JP2017185440A - Heavy metal removal agent, method for production of flocculant for heavy metal removal and treatment method for raw material liquid including heavy metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heavy metal removal agent, a method for production of a flocculant for heavy metal removal, and a treatment method for a raw material liquid including heavy metals.SOLUTION: An objective heavy metal removal agent is a liquid mixture of ferric compounds such as poly(ferric sulfate) and an alkali aqueous solution such as aqueous sodium hydroxide. The hydrogen-ion exponent of the liquid mixture is preferably 8 to 12. A flocculant for heavy metal removal is prepared by blending the ferric compounds such as poly(ferric sulfate) and the alkali aqueous solution such as aqueous sodium hydroxide. The hydrogen-ion exponent at preparation is preferably 8 to 12. A treatment method for a raw material liquid comprises adding a flocculant to the raw material liquid including heavy metals, and precipitating the flocculant to generate a supernatant and a precipitate. The flocculant brings in the heavy metal included in the raw material liquid to be precipitated.SELECTED DRAWING: None

Description

  The present invention relates to a heavy metal removing agent, a method for producing a heavy metal removing flocculant, and a method for treating a raw material liquid containing heavy metal. More specifically, the present invention relates to a heavy metal removing agent that is a mixed solution of an iron-based compound and an aqueous alkaline solution, a method for producing a heavy metal removing flocculant that is prepared by mixing an iron-based compound and an aqueous alkaline solution in a predetermined amount ratio, Further, the present invention relates to a processing method for a raw material liquid containing a heavy metal, in which a flocculant prepared by mixing an iron-based compound and an alkaline aqueous solution is added to a raw material liquid containing heavy metal, and the flocculant incorporating the heavy metal is precipitated.

  Conventionally, useful inorganic salts that can be used as raw materials in various applications have been recovered by treating waste liquid containing such inorganic salts. In this case, heavy metals such as lead contained in the waste liquid It is necessary to remove impurities such as. For example, a flocculant such as polyiron is added to mirabilite waste liquid, and then the hydrogen ion index (hereinafter also referred to as pH) is adjusted and allowed to stand to precipitate the flocculant that has incorporated impurities. Then, the method of collect | recovering inorganic salts from the supernatant liquid from which impurities were removed by solid-liquid separation is mentioned.

  Moreover, in order to recycle slag, a method of deleading molten slag is known (for example, refer to Patent Document 1). In this treatment method, molten slag containing lead is immersed in water under alkaline conditions, and then adjusted to pH 9 to 12 with an alkali. Then, an iron compound is added to elute lead, and the eluted lead is converted into iron. Adsorption and aggregation are performed by the cohesive force of the compound. Further, NaOH and the like are exemplified as the alkali agent, and iron-based inorganic flocculants such as polyiron are exemplified as the iron-based compound. However, the technique described in Patent Document 1 is a method of deleading molten slag. After adjusting the pH of the molten slag soaked with alkali to pH 9-12, an iron compound is added to elute lead. I am letting.

JP 2001-89203 A

  The above-mentioned method for treating and recovering waste liquids containing useful inorganic salts is advantageous in terms of cost compared to the use of other expensive heavy metal removal agents. It takes a long time to make it happen, and it cannot be said that it is efficient. In addition, the aggregate floc floats in the supernatant after sedimentation of the aggregate by standing, the recovery yield of the inorganic salt aqueous solution by solid-liquid separation is low, and the aggregate floc may be mixed into the inorganic salt aqueous solution. . Furthermore, in order to remove the aggregate floc floating in the supernatant, filtration equipment such as a filter press is required for solid-liquid separation, and the amount of sludge is increased by using a filter aid, and a large amount of equipment is used. There are also problems such as costs.

Further, when metal ions such as iron and aluminum are diluted and dispersed at a high magnification and then neutralized, the produced hydroxide is usually fine colloidal particles. Further, the resulting hydroxides are polymerized by olation reaction ^{(~ Fe- (OH) -Fe ~} ), a three-dimensional gel structure. And by neutralizing with a high concentration in a high alkali region, agglomeration between colloidal particles and dehydration reaction by oxolation reaction ( ^~ Fe-O-Fe ^~ ) proceed, depending on the reaction temperature etc. It is presumed that particles are generated.

  During the above-mentioned particle generation, particles that grow large and have a large diameter settle quickly, but particles with a small diameter require a long time to settle and may float in the supernatant. This is presumably because large-growth particles settle quickly, but small-diameter particles have a small specific surface area and poor adsorption capacity, so that they cannot settle by entraining fine particles.

  As described above, in order to solve the problem that it takes a long time to settle the aggregates by standing and the efficiency is low, polyferric sulfate is added to the raw liquid such as a waste liquid containing a useful inorganic salt. Instead of adding an iron-based compound such as, and then adjusting the pH, the inventors focused on using an aggregating agent in which an alkali was added to the iron-based compound and the pH was adjusted in advance. That is, as described in Patent Document 1, after adjusting the pH to 9 to 12 with an alkali, the iron compound is not added, but by adding a flocculant whose pH is adjusted in advance to the raw material liquid, impurities are removed. It was thought that it could be settled quickly and efficiently.

  Furthermore, as described above, the small-diameter particles generated by the oleation reaction and the coagulation between the colloidal particles and the oxolation reaction take a long time to settle and float in the supernatant. Here, by adding an additional iron-based compound such as polyferric sulfate, a small amount of a gel-like material entrains and settles, so that a clear supernatant can be obtained in a short time. It was found that it was possible.

  The present invention has been made in view of the above-described conventional situation. A heavy metal removing agent obtained by previously mixing an iron-based compound and an alkaline aqueous solution, an iron-based compound and an alkaline aqueous solution, and particularly having a pH within a predetermined range. Add a flocculant prepared by mixing an iron-based compound and an aqueous alkali solution to a raw material liquid containing heavy metals such as lead, and then take in the heavy metals. It is an object of the present invention to provide a method for treating a raw material liquid containing heavy metal that causes the flocculant to settle and remove heavy metals from the raw material liquid.

The present invention is as follows.
1. A heavy metal removing agent, which is a mixed solution of an iron-based compound and an alkaline aqueous solution.
2. 1. The hydrogen ion index of the mixed solution is 8-12. The heavy metal removing agent described in 1.
3. A method for producing a flocculant used for heavy metal removal,
A method for producing an aggregating agent for removing heavy metals, comprising mixing an iron-based compound and an aqueous alkali solution in a predetermined amount ratio to prepare the aggregating agent.
4). 2. The hydrogen ion index of 8-12 at the time of the adjustment. The manufacturing method of the flocculant for heavy metal removal as described in any one of.
5. A method of processing the raw material liquid, wherein a flocculant is added to a raw material liquid containing heavy metal, the flocculant is precipitated, and a supernatant and a precipitate are generated.
The coagulant is prepared by mixing an iron-based compound and an alkaline aqueous solution at a predetermined ratio, and takes in and settles the heavy metal contained in the raw material liquid.
6). 4. The hydrogen ion index of 8 to 12 at the time of the adjustment. The processing method of the raw material liquid containing the heavy metal of description.
7). After the supernatant and the sediment are generated, the iron-based compound is additionally added. Or 6. The processing method of the raw material liquid containing the heavy metal of description.

In the heavy metal removing agent of the present invention, an iron-based compound and an alkaline aqueous solution are mixed, and when added to a liquid containing heavy metal, the heavy metal can be taken in and efficiently removed.
Moreover, when the hydrogen ion index of a liquid mixture is 8-12, heavy metal is fully taken in and can be removed more efficiently.
In the method for producing a heavy metal removing flocculant according to the present invention, the flocculant is produced by previously mixing an iron-based compound and an aqueous alkali solution. Therefore, when the flocculant is added to the liquid containing the heavy metal, the heavy metal is taken in and quickly collected. It is possible to efficiently remove heavy metals that have settled in the liquid and contained in the liquid.
Moreover, when the hydrogen ion index is set to 8 to 12 when adjusting the flocculant, the flocculant that has taken in the heavy metal settles more quickly, and the heavy metal can be more efficiently removed.
In the method for treating a raw material liquid containing heavy metal according to the present invention, an aggregating agent in which an iron-based compound and an alkaline aqueous solution are mixed in advance is used. Therefore, the aggregating agent incorporating the heavy metal contained in the raw material liquid quickly settles, Heavy metals contained in the liquid can be efficiently removed.
Moreover, when the hydrogen ion index is set to 8 to 12 when adjusting the flocculant, the flocculant that has taken in the heavy metal settles more quickly, and the heavy metal can be more efficiently removed.
Furthermore, after adding supernatant and sediment, when adding an iron-based compound, flocculent flocs floating in the supernatant can be easily settled. The heavy metal that has been removed can be removed more efficiently. Further, when separating the supernatant and the sediment, a specific filtration facility such as a filter press is not required, and solid-liquid separation can be easily performed by a normal method such as membrane separation. Furthermore, since solid-liquid separation can be easily performed without using a filter aid, there is no increase in the amount of sludge, and it is advantageous in terms of processing cost in addition to the fact that a filter press or the like is not required.

The present invention will be described in detail below.
[1] Heavy metal removing agent The heavy metal removing agent of the present invention is a mixed solution of an iron-based compound and an alkaline aqueous solution. Thus, the iron-based compound and the alkaline aqueous solution are mixed in advance, and this mixed solution is used as a heavy metal removing agent.

  The iron compound is not particularly limited, and various iron compounds can be used. Examples of the iron-based compound include polyferric sulfate, ferric sulfate, ferrous sulfate, ferrous chloride, ferric chloride, ferrous hydroxide, and ferric hydroxide. Among these iron-based compounds, polyferric sulfate, ferric sulfate and ferrous sulfate are preferable, and polyferric sulfate capable of forming a flocculant that takes in heavy metals and quickly settles is more preferable. . In addition, a sulfate-based compound hardly corrodes a metal unlike a compound having chlorine.

  The alkaline aqueous solution is used to adjust the pH of the mixed solution. The pH of the mixed solution, that is, the heavy metal removing agent is preferably 8 to 12, more preferably 8 to 11, and particularly preferably 9 to 11. If it is pH of such a numerical range, when a heavy metal removal agent is used as a flocculant for removing heavy metal, it can be set as the flocculant which takes in heavy metal fully and precipitates quickly.

  The alkali used in the aqueous alkali solution is not particularly limited, and examples thereof include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide. The alkali is preferably an alkali that can be easily neutralized with a small amount so that the pH of the mixed solution falls within the above numerical range. That is, it is preferable to use an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, particularly an aqueous sodium hydroxide solution for neutralization. Further, the concentration of alkali in the aqueous solution is not particularly limited. For example, in the case of a sodium hydroxide aqueous solution, a 48% by mass aqueous solution that is usually supplied and distributed can be used.

  The mixing method of the iron-based compound and the alkaline aqueous solution is not particularly limited, but the total amount of each of the iron-based compound and the alkaline aqueous solution is not mixed at once, for example, while stirring the mixed solution of the alkaline aqueous solution into the iron-based compound. It is preferable to mix. Furthermore, as for an iron-type compound, polyferric sulfate is a liquid, but others are solid. These iron-based compounds may be mixed with an alkaline aqueous solution as they are, or may be used as an iron-based compound aqueous solution by adding water, but a solid iron-based compound is particularly preferably used as an aqueous solution.

  Moreover, when using an iron-type compound previously as aqueous solution, the density | concentration is not specifically limited, Even if it is a high concentration, the performance as a heavy metal removal agent does not fall. On the other hand, when a heavy metal removing agent is used as a flocculant, the amount of water added to the iron-based compound is about equal to or less than that of the iron-based compound in terms of being able to quickly settle the flocculant incorporating impurities. And a small amount.

  Furthermore, at the time of mixing, depending on the type of the iron-based compound and the concentration of the iron-based compound aqueous solution, the mixed solution may generate heat and the temperature may rise. And when not raising temperature, you may heat a mixed liquid and raise it. However, the temperature range of the mixed solution is preferably 50 to 90 ° C, particularly preferably 70 to 90 ° C. When the temperature of the mixed solution is 50 to 90 ° C., particularly 70 to 90 ° C., when the heavy metal removing agent is used as the flocculant, the flocculant can be precipitated more quickly. Although the heating time is not particularly limited, it is preferable to keep the above-mentioned preferable temperature range for a longer time because the effect of heating is not sufficiently exhibited in a short time.

[2] Method for Producing Heavy Metal Removal Flocculant The method for producing a heavy metal removal flocculant of the present invention is a method for producing a flocculant used for heavy metal removal. In addition, the coagulant is prepared by mixing an iron-based compound and an aqueous alkali solution in a predetermined amount ratio.
Types of iron compounds used for the preparation of flocculants and preferred iron compounds, types of alkali used in alkaline aqueous solutions, preferred alkalis and alkali concentrations of alkaline aqueous solutions, mixing methods of iron compounds and alkaline aqueous solutions, and temperature during mixing With regard to, the description relating to each of the above [1] heavy metal removing agent can be applied as it is.

  The iron-based compound and the alkaline aqueous solution are mixed and prepared at a predetermined ratio. This predetermined ratio means that the iron-based compound and the alkali are easily and sufficiently dissolved in water, respectively. Especially, the pH of the mixed solution, that is, the flocculant used for heavy metal removal is 8 to 12, more preferably 8 to 11. In particular, it means that the quantity ratio is 9 to 11. If the flocculant has a pH in such a numerical range, when used as a flocculant for removing heavy metals, the flocculant can take in heavy metals and quickly settle.

  Moreover, it is preferable to set the aging time after mixing the iron-based compound and the aqueous alkali solution to prepare the flocculant. As a result, it is possible to minimize the amount of sediment formed from the flocculant that has taken in and settled heavy metal, that is, sludge. The aging time is not particularly limited, but it is preferable to ripen the flocculant for 0.5 to 48 hours, particularly 0.5 to 36 hours. Furthermore, the temperature at the time of aging is not particularly limited, but is preferably 20 to 100 ° C, particularly 20 to 90 ° C, and may be heated if necessary.

[3] Method for treating raw material liquid containing heavy metal In the method for treating a raw material liquid containing heavy metal according to the present invention, a flocculant is added to a raw material liquid containing heavy metal, the flocculant is allowed to settle, and a supernatant and a sediment are obtained. Is a processing method of the raw material liquid for generating. In addition, the flocculant is prepared by mixing an iron-based compound and an aqueous alkali solution at a predetermined amount ratio, and takes in and precipitates the heavy metal contained in the raw material liquid.
Types of iron compounds used for the preparation of flocculants and preferred iron compounds, types of alkali used in alkaline aqueous solutions, preferred alkalis and alkali concentrations of alkaline aqueous solutions, mixing methods of iron compounds and alkaline aqueous solutions, and temperature during mixing With regard to, the description relating to each of the above [1] heavy metal removing agent can be applied as it is.

  As a raw material liquid containing a heavy metal, an aqueous solution containing a useful inorganic salt is preferable. Heavy metals are mixed as impurities in the raw material liquid. By treating this raw material liquid, heavy metals are removed or at least reduced, and useful inorganic salts with high purity can be recovered. A heavy metal is a metal element having a specific gravity of 4 to 5 or more, and is usually a metal element having a specific gravity of iron or more, and examples thereof include iron, lead, antimony, and arsenic.

  Although the raw material liquid containing the heavy metal which is an impurity and containing a useful inorganic salt is not specifically limited, As a raw material liquid, the waste liquid containing a useful inorganic salt can be used. The waste liquid only needs to contain a useful inorganic salt, and may be a waste liquid generated in any operation process. For example, waste liquids generated by operations such as pickling and desulfurization of steel, and waste liquids such as electrolytes used for batteries and the like can be mentioned.

  In the treatment method of the present invention, the flocculant added to the raw material liquid can be quickly settled, and a supernatant liquid containing a useful inorganic salt, and a sediment composed of the flocculant that has taken in and precipitated heavy metals, Can be generated. Further, by separating the supernatant and the sediment, useful inorganic salts can be easily recovered from the supernatant, and the iron-based compound contained in the sediment can be recovered. And this collect | recovered iron-type compound can also be utilized as an iron raw material.

  Useful inorganic salts contained in the raw material liquid are not particularly limited, and examples thereof include sodium sulfate, sodium chloride, sodium sulfite, and sodium nitrite. These inorganic salts are produced when an alkaline or acidic waste liquid generated by operations such as pickling and desulfurization is neutralized with an acid or alkali, and are contained in many waste liquids. Only one of these inorganic salts may be contained in the waste liquid, or two or more thereof may be contained.

  Further, when the inorganic salt is sodium sulfate, the sodium sulfate is contained in a waste liquid obtained by neutralizing a waste liquid containing sulfuric acid with sodium hydroxide or a waste liquid obtained by neutralizing a waste liquid containing sodium hydroxide with sulfuric acid. This waste liquid is a kind of waste liquid generated in a large amount in the industry due to pickling of steel. This sodium sulfate has applications such as dye diluents, glass and pulp production, and detergent builders, and the anhydride is hygroscopic and is also used as a desiccant for organic solvents.

  As described above, sodium sulfate is useful among the inorganic salts contained in the waste liquid, and is an inorganic salt to be reused. Therefore, heavy metals such as lead contained in sodium sulfate are preferably reduced as much as possible when supplied as a diluent for dyes, etc., but according to the treatment method of the present invention, lead and the like are specified values. It can be set as the sodium sulfate reduced below.

  Furthermore, the sodium sulfate recovered from the supernatant when impurities are precipitated together with the flocculant by the flocculant is usually a decahydrate (also known as mirabilite). And by using this decahydrate to produce sodium sulfate anhydride, it is possible to obtain higher purity sodium sulfate anhydride regardless of the type of waste liquid. Moreover, the water evaporated when heat-concentrating sodium sulfate decahydrate with a small amount of impurities to recover the anhydride has high purity and can be used as a raw material for producing pure water.

  As an aggregating agent for taking in and precipitating heavy metals, an aggregating agent obtained by previously neutralizing an iron-based compound and an aqueous alkaline solution so that the pH of the mixed solution is 8 to 12, more preferably 8 to 11, and particularly 9 to 11. Is used. Moreover, the liquid temperature after adding a flocculant to a raw material liquid is although it does not specifically limit, It is preferable that it is 10-70 degreeC, especially 40-60 degreeC. If the liquid temperature after adding the flocculant to the raw material liquid is within the above range, the flocculant incorporating the heavy metal can be precipitated more rapidly. Thus, in order to bring the liquid temperature into a predetermined temperature range, it is effective to preheat a raw material liquid having a larger capacity than the flocculant if necessary.

  Moreover, the temperature of the liquid mixture when mixing an iron-type compound and aqueous alkali solution and adjusting a coagulant | flocculant is although it does not specifically limit, It is preferable that it is 70-90 degreeC. Further, as described above, if the raw material liquid is heated in advance before adding the flocculant, and a mixed liquid having a temperature of 70 to 90 ° C., that is, the flocculant is added thereto, the flocculant becomes more efficient. Can settle well.

  According to the raw material liquid treatment method of the present invention, the flocculant can be precipitated more efficiently, and useful inorganic salts contained in the raw material liquid can be recovered from the supernatant. However, in the process of adding a flocculant to a raw material liquid such as a waste liquid and allowing it to settle, normally, the aggregate floc floats in the supernatant and the aggregate floc is mixed into the supernatant when solid-liquid separation occurs.

  Therefore, solid-liquid separation is generally performed by filtering with a filter press or the like. On the other hand, according to the treatment method of the present invention, after the heavy metal is taken into the flocculant and settled, an iron-based compound is added and added to the raw material liquid, so that the aggregate floc floating in the supernatant is efficiently added. Sedimentation can be carried out well, and solid-liquid separation, which is a subsequent process, can be efficiently carried out by a simple method. When the iron-based compound is added and added in this way, the pH changes to the neutral side, and therefore an alkaline aqueous solution may be added as necessary to adjust the pH.

  Furthermore, the method of solid-liquid separation is not particularly limited, and examples thereof include various methods such as centrifugal separation and sedimentation separation. The raw material liquid in which the supernatant and sediment are generated by this separation is separated into a liquid and a solid. And useful inorganic salt can be collect | recovered from a liquid part, and the heavy metal and iron-type compound which were contained in the raw material liquid can be collect | recovered from solid content. The recovered iron-based compound can also be used as an iron raw material.

Examples of the present invention will be specifically described below, but the present invention is not limited to the following examples.
Example 1 (test for confirming the effect of the flocculant quickly settled and the addition of an iron-based compound)
A flocculant was prepared by mixing 20 milliliters of polyferric sulfate and a 48% strength by weight aqueous sodium hydroxide solution in an amount ratio such that the pH of the mixed solution was approximately 10. At the time of mixing, the temperature of the mixture was raised to around 80 ° C. Thereafter, the flocculant was added to 1 liter of water at room temperature (20 to 25 ° C.) in a beaker, and the mixture was stirred a little and allowed to stand at room temperature. Further, after 10 minutes had passed, 12 ml of polyferric sulfate was added and allowed to stand.

Comparative Example 1
20 ml of polyferric sulfate is added to 1 liter of room temperature water in a beaker, and then a 48% strength by weight aqueous sodium hydroxide solution is mixed in a quantitative ratio such that the pH of the mixture is approximately 10. The mixture was a little stirred and allowed to stand at room temperature. In Comparative Example 1, no additional ferric sulfate was added.

  The appearance of each of the treatment liquids of Example 1 and Comparative Example 1 after standing at room temperature was visually observed. As a result, immediately after standing, the appearance of the treatment liquid was black brown in the same manner as in Example 1 and Comparative Example 1. In addition, after 10 minutes, in Example 1, a considerable amount of sediment was generated, but the supernatant liquid was light brown and the flocculant floc was thought to have floated. On the other hand, in Comparative Example 1, the supernatant was clear, but the sedimentation rate was small to the extent that the upper part was slightly settled and became clear.

  Further, in Example 1, in which polyferric sulfate was added at the time when 10 minutes passed, the sedimentation was almost completed after 90 minutes, and the supernatant became lighter, and a considerable amount of flocculant floc was added. Was found to have settled. On the other hand, in Comparative Example 1, the supernatant was clarified, but only a small amount was clarified after 10 minutes, in other words, only a small amount was settled. In addition, it was found that even after 90 minutes had passed, it was about 1/3 of the total height of the liquid, it was not sufficiently settled and it was difficult to settle.

Example 2 (Evaluation when ferric chloride is used as an iron-based compound)
20 ml of ferric chloride aqueous solution prepared to contain 110 g of Fe per kg of solution and 48% by mass of sodium hydroxide aqueous solution in such a quantitative ratio that the pH of the mixed solution becomes approximately 10. A flocculant was prepared by mixing. Thereafter, the flocculant was added to 1 liter of water at room temperature (20 to 25 ° C.) in a beaker, and the mixture was stirred a little and allowed to stand at room temperature.

  In Example 2, the entire liquid was dark brown immediately after standing, but after 15 minutes, the lower part of about 10 to 15% of the total height of the liquid was dark brown, and the upper part was brown. Thus, the flocculant settled quickly and the aggregate floc was in a suspended state. Further, after 30 minutes in diameter, the upper part where the aggregate flocs floated was slightly light in color, and a part of the aggregate flocs also settled. Further, after 12 hours, most of the aggregated flocs that had floated settled, and the upper part was clear enough to feel a slight brown color.

Example 3 (Evaluation of sedimentation rate when water is not added to an iron-based compound or a predetermined amount of water is added)
Water is not added to 20 milliliters of ferric sulfate, or 20 milliliters, 60 milliliters and 140 milliliters of water are added, and a 48% strength by weight aqueous sodium hydroxide solution is added to this, and the pH of the mixture becomes approximately 10. The flocculant was prepared by mixing in such a quantitative ratio. Thereafter, this flocculant was added to 1 liter of water in a graduated cylinder and allowed to stand at room temperature for 24 hours to evaluate the sedimentation rate of the flocculant.

  As a result, the height of the sediment was 7.5% of the total height of the liquid when no water was added to the polyferric sulfate, and 8% of the total height of the liquid when 20 ml of water was added. 0.0%, when 60 ml of water was added, it was 10% of the total height of the liquid, and when 140 ml of water was added, it was 15% of the total height of the liquid. Thus, when polyferric sulfate is used, it is preferable that polyferric sulfate is used without adding water, and when adding water, it is preferable to add water of the same amount or less by mass. It was supported.

Example 4 (Used mirabilite waste liquid as a raw material liquid and evaluated the amount of lead contained as an impurity)
1 liter of mirabilite waste solution in a beaker was heated to 50 ° C., concentrated sulfuric acid was added to adjust the pH to 3 or less, and the mixture was allowed to stand for 30 minutes for decarboxylation. Thereafter, 13.8 ml of a 25% strength by weight aqueous sodium hydroxide solution was added to adjust the pH to 7. On the other hand, 3.3 grams of polyferric sulfate was neutralized by adding a 48% strength by weight aqueous sodium hydroxide solution, and 3.2 ml of the neutralized solution at pH 9.5 was added to the above pH of 7. Was added to the waste solution. Next, 0.7 g of polyferric sulfate was further added to the mirabilite waste liquid, and 0.4 ml of a 25% strength by weight aqueous sodium hydroxide solution was added thereto to adjust the pH to 8. For 24 hours.

Comparative Example 2
In the same manner as in Example 4, the mirabilite waste liquor was decarboxylated, 4 grams of polyferric sulfate was added thereto, and 16.3 ml of a 25% strength by weight aqueous sodium hydroxide solution was added to adjust the pH to 7. And left at room temperature for 24 hours.

  The supernatant was taken from the test solutions of Example 4 and Comparative Example 2, and lead contained was quantified according to a conventional method. In addition, the initial concentration of lead contained in the mirabilite waste liquid was also quantified. As a result, the lead having an initial concentration of 57 milligram / liter was reduced to 0.1 milligram / liter in both cases of Example 4 and Comparative Example 2. Thus, in Example 3, the lead contained in the supernatant was sufficiently removed as in the conventional method.

Example 5 (Evaluation of sedimentation when ferrous sulfate is used as the iron-based compound)
To 20 ml of ferrous sulfate aqueous solution prepared to contain 5.5 grams of iron, a 48% strength by weight aqueous sodium hydroxide solution was added to adjust the pH to 9-10. Thereafter, water was added thereto to make up a total volume of 1 liter, and the mixture was allowed to stand at room temperature for 24 hours. A graduated cylinder was used as a test container.

Comparative Example 3
Water was added to 20 ml of an aqueous ferrous sulfate solution prepared to contain 5.5 grams of iron to make a total volume of 1 liter. Thereafter, a 48 mass% sodium hydroxide aqueous solution was added to adjust the pH to 9 to 10, and the mixture was allowed to stand at room temperature for 24 hours. A graduated cylinder was used as a test container.

Example 6 (Evaluation of sedimentation when using sulfuric acid used for pickling iron and steel as an iron-based compound)
The pH was adjusted to 9 to 10 by adding a 48 mass% sodium hydroxide aqueous solution to 20 ml of sulfuric acid used for pickling of steel collected on site. after that. Water was added thereto to make up a total volume of 1 liter, and the mixture was allowed to stand at room temperature for 24 hours. A graduated cylinder was used as a test container.

Comparative Example 4
Water was added to 20 ml of sulfuric acid used for pickling steel collected at the site to make the total volume 1 liter. Thereafter, a 48 mass% sodium hydroxide aqueous solution was added to adjust the pH to 9 to 10, and the mixture was allowed to stand at room temperature for 24 hours. A graduated cylinder was used as a test container.

  The sedimentation properties of the test solutions of Examples 5 and 6 and Comparative Examples 3 and 4 were evaluated. As a result, in Example 5, the height of the sediment was 8% of the total height of the liquid, and in Example 6, the height of the sediment was 5% of the total height of the liquid. On the other hand, in Comparative Example 3, the height of the sediment was 10% of the total height of the liquid, and in Comparative Example 4, the height of the sediment was 13% of the total height of the liquid. Thus, even if the iron-based compound is ferrous sulfate or sulfuric acid used for pickling iron and steel (it is considered that ferrous sulfate is generated), the pH is previously adjusted with alkali. It can be seen that the sedimentation property is improved by using a flocculant adjusted to the above.

  The present invention includes, for example, technical fields for removing heavy metals such as lead from raw material liquids containing various useful inorganic salts such as sodium sulfate and efficiently recovering useful inorganic salts, and waste liquids. It can be used in the technical field of removing heavy metals and purifying waste liquid.

Claims (7)

  A heavy metal removing agent, which is a mixed solution of an iron-based compound and an alkaline aqueous solution.   The heavy metal removing agent according to claim 1, wherein the mixed solution has a hydrogen ion index of 8 to 12. A method for producing a flocculant used for heavy metal removal,
A method for producing an aggregating agent for removing heavy metals, comprising mixing an iron-based compound and an aqueous alkali solution in a predetermined amount ratio to prepare the aggregating agent.   The manufacturing method of the flocculant for heavy metal removal of Claim 3 which makes a hydrogen ion index | exponent 8-12 at the time of the said adjustment. A method of processing the raw material liquid, wherein a flocculant is added to a raw material liquid containing heavy metal, the flocculant is precipitated, and a supernatant and a precipitate are generated.
The coagulant is prepared by mixing an iron-based compound and an aqueous alkaline solution at a predetermined ratio, and takes in and settles the heavy metal contained in the raw material liquid.   The processing method of the raw material liquid containing the heavy metal of Claim 5 which makes a hydrogen ion index 8-12 at the time of the said adjustment.   The method for treating a raw material liquid containing heavy metal according to claim 5 or 6, wherein the iron-based compound is additionally added after the supernatant and the sediment are generated.