JPS6161880B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating wastewater containing sulfur compounds, fluorine, heavy metals, etc., and in particular, a method for treating wastewater containing sulfur compounds, fluorine, and heavy metals such as mercury and lead. The present invention relates to a method for treating down wastewater. Taking the limestone-gypsum method as an example, the blowdown water discharged from a wet flue gas desulfurization equipment (hereinafter referred to as membrane sulfur wastewater) is the water discharged from the circulation system that removes dust or cools the flue gas, and the water discharged from the flue gas and limestone slurry. Some are discharged from the reaction process in which sulfur dioxide in the exhaust gas is converted into gypsum via calcium sulfite through contact with sulfur dioxide and oxidation with air. This desulfurization wastewater contains pollutants such as suspended solids, dissolved inorganic substances, and dissolved organic substances, and in particular contains COD components that are difficult to remove by normal means. This COD component mainly consists of sulfur compounds such as thionate ions (S ₂ O ₆ ^2- , S ₄ O ₆ ^2- , S ₅ O ₆ ^2- ), and is generally known as a method for removing COD components. It is difficult to remove by coagulation precipitation method, chemical oxidation method, ozone oxidation method, activated carbon adsorption method, ultraviolet irradiation method, etc. Conventionally, the method of treating such desulfurization wastewater is to make the wastewater alkaline by adding one or two or more types of calcium salts and alkaline agents such as slaked coal, slaked coal, calcium chloride, caustic soda, and soda carbonate to the wastewater in advance. After adjusting the pH to preferably 10 or higher and removing most of the fluorine, heavy metals and suspended solids by coagulation-sedimentation, filtration, etc., the remaining COD components are then removed in a neutral or weakly acidic region. The COD component was selectively removed by contacting with an anion exchange resin having either a strong base type, medium base type, or weak base type active group. However, untreated fluorine and trace amounts of heavy metals remain in the coagulated and precipitated and overtreated water, and if they exceed the wastewater discharge standards, the coagulated and precipitated and overtreated treated water will be further removed to remove fluorine. In order to remove trace amounts of heavy metals, it was necessary to bring them into contact with activated alumina, and in order to remove trace amounts of heavy metals, they had to be brought into contact with a cation exchange resin to adsorb and remove the substances. Here, the contact between the waste water and the adsorbent such as activated alumina or cation exchange resin is carried out by passing the waste water through a column filled with each adhesive. Therefore, the coagulation and sedimentation, untreated residual fluorine, trace amounts of heavy metals and
In order to remove COD components, an activated alumina packed tower, a cation exchange resin tower, and an anion exchange resin packed tower having an active group type of strong base type, medium base type, or weak base type are installed. It was necessary to remove the substances by sequentially (in random order) passing treated water that had been coagulated and precipitated and overtreated through each column. However, in the methods for removing fluorine, heavy metals, and COD components using each adsorbent, the PH range during water flow is different, and the type, quantity, and usage conditions of the chemicals used to regenerate the adsorbent are different. As a result, the PH adjustment before water is passed through each tower, the operation for regeneration, and the equipment involved are complicated, and there are also disadvantages in that many types of regenerated wastewater are generated. An object of the present invention is to eliminate the drawbacks of the prior art, and to selectively remove and easily render harmless wastewater containing sulfur compounds such as thionate ions, fluorine, and heavy metals such as mercury and lead. It is an object of the present invention to provide a wastewater treatment method that simplifies the operation and configuration equipment for treatment and regeneration, and reduces the types of recycled wastewater and the amount of recycled wastewater. In order to achieve the above object, the present invention aims to convert wastewater containing sulfur compounds such as thionate ions, fluorine, and heavy metals such as mercury and lead to weak Formula () using a basic anion exchange resin as a base and quaternizing its tertiary amino group: The substance can be removed by bringing it into contact with an amphoteric adsorption resin having a quaternary ammonium group as a functional group, and is characterized by being regenerated using an alkaline agent and a mineral acid. Here, X is a halogen atom, OH or
SO ₃ H and R is CH ₃ , C ₂ H ₅ or CH ₂ ―
It represents CH ₂ --OH, n represents 1 to 3, and R' represents H or an alkaline earth metal. In the present invention, desulfurization wastewater is treated with slaked coal, calcium chloride, caustic soda, etc., and calcium salts such as caustic soda, etc., and alkaline agents, alone or in combination, and coagulated and precipitated and overtreated in an alkaline region. , remove most of the heavy metals and suspended solids, then adjust the pH, and then bring it into contact with the amphoteric adsorption resin. Since treated water that has undergone coagulation and precipitation shows alkalinity, sulfuric acid,
The pH is adjusted to about 3-8, preferably 4-6 by adding a mineral acid such as hydrochloric acid. Examples of the substrate in the amphoteric adsorption resin used in the present invention include styrene-divinylbenzene resin, vinyl chloride resin, epoxy resin, methacrylic acid resin, MMA resin, etc., and at least one tertiary amino acid resin as an ion exchange group. Any weakly basic anion exchange resin containing groups can be used. The tertiary amino group is

[Formula] or

[Formula] [In the formula, R represents CH ₃ , C ₂ H ₅ or CH ₂ — CH ₂ —OH]. The amphoteric adsorption resin used in the present invention is a basic anion exchange resin having at least one tertiary amino group as described above, and has the formula X-(CH ₂ ) n-
COOR' [in the formula, X represents a halogen atom, n is 1
~3 and R' represents H, an alkali metal or an alkaline earth metal] or a salt thereof. Examples of the monohalogen alkylcarboxylic acids include monochloroacetic acid, monochloropropionic acid, and monochlorovaleric acid. In this way, by bringing the wastewater into contact with the amphoteric adsorption resin, most of the COD components are removed by substitution at the X part of the resin, while trace amounts of heavy metals and metals such as aluminum are similarly removed at the R' part. Ru. Further, at the same time as the heavy metals, aluminum, etc. are removed, a part of the COD components and fluorine are efficiently and selectively removed without being affected by coexisting ions such as chlorine and sulfuric acid that coexist in the wastewater. As a result, COD _Mo in the treated water can be removed to 10 mg/or less, fluorine to 10 mg/or less, trace heavy metals such as mercury to below the detection limit, and lead to 0.1 mg/or less. After adsorption, the amphoteric adsorption resin is then regenerated. Regeneration is performed using alkaline agents such as caustic soda and sulfuric acid,
COD components, fluorine, and heavy metals can be easily desorbed by sequentially passing an aqueous solution of a mineral acid such as hydrochloric acid. In other words, by passing water through an aqueous solution of an alkaline agent such as caustic soda, some of the fluorine and COD are removed.
The components are desorbed, and then the remaining fluorine and heavy metals are desorbed by passing water through an aqueous solution of mineral acids such as sulfuric acid. Therefore, by separately collecting each recycled wastewater, it is possible to obtain two types of recycled wastewater containing high concentrations of COD component heavy metals. A preferred method for treating recycled wastewater containing a high concentration of COD components is thermal decomposition using a sulfuric acid solution. In this method, the recycled wastewater is treated in a low PH region, preferably in a low PH region.
The decomposition treatment is carried out by heating to PH≦1.5 and 60°C or higher, and sulfur compounds that cannot be removed by normal oxidation treatment are easily thermally decomposed, ultimately yielding sulfur dioxide. This sulfur dioxide is easily removed by normal desulfurization treatment. In addition, since fluorine is contained in the water treated for thermal decomposition of COD components, by returning it to the coagulation-sedimentation treatment equipment in the previous stage and reacting with calcium salts, it becomes insolubilized as calcium fluoride, which is then precipitated and decomposed and removed. Ru. A preferred treatment method for reclaimed wastewater containing a high concentration of heavy metals is to return it to the previous coagulation-sedimentation treatment facility and react with an alkali agent, in the same way as thermally decomposed water, to precipitate and remove it as hydroxides. can be given. In addition, the method of the present invention can be used for blowdown of exhaust gas desulfurization equipment if the wastewater contains one or more of sulfur compounds, fluorine, and heavy metals, which are difficult to treat by normal oxidation treatment such as thionate ions. It can be applied not only to water. As described above, according to the present invention, wastewater containing sulfur compounds such as thionate ions, fluorine, and heavy metals discharged from an exhaust gas desulfurization device is used as a functional group. By bringing the substance into contact with an amphoteric adsorption resin having the following structure, it is possible to easily detoxify the substance at the same time. Advanced treatments such as fluoride removal using activated alumina and heavy metal removal using cation exchange resin or chelate resin, which are required when wastewater discharge standards are exceeded, can be eliminated. In addition, it is possible to simplify the conventionally complicated pH adjustment before water flow to each tower, the operation and configuration equipment for regeneration, and further reduce the types of recycled wastewater and the amount of recycled wastewater. Production Example of Resin Production Example 1 1 Styrene-divinylbenzene resin with -N(CH ₃ ) ₂ as an ion exchange group, a spherical macroporous weakly basic anion exchange resin (OH type, 1.6 meq. /ml) and 1000ml of ion-exchanged water into a flask equipped with a stirrer, thermometer and reflux device, and stir at 25℃.
After adjusting the pH to 7.0 with 3N hydrochloric acid, raise the temperature to 50℃,
Add 46.6g of 50% monochlorosodium acetate aqueous solution, stir at 50 to 60°C for 2 hours, and then heat to 85°C.
The temperature was raised to , and stirring was continued for 3 hours. After cooling, the resin was separated and thoroughly washed with ion-exchanged water to obtain a pale yellow amphoteric ion-exchange resin (water content: 53
%). 2 The thus obtained amphoteric ion exchange resin was packed in a column, and a sulfuric acid aqueous solution was sufficiently passed through the column at SV2h ^-2 to obtain resin A having the functional groups shown in Table 1 below. Production Example 2 A monochloropyropionic acid aqueous solution was used in place of the monochlorosodium acetate aqueous solution in 1 of Production Example 1, and the same procedure as in 1 was carried out to obtain a resin B having the functional groups shown in Table 1 below. Production Example 3 Resins C to E each having the functional groups shown in Table 1 below were produced by the same operation as in Production Example 1 above. Example 1 As a functional group Experiments were conducted to remove COD components, heavy metals, and fluorine using model liquids using resins having the functional groups A to D shown in Table 1 as amphoteric adsorption resins having the following structure.

【table】

[Table] Dithionate ion (S ₂ O ₆ ^2- ) 1000 as raw water
After preparing an aqueous solution containing copper ions (Cu ²⁺ ) 50 mg/ and fluorine ions (F ^- ) 20 mg/, 1 ml of resin was added to raw water 1, and 1 ml of resin was added to raw water 1.
Stirred in a beaker at room temperature for 3 hours. After solid-liquid separation, residual dithionate ions in the aqueous solution were measured by the cetyltrimethylammonium bromide method, and copper ions and fluorine ions were measured according to JISK0102, and the adsorption amount was calculated from the difference from the raw water. The results are shown in Table 2.

[Table] Example 2 Based on the results of Example 1, the effect of removing di-thionate ions by passing water through the column was confirmed using resin A which has an excellent adsorption amount of di-thionate. Sodium dithionate solution (as S ₂ O ₆ ^2-
2000mg/, COD _Mo : 70mg/) was added to a column packed with 200ml of amphoteric adsorption resin at space velocity (SV).
The liquid was passed through the water for 10 h ^-1 and brought into contact with the treated water.
COD _Mo was analyzed to examine the COD component removal effect of the present invention. The resin is used by passing a sulfuric acid aqueous solution through it in advance at SV2h ^-1 , and the COD _Mo in the treated water is
Measured according to JISK0102. Figure 1 shows the relationship between each water flow rate (ratio of liquid flow rate to resin capacity) and the COD _Mo in the treated water at that time. As can be seen from Figure 1, according to the method of the present invention, the COD _Mo in the treated water caused by dithionic acid can be maintained at 10 mg/or less even when the water flow rate is 45 times the water flow rate, and when the exchange capacity of the resin is calculated, The amount was approximately 1.1 equivalent/-resin, and a remarkable effect of removing COD components was observed. Furthermore, the COD components captured in the resin are desorbed,
To confirm that the resin can be used repeatedly, water was passed up to 50 times the amount of resin, and a caustic soda solution (80 g/) was passed through the treated column at SV2h ^-1 to regenerate the COD in the regenerated effluent. I looked into _Mo. The results are shown in FIG. As is clear from Figure 2,
By regenerating the resin by passing a caustic soda solution in an amount of 1 to 2 times the volume of the resin, COD _Mo is effectively desorbed from the resin, and the resin can be used repeatedly. Example 3 Using actual wastewater containing thionate ions, fluorine, and various heavy metal ions, the resin of Example 1 was used.
The effectiveness of removing COD components, fluorine, and heavy metals was confirmed. The actual wastewater was taken from blowdown wastewater from the limestone-gypsum wet flue gas desulfurization equipment at thermal power plant A, and after adjusting the pH to approximately 10 with a slaked lime solution, the suspended solids were separated and the resulting liquid was collected. PH by adding hydrochloric acid
was adjusted to 5 and used as sample wastewater. The amphoteric adsorption resin used was a sulfuric acid aqueous solution sufficiently watered at SV2h ^-1 , and the other conditions were the same as in Example 2. COD components,
The removal effect of fluorine and heavy metals was investigated. Figure 3 shows the water flow rate of the sample wastewater and the measurement results of COD _Mo in the treated water. Table 3 also shows the concentrations of COD, fluorine, and heavy metals in sample wastewater and treated water. From FIG. 3, it was found that the COD _Mo during treatment caused by thionic acid could be maintained at 10 mg/distance up to a water flow rate of 44 times, and a remarkable effect of removing COD components was observed. Also the third
From the table, it was confirmed that heavy metals such as fluorine, mercury, cadmium, lead, and zinc, which coexisted in the sample wastewater with a pH of approximately 5, were removed to extremely low concentrations at the same time as COD components.

【table】 [Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the relationship between water flow rate and treated water COD in Example 2 of the present invention. FIG. 2 is an explanatory diagram showing the relationship between the water flow rate of the regenerating liquid and the COD in the regenerating waste liquid in Example 2. Figure 3: Water flow rate and treated water in Example 3 of the present invention
FIG. 2 is an explanatory diagram showing the relationship between CODs.

Claims (1)

[Scope of Claims] 1. Wastewater containing sulfur compounds such as thionate ions, fluorine, and heavy metals, which are generated when gas generated by burning coal or petroleum, is treated as an ion exchange group with at least one ion exchange group. The base is a weakly basic anion exchange resin having a tertiary amino group, and the formula () is obtained by quaternizing the tertiary amino group: [In the formula, X is a halogen atom, OH or SO ₃ H
and R is CH ₃ , C ₂ H ₅ or CH ₂ -CH ₂ -
OH, n represents 1 to 3, and R' represents H, an alkali metal or an alkaline earth metal] is brought into contact with an amphoteric adsorption resin having a quaternary ammonium group as a functional group. processing method. Claim 1 using an amphoteric adsorption resin having a quaternary ammonium group of the formula () in which 2 X represents a halogen atom or SO ₃ H as a functional group.
Wastewater treatment method described in section. 3 Add calcium salts and alkaline agents to the desulfurization wastewater, coagulate and precipitate it in an alkaline region, over-treat it, add mineral acid to adjust the pH to about 3 to 8, and then add the quaternary ammonium group of formula (). The method for treating wastewater according to claim 1 or 2, which comprises bringing the wastewater into contact with an amphoteric adsorption resin having a functional group.