JP2007283216A - Boron-containing wastewater treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boron-containing wastewater treatment method which enables wastewater treatment using only low-cost chemicals by a low-cost device and generation of a small amount of sludge, and to provide a collection method of boron resources. <P>SOLUTION: In the boron-containing wastewater treatment method, precipitate of boron-containing compounds is formed by adjusting pH to ≥8 in coexistence of a peroxide and a polyvalent metal compounds, and then the precipitate is separated or collected from the wastewater to reduce the concentration of boron in the wastewater. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for treating boron-containing wastewater and a method for recovering boron resources.

  Since boron has been shown to affect human health, emission regulations are currently being implemented. For example, the drainage standard for boron is 10 mg / liter or less in rivers and lakes. Boron compounds are used, for example, in the production of glass products, pharmaceuticals, cosmetics, semiconductors, plated products, etc., and are contained in the production waste water. It is also often included in thermal power plant wastewater, flue gas desulfurization wastewater, waste incineration facility wastewater, some hot spring water, and other industrial wastewater. For this reason, in these waste water treatment, the boron compound contained in the waste water must be removed from the waste water.

  As a method for removing boron in the wastewater, for example, a method of removing by adsorbing with an ion exchange resin (see Patent Document 1) or an agglomeration precipitation in which an insoluble precipitate is formed and removed using an aluminum compound and a calcium compound. The method (see Patent Document 2) has been used.

  However, the method of removing boron with an ion exchange resin requires a large amount of ion exchange resin and requires an excessive initial investment. In addition, it is necessary to regenerate the ion exchange resin that adsorbs boron, and the cost of the regenerating process is high, and in addition, it is necessary to process the regenerated waste liquid containing high-concentration boron generated by the regenerating process. There is.

  The method of removing boron using an aluminum compound and a calcium compound has insufficient ability to remove boron except when using a sulfate band and slaked lime, and even when using a sulfate band and slaked lime, In order to remove the boron compound below the drainage standard, a large amount of chemicals is required, and a large amount of sludge is generated.

  As a method for removing boron in wastewater as a hardly soluble or insoluble precipitate of a boron compound, a treatment method using a rare earth compound (see Patent Document 3) and an alkaline earth metal hydroxide are added to form subcriticality. A method of treating under conditions (see Patent Document 4) is known.

  The method of removing boron in wastewater as a poorly soluble or insoluble precipitate of boron compounds does not involve a large amount of sludge and does not require excessive initial investment, but each has its own problems. is doing.

  In the treatment method using rare earth compounds, the rare earth compound is expensive, and in the treatment method using peroxide, hydroxy polyvalent carboxylic acid and alkaline earth metal compound, the hydroxy polyvalent carboxylic acid is expensive. There was a problem with increasing.

The method of adding alkaline earth metal hydroxide and treating it under subcritical conditions requires subcritical conditions as reaction conditions, so the boron waste water cannot be treated continuously. There were problems such as requiring large energy for the treatment.
JP-B-1-43594 JP 2003-236562 A JP 2004-963 A JP 2005-279468 A

  The object of the present invention is to provide a method for treating boron-containing wastewater and a method for treating boron resources, which can be used to treat wastewater with inexpensive equipment using only inexpensive chemicals, and generate a small amount of sludge. It is to provide a recovery method.

  As a result of intensive studies to achieve the above object, the present inventors have determined that boron is adjusted by adjusting pH to 8 or more in the coexistence of peroxide and polyvalent metal compound in the treatment method of boron-containing wastewater. After forming the precipitate of the contained compound, it was found that the boron concentration in the wastewater was reduced by separating or recovering the precipitate from the wastewater, and the present invention was completed.

That is, the present invention provides the following boron-containing wastewater treatment method and boron resource recovery method.
1. In the method for treating boron-containing wastewater, after the pH is adjusted to 8 or more in the coexistence of a peroxide and a polyvalent metal compound, a precipitate of the boron-containing compound is formed, and then the precipitate is separated from the wastewater or A method for treating boron-containing wastewater, wherein the boron concentration in the wastewater is reduced by recovery.
2. 2. The method for treating boron-containing wastewater according to 1 above, wherein the peroxide is hydrogen peroxide or a peroxide that reacts in water to produce hydrogen peroxide.
3. 3. The method for treating boron-containing wastewater according to 1 or 2, wherein the polyvalent metal compound is a barium-containing compound.
4). pH is adjusted to 10-12, The processing method of the boron containing waste water of any one of said 1-3 characterized by the above-mentioned.
5). The boron collection method from the waste_water | drain which collect | recovers the deposit isolate | separated from waste water by giving the waste water treatment method as described in any one of said 1-4 with respect to a boron containing waste_water | drain as a boron resource.

  In the present invention, boron can be removed with a small amount of sludge by using only inexpensive chemicals with inexpensive equipment for boron-containing wastewater. Moreover, boron resources can be effectively utilized by recovering boron.

  The present invention relates to a method for treating boron-containing wastewater and a method for recovering boron resources, and the target wastewater is not particularly limited, for example, manufacturing wastewater such as the above-described glass products, pharmaceuticals, cosmetics, semiconductors, plating products, etc. It includes thermal power plant wastewater, flue gas desulfurization wastewater, waste incineration facility wastewater, some hot spring water, wastewater from other factories and research facilities, and general household wastewater.

  A boron-containing compound precipitate can be formed in the wastewater by adjusting the pH to 8 or more in the presence of a peroxide and a polyvalent metal compound with respect to the boron-containing wastewater.

  In the present invention, it is necessary to coexist the peroxide in the waste water, but when the peroxide is previously contained in the waste water, even if the peroxide contained in the waste water is used. Moreover, you may add a peroxide further.

  In the present invention, it is necessary to allow a peroxide to coexist in the waste water, but the peroxide to be used is not particularly limited. For example, hydrogen peroxide, lithium peroxide, sodium peroxide, potassium peroxide, magnesium peroxide, peracetic acid, persulfuric acid, percarbonate and the like can be used. The peroxide to be used may be one kind or a combination of plural kinds. Among these peroxides, it is preferable to use hydrogen peroxide because of easy handling.

  In the present invention, there is no particular limitation on the polyvalent metal compound to coexist in the wastewater, for example, calcium chloride, calcium carbonate, calcium acetate, quicklime, slaked lime, barium chloride, barium acetate, barium nitrate, barium oxide, barium sulfide, Strontium chloride, strontium carbonate, strontium nitrate, strontium oxide and the like can be used. However, any compound may be used as long as all or part of the wastewater dissolves to generate polyvalent metal ions, and the present invention is not limited to the compounds listed above.

  In the present invention, calcium-containing compounds such as calcium chloride, calcium carbonate, calcium acetate, quicklime, slaked lime, barium chloride, barium acetate, barium nitrate, and barium oxide are preferably used as the polyvalent metal compound to coexist in the waste water. More preferably, barium chloride, barium acetate, or barium nitrate can be used.

  In forming the precipitate, the polyvalent metal compound only needs to be dissolved in the waste water. When the wastewater contains a polyvalent metal compound in advance, the polyvalent metal compound contained in the wastewater may be used, and a polyvalent metal compound may be added. When the polyvalent metal compound previously contained in the waste water is contained as a precipitate, it may be dissolved by adding an acid or an alkali.

  In the present invention, the pH of the waste water when forming the precipitate may be 8 or more. Preferably, it may be in the range of pH 10-12. Outside this range, the formation of the boron-containing compound precipitate may be insufficient, or a long time may be required for the formation of the precipitate, and the drainage processability may deteriorate.

  In the present invention, the pH adjuster added for controlling the pH of the waste water is not particularly limited, but sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, sodium carbonate, potassium carbonate, Ammonia, methylamine, ethylamine, diethylamine, diisopropylamine, nitric acid, hydrochloric acid and the like can be used.

  In the present invention, when the peroxide and the polyvalent metal compound are allowed to coexist in the wastewater in order to form the boron-containing compound precipitate, one of the peroxide, the polyvalent metal compound, and the pH adjuster in the wastewater or When adding a plurality of species, the order of addition is not particularly limited. For example, a peroxide, a polyvalent metal compound and a pH adjuster may be sequentially added to the waste water, or a peroxide, a polyvalent metal compound and a pH adjuster may be added simultaneously. In addition, a boron-containing compound precipitate may be formed in the wastewater through a step of adding a chemical prepared by previously mixing a plurality of peroxides, polyvalent metal compounds, and pH adjusting agents into the wastewater. .

  By separating or recovering the boron-containing compound precipitate formed in the wastewater from the wastewater, the boron concentration in the wastewater can be reduced.

  In the present invention, the method for separating or recovering the precipitate is not particularly limited. For example, sedimentation separation, centrifugation, filtration or membrane separation can be used. The precipitate may be separated in the state containing a part of the treated water as sludge or slurry, and the treated water obtained after the separation of the precipitate may contain a part of the precipitate. When combustible material is included in a part of the precipitate, it is preferable that a part of the treated water is included from the viewpoint of safety. The precipitate containing a part of the treated water separated from the treated water may be subjected to a multistage separation operation in which the precipitate and the treated water are separated again by a centrifugal filtration device or the like after separation. In these separation operations, any inorganic flocculant and / or organic flocculant may be used.

  In the present invention, it is preferable to perform a mixing operation on the waste water in order to mix the added drug. Although there is no restriction | limiting in particular in the method of mixing, For example, the method of mixing using a stirrer, the mixing by a line mixer, aeration mixing using air etc. can be used.

  In the present invention, the formation of the boron-containing compound precipitate and the separation or recovery of the precipitate may each be performed a plurality of times. The number of times may be different, and there is no particular limitation as long as the precipitate is finally separated from the waste water. For example, the formation of the boron-containing compound precipitate and the separation or recovery of the precipitate may each be performed once, or the precipitate may be separated after repeating the step of forming the boron-containing compound precipitate a plurality of times. .

  In this invention, you may use together the formation method of well-known boron containing compound deposits other than having described in this invention as a formation method of a boron containing compound deposit. The formation of the boron-containing compound precipitate described in the present invention and the formation of a known boron-containing compound precipitate other than those described in the present invention may be performed sequentially or simultaneously.

  The wastewater containing the boron compound to be treated in the present invention may be treated by a known boron wastewater treatment method as part of the multistage treatment. Moreover, you may give again the processing method of this invention, or the well-known boron wastewater processing method with respect to the treated water obtained by the processing method of the boron containing waste water of this invention. For example, other boron treatment methods such as using an ion exchange resin may be performed in combination with the treatment method of the present invention. By performing such multi-stage treatment, the boron concentration of the treated water can be further reduced.

  The wastewater containing the boron compound to be treated in the present invention may be treated by a known wastewater treatment method other than boron as part of the multistage treatment. In particular, wastewater containing substances that prevent the coexistence of peroxides and polyvalent metal compounds is preferably preliminarily treated to remove substances that prevent the coexistence of peroxides and polyvalent metal compounds.

  In the present invention, since the boron-containing compound precipitate formed in the wastewater contains boron, it can be reused by collecting it from the wastewater. For example, the collected precipitate can be used as a raw material for producing orthoboric acid, borax, or metaboric acid.

  In carrying out the processing method of the present invention, either a batch processing apparatus or a continuous processing apparatus may be used.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples.

Example 1
Boric acid was dissolved in pure water to prepare a model waste water having a boron concentration of 100 mg / liter. The pH was 5.2. 100 g of this model wastewater was collected, 1.13 g of a 35 wt% aqueous solution of hydrogen peroxide was added, and the mixture was stirred well for 30 minutes. Next, 2.36 g of a 23.5 wt% aqueous solution of barium chloride dihydrate was added and stirred well. Further, a 20% by weight aqueous solution of sodium hydroxide was added to adjust the pH of the treated water to 11.5. The precipitate formed at the time of stirring for 30 minutes after adding sodium hydroxide and the treated water were separated by filtration. The boron concentration of the treated water was measured and found to be 16.8 mg / liter.

  The boron concentration was measured using an ICP emission analyzer. Hereinafter, the boron concentration in the waste water was all measured by this method. When the dry weight of the separated precipitate was measured, the dry weight was 0.11 g. When the boron content in the dried sludge was measured, the boron content was 7.0% by weight.

Example 2
The treatment was performed in the same manner as in Example 1 except that 1.15 g of a 35 wt% aqueous solution of hydrogen peroxide was added and the pH of the treated water was adjusted to 9.1 by adding a 20 wt% aqueous solution of sodium hydroxide. The results of measuring the boron concentration of the treated water are shown in Table 1.

Example 3
The treatment was performed in the same manner as in Example 1 except that 1.13 g of a 35 wt% aqueous solution of hydrogen peroxide was added and the pH of the treated water was adjusted to 12.2 by adding a 20 wt% aqueous solution of sodium hydroxide. The results of measuring the boron concentration of the treated water are shown in Table 1.

Example 4
The treatment was performed in the same manner as in Example 1 except that 0.22 g of a 35 wt% aqueous solution of hydrogen peroxide was added and the pH of the treated water was adjusted to 11.5 by adding a 20 wt% aqueous solution of sodium hydroxide. The results of measuring the boron concentration of the treated water are shown in Table 1.

Comparative Example 1
100 g of the same model wastewater as that used in Example 1 was collected, and 2.3 g of a 23.5% by weight aqueous solution of barium chloride dihydrate was added and stirred well. Further, a 20% by weight aqueous solution of sodium hydroxide was added to adjust the pH of the treated water to 11.5 and stirred for 30 minutes, but no precipitate was formed.

Comparative Example 2
100 g of the same model wastewater as that used in Example 1 was collected, 0.50 g of sulfate band 18 hydrate was added, and the mixture was thoroughly stirred and dissolved. Next, 1.00 g of powdered slaked lime was added and stirred well. The produced precipitate and treated water were separated by decantation, and the boron concentration of the treated water was measured. The boron concentration was 54.2 mg / liter. When the dry weight of the precipitate separated by decantation was measured, the dry weight was 1.01 g.

Example 5
100 g of industrial wastewater (pH 7.9) having a boron concentration of 104 mg / liter was taken, 1.13 g of a 35 wt% aqueous solution of hydrogen peroxide was added, and the mixture was stirred well for 30 minutes. Next, 2.31 g of a 23.5 wt% aqueous solution of barium chloride dihydrate was added and stirred well. Further, a 20% by weight aqueous solution of sodium hydroxide was added to adjust the pH of the treated water to 11.4. The precipitate formed at the time of stirring for 30 minutes after adding sodium hydroxide and the treated water were separated by filtration. The boron concentration of the treated water was measured and found to be 17.2 mg / liter.

Example 6
A model wastewater having a boron concentration of 20 mg / liter was prepared. 100 g of this model wastewater was collected, 0.23 g of a 35 wt% aqueous solution of hydrogen peroxide was added, and the mixture was stirred well for 30 minutes. Next, 0.46 g of a 23.5 wt% aqueous solution of barium chloride dihydrate was added and stirred well. Further, a 20% by weight aqueous solution of sodium hydroxide was added to adjust the pH of the treated water to 11.3. The precipitate formed at the time of stirring for 30 minutes after adding sodium hydroxide and the treated water were separated by filtration. The boron concentration in the treated water was measured and found to be 8.4 mg / liter.

Claims (5)

  In a method for treating boron-containing wastewater, a precipitate of boron-containing compound is formed by adjusting the pH to 8 or more in the presence of a peroxide and a polyvalent metal compound, and then the precipitate is separated from the wastewater. Alternatively, the boron-containing wastewater treatment method is characterized by reducing the boron concentration in the wastewater by collecting the boron.   The method for treating boron-containing wastewater according to claim 1, wherein the peroxide is hydrogen peroxide or a peroxide that reacts in water to produce hydrogen peroxide.   The method for treating boron-containing wastewater according to claim 1 or 2, wherein the polyvalent metal compound is a barium-containing compound.   pH is adjusted to 10-12, The processing method of the boron containing wastewater of any one of Claims 1-3 characterized by the above-mentioned.   The boron recovery method from the waste_water | drain which collect | recovers the deposit isolate | separated from the waste_water | drain by performing the waste water treatment method as described in any one of Claims 1-4 with respect to boron containing waste_water | drain as a boron resource.