that has been subjected to an electrowinning process of metallic zinc in a zinc electrolytic cell. However, since the aforementioned zinc sulfide ore contains not a little iron, zinc ferrite is formed in the burned ore obtained by roasting at a high temperature. Since this zinc ferrite does not dissolve in the dissolution and leaching step, it becomes a main component of a residue (hereinafter referred to as “undissolved residue”) that has been solid-liquid separated using a thickener or a filter press.

  The zinc leachate obtained in the solid-liquid separation step (hereinafter referred to as “neutral Th / OF”) contains impurities (mainly metals having a smaller ionization tendency than zinc) that adversely affect the electrowinning step. Yes. Therefore, it is set as the cleaning liquid which removed the said impurity in a liquid purification process. This cleaning solution is used for adjusting the zinc concentration of the zinc electrolyte circulating in the electrolytic collection process. The zinc electrolytic solution is used for electrolysis in a zinc electrolytic cell provided in the circulation process, and an anode plate made of a lead-based alloy and an aluminum cathode plate are arranged in the zinc electrolytic cell. When the electrolysis is completed, the zinc electrodeposited on the cathode plate is peeled off to obtain electrozinc. In the present invention, the electrolytic tail solution, zinc electrolytic solution, neutral Th / OF and cleaning solution, which are sulfuric acid acidic solutions related to the wet zinc smelting process, are collectively referred to as “process solution for wet zinc smelting”.

  On the other hand, in recent years, steelmaking dust discharged in the steelmaking process of steelworks and zinc soot generated in the galvanizing process are regenerated and recovered as zinc-containing materials such as crude zinc oxide. And the method of mixing and using these zinc containing materials with the above-mentioned calcination is also adopted. However, since this zinc-containing material contains a halogen element, if the zinc-containing material is handled in the same manner as sinter, the halogen element concentration in the process solution for wet zinc smelting increases, and the wet zinc smelting process Causes various problems. Among halogen elements, fluorine causes a particularly serious problem in the wet zinc smelting process.

  The upper limit of the allowable range of the fluorine concentration in the zinc electrolyte is generally 20 mg / L. When the fluorine concentration in the zinc electrolyte exceeds 20 mg / L, the aluminum plate, which is a cathode for electrodepositing zinc, tends to be corroded. As a result, a so-called contact plate is generated in which the electrodeposited zinc cannot be peeled off from the cathode plate. When the contact plate is generated, in order to maintain the continuous operation of the electrolysis process, it is necessary to remove the contact plate from the continuous line and replace it with an alternative cathode plate. That is, man-hours for processing the contact plate off-line are generated, and the cathode plate is corroded and mechanically damaged. Therefore, fluorine management in the process liquid for wet zinc smelting is important in maintaining stable operation.

  Therefore, several methods have been proposed as a method for preventing fluorine from being mixed into the zinc electrolyte. Patent Document 1 discloses three methods. The first is a method of performing water washing at the raw material stage (referred to as “conventional method 1”). However, in this conventional method 1, since not all the chemical bonding states of fluorine contained in the zinc-containing material are readily water-soluble, sufficient removal of fluorine cannot be expected with water washing alone.

  The second is a method of removing fluorine by a sulfated roasting method (referred to as “conventional method 2”). This conventional method 2 requires a special process called sulfation roasting, and therefore requires additional equipment, and therefore has a drawback of increasing running costs and impairing economy.

  Thirdly, the zinc electrolytic smelting process is divided into two stages. In the first stage, a predetermined amount of zinc is deposited using a zinc electrolyte containing no fluorine ions. In the second stage, zinc that has already been deposited is deposited. Is a two-stage electrowinning method in which zinc is deposited using a zinc electrolyte containing fluorine ions (referred to as “conventional method 3”). In this conventional method 3, since the electrowinning process is divided into two stages, at least two sets of similar electrowinning equipment are required, the capital investment cost increases, the process management becomes complicated, and the cost rises. There is a disadvantage of damaging.

  Patent Document 2 discloses a method of removing fluorine directly from a zinc electrolyte using cerium hydroxide (referred to as “conventional method 4”).

  Further, Patent Document 3 discloses a method of removing fluorine directly from a zinc electrolyte using titanur sulfate (referred to as “conventional method 5”).

  In the conventional method 4 and the conventional method 5, the price of cerium hydroxide or titanur sulfate having a function of adsorbing fluorine is high, the running cost is increased, and the economy is impaired.

  Patent Documents 4 to 9 disclose a method for removing fluorine in a wastewater treatment process.

  When the methods shown in Patent Document 4 and Patent Document 5 are used on an aqueous solution containing a sulfate radical, calcium sulfate is generated, and it is difficult to obtain the effect of removing fluorine that would be originally exhibited. . In particular, the process solution for wet zinc smelting is difficult to apply because calcium sulfate is produced in a large amount.

  Even the techniques disclosed in Patent Documents 6 to 9 are difficult to apply because calcium sulfate is generated in a sulfuric acid acidic solution.

JP-A-4-22189 JP 2002-105685 A JP-A-6-57476 JP-A-6-262170 Japanese Patent Laid-Open No. 10-137744 JP-A-11-57747 JP 2001-17982 A JP 2001-232373 A JP 2003-266083 A

  As described above, it has been a major proposition of a zinc smelter to effectively use zinc-containing materials such as crude zinc oxide containing fluorine in the wet zinc smelting process while eliminating the influence of fluorine.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have found a method for removing fluorine from a process liquid for hydrometallurgical smelting by using an iron precipitate as an adsorbent and removing fluorine by adsorption. The invention relating to the present application will be described below.

Fluorine removal method according to the present invention: The fluorine removal method according to the present invention is a method for removing fluorine from a process liquid for wet zinc smelting by adsorbing and removing fluorine using an iron precipitate as an adsorbent, comprising the following steps: The iron compound used in Step A of the nth cycle of the process of removing fluorine by repeating A to Step C as one cycle and repeating this one cycle for a plurality of cycles (1st cycle to nth cycle: n ≧ 2). The fluorine-adsorbed iron precipitate obtained in Step C of the (n-1) th cycle.

Step A: A fluorine adsorption iron solution preparation step in which an iron compound is dissolved in a sulfuric acid acidic solution to obtain a fluorine adsorption iron solution.
Step B: A fluorine coprecipitation step of obtaining a fluorine coprecipitation slurry in which the iron solution for fluorine adsorption is neutralized to form an iron precipitate and adsorbed and coprecipitated on the iron precipitate that deposits fluorine ions in the solution.
Step C: Fluorine removal liquid recovery step of separating the fluorine coprecipitation slurry obtained in Step B into a fluorine removal liquid and a fluorine adsorbed iron precipitate.

  In the fluorine removal method according to the present invention, the fluorine adsorption iron solution prepared in Step A of the first cycle uses an electrolytic tail solution as the sulfuric acid solution, and uses an undissolved residue as the iron compound. It is also preferable that iron and zinc contained in the residue are extracted into an electrolytic tail solution.

  In the fluorine removal method according to the present invention, it is also preferable to use a zinc-containing material containing fluorine for the neutralization in Step B.

In the fluorine removing method according to the present invention, the fluorine removing liquid obtained in Step C of the nth cycle is the same as that of Step A of the (n-1) cycle or Step B of the (n-1) cycle. It is also preferred to use either or both.

  If the fluorine removal method according to the present invention is used, the fluorine concentration of the process liquid for wet zinc smelting can be stably reduced to 20 mg / L or less. This is because the method for removing fluorine according to the present invention uses the iron precipitate precipitated from the iron solution for adsorption of fluorine as an adsorbent, so that the adsorption site of the iron precipitate can be utilized to the maximum. And since the iron precipitate which adsorb | sucked the fluorine is redissolved and used as an iron raw material for fluorine adsorption several times, an iron precipitate can be utilized to the maximum as a fluorine adsorbent. Moreover, in the process using an iron precipitate for a fluorine adsorbent, undissolved residue generated in the wet zinc smelting process can be used as a raw material for iron as an adsorbent. Furthermore, the operations to be performed are mainly dissolution, neutralization and solid-liquid separation, and no large capital investment such as introduction of new chemicals or introduction of special equipment is required.

  Before explaining the fluorine adsorption process according to the present invention, a mechanism for adsorbing fluorine by iron precipitate will be explained so that the explanation can be easily understood. The adsorption mechanism of fluorine by the iron precipitate is chemical adsorption, and the adsorption reaction is considered to be an equilibrium reaction due to ion exchange. That is, it is different from the adsorption mechanism by physical uptake of molecules by micropores such as activated carbon adsorption.

Form of Fluorine Removal Method According to the Present Invention: The fluorine removal method according to the present invention is a method for removing fluorine from a process liquid for wet zinc smelting, characterized by removing fluorine using an iron precipitate as an adsorbent. is there. Specifically, the following step A to step C are defined as one cycle, and this one cycle is repeated a plurality of cycles (first cycle to nth cycle, where n ≧ 2), and the nth cycle of the process of removing fluorine. As the iron compound used in Step A, the fluorine-adsorbed iron precipitate obtained in Step C of the (n-1) th cycle is used. Hereinafter, explanation will be added for each step.

  Step A in the fluorine removal method according to the present invention is a fluorine adsorption iron solution preparation step in which an iron compound is dissolved in a sulfuric acid acidic solution to obtain a fluorine adsorption iron solution. Step A is characterized in that iron contained in the prepared iron solution for adsorption of fluorine is in the form of ferric ions. This is because ferric ions tend to form precipitates by neutralization, and the resulting precipitates also have good filterability. When ferrous ions are present in the iron solution, aeration is preferably performed in a sulfuric acid state before neutralization, or ferric ions are preferably used in advance using an oxidizing agent such as manganese dioxide. .

  As the iron compound used in the preparation of the iron solution for fluorine adsorption in this step, ferric sulfate at the industrial chemical level can be used. In this case, an iron solution for fluorine adsorption that can be suitably used can be obtained by dissolving ferric sulfate in a sulfuric acid acidic solution such as dilute sulfuric acid to obtain an aqueous solution having an iron concentration of about 30 g / L. If an iron solution for fluorine adsorption is prepared using only ferric sulfate at the industrial chemical level, it can be applied to a defluorination operation for waste water containing fluorine. However, if the cost is preferentially taken into consideration, it is preferable to use an iron compound generated accompanying production activities such as an undissolved residue generated in the wet zinc smelting process. In particular, it is most preferable to use a by-product to be discarded. As the by-product here, for example, red mud which is a by-product of alumina production and treated as waste also contains a large amount of iron and can be selected as an iron compound.

  And it is preferable that the iron concentration in the iron solution for fluorine adsorption prepared in Step A is 5 g / L to 40 g / L. If the iron concentration is less than 5 g / L, the amount of fluorine adsorbed on the iron precipitate formed by neutralization decreases, which is not preferable. On the other hand, when the iron concentration exceeds 40 g / L, the sedimentation property and filterability of the obtained fluorine coprecipitation slurry are deteriorated, which is not preferable. Therefore, considering the fluorine adsorption capacity, sedimentation and filterability, the iron concentration in the iron solution is more preferably 15 g / L to 30 g / L.

  The fluorine adsorption iron solution prepared in Step A of the first cycle should be prepared using an electrolytic tail solution for the sulfuric acid acidic solution and an undissolved residue generated in the wet zinc smelting process for the iron compound. Is preferred. This is because when iron is extracted from zinc ferrite in the undissolved residue to prepare an iron solution for fluorine adsorption, coexisting zinc is also extracted and the recovery rate of zinc is improved.

  Step B in the method for removing fluorine according to the present invention comprises the step of neutralizing the iron solution for adsorbing fluorine to obtain a fluorine coprecipitation slurry in which fluorine ions in the solution are adsorbed and coprecipitated to the precipitated iron precipitate. It is a process. This step B is characterized by depositing ferric ions in the iron solution for adsorption of fluorine as iron precipitates such as iron hydroxide by neutralization. When the neutralization operation is performed in the state where fluorine ions coexist, it is preferable because the iron precipitate is deposited and at the same time the fluorine ions are adsorbed, so that the adsorption site of the iron precipitate as the adsorbent can be utilized to the maximum.

  The iron precipitates deposited at this time are considered to be in the form of basic iron sulfate, iron hydroxide, iron oxyhydroxide, iron oxide, or a mixture thereof, since sulfate groups coexist. It is done. The fluorine adsorption iron solution does not necessarily contain fluorine ions. If a fluorine-containing substance is used as a neutralizing agent, this substance dissolves in the fluorine adsorption iron solution, so that fluorine ions are eluted in the fluorine adsorption iron solution. And this fluorine ion is adsorbed by the iron deposit which precipitates.

  The neutralizing agent used in Step B is not particularly limited as long as it can be adjusted to the target pH. That is, it can be used regardless of whether fluorine is contained or not contained as described above. However, the use of an alkaline earth metal or the like that reacts with a sulfate group in a solution to form a precipitate, such as Ca, is not preferable because the amount of residue increases.

  The liquid temperature during neutralization is preferably set to a higher temperature in order to improve the filterability of the fluorine-adsorbed iron precipitate. For example, the temperature is set to 60 ° C to 80 ° C. In general physical adsorption, the adsorption capacity tends to decrease as the temperature rises. However, the adsorption of fluorine by iron precipitate is chemical adsorption, so it is less affected by the temperature during the adsorption operation than physical adsorption. .

  The target pH for neutralization is set to 3.5 to 4.5 at which zinc precipitate formation does not occur, and a reaction residence time of about 60 minutes to 120 minutes can be taken to complete the iron precipitate formation reaction sufficiently. preferable.

  For the neutralization in Step B, a zinc-containing material containing fluorine can be suitably used. When a fluorine-containing solid is used as a neutralizing agent, the solid dissolves and the fluorine ionizes and elutes. At the same time, the pH around the eluted region rises, an iron precipitate is formed, and the adsorption of fluorine occurs. Occur. Therefore, in the wet zinc smelting process, crude zinc oxide containing fluorine can be suitably used. When crude zinc oxide is used directly as a neutralizing agent, it is stored in a container or the like and added while monitoring the pH change of the fluorine adsorption iron solution using a vibration feeder or the like. Further, the crude zinc oxide can be mixed with a fluorine removing liquid or water and used as a slurry. Moreover, not only solid but the alkaline solution containing a fluorine ion and zinc ion can also be used as a neutralizing agent.

  Step C is a fluorine removal liquid recovery process in which the fluorine coprecipitation slurry obtained in Step B is separated into a fluorine removal liquid and a fluorine adsorbed iron precipitate. In Step C, a method that allows easy handling of the separated solid material may be used. In order to increase the recovery rate of the fluorine removing liquid, it is preferable to use a filtration device such as a filter press. However, if the fluorine-adsorbed iron precipitate obtained here is used again as an iron raw material for fluorine adsorption, the fluorine co-precipitation slurry may only be concentrated. If the fluorine coprecipitation slurry is concentrated using a thickener or the like and the bottomed sludge is sent to the next process, the equipment can be made inexpensive.

  Furthermore, the fluorine removing liquid obtained in Step C of the nth cycle can also be used in one or both of Step A of the (n-1) cycle and Step B of the (n-1) cycle. . If the fluorine removal liquid obtained in the nth cycle is added to the iron solution for fluorine adsorption in step A of the (n-1) th cycle, the iron concentration and fluorine concentration in the iron solution for fluorine adsorption can be adjusted. In Step B of the (n-1) th cycle, a fluorine removing liquid can be used as a liquid for slurrying crude zinc oxide used as a neutralizing agent.

  In order to facilitate understanding of the process flow described above, the flow sheet of the adsorption treatment applied to the wet zinc smelting process is shown in FIG. 1, and the process flow is clarified below with reference to FIG. . In the process shown in FIG. 1, the adsorption operation is performed in two cycles. The first cycle is a step of adjusting the fluorine concentration in the process liquid for wet zinc smelting to a target value, and is referred to as “main adsorption step”. The second cycle is a step of adjusting in advance the fluorine concentration in the wet zinc smelting process liquid in which the fluorine is adsorbed in the main adsorption process, and is referred to as a “pre-adsorption process”.

  The iron compound used in the preparation of the iron solution (I) for fluorine adsorption in the main adsorption step (first cycle) is an undissolved residue. First, an undissolved residue is dissolved in a sulfuric acid acidic solution to obtain a zinc ferrite extract (hereinafter referred to as “ZF solution”). And this ZF liquid and the fluorine removal liquid (II) obtained by the prior adsorption process (2nd cycle) are mixed, and the iron solution (I) for fluorine adsorption used by this adsorption process (1st cycle) is prepared. . Then, this zinc adsorption iron solution (I) is neutralized by adding crude zinc oxide or the like to obtain a fluorine coprecipitation slurry (I) in which fluorine is adsorbed on the iron precipitate that is precipitated and precipitated. This fluorine coprecipitation slurry (I) is subjected to solid-liquid separation to obtain a fluorine removal liquid (I) and a fluorine-adsorbed iron precipitate (I).

  In the pre-adsorption step (second cycle), the fluorine-adsorbed iron precipitate (I) obtained in the main adsorption step (first cycle) is dissolved in a sulfuric acid acidic solution to obtain a fluorine-adsorbed iron solution (I). obtain. This fluorine-adsorbed iron solution (I) becomes a basic solution for preparing the fluorine-adsorbing iron solution (II). Therefore, the iron solution (II) for fluorine adsorption when the basic solution is used as it is is the fluorine-adsorbed iron solution (I) itself. The fluorine-adsorbing iron solution (I) can be mixed with a fluorine removing liquid obtained in a subsequent step as necessary to obtain a fluorine-adsorbing iron solution (II).

  Crude zinc oxide or the like is added to the thus prepared iron solution for adsorption of fluorine (II) for neutralization to obtain a fluorine coprecipitation slurry (II) in which fluorine is adsorbed on the iron precipitate that precipitates and precipitates. This fluorine coprecipitation slurry (II) is subjected to solid-liquid separation to obtain a fluorine removal liquid (II) and a fluorine-adsorbed iron precipitate (II). In the two-cycle operation shown in FIG. 1, the fluorine removal liquid (II) is further subjected to an adsorption treatment of fluorine in the solution in the main adsorption step (first cycle). Then, the fluorine-adsorbed iron precipitate (II) is extracted out of the process.

  In the above description, the case of two cycles has been described along the flow sheet, but the number of cycles can be further increased. For example, if the number of cycles is 3, a step similar to the pre-adsorption step (second cycle) of the flow sheet shown in FIG. 1 may be added as a third cycle that is performed following the second cycle. In this case, a fluorine-adsorbed iron solution (II) obtained by dissolving a fluorine-adsorbed iron precipitate (II) in a sulfuric acid acidic solution is used as the basic solution for the iron solution (III) for fluorine adsorption in the third cycle. Then, the fluorine removing liquid (III) obtained in the third cycle is mixed with the iron solution (II) for fluorine adsorption in the second cycle.

  As described above, in the fluorine removal process according to the present invention, the more the stage of the treatment process, the easier the management of the fluorine concentration of the process liquid for wet zinc smelting. As a result, in the first cycle, the fluorine concentration in the fluorine removing liquid obtained after Step C can be stably set to 20 mg / L or less.

  In the example, the fluorine adsorption operation was performed in two cycles of the main adsorption step (first cycle) and the pre-adsorption step (second cycle) in the same manner as in FIG.

<Preparation of ZF solution>
1000 g of undissolved residue and 4.0 L of electrolytic tail solution were mixed and stirred at 90 ° C. for 4 hours to extract zinc ferrite contained in the undissolved residue. Then, after confirming that the iron concentration reached the maximum value, solid-liquid separation was performed to obtain 3.8 L of ZF solution. The ZF liquid obtained by repeating this operation 12 times was mixed to prepare ZF liquids used in the following Examples and Comparative Examples. Table 1 shows the composition of the ZF solution after mixing and the component contents of the crude zinc oxide (I) and crude zinc oxide (II) used in the subsequent steps. As shown in Table 1, the fluorine concentration in the ZF solution was 12.7 mg / L, the iron concentration was 25.1 g / L, and the zinc concentration was 83.7 g / L. Moreover, the fluorine content of crude zinc oxide (I) was 0.05 wt%, and the fluorine content of crude zinc oxide (II) was 0.13 wt%.

<Initial preparation of fluorine-adsorbed iron precipitate (I)>
As preparation for repeating two cycles, a fluorine-adsorbed iron precipitate (I) was prepared.

  First, 2.0 L of neutral Th / OF solution was added to the neutralization tank, and the solution temperature was maintained at 80 ° C. and stirred. In this neutralization tank, the ZF solution obtained above was used as an iron solution (I) for fluorine adsorption at 20 mL / min. Added at. At the same time, crude zinc oxide (I) slurried with pure water was added to the neutralization tank to maintain the pH at 3.7. Then, 270 minutes after the start of the addition, the neutral Th / OF in the neutralization tank is replaced with the added fluorine adsorption iron solution (I) and the like, and the formation of the fluorine adsorbed iron precipitate (I) is formed. It was judged that the steady state was reached.

  After reaching the steady state as described above, as shown in FIG. 2, the addition of the ZF liquid and the crude zinc (I) slurry to the neutralization tank is continued, and the liquid level of the neutralization tank is kept constant. Thus, the fluorine coprecipitation slurry (I) was extracted from the bottom of the neutralization tank using a metering pump. The fluorine coprecipitation slurry (I) extracted from the neutralization tank in a steady state during this period was subjected to solid-liquid separation using a Nutsche to obtain a fluorine-adsorbed iron precipitate (I) and a fluorine removal liquid (I). Hereinafter, the first fluorine pre-adsorption process → the first fluorine main adsorption process → the second fluorine pre-adsorption process → the second fluorine main adsorption process → the third fluorine pre-adsorption process → the third fluorine main adsorption process The process of adsorbing and removing fluorine will be described.

<First fluorine pre-adsorption treatment>
In the first pre-adsorption treatment, the fluorine-adsorbed iron precipitate (I) was used. This fluorine-adsorbed iron precipitate (I) is dissolved in an electrolytic tail solution at room temperature for 6 hours to prepare a fluorine-adsorbed iron solution (I-1), which is then prepared as an iron solution for fluorine adsorption (II-1). It was. First, 1.0 L of neutral Th / OF was added to the neutralization tank, and the liquid temperature was maintained at 80 ° C. and stirred. In this neutralization tank, the iron solution (II-1) for fluorine adsorption was 10 mL / min. At the same time, crude zinc oxide (II) slurried with pure water was added to maintain the pH at 3.7. 270 minutes after the start of the addition, the neutral Th / OF in the neutralization tank is replaced with the added fluorine adsorption iron solution (II) and the like, and the formation of the fluorine adsorbed iron precipitate (II) is steady. Judged that the condition was reached. After reaching the steady state, the pre-adsorption step shown in FIG. 3 is performed. Continue to add the iron solution (II) for fluorine adsorption to the neutralization tank and the crude zinc oxide (II) slurry, and use a metering pump to neutralize the liquid level in the neutralization tank. The fluorine coprecipitation slurry (II) was extracted from the bottom of the tank. Fluorine coprecipitation slurry (II) extracted from the neutralization tank in a steady state during this period is solid-liquid separated using a Nutsche, and the fluorine adsorbed iron precipitate (II-1) and fluorine removal liquid in the first pre-adsorption treatment (II-1) was obtained.

<First fluorine main adsorption treatment>
In the first fluorine main adsorption treatment, the fluorine removal liquid (II-1) and the ZF liquid were mixed to prepare a fluorine adsorption iron solution (I-1). Then, 2.0 L of neutral Th / OF was added to the neutralization tank, and the liquid temperature was maintained at 80 ° C. and stirred. In this neutralization tank, the iron solution (I-1) for fluorine adsorption is 20 mL / min. At the same time, crude zinc oxide (I) slurried with pure water was added to maintain the pH at 3.7. 270 minutes after the start of the addition, the neutral Th / OF in the neutralization tank is replaced with the added iron solution for fluorine adsorption (I-1) and the like, and the fluorine adsorbed iron precipitate (I-1) Was judged to have reached a steady state.

  After reaching the steady state, the main adsorption step shown in FIG. 3 is performed. In order to continue the addition of the iron solution for fluorine adsorption (I-1) and the crude zinc oxide (I) slurry to the neutralization tank and maintain the liquid level of the neutralization tank constant, using a metering pump, The fluorine coprecipitation slurry (I) was extracted from the bottom of the neutralization tank. The amount of ZF solution used for the addition for 300 minutes after reaching the steady state was 4.4 L, the amount of fluorine removal solution (II-1) was 1.62 L, the amount of crude zinc oxide (I) was 540 g (the amount of pure water was 1 .0L). The fluorine coprecipitation slurry (I) extracted from the neutralization tank in a steady state during this period was subjected to solid-liquid separation using a Nutsche, and 7.1 L of a fluorine removal liquid (I-1) and a fluorine-adsorbed iron precipitate (I-1) ) To obtain 610 g.

<2nd fluorine pre-adsorption treatment>
In the second fluorine pre-adsorption treatment, the fluorine-adsorbed iron precipitate (I-1) was dissolved in an electrolytic tail solution to prepare a fluorine-adsorbed iron solution (I-2). And it implemented similarly to the 1st fluorine preadsorption process except having used the said fluorine adsorption iron solution (I-2) as an iron solution (II-2) for fluorine adsorption.

  In the second fluorine pre-adsorption treatment, the amount of the fluorine-adsorbed iron precipitate (I-1) used for the addition for 200 minutes after reaching the steady state was 510 g, the electrolytic tail solution was 1.8 L, and the crude zinc oxide The amount of (II) was 260 g (the amount of pure water was 0.24 L). The fluorine coprecipitation slurry (II) extracted from the neutralization tank during this steady state was subjected to solid-liquid separation using a Nutsche, and 1.66 L of fluorine removal liquid (II-2) and fluorine adsorbed iron precipitate (II) -2) 540 g was obtained.

  Following the second fluorine pre-adsorption treatment, the second main adsorption treatment using the fluorine removal liquid (II-2) and the ZF liquid, and the third pre-treatment using the fluorine-adsorbed iron precipitate (I-2). The adsorption treatment and the third main adsorption treatment using the fluorine removing liquid (II-3) and the ZF liquid were carried out in the same procedure as described above. That is, in this example, the main adsorption process and the pre-adsorption process were each performed three times in total. The description of specific implementation details regarding the processes after the second main adsorption process is omitted to avoid duplication of explanation.

  As a result of carrying out the three repeated tests, the fluorine concentrations of the fluorine removal solution (I) were 16 mg / L, 15 mg / L, and 17 mg / L, respectively, and the target was achieved. And the fluorine concentration of fluorine removal liquid (II) was 41 mg / L, 45 mg / L, and 48 mg / L, respectively. The zinc concentration in these liquids was 139 g / L on average for the fluorine removal liquid (I) and 146 g / L on average for the fluorine removal liquid (II). The results are summarized in Table 2.

  In addition, the fluorine content of the fluorine-adsorbed iron precipitate (I) is 0.046 wt%, 0.043 wt%, and 0.039 wt%, respectively, and the iron content is 19.9 wt%, 20.5 wt%, It was 20.4 wt%. And fluorine content of fluorine adsorption iron precipitate (II) is 0.093 wt%, 0.098 wt%, 0.098 wt%, respectively, and iron content is 16.0 wt%, 15.8 wt%, 15. It was 5 wt%. The results are summarized in Table 3.

  From the above results, the amount of iron (g) required to adsorb 1 g of fluorine when the treatment process according to the present invention is carried out is calculated and shown in Table 4.

<Iron fluoride adsorption capacity>
From Table 4 above, the [Fe (g) / F (g)] ratio of the fluorine-adsorbed iron precipitate (II) finally extracted out of the process when the iron introduced into the fluorine adsorption process adsorbs fluorine is: The average is 164. The amount of fluorine adsorbed by 1 g of iron obtained by back calculation is 6.1 mg.

Comparative example

  In the comparative example, a method of using an individual fluorine adsorbent in a process corresponding to the second cycle of the present invention and adsorbing and removing fluorine from a solution containing fluorine was adopted. In the comparative example, in order to avoid confusion with each adsorption treatment process of the embodiment, a process corresponding to the pre-adsorption process of the second cycle of the present invention is referred to as “fluorine initial adsorption process”, and the main adsorption process of the first cycle. The process corresponding to is called “fluorine final adsorption treatment”. And the fluorine adsorption iron precipitate (I) obtained at the fluorine final adsorption treatment process was used for the fluorine adsorption agent of the solid.

<Fluorine final adsorption treatment>
In the final fluorine adsorption treatment, 2.0 L of neutral Th / OF solution was added to the neutralization tank, and the solution temperature was maintained at 80 ° C. and stirred. To this neutralization tank, the ZF solution, the fluorine removing solution (II) obtained by the fluorine initial adsorption treatment and the crude zinc oxide (I) slurried with pure water were added to maintain the pH at 3.7. Then, 270 minutes after the start of the addition, the neutral Th / OF in the neutralization tank and the added fluorine adsorption iron solution are exchanged, and the formation of the fluorine adsorbed iron precipitate (I) is in a steady state. Judged to have reached.

  After reaching the steady state, the fluorine final adsorption treatment step shown in FIG. 4 is performed. Continue to add ZF liquid, fluorine removal liquid (II) and crude zinc oxide (I) slurried with pure water to the neutralization tank, and keep the liquid level in the neutralization tank constant. Using, the fluorine coprecipitation slurry was extracted from the bottom of the neutralization tank. The amount of ZF solution used for addition for 300 minutes after reaching the steady state was 4.5 L, the amount of fluorine removing solution (II) was 1.7 L, and the amount of crude zinc oxide (I) was 584 g. Then, the fluorine coprecipitation slurry extracted from the bottom of the neutralization tank for 300 minutes is subjected to solid-liquid separation using a Nutsche to obtain 582 g of fluorine adsorbed iron precipitate (I) and 7.2 L of fluorine removal liquid (I). It was. The fluorine removal solution (I) had a fluorine concentration of 19.0 mg / L and a zinc concentration of 115 g / L. Moreover, the fluorine content of the fluorine-adsorbed iron precipitate (I) was 0.055 wt%, and the iron content was 21.2 wt%. The results are summarized in Table 5.

<Fluorine initial adsorption treatment>
As the liquid to be subjected to the fluorine initial adsorption treatment, a crude zinc oxide solution (hereinafter referred to as “mother liquid”) prepared by dissolving 300 g of crude zinc oxide (II) in 1.7 L of electrolytic tail liquid is used. It was. As shown in Table 6, the fluorine concentration of the mother liquor was 229 mg / L.

  In the fluorine initial adsorption treatment, 1.7 L of mother liquor and 572 g of fluorine adsorbed iron precipitate (I) were mixed, and the fluorine adsorption operation was performed while stirring at 60 ° C. After the adsorption operation for 90 minutes, the mixed slurry was subjected to solid-liquid separation using a Nutsche to obtain a fluorine removing liquid (II) and a fluorine-adsorbed iron precipitate (II). The fluorine removal solution (II) had a fluorine concentration of 80.0 mg / L and a zinc concentration of 155 g / L. And fluorine content of fluorine adsorption iron precipitate (II) was 0.086 wt%, and iron content was 20.7 wt%. Table 7 summarizes the results and the [Fe (g) / F (g)] ratio of the fluorine-adsorbed iron precipitate (II) obtained by calculation.

<Iron fluoride adsorption capacity>
In the comparative example, the iron introduced into the fluorine adsorption process adsorbs fluorine, and the [Fe (g) / F (g)] ratio of the fluorine adsorbed iron precipitate (II) finally extracted out of the process is 241. Met. In reverse calculation, the amount of fluorine adsorbed by 1 g of iron is 4.1 mg. In the example, 1 g of iron adsorbs 6.1 mg of fluorine, and the fluorine adsorption capacity of the iron precipitate in the example is about 1.5 times that of the comparative example.

<Contrast between Example and Comparative Example>
In both the example and the comparative example, two cycles of adsorption were performed, and the target of setting the fluorine concentration in the process solution for wet zinc smelting to 20 mg / L or less could be achieved. However, in comparison with the fluorine adsorption capacity of iron, the amount of fluorine adsorbed by 1 g of iron is 6.1 mg in the example compared to 4.1 mg in the comparative example, which is increased by about 1.5 times. Therefore, the superiority of the method of adsorbing fluorine while forming an iron precipitate, which is a process according to the present invention, is clear.

  Although the contents of the present invention have been specifically shown in the above embodiments and examples, those skilled in the art can easily make various arrangements based on the basic idea and teaching of the present invention. For example, it does not necessarily mean that crude zinc oxide must be used in the neutralization step. In addition, when implemented on a pilot scale or mass production scale, there may be some variation in parameters and various conditions. Therefore, the present invention is not limited to the conditions of the embodiments described above.

  If the fluorine removal method according to the present invention is used, the fluorine concentration of the process liquid for wet zinc smelting can be stably reduced to 20 mg / L or less. This is because the adsorption sites of the adsorbent can be utilized to the maximum because fluorine ions are adsorbed and co-precipitated on the iron precipitate to be deposited. Moreover, since the iron precipitate which adsorb | sucked fluorine is used as an iron raw material for fluorine adsorption in multiple times, the fluorine adsorption capability which an iron precipitate has can be utilized effectively to the maximum. Moreover, in the said wet zinc smelting process, it can use as a raw material of the iron compound which uses the undissolved residue containing the zinc ferrite generated in a self process as a fluorine adsorbent. Furthermore, the operations to be performed are mainly dissolution, neutralization, and solid-liquid separation, and should be used effectively as a technique for managing the fluorine concentration in the process liquid for wet zinc smelting, without the need for a new process. It is a method that can be. And if an industrial chemical level thing is used for an iron compound and a sulfuric acid acidic solution, it is applicable also to processing of the waste water etc. which contain fluorine.

It is a flow sheet in a steady state when the process of removing fluorine from the process liquid for wet zinc smelting according to the present invention is performed in two cycles. In an Example, it is the flow sheet in the steady state applied to the preforming of the fluorine adsorption iron precipitate (I) used by a 2nd cycle. It is the flow sheet in the steady state applied to the Example. It is the flow sheet in the steady state applied to the comparative example.

Claims (4)

A method of removing fluorine from a process liquid for wet zinc smelting using an iron precipitate as an adsorbent to adsorb and remove fluorine,
The following Step A to Step C are defined as one cycle, and this one cycle is used in Step A of the nth cycle of the process of removing fluorine by repeating a plurality of cycles (1st cycle to nth cycle: where n ≧ 2). The method for removing fluorine from a process liquid for wet zinc smelting, wherein the iron compound is a fluorine-adsorbed iron precipitate obtained in Step C of the (n-1) th cycle.
Step A: A fluorine adsorption iron solution preparation step in which an iron compound is dissolved in a sulfuric acid acidic solution to obtain a fluorine adsorption iron solution.
Step B: A fluorine coprecipitation step of obtaining a fluorine coprecipitation slurry in which the iron solution for fluorine adsorption is neutralized to form an iron precipitate and adsorbed and coprecipitated on the iron precipitate that deposits fluorine ions in the solution.
Step C: Fluorine removal liquid recovery step of separating the fluorine coprecipitation slurry obtained in Step B into a fluorine removal liquid and a fluorine adsorbed iron precipitate. The iron solution for fluorine adsorption prepared in Step A of the first cycle uses an electrolytic tail solution as the sulfuric acid acidic solution, and uses an undissolved residue as the iron compound, and converts the iron and zinc contained in the undissolved residue into an electrolytic tail. The method for removing fluorine according to claim 1, which is extracted into a liquid. The fluorine removal method according to claim 1 or 2, wherein a zinc-containing material containing fluorine is used for neutralization in the step B. The fluorine removing liquid obtained in Step C of the nth cycle is used in one or both of Step A of the (n-1) cycle and Step B of the (n-1) cycle. Item 4. The method for removing fluorine according to any one of Items 3 to 4.

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