JP4407236B2 - Treatment method of wastewater containing antimony - Google Patents

Description

  The present invention relates to a method for efficiently removing antimony from antimony-containing wastewater.

Antimony is widely used as a raw material for electronic parts and a flame retardant. In recent years, there has been a strong demand for solving environmental pollution problems caused by harmful substances, and antimony emission concentrations are also becoming increasingly regulated in the future. Conventionally, as a method for removing antimony in antimony-containing wastewater, for example, as described in Patent Document 1, after adding an iron salt to antimony-containing wastewater, the pH of the solution is adjusted to a range of 4 to 7 and insoluble. A method for generating and removing the precipitate is proposed.
JP 63-236592 A

  However, the method described in Patent Document 1 has a problem that the running cost is high because a large amount of iron salt needs to be added. Further, since the amount of generated sludge is large, the complexity of the secondary processing becomes a problem. Furthermore, in the case of trivalent antimony, the advanced treatment of antimony concentration after treatment of 0.02 mg / L or less has not been achieved, and additional operation for oxidizing antimony to pentavalent is necessary to achieve this. .

  The present invention is an antimony-containing wastewater treatment that is excellent in running cost, alleviates the complexity of secondary treatment associated with sludge, and can remove antimony to a high degree without requiring additional operation regardless of the valency of antimony. The purpose is to provide a method.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the present invention is a method for treating wastewater containing antimony, in the first step, after adding a sulfiding agent to wastewater containing antimony, by adjusting the pH of the wastewater to a range of 5 to 7. Antimony sulfide is generated, and the sulfiding agent is an alkali metal or alkaline earth metal sulfide, and the addition amount of the sulfiding agent is 0.6 times or more as sulfur (metal) with respect to antimony (metal). Yes, in the second step, after adding the ferric salt compound to the liquid obtained in the first step, adjusting the pH of the liquid to the range of 5 to 7 to produce a precipitate, In the third step, a ferric salt compound is added to the liquid separated in the second step, and then the pH of the liquid is adjusted to a range of 8 to 12 to generate a precipitate. Te, separating the precipitate from the liquid, Anne Total amount of iron ions to the Mont (Fe / Sb) consists of processing method antimony-containing waste water, characterized in that it is 9 times by weight or more.

  According to the treatment method of the present invention, after producing antimony sulfide in the antimony-containing wastewater, adding a ferric salt compound to aggregate the precipitate, and further adjusting the pH of the filtrate to alkali, Since the addition amount of the ferric salt compound becomes small, the running cost is improved, and the sludge generation amount is further reduced, so that the complexity of the secondary treatment is eased. In addition, antimony can be highly removed regardless of the valency of antimony without requiring additional operation.

Hereinafter, the present invention will be described in detail.
The first step of the present invention is a step of generating antimony sulfide by adding a sulfiding agent to wastewater containing antimony and then adjusting the pH of the wastewater from 5 to 7.
Any wastewater containing antimony may be used as long as the treatment method of the present invention can be applied. Examples thereof include wastewater generated from a gasification process using waste plastic containing antimony flame retardant as a raw material. . The valence of antimony in the waste water may be trivalent, pentavalent, or a mixture of trivalent and pentavalent. Further, the antimony concentration in the wastewater is not particularly limited, but the treatment method of the present invention is applied to wastewater having an antimony concentration of 4 to 500 mg / L, for example. Also, the drainage may contain heavy metals other than antimony.

  The sulfiding agent used in the first step is not particularly limited as long as it generates antimony sulfide. For example, alkali metal or alkaline earth metal sulfide, specifically, calcium polysulfide (such as calcium pentasulfide) or sulfide. Sodium is preferably used. The sulfurizing agent is preferably added as an aqueous solution, but may be a solid. Further, it is sufficient that the addition amount of the sulfurizing agent is 0.6 times or more (for example, 0.6 to 9 times) as sulfur (metal) with respect to antimony (metal). In addition, when adding a sulfurizing agent as aqueous solution, the density | concentration of a sulfurizing agent will not be restrict | limited especially if it is the range which does not increase the load of wastewater treatment remarkably.

The pH of the waste water after the addition of the sulfiding agent is preferably adjusted to a neutral to weakly acidic region, specifically 5 to 7, in order to maximize the amount of antimony sulfide produced. When this pH is biased to the acidic side, hydrogen sulfide is generated and gas treatment must be taken into account, which is not an industrially favorable condition.
The stirring time after pH adjustment is sufficient for 30 minutes or longer (for example, 30 to 60 minutes).

The second step of the present invention is a step of separating the precipitate formed by adjusting the pH from 5 to 7 after adding the ferric salt compound to the liquid obtained in the first step. . The iron hydroxide produced by adding the ferric salt compound and adjusting the pH aggregates the antimony sulfide produced in the first step.
The ferric salt compound supplying agent used in the second step is not limited as long as it supplies a ferric salt compound, and examples thereof include iron salts such as ferric chloride and ferric sulfate. . The ferric salt compound is preferably added as an aqueous solution, but may be a solid. Further, it is sufficient that the addition amount of the ferric salt compound is 6 times or more (for example, 6 to 62 times) as metallic iron with respect to antimony.

  The pH of the solution after adding the ferric salt compound in the second step is preferably adjusted to a range of 5 to 7. Usually, in order to form a large floc of iron hydroxide, the pH is preferably alkaline. However, in the present invention, adjusting the pH to alkaline is not preferable because the removal rate of antimony decreases. The stirring time after pH adjustment is sufficient for 30 minutes or longer (for example, 30 to 60 minutes). If a polymer flocculant described later is added before solid-liquid separation, the solid-liquid separation time can be further shortened, which is favorable.

The third step of the present invention is a step of separating the precipitate generated from the solution by adjusting the pH to 9 or higher after adding the ferric salt compound to the solution from which the precipitate was separated in the second step. is there. This step is for further removing the antimony remaining in the liquid separated in the second step, and aims to make the antimony concentration in the liquid after the treatment 0.02 mg / L or less.
The supply agent and the shape of the ferric salt compound used in the third step are the same as those in the second step. Further, the addition amount of the ferric salt compound is sufficient to be at least one half of the weight added in the second step (for example, from 1/2 to 1).

  It is desirable that the pH of the liquid after adding the ferric salt compound in the third step is in the range of 8 to 12, preferably 9 to 10. When the pH is neutral or acidic, iron ions remain in the liquid and cause coloration of the treated water. The stirring time after pH adjustment is sufficient for 30 minutes or longer (for example, 30 to 60 minutes). If a polymer flocculant described later is added before solid-liquid separation, the solid-liquid separation time can be further shortened, which is favorable.

  An acid or an alkali is used as necessary for the pH adjustment performed in each step. An inorganic acid such as sulfuric acid or hydrochloric acid can be used as the acid, and an alkali metal or alkaline earth metal hydroxide such as sodium hydroxide or calcium hydroxide can be used as the alkali.

  The polymer flocculant used in the present invention facilitates solid-liquid separation by promoting the aggregation of precipitates mainly composed of iron hydroxide. Commercially available acrylamide polymer flocculants can be used effectively regardless of nonionic, cationic or anionic. The amount of the polymer flocculant added may be 1 to 4 mg / L with respect to the raw water.

  In the present invention, the solid-liquid separation operation is performed twice. As a solid-liquid separation method, a generally used method such as a filtration method, a centrifugal separation method, a sedimentation separation method, or the like can be used.

  EXAMPLES Next, an Example is given and this invention is demonstrated still in detail. The analysis of antimony in the present invention followed the method described in “Measurement of Environmental Standards for the Protection of Human Health Related to Water Pollution and Measurement Methods of Items to be Monitored (Hei 5 Water Regulation No. 121)”.

[Example 1]
After adding 415 mg of sodium sulfide nonahydrate (S / Sb = 1 (weight ratio)) to 200 mL of an aqueous solution (hereinafter referred to as raw water) containing 350 mg / L of trivalent antimony in terms of metal, the pH was adjusted to 6.2. The mixture was stirred and mixed for 30 minutes (first step). Next, 7.2 mL of a 1 mol / L ferric chloride aqueous solution was added, and then the pH was adjusted to 6.2, followed by stirring and mixing for 30 minutes. Thereafter, a polymer flocculant (Diafloc AP120C; manufactured by Dianitics; the same applies hereinafter) was added to the raw water so as to have a concentration of 1 mg / L, and the mixture was stirred and mixed for 10 minutes. Was filtered with No5A quantitative filter paper (second step). Next, 3.6 mL of a 1 mol / L ferric chloride aqueous solution was added to the filtrate, and then the pH was adjusted to 9.5 and mixed with stirring for 30 minutes. Next, a polymer flocculant was added to the raw water so as to have a concentration of 1 mg / L, and the mixture was stirred and mixed for 10 minutes. After standing for 10 minutes, the treated liquid was filtered with a No5A quantitative filter paper (third step). . The antimony content in the filtrate was 0.01 mg / L or less. The total addition amount of iron ions (Fe / Sb) to antimony was 9 times by weight. In addition, the amount of sludge generated was small and did not hinder solid separation.

[Example 2]
After adding 936 mg (S / Sb = 2.7 (weight ratio)) of 27.5 wt% aqueous solution of calcium pentasulfide to 200 mL of an aqueous solution (hereinafter referred to as raw water) containing 390 mg / L of trivalent antimony in terms of metal, The pH was adjusted to 6.2 and stirred and mixed for 30 minutes (first step). Next, 8.1 mL of a 1 mol / L ferric chloride aqueous solution was added, the pH was adjusted to 6.1, and the mixture was stirred for 30 minutes. Thereafter, a polymer flocculant was added to the raw water so as to have a concentration of 1 mg / L, and the mixture was stirred and mixed for 10 minutes, and after standing for 10 minutes, the treated liquid was filtered with a No5A quantitative filter paper (second step) ). Next, after adding 4.1 mL of 1 mol / L ferric chloride aqueous solution to a filtrate, pH was adjusted to 9.9 and it stirred and mixed for 30 minutes. Next, a polymer flocculant was added to the raw water so as to have a concentration of 1 mg / L, and the mixture was stirred and mixed for 10 minutes. After standing for 10 minutes, the treated liquid was filtered with a No5A quantitative filter paper (third step). . The antimony content in the filtrate was 0.007 mg / L. The total addition amount of iron ions (Fe / Sb) to antimony was 11.6 times by weight. In addition, the amount of sludge generated was small and did not hinder solid separation.

[Example 3]
In Example 1, the same treatment was performed on an aqueous solution containing pentavalent antimony. As a result, the antimony concentration in the filtrate was 0.02 mg / L or less. In addition, the amount of sludge generated was small and did not hinder solid separation.

[Comparative Example 1]
After adding 150 mg of a 27.5 wt% aqueous solution of calcium pentasulfide to 200 mL of an aqueous solution containing 12 mg / L of trivalent antimony in terms of metal (hereinafter referred to as raw water) (S / Sb = 14 (weight ratio)), the pH was adjusted. The mixture was adjusted to 7.8 and stirred for 30 minutes. Next, a polymer flocculant was added to the raw water so as to have a concentration of 1 mg / L, and the mixture was stirred and mixed for 10 minutes. After 10 minutes of standing, the treated liquid was filtered with a No5A quantitative filter paper. The antimony content in the filtrate was 5 mg / L. Thus, when not performing operation of a 2nd process and a 3rd process, even if there was much addition amount of a sulfurizing agent, antimony was not able to be removed highly.

[Comparative Example 2]
After adding 5.5 mL of 1 mol / L ferric chloride aqueous solution (Fe / Sb = 24 (weight ratio)) to 200 mL of an aqueous solution (hereinafter, raw water) containing 65 mg / L of trivalent antimony in terms of metal, The pH was adjusted to 7 and mixed with stirring for 30 minutes. Thereafter, a polymer flocculant was added to the raw water so as to have a concentration of 1 mg / L, and the mixture was stirred and mixed for 10 minutes. After standing for 10 minutes, the treatment liquid was filtered with a No5A quantitative filter paper. The antimony content in the filtrate was 10 mg / L. Thus, when operation of the 1st process and the 3rd process was not performed, even if there was much addition amount of an iron ion, antimony was not able to be removed highly. Further, since the amount of sludge generated is larger than that in Example 1, solid-liquid separation is complicated.

[Comparative Example 3]
In Example 1, it processed similarly except not having operated the 3rd process. As a result, the antimony concentration in the filtrate when the second step was performed was 0.2 mg / L. Thus, when operation of the 3rd process was not performed, antimony was not able to be removed highly.

  INDUSTRIAL APPLICATION This invention can be utilized for the waste water treatment which removes antimony from antimony containing waste water highly efficiently.

Claims (5)

In a method for treating wastewater containing antimony,
In the first step, after adding a sulfurizing agent to the wastewater containing antimony, the antimony sulfide is generated by adjusting the pH of the wastewater to a range of 5 to 7,
The sulfiding agent is an alkali metal or alkaline earth metal sulfide,
The addition amount of the sulfiding agent is 0.6 times or more as sulfur (metal) with respect to antimony (metal),
In the second step, after adding the ferric salt compound to the liquid obtained in the first step, the pH of the liquid is adjusted to a range of 5 to 7, thereby generating a precipitate. Separate from the liquid,
In the third step, after adding the ferric salt compound to the liquid separated in the second step, the pH of the liquid is adjusted to a range of 8 to 12, and a precipitate is generated. Separate from
An antimony-containing wastewater treatment method, wherein the total amount of iron ions added to antimony (Fe / Sb) is 9 times by weight or more . The method for treating antimony-containing wastewater according to claim 1, wherein the sulfurizing agent is calcium polysulfide or sodium sulfide. 2. The method for treating antimony-containing wastewater according to claim 1, wherein ferric chloride is used as a supply agent for the ferric salt compound. The addition amount of the ferric salt compound in the second step is 6 times or more as metallic iron with respect to antimony,
The addition amount of the ferric salt compound in the third step is at least one half of the weight added in the second step.
The processing method of the antimony containing waste water of any one of Claim 1 to 3. The antimony according to any one of claims 1 to 4, wherein an acid or an alkali is used for pH adjustment performed in each step of the first to third steps, and the alkali is sodium hydroxide or calcium hydroxide. Treatment method of contained wastewater.