JPH07108281A - Method for removing manganese ion - Google Patents

Abstract

PURPOSE:To efficiently process maganese ions in water in a pH neutral zone by adding permanganate to water to control pH to a specified value. CONSTITUTION:Raw water (desulfurization waste water) is introduced into a first reactor tank 1 and KMnO4, as permanganate, is added thereto from a pipe 12 and, if required, acid or alkali is added from a pipe 13 to adjust pH in the range of 3-8 to effect reaction. The reaction liquid is taken out through a filtration part 1A. Further, when a heavy metal chelate aggregation agent is added, the reaction liquid is introduced into a second reactor tank 2 and the heavy metal aggregation agent is added to insolubilize excessive KMnO4. And when fluorine ions coexist, calcium compound or aluminum compound is added to insolubilize the fluorine ions. The reaction liquid is led to an ultrafiltration membrane separation tank 4 through a circulation tank 3 to be subjected to membrane separation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing manganese ions, and more particularly to a method for efficiently removing manganese ions contained in desulfurization effluent in a pH neutral range.

[0002]

2. Description of the Related Art Conventionally, as a method for treating fluoride-containing wastewater such as desulfurization wastewater, after adding a calcium compound and / or an aluminum compound to the wastewater and adjusting the pH to 6 to 8,
A method has been proposed in which membrane separation is performed and a membrane permeate is adsorbed (Japanese Patent Laid-Open No. 3-118897).

[0003]

However, this method hardly removes manganese ions contained in the desulfurization wastewater. Therefore, it cannot be applied to desulfurization wastewater containing 10 mg / l or more of manganese.
Alternatively, the treatment of such desulfurization wastewater requires further treatment with an expensive chelating resin in order to remove manganese ions.

The desulfurization effluent containing manganese ions is preferably subjected to a manganese ion removal treatment prior to the treatment by adding the above-mentioned calcium compound and / or aluminum compound. In order to remove the ions, it is desirable that the treatment can be carried out in the subsequent treatment pH, that is, in the neutral range of pH 6 to 8.

However, all conventional methods for removing manganese ions require treatment in an alkaline region, and no method for removing manganese ions in water in a pH neutral region has been proposed.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a method for efficiently treating manganese ions in water in a neutral pH range.

[0007]

The method of claim 1 is a method for removing manganese ions in water, which is characterized in that pH is adjusted to 3 to 8 by adding permanganate to the water.

The method of claim 2 is a method for removing manganese ions in water, wherein permanganate is added to the water to adjust the pH to 3 to 8, and then a heavy metal chelate aggregating agent is added. To do.

The present invention will be described in detail below.

In the present invention, potassium permanganate (KMnO) is used as the permanganate added to water.
₄ ), sodium permanganate (NaMnO ₄ ), ammonium permanganate (NH ₄ M _n O ₄ ) and the like can be used.

By adding permanganate to adjust the pH to 3 to 8, manganese ions in water are oxidized and easily insolubilized as manganese dioxide.

This oxidation reaction easily proceeds in the range of pH 3 to 8, but as shown in the reaction formula described later, hydrogen ions are released from water molecules as the oxidation reaction progresses, and in an aqueous system without pH buffering property. , The acidity increases due to the released hydrogen ions.

In this case, since the oxidation reaction rate decreases, an alkali such as sodium hydroxide (NaOH) is appropriately added to adjust the pH to 3 to 8, preferably 4 or more to proceed the reaction. To do so.

In the present invention, the amount of permanganate added is preferably such that it will be the required theoretical amount in the reaction formula described below, and is appropriately determined according to the manganese ion content of the water to be treated.

In order to facilitate the control of the addition of permanganate, it is practical to add permanganate in an amount larger than the theoretical amount required for the oxidation reaction, but an excessive amount of permanganate is added. When manganate is added, unreacted permanganate remains, which increases the manganese concentration in the treated water.

In this case, an excessive amount of permanganate can be easily insolubilized and removed by adding a heavy metal chelate aggregating agent. Examples of the heavy metal chelate aggregating agent include compounds containing a dithiocarbamic acid group and the like. Among these, examples of the compound having a dithiocarbamic acid group or a salt thereof include a reaction product of polyamine, polyethyleneimine and carbon disulfide. Can be mentioned.

As the polyamine, ethylenediamine,
Propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, dibutylenetriamine, triethylenetetramine, tripropylenetetramine, tributylenetetramine, tetraethylenepentamine, tetrapropylenepentamine, tetrabutylenepentamine, pentaethylenehexamine Polyalkylene polyamines such as phenylenediamine, o-, m-, p-xylene diamine, 3,5-
Diaminochlorobenzene, diaminophenyl ether,
Aromatic amines such as trizine and m-toluylenediamine;
Iminobispropylamine, monomethylaminopropylamine, methyliminobispropylamine, 1,3-bis (aminomethyl) cyclohexane, 1,3-diaminopropane, 1,4-diaminobutane, melamine, 1-aminoethylpiperazine, piperazine , 3,3′-dichlorobenzidine and the like. Furthermore, polycondensation polyamines obtained by polycondensing these polyamines with epihalohydrin can also be used.

The polyethyleneimine has an average molecular weight of 300 to 100,000, particularly 1000 to 1000.
00 is preferable.

The amount of these heavy metal chelate aggregating agents added is
It is appropriately determined depending on the amount of excess permanganate.

Such a method of the present invention is extremely effective for removing manganese ions as a pretreatment in the treatment of desulfurization effluent, and in this case, the removal treatment of manganese ions and the treatment of the subsequent step are the same. Since it can be carried out at pH, the work for adjusting the pH and the cost of the medicine can be reduced.

An embodiment in which the present invention is applied to the treatment of desulfurization wastewater will be described below with reference to FIG.

In the method shown in FIG. 1, raw water (desulfurization waste water) is supplied from a pipe 11 to a first reaction tank 1 equipped with a filtration section 1A.
Was introduced into the pipe, and KMnO as permanganate was supplied from the pipe 12.
_In addition to adding ₄ , acid or alkali is added from the pipe 13 as needed to adjust the pH to 3 to 8 and react.
In addition, this pH adjustment is preferably adjusted to pH 6 to 8 in order to adapt it to the treatment pH of the subsequent stage. The reaction liquid is withdrawn from the first reaction tank 1 through the filtration unit 1A. When the heavy metal chelate coagulant is further added, the heavy metal chelate coagulant is introduced into the second reaction tank 2 through the pipe 14 and the heavy metal chelate coagulant is added through the pipe 15 to insolubilize excess KMnO ₄ . Further, in the case where fluorine ions coexist, the calcium ions or aluminum compounds are added to make the fluorine ions insoluble. In the second reaction tank 2, the pH is further adjusted as necessary to adjust the pH to 6 to 8, and then the reaction solution is passed through the pipe 16, the circulation tank 3 and the pipe 17 for microfiltration (MF) membrane. It is introduced into the separation device 4 and subjected to membrane separation treatment.
The permeated water of the membrane separation is discharged as treated water to the outside of the system through the pipe 18, and the concentrated water is circulated to the circulation tank 3 through the pipe 19. In this circulation pipe 19, a part of the concentrated water is discharged out of the system through the pipe 20 as drawn sludge.

By this method, manganese ions and fluorine ions in the desulfurization wastewater can be efficiently removed, and treated water of high water quality can be obtained.

[0024]

The soluble manganese contained in the desulfurization wastewater exists as divalent manganese ions. When such divalent manganese is made alkaline, it undergoes the following reaction to become insoluble. It is necessary to adjust the pH to 10 or more in order to sufficiently proceed this reaction within 10 minutes.

[0025]

[Chemical 1]

However, the manganese hydroxide produced by this reaction is easily redissolved as a divalent manganese ion by a reversible reaction when the pH in the system is returned to neutral.

On the other hand, when divalent manganese is oxidized to tetravalent manganese with an oxidizing agent, it is insolubilized as manganese dioxide and can be removed by solid-liquid separation treatment such as precipitation or membrane separation. By generating manganese dioxide in this way, it becomes possible to efficiently remove manganese ions without causing redissolution even in the neutral pH range.

However, when hydrogen peroxide (H ₂ O ₂ ) is used as the oxidizing agent, the manganese dioxide production efficiency is poor, and sufficient oxidizing power can be obtained in the alkaline region. When this is set to a pH neutral region, redissolution occurs, and the removal efficiency of manganese ions is poor.

On the other hand, according to the present invention, by adding a permanganate such as potassium permanganate as an oxidizing agent, the following reaction proceeds, and divalent manganese is converted into tetravalent manganese even in the neutral pH range. It can efficiently oxidize up to manganese.

[0030]

[Chemical 2]

The heavy metal chelate flocculant can insolubilize an excess amount of permanganate.

[0032]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

Example 1 Manganese sulfate was added to Atsugi city water to obtain a Mn ²⁺ concentration of 51 mg.
Using the sample (pH 7.8) adjusted to 1 / l, the agents shown in Table 1 were added at the ratio shown in Table 1. The pH after addition is shown in Table 1.
It was as shown in. Therefore, if necessary, H ₂ SO ₄
Alternatively, the solution was neutralized by adding NaOH to the pH shown in Table 1 and then reacted for the time shown in Table 1. The obtained reaction solution is J
IS No. It was filtered with a 5 A filter paper, and the manganese concentration in the filtered water was measured. The results are shown in Table 1.

No. When H ₂ O _{2 is} added to H ₂ O ₂ , it acts in an alkaline region, so that H ₂ O ₂ and Na
OH was added to pH 9.1 and then HCl was added to pH 7.0.

[0035]

[Table 1]

The following is clear from Table 1.

When H ₂ O ₂ is added as an oxidizing agent (N
o. In 2), the production efficiency of manganese dioxide is poor, and
Redissolution occurs in the neutral pH range and the concentration of manganese in the resulting filtered water is high.

On the other hand, when KMnO ₄ is used (N
o. 3 to 7) have the effect of removing manganese depending on the amount added. That is, the Mn ²⁺ concentration in the sample is 51 m
The theoretical amount of KMnO ₄ with respect to g / l (≈0.93 mol) is about 98 (= 158 × 0.93 × 2/3) mg / l. Therefore, No. In 3 to 5, unreacted Mn
²⁺ remains in the filtered water. On the other hand, No. In Nos. 6 and 7, almost all Mn ²⁺ in the sample was insolubilized as manganese dioxide, but an excessive amount of KMnO ₄ remained, and particularly No.
In the case of 7, pink coloration due to KMnO ₄ was observed in the filtered water.

Example 2 KMnO ₄ in the amount shown in Table 2 was added to a sample (pH 7.7) in which manganese sulfate was added to desulfurization wastewater so that Mn ²⁺ was 50 mg / l (added in No. 8). No). KM
Since the pH after addition of nO ₄ was as shown in Table 2,
Neutralize to pH shown in Table 2 by adding NaOH, and
The reaction was allowed for 0 minutes. Then, as a heavy metal chelate aggregating agent, Welkulin K-100 (manufactured by Kurita Water Industries Ltd.) was used in Table 2.
The amount shown in (1) was added, and the reaction was continued for 5 minutes.

The reaction solution was JIS No. Filtration was performed with a 5 A filter paper, and the manganese concentration in the obtained filtered water was measured. The results are shown in Table 2.

[0041]

[Table 2]

The following is clear from Table 2.

That is, without KMnO ₄ addition (No. 8), manganese ions are not removed, but by adding KMnO ₄ , an effect of removing manganese ions can be obtained according to the amount added. In this example, 50 mg / l
The theoretical amount of KMnO ₄ required for the oxidation of Mn ²⁺ is about 96 m
g / l, and when KMnO ₄ is added at 120 mg / l (No. 11), KMnO ₄ becomes excessive, but addition of heavy metal chelate coagulant causes excess KMnO ₄ to react with heavy metal chelate coagulant. Is insolubilized and removed,
It is possible to obtain filtered water having an extremely low manganese concentration.

[0044]

As described in detail above, according to the method for removing manganese ions of the present invention, the pH of manganese ions in water is adjusted.
It can be removed easily and efficiently in the neutral region.

In particular, according to the method of claim 2, it is possible to more reliably remove manganese ions to an extremely low concentration.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example method of a method for removing manganese ions of the present invention.

[Explanation of symbols]

 1 1st reaction tank 2 2nd reaction tank 3 Circulation tank 4 MF membrane separation device

Claims (2)

[Claims] 1. A method for removing manganese ions in water, which comprises adding permanganate to the water to adjust the pH to 3-8. 2. A method for removing manganese ions in water, which comprises adding a permanganate to the water to adjust the pH to 3 to 8 and then adding a heavy metal chelate aggregating agent. Method.