JP2007283217A - Boron-containing wastewater treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boron-containing wastewater treatment method which enables the sure application to a strict effluent standard value with a low-cost device and generation of a small amount of sludge. <P>SOLUTION: In the boron-containing wastewater treatment method, after wastewater is treated with a peroxide, a precipitate is deposited in coexistence of a hydroxypolycarboxylic acid and an alkaline earth metal compound, and then the precipitate is separated 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 waste water containing a boron compound.

  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. On the other hand, a method is known in which an alkaline earth metal hydroxide is added and treated under subcritical conditions (see Patent Document 3).

  However, the method of removing boron with an ion exchange resin requires that the ion exchange resin adsorbing boron be subjected to a regeneration treatment, which requires a cost for the regeneration treatment and includes a high concentration of boron generated by the regeneration treatment. There is a problem that it is necessary to treat the recycled waste liquid.

  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.

  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.

  In Non-Patent Document 1, although not as a method for removing boron from wastewater, a compound containing boron is quantitatively added by adding ammonium chloride, tartaric acid, barium chloride and aqueous ammonia to an aqueous solution containing specific boron. The method of forming and obtaining as a precipitate is shown.

This method is not a method for removing boron in wastewater but a method for analyzing the boron concentration in wastewater. In this method, boron is separated from waste water by quantitatively forming an insoluble compound containing boron. When this method is used to remove boron in wastewater, a large amount of chemical is required. Therefore, there was a problem in using as a method of removing boron in waste water.
JP-A-9-314130 JP 2003-236562 A JP 2005-279468 A JIS G 1227 (1963) 4.8

  The objective of this invention is providing the processing method of the waste_water | drain containing the boron compound which can be reliably applied also to a severe effluent standard value with the cheap facilities from the above situations, and the amount of generated sludge is small. .

  The wastewater treatment method containing a boron compound according to the present invention is a method in which a precipitate is deposited in the coexistence of a peroxide, a hydroxy polyvalent carboxylic acid and an alkaline earth metal compound, and then the precipitate is separated from the wastewater. It is characterized by lowering the boron concentration in the waste water.

That is, the present invention provides the following wastewater treatment method.
1. A method for treating wastewater containing a boron compound, wherein after treating wastewater with a peroxide, depositing a precipitate in the presence of a hydroxy polyvalent carboxylic acid and an alkaline earth metal compound, the precipitate is A wastewater treatment method characterized by lowering the boron concentration in wastewater by separating it from the wastewater.
2. 2. The wastewater treatment method according to 1 above, wherein the peroxide is hydrogen peroxide or a peroxide that reacts in water to produce hydrogen peroxide.
3. The amount of the hydroxy polycarboxylic acid coexisting in the waste water is 2 molar equivalents or more with respect to the amount of boron, and the amount of the alkaline earth metal compound coexisting in the waste water is based on the amount of the hydroxy polycarboxylic acid. 3. The waste water treatment method according to 1 or 2 above, which is 1 molar equivalent or more.
4). The wastewater treatment method according to any one of 1 to 3, wherein the pH when depositing the precipitate is in the range of 8.5 to 10.5.

  In the present invention, boron can be reliably removed to a wastewater standard value (10 mg / liter or less as boron) with an inexpensive facility for wastewater containing a boron compound.

  The present invention relates to a method for treating wastewater containing a boron compound, and the target wastewater is not particularly limited. For example, manufacturing wastewater such as the aforementioned glass products, pharmaceuticals, cosmetics, semiconductors, plating products, and thermal power plant wastewater. , Waste gas desulfurization wastewater, waste incineration facility wastewater, some hot spring water, wastewater from other factories and research facilities, and wastewater from general households.

  In the present invention, it is necessary to treat the waste water with a peroxide. When the peroxide is previously contained in the waste water, the peroxide contained in the waste water may be used. Further, a peroxide may be added.

  In the present invention, the waste water needs to be treated with peroxide, 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, etc. can be used. Among them, hydrogen peroxide should be used for ease of handling. Is preferred.

  In the present invention, it is necessary to make hydroxy polyvalent carboxylic acid exist in the waste water, but when the hydroxy polyvalent carboxylic acid is previously contained in the waste water, the hydroxy polyvalent carboxylic acid contained in the waste water is included. An acid may be used, and a hydroxy polyvalent carboxylic acid may be added.

  There is no particular limitation on the hydroxy polyvalent carboxylic acid to be added to the waste water. Examples include glucaric acid, idalic acid, mannal acid, and mucous acid. Tartaric acid, glucaric acid or mucous acid is preferably used, and tartaric acid is particularly preferably used.

  When depositing the precipitate, the hydroxy polycarboxylic acid may be dissolved in the waste water. When the hydroxy polycarboxylic acid is previously contained in the waste water as a precipitate, it may be dissolved by adding an acid or an alkali.

  The amount of the hydroxy polycarboxylic acid added to the waste water in the treatment of the present invention is the molar ratio of the sum of the hydroxy polycarboxylic acid previously contained in the waste water and the hydroxy polycarboxylic acid added in the treatment. However, what is necessary is just 2 mol equivalent or more with respect to the boron contained in waste_water | drain.

  In the present invention, the alkaline earth metal compound coexisting in the waste water is not particularly limited, but for example, calcium chloride, calcium carbonate, calcium acetate, quicklime, slaked lime, barium chloride, barium acetate, barium nitrate, barium oxide, hydroxylation Barium, strontium chloride, strontium carbonate, strontium nitrate, strontium oxide, etc. can be used. However, any compound may be used as long as all or part of the wastewater dissolves to generate alkaline earth metal ions, and the invention is not limited to the compounds listed above.

  In the present invention, barium chloride, barium acetate, and barium nitrate can be preferably used as the alkaline earth metal compound to coexist in the waste water.

  In depositing the precipitate, the alkaline earth metal compound may be dissolved in the waste water. When the alkaline earth metal compound is previously contained in the waste water as a precipitate, it may be dissolved by adding an acid or an alkali.

  The amount of the alkaline earth metal compound added to the wastewater in the treatment of the present invention is the molar ratio of the sum of the alkaline earth metal compound previously contained in the wastewater and the alkaline earth compound added in the treatment. The molar amount may be 1 molar equivalent or more with respect to the hydroxy polyvalent carboxylic acid contained in the waste water.

  In the treatment method of the present invention, the pH of the waste water when depositing the precipitate may be in the range of 8.5 to 10.5. Outside this range, precipitation of boron-containing precipitates becomes insufficient, making it difficult to keep the boron concentration in the wastewater below the wastewater standard, or it takes a long time for precipitation to occur, The processability may deteriorate.

  In the treatment method of the present invention, the pH adjuster added for controlling the pH of the wastewater is not particularly limited, but sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonia, methylamine, ethylamine, diethylamine, Diisopropylamine, nitric acid, hydrochloric acid, etc. can be used.

  In the treatment method of the present invention, the treatment of the waste water with the peroxide is not particularly limited as long as it is before the precipitate is deposited. For example, after treating the waste water with peroxide, the hydroxy polyvalent carboxylic acid and the alkaline earth metal compound may coexist in the waste water, and one or both of the hydroxy polyvalent carboxylic acid and the alkaline earth metal compound are in the waste water. In this state, the treatment with the peroxide may be performed, or one or both of the hydroxy polyvalent carboxylic acid and the alkaline earth metal compound may coexist with the treatment with the peroxide.

  Although there is no restriction | limiting in particular in the method of separation of the precipitate in this invention, For example, sedimentation separation, filtration, membrane separation, etc. 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. 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.

  The treatment with the peroxide, the precipitation of the precipitate, and the separation 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 finally deposited precipitate is separated from the waste water. For example, treatment with peroxide, precipitation of precipitates and separation of precipitates may each be performed once, and after repeating the treatment with peroxide and subsequent precipitation of precipitates a plurality of times, The separation may be performed, and the treatment with the peroxide may be performed only once, and the precipitate may be separated after performing the precipitation of the precipitate a plurality of times.

  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 waste-water-treatment method with respect to the treated water obtained by the processing method 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.

  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 solution having a boron concentration of 100 mg / liter. The pH was 5.2. 100 g of this aqueous solution was taken, 1.13 g of a 35% by weight aqueous solution of hydrogen peroxide was added and stirred well. Next, 1.74 g of a 20 wt% aqueous solution of L-tartaric acid was added and stirred well. Next, 2.89 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 9.1, and the mixture was stirred well. After adding sodium hydroxide, the precipitate formed after 30 minutes and the treated water were separated by decantation, and the same separation was performed again after 60 minutes. When the boron concentration of the treated water was measured, it was 9.7 mg / liter, and the boron concentration could be reduced to 10 mg / liter or less.

  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 precipitate separated by decantation was measured, the dry weight was 0.37 g.

Comparative Example 1
100 g of the same boric acid aqueous solution as used in Example 1 was collected, and 0.80 g of sulfuric acid band 18 hydrate was added and stirred well to dissolve. Next, 1.60 g of powdered slaked lime was added and stirred in the bath. The produced precipitate and the treated water were separated by decantation, and the boron concentration of the treated water was measured. The boron concentration was 13.7 mg / liter. When the dry weight of the precipitate separated by decantation was measured, the dry weight was 1.85 g.

Comparative Example 2
100 g of the same boric acid aqueous solution as used in Example 1 was collected, and then 1.74 g of a 20 wt% aqueous solution of L-tartaric acid was added and stirred well. Next, 2.88 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 9.0, and the mixture was stirred well. After adding sodium hydroxide, the precipitate formed after 30 minutes and the treated water were separated by decantation, and the same separation was performed again after 60 minutes. The boron concentration of the treated water was measured and found to be 23.5 mg / liter.
Table 1 shows the boron concentration of the treated water of Examples and Comparative Examples and the dry weight of the precipitate.

Claims (4)

  A method for treating wastewater containing a boron compound, wherein after treating wastewater with a peroxide, depositing a precipitate in the coexistence of a hydroxy polyvalent carboxylic acid and an alkaline earth metal compound, the precipitate is A wastewater treatment method characterized by lowering the boron concentration in wastewater by separating it from the wastewater.   The wastewater treatment method according to claim 1, wherein the peroxide is hydrogen peroxide or a peroxide that reacts in water to produce hydrogen peroxide.   The amount of hydroxy polyvalent carboxylic acid coexisting in the waste water is 2 molar equivalents or more with respect to the amount of boron, and the amount of alkaline earth metal compound coexisting in the waste water is based on the amount of hydroxy polyvalent carboxylic acid. The wastewater treatment method according to claim 1 or 2, wherein the amount is 1 molar equivalent or more. The wastewater treatment method according to any one of claims 1 to 3, wherein the pH when depositing the precipitate is in the range of 8.5 to 10.5.