JPH11235595A - Treatment of boron-containing waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of removal of boron in waste water by concentrating the boron-contg. waste water, then, adding a compd. which releases rare earth element ions or IVb group element ions by being dissolved in water to the concentrated liquid to produce an insoluble precipitate and then, separating the produced insoluble precipitate into the solid and the liquid. SOLUTION: In a process of treating boron-contg. waste water, after the waste water is concentrated, a compd. which releases rear earth element ions and/or IVb group element ions by being dissolved in water is added to the concentrated liquid to remove boron from the boron-contg. waste water. As to a method for concentrating the boron-contg. waste water, for example, a concentrating method by using an anion exchange resin or a boron-selective adsorbing resin or a concentrating method by using a reverse osmosis membrane can be used. By the concentrating method using the anion exchange resin, the boron-contg. waste water is first brought into contact with the anion exchange resin to adsorb the boron to the resin, then, the boron is desorbed by using a mineral acid or the like and the desorption liquid (concentrated liquid) is recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for treating boron-containing wastewater, and more particularly, to a method for treating boron-containing wastewater that can efficiently remove boron from wastewater.

[0002]

2. Description of the Related Art Boron compounds represented by boric acid and sodium borate are widely used in the glass industry, nickel plating additives, preservatives, dyes, pigments, cosmetics, soaps, photographs, and the like. In addition, wastewater generated from these manufacturing processes contains boron compounds. In addition, boron compounds are also contained in radioactive waste fluids generated from nuclear power plants, flue gas desulfurization wastewater, smokewash wastewater in garbage incineration plants, and the like. Boron is an essential element for plants, but it is known that excessive addition inhibits its growth. In Japan, a very strict allowable concentration in wastewater of 1-2 mg / l or less has been established by ordinance. Some are. As a method of treating such boron-containing wastewater, aluminum sulfate, slaked lime, etc.,
A method of removing as an insoluble precipitate (first method), a method of adsorbing with an anion exchange resin or a boron selective adsorption ion exchange resin (second method), a method of treating with a reverse osmosis membrane (third method), and the like. Are known.

However, in the first of these methods, the efficiency of removing boron is low. Therefore, in order to force the concentration of boron in the treatment solution to be low, the amount of a coagulant such as aluminum sulfate must be reduced. It has to be increased, and there is a problem that a large amount of sludge is generated. Also, the second
In the method (1), when the resin is regenerated and used, there is a problem that it is difficult to treat the regenerated waste liquid. Further, in the third method, a generally used reverse osmosis membrane has a removal rate of 50 to 60% for a boron compound.
Therefore, there are problems that multi-stage equipment is required to process the wastewater below the wastewater regulation value, and the initial cost becomes excessive.

Further, a method has been proposed which combines the coagulation sedimentation method with the removal of boron by an anion exchange resin or a boron selective adsorption ion exchange resin (JP-A-57-1804).
93, JP-A-58-193786), but also in this method, the load on the adsorbent resin in the latter stage increases due to the low removal efficiency in the first-stage coagulation-sedimentation method, and the waste liquid There is a problem that the processing amount is not enough,
In addition, even when the coagulation sedimentation method is used when treating the recycled waste liquid from the resin, the removal efficiency of the coagulation sedimentation method is low, so it is necessary to return high-concentration treated water to the resin tower, and the equipment is large. However, there remains a problem that the removal efficiency of boron in the coagulation sedimentation method is increased in any of the methods. Further, a method of treating low-concentration boron wastewater by using a hydrated oxide of a rare earth element has also been proposed (see Japanese Patent Publication No. 3-22238).

[0005]

However, even with this method, the processing efficiency is poor, and there is a problem that a large amount of addition or a long-time reaction (stirring) is required for processing boron to a low concentration. An object of the present invention is to provide a method for treating boron-containing wastewater that can efficiently remove boron from the boron-containing wastewater and that can reduce the amount of sludge generated.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve such problems, and as a result, after concentrating a boron-containing wastewater, the boron-containing wastewater is dissolved in water to obtain rare earth element ions and / or IVb group ions. It has been found that boron can be efficiently removed from a boron-containing wastewater by adding a compound that releases elemental ions, and the present invention has been achieved. That is, the first invention concentrates the boron-containing wastewater,
Adding a compound that dissolves in water to the concentrated solution to release a rare earth element ion or a group IVb element ion to form an insoluble precipitate, and then performs solid-liquid separation of the formed insoluble precipitate; The gist is a method of treating wastewater. Further, the second invention has a gist of the above-mentioned method for treating boron-containing wastewater, wherein the boron-containing wastewater is concentrated using an anion exchange resin.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The method for concentrating the boron-containing wastewater in the present invention includes a method of concentrating using an anion exchange resin or a boron selective adsorption resin, a method of condensing water by heating or depressurizing, a method of concentrating using a reverse osmosis membrane, and an electrical property. And the like. In the present invention, the boron-containing wastewater to be treated
When S, heavy metal, or the like is contained, SS, heavy metal, or the like may be removed by coagulation precipitation or the like before concentration.

[0008] To concentrate the boron-containing wastewater using an anion exchange resin, for example, the following method may be used. First, contact the boron-containing wastewater with the anion exchange resin,
Adsorb boron to resin. As the anion exchange resin to be used, for example, a matrix resin formed from a solid, water-insoluble organic polymer in a normal state is used as a base,
Examples include those having a cationic ion exchange group sufficient to control ion exchange. Specifically, a quaternary ammonium group is exchanged in a resin matrix formed from a phenolic, styrene, or acrylic polymer. -Selective adsorption ion exchange with ion-exchange groups such as strongly basic anion-exchange resin having as a base, weakly basic anion-exchange resin having a primary to tertiary amino group as an exchange group, N-methylglucamine, and complex amino group Resins. Among these, the boron selective adsorption ion exchange resin is capable of selectively adsorbing boron even if the wastewater contains anions such as chloride ions and sulfate ions other than boron, so that the amount of wastewater treated Is particularly preferable since it is more than a general anion exchange resin.

The contact method may be either a column method or a batch method. However, the column method is preferred because the amount of the resin with respect to boron can be small and the boron can be treated to a low concentration. preferable. In addition, since the contact condition depends on the type of the resin used and the boron concentration in the waste water, it is preferable to appropriately determine the contact condition. Further, since the amount of the boron-containing wastewater to be contacted also depends on the type of the resin to be used and the boron concentration in the wastewater, it is preferable to appropriately determine the amount. For example, as an anion exchange resin, N-methylglucamine is a functional group. When treating a boron-containing wastewater of about 10 mg / l using a boron selective adsorption resin having a
1. Resin wastewater can be treated.

Next, the boron adsorbed on the anion exchange resin is desorbed using a mineral acid or the like, and the desorbed liquid (concentrated liquid) is recovered. The mineral acid used in the elimination is not particularly limited, for example, as an anion exchange resin,
When a boron selective adsorption resin having N-methylglucamine as a functional group is used, 0.5N / L of 2N hydrochloric acid is used.
After using about the resin, boron can be desorbed by washing with about 2 to 5 l / l resin using ion-exchanged water.

The boron concentration of the desorbed solution is low at the beginning of desorption,
Thereafter, it rises with time, and falls in the latter period. In the present invention, the higher the boron concentration of the desorbed liquid (concentrated liquid), the higher the boron removal effect in the subsequent coagulation and sedimentation. Therefore, it is preferable that the boron concentration of the desorbed liquid (concentrated liquid) be high. Specifically, it is preferably at least 100 mg / l, particularly preferably at least 500 mg / l. For this reason,
It is preferable to separate and collect only the portion having a high boron concentration, and it is preferable to concentrate the portion having a low boron concentration again.

In the present invention, the concentrated solution thus concentrated is dissolved in water to obtain rare earth element ions and / or
Alternatively, a compound that releases a group IVb element ion is added to generate an insoluble precipitate, and then the insoluble precipitate is subjected to solid-liquid separation.
Rare earth element ions or I dissolved in water used in the present invention
Examples of the compound that emits a group Vb element ion include scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, which are rare earth elements and group IVb elements.
Among compounds containing promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, titanium, zirconium, and hafnium, those that release these element ions by dissolving in water, There is no particular limitation, and examples thereof include compounds containing a rare earth element and a group IVb element in the form of chloride, nitrate, sulfate, carbonate, ammonium salt, acetate, acetylacetonate, alkoxide and the like. Among these element ions, compounds containing zirconium, cerium, yttrium, neodymium, lanthanum, samarium, gadolinium, and the like are preferable because they have a high effect of fixing and removing boron. In the present invention, these compounds may be used alone or as a mixture of two or more.

These compounds may be in the form of a liquid such as a liquid or an aqueous solution, a powder, a flake, a slurry, or the like. For ease of use, the solid compound is dissolved in water before use. Then, it is preferable to use it as an aqueous solution. As for the addition amount of these compounds, the processing accuracy tends to be improved as the amount added becomes large, but naturally the amount of sludge generated also increases. Therefore, it is usually necessary to add 0.05 to 10 equivalents to boron. Preferably, 0.1 to 2
Optimally, it is added in an equivalent amount range.

In the present invention, when an insoluble precipitate is not generated even when these compounds are added, the pH is adjusted to 2 to 14, preferably 5 to 12 by adding an alkali agent or the like, and the insoluble precipitate is added. Should be generated. Also, the desorbed liquid from the boron-selective adsorption ion exchange resin or the anion exchange resin may contain a strongly acidic mineral acid,
These compounds may be added after adjusting the pH of the desorption water in advance. As the alkaline agent used for adjusting the pH,
There is no particular limitation, and calcium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, ammonia and the like are used. In the present invention, a coagulant other than such a compound can be used as a supplement. Such a flocculant is not particularly limited, and examples thereof include an aluminum compound, an iron compound, and a zinc compound.

[0015] The method of solid-liquid separation is not particularly limited, and may be performed by a commonly used method.
For example, sedimentation separation, flotation separation, filtration, centrifugation and the like can be mentioned. Further, at the time of these solid-liquid separations, a polymer coagulant or the like may be used in combination. The treated water thus obtained may be released as it is when the boron concentration is sufficiently low, and if it is not sufficiently low, the treatment water may be returned as it is or returned to the raw water-containing wastewater containing boron. Just do it.

[0016]

Next, the present invention will be described in detail with reference to examples. Example 1 A wastewater containing boron at a concentration of 5 mg / l was adsorbed on a boron selective adsorption ion exchange resin UR-3500 (manufactured by Unitika), and then boron was desorbed using 2N hydrochloric acid to remove boron. Was obtained at a concentration of 1,200 mg / l. After adding sodium hydroxide to the concentrated solution to adjust the pH to 7, a rare earth chloride aqueous solution (concentration: 200 g / l, composition (in terms of oxide): cerium 5
1.4% by weight, 17.8% by weight of neodymium, 4.8% by weight of praseodymium)
The pH was adjusted to 9 with an aqueous sodium hydroxide solution to generate an insoluble precipitate. In this solution, a polymer flocculant UF-105 was added.
The precipitate was aggregated by adding 30 mg (manufactured by Unitika), filtered through a filter paper (No. 5C), and then the boron concentration of the filtrate was measured by ICP (high frequency inductively coupled plasma) emission spectrometry. 1 and the boron removal rate at this time was 96%. The amount of sludge generated at this time was 23.3 g by dry weight.

Example 2 A concentrated solution obtained by using a boron selective adsorption ion exchange resin in the same manner as in Example 1 (boron concentration: 1,200 mg /
l) To 1,000 ml of sodium hydroxide was added to adjust the pH to 7, then 50 ml of an aqueous zirconium oxychloride solution (concentration: 200 g / l) was added, and p
H was adjusted to 9 to generate an insoluble precipitate. 30 mg of a polymer flocculant UF-105 (manufactured by Unitika) is added to this solution.
The precipitate was added to aggregate the precipitate, and after filtration through filter paper (No. 5C), the boron concentration of the filtered water was measured by ICP emission spectrometry to be 56.8 mg / l, and the boron removal rate was 95%.
Met. The amount of sludge generated at this time was 37.8 g by dry weight.

Comparative Example 1 0.31 to 10 ml of the same rare earth chloride aqueous solution as in Example 1 was added to 1 liter of wastewater containing boron at a concentration of 5 mg / l, and the pH was adjusted to 9 with a sodium hydroxide solution. An insoluble precipitate developed. In this solution, a polymer flocculant UF-1 was added.
05 (manufactured by Unitika) was added to aggregate the precipitate,
After filtration through filter paper (No. 5C), the boron concentration of the filtered water was measured by ICP emission spectrometry. Table 1 shows the results.

[0019]

[Table 1]

A rare earth chloride aqueous solution of 0. 5 mg of boron is added to 5 mg of boron.
Adding 33 ml means 1,200 mg of boron
When the boron-containing wastewater is not concentrated, the boron removal rate is 18% as shown in Table 1, and the boron-containing wastewater is concentrated beforehand. In this case (Example 1), the boron removal rate is 96%, which means that boron can be removed very efficiently by pre-concentrating the boron-containing wastewater and then reacting with rare earth chloride. Further, when not concentrated, the addition amount of the rare earth chloride aqueous solution required to achieve a boron removal rate of 90% or more was 5 ml (boron 1,20).
(1,200 ml for 0 mg), which requires a 15-fold or more addition amount as compared with the case of concentration (Example 1).

[0021]

According to the present invention, the boron-containing wastewater can be efficiently treated, and the amount of the compound that dissolves in water and releases rare earth element ions or IVb group element ions can be significantly reduced. As a result, the amount of sludge generated can be reduced.

Claims (2)

[Claims] After concentrating a boron-containing wastewater, a compound that is dissolved in water and releases a rare earth element ion or a group IVb element ion is added to the concentrated liquid to form an insoluble precipitate,
Next, a method for treating boron-containing wastewater, wherein the produced insoluble precipitate is subjected to solid-liquid separation. 2. The method for treating boron-containing wastewater according to claim 1, wherein the boron-containing wastewater is concentrated using an anion exchange resin.