JPH08168798A - Treatment of heavy metal-containing waste water - Google Patents

Abstract

PURPOSE: To reduce a heavy metal concn. by adsorbing and removing heavy metal ions with a chelating resin, etc., in which an alkali metal type and an H type in an exchange group are at a specified ratio after adjusting an alkaline waste water after solid-liq. separation to be below a specified pH. CONSTITUTION: At first, a heavy metal-containing waste water 11 is introduced into a flocculating/settling tank 1 after adding previously alkali to the waste water to make hydroxide and adjusting pH so that solubility becomes minimum. Then, a supernatant liq. in the flocculating/settling tank 1 is transferred to a filter 3 through an intermediate tank 2, and after filtering a fine flock, the liq. is transferred to a pH adjusting tank 4 and adjusted to <=pH5. Then, an acidic waste water overflowing the pH adjusting tank 4 is transferred to a neutralizing tank 5, and also a neutral waste water overflowing the neutralizing tank 5 is transferred to a storage tank 6. Then, the waste water having pH adjusted within a specified range is transferred to a heavy metal removing column 8 through the filter 7, and heavy metal ions in the waste water are adsorbed and removed with the chelating resin, etc., 33 in which 60-100 equivalence % of the exchange group is the alkali metal type and 0-40 equivalence % is the H type.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment method for efficiently removing heavy metals from wastewater containing heavy metals.

[0002]

2. Description of the Related Art The following methods are conventionally known as methods for removing heavy metals from wastewater containing heavy metals such as cadmium, zinc, nickel, lead and divalent iron that do not precipitate in the vicinity of acidity or neutrality. It was

That is, alkali is added to the heavy metal-containing wastewater to convert the heavy metal into hydroxide, and the pH is adjusted so that the solubility of the heavy metal hydroxide is minimized. The precipitate and the supernatant water are separated by a separating means. Since supernatant water contains fine flocs of heavy metals, the supernatant water is filtered to remove the fine flocs, which are then neutralized to remove residual heavy metal ions dissolved in a chelate resin or weakly acidic cation exchange resin. Is a method of adsorbing and removing.

[0004]

However, in recent years, the emission regulations of heavy metals have become strict, and the above-mentioned conventional methods may not always be able to clear the regulation values. This is because the above conventional method has the following drawbacks.

In the waste water to be adsorbed by a chelate resin or a weakly acidic cation exchange resin, fine heavy metal hydroxides, carbonates, silicates, in addition to trace amounts of SS components leaked by filtration, Some heavy metal oxides are present, and these heavy metal hydroxides are not adsorbed and removed by chelating resins or weakly acidic cation exchange resins, so that trace amounts of heavy metals leak and the concentration of heavy metals in the treated water increases. It is not constant and has variations.

Further, since the exchange group of the weakly acidic cation exchange resin or the chelate resin used for removing heavy metal ions is usually Na type, the Na type exchange group is hydrolyzed to give NaO.
Since H is generated, the pH of the water in the resin layer and eventually the pH of the treated water
Is as high as 9-10. Therefore, hydroxides of heavy metal ions are likely to be generated in the resin layer, which also contributes to an increase in the amount of leakage of heavy metals into the treated water.

The problem to be solved by the present invention is to reduce the concentration of heavy metals in treated water as much as possible in a method for adsorbing and removing heavy metals in wastewater containing heavy metals using a chelate resin or an ion exchange resin for weak acidity. Is to provide a method.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have made the pH of the alkaline separation liquid after the coagulation and removal of heavy metals in the form of hydroxides acidic. After that, it was found that the heavy metal in the waste water can be significantly reduced by adsorbing with a chelate resin or the like, and the present invention has been completed.

That is, according to the present invention, an alkali is added to wastewater containing heavy metals to aggregate the heavy metals in the wastewater as hydroxides for solid-liquid separation, and then a chelate resin or a weakly acidic cation exchange resin is used to remove heavy metals in alkaline wastewater. In the method of removing ions by adsorption, the alkaline wastewater after solid-liquid separation is
After H5 or less, 60 to 100 equivalent% of the exchange group is in an alkali metal form or an alkaline earth metal form and is 0 to 40.
The present invention relates to a method for treating heavy metal-containing wastewater, characterized in that heavy metal ions in the wastewater are adsorbed and removed by a chelate resin having an equivalent% of H type or a weakly acidic cation exchange resin.

A feature of the present invention is that the alkaline wastewater after solid-liquid separation is acidified to have a pH of 5 or less to dissolve the fine hydroxides and carbonates of heavy metals contained in the alkaline wastewater, and to dissolve heavy metal ions. By dissociating into a chelate resin or a weakly acidic cation exchange resin in the latter stage, the adsorption is more complete.

In the present invention, the method for adjusting the alkaline waste water after solid-liquid separation to pH 5 or less is not particularly limited, but for example, there is a method of adding a strong acid such as hydrochloric acid, sulfuric acid and nitric acid.

The alkaline waste water may be passed through a weakly acidic cation exchange resin to have a pH of 5 or less. In this case, the alkaline waste water is simply passed through the weakly acidic cation exchange resin to adjust the pH of the waste water. It is possible to make sure that it is 5 or less, and since a part of the heavy metal ions in the wastewater is adsorbed by the weak acid cation exchange resin, a chelate resin or a weak acid cation exchange for adsorbing heavy metal ions in the latter stage. There is an advantage that the load on the resin can be reduced.

The weakly acidic cation exchange resin for adjusting the pH of the alkaline drainage to 5 or less may have 100 equivalent% H type exchange groups, but 40 equivalent% or less of all exchange groups are Na type and 60 equivalent%. % Of H type mixed resin may be used, and if the mixing ratio of Na type is within this range, the pH of the waste water is sufficiently maintained at 5 or less. In order to adjust the pH of the alkaline wastewater to 5 or less by using the weakly acidic cation exchange resin, the alkaline wastewater may be passed as it is, but the pH is 8 to 10
It is preferable that the liquid is passed after the adjustment. When the pH of the alkaline wastewater becomes 10 or more, the amount of alkali increases and H
This is because the shaped resin changes to the Na type relatively quickly and the treatment amount decreases. Examples of the weakly acidic cation exchange resin used to adjust the pH of the alkaline wastewater to 5 or less include Amberlite (registered trademark, manufactured by Rohm and Haas Co., Ltd.).
The same applies hereinafter) IRC-50, IRC-76, DIAION (registered trademark, the same applies hereinafter) WK10, W20, etc. manufactured by Mitsubishi Chemical Corporation.

Examples of the chelate resin or weakly acidic cation exchange resin used for adsorbing a trace amount of heavy metal ions contained in acidified wastewater having a pH of 5 or less include Amberlite IRC-718 and Diaion CR-10.
Iminodiacetic acid type chelating resin such as DIAION CR-
Examples thereof include polyamine type chelate resins such as 20 and resins such as weakly acidic cation exchange resins similar to those used for the above neutralization.

The exchange group of the chelate resin or the weakly acidic cation exchange resin which adsorbs these heavy metal ions can adsorb heavy metal ions sufficiently even in the alkali metal form such as Na or the alkaline earth metal form such as Ca. However, for example, when acidic wastewater is passed through a 100 equivalent% Na-type resin, the Na-type exchange groups are hydrolyzed to generate NaOH, so that the pH of the treated water becomes as high as 9 to 10, and In, the hydroxide of heavy metal is easily generated, and although the amount of heavy metal is very small,
It is easy to leak. In order to prevent this pH increase and maintain the pH of the treated water in the vicinity of neutrality, and to prevent the leakage of a trace amount of heavy metals, 60 equivalent% or more, preferably 60 equivalent% or more, of the exchange groups of the chelate resin or the weakly acidic cation exchange resin is preferable. Is 60-9
0 equivalent% is an alkali metal form or alkaline earth metal form, 40 equivalent% or less, preferably 10 to 40 equivalent% is H
It is preferred to use mixed resins of the form. Examples of the alkali metal type exchange group include Na type, NH _{4 type} and K type, and examples of the alkaline earth metal type exchange group include Ca type and Mg type. Among the exchange groups of the chelate resin or the weakly acidic cation exchange resin, the alkali metal type is preferable to the alkaline earth metal type. That is, both the chelate resin and the weakly acidic cation exchange resin,
This is because the selectivity for heavy metal ions is generally higher for alkaline earth metal ions than for alkali metals, and the use of an alkali metal type resin having a lower selectivity is superior in the adsorption of heavy metal ions.

As a method of preparing a mixed resin of an alkali metal type or an alkaline earth metal type and an H type, for example, a chelating resin or a weakly acidic cation exchange resin is prepared by passing a reagent such as caustic soda or calcium chloride during regeneration. There is a method in which the exchange group is changed to 100 equivalent% alkali metal type or alkaline earth metal type, and then a predetermined amount of acid such as hydrochloric acid is passed through to partially convert the exchange group into H type. It should be noted that these resins must be mixed prior to the passage of waste water so that they are sufficiently uniform in the vertical direction in the resin tower.

Wastewater having a pH of 5 or less which is passed through the chelate resin or the weakly acidic cation exchange resin may be directly passed through the chelate resin or the weakly acidic cation exchange resin at a pH of 5 or less, but it is about pH 7 before and after. After the addition, water may be passed through the chelate resin or the weakly acidic cation exchange resin.

In the first stage of the method of the present invention, alkali is added to the heavy metal-containing wastewater to aggregate as a hydroxide, and solid-liquid separation is performed. At this time, if the pH is selected so that the solubility of the hydroxide is minimum, Good. The pH at which the solubility of hydroxides of heavy metals is the minimum depends on the type of heavy metal. For example, pH is 11 or more for cadmium, pH 8 to 9 for zinc, pH 9 to 11 for nickel, and lead for pH is 9-10.

The method of aggregating the heavy metal hydroxide and solid-liquid separating it in the preceding stage of the method of the present invention is not particularly limited. For example, a heavy metal hydroxide is added by adding an aggregating agent such as an anionic polymer aggregating agent. The substance may be aggregated and allowed to settle, and then the supernatant water may be filtered to remove fine flocs using a filter medium such as sand or anthracite.

The method of the present invention will be described below with reference to FIG.

FIG. 1 shows an example of a heavy metal removing apparatus for carrying out the method of the present invention. Alkali is added to the heavy metal-containing wastewater to convert the heavy metal into hydroxide, and the wastewater 11 whose pH is adjusted so that the solubility thereof is minimized is caused to flow into the coagulating sedimentation tank 1. In order to coarsen the heavy metal hydroxide in the coagulating sedimentation tank 1 to facilitate sedimentation,
Polymer flocculant 12 is added. The sludge aggregated and settled is collected at the bottom by the sludge scraper 34 and discharged from the pipe 13 at the bottom.

On the other hand, the supernatant water is sent to the relay tank 2 from the overflow pipe 14 above the coagulating sedimentation tank 1. Since fine flocs of heavy metals remain in this supernatant water, they are transported from the pump 9 to the filter 3 via the pipe 15. Filter 3
The inside of the is filled with a filter medium 31 such as anthracite or sand, where fine flocs are removed by filtration, and the filtered water is sent to the pH adjusting tank 4 via the pipe 16. p
The filtered water in the H adjusting tank 4 is sufficiently mixed by the stirrer 35, and the acid is injected from the pipe 17.

A pH meter is installed in the pH adjusting tank 4,
The pH of the filtered water in the H adjustment tank should be in the range of 2-5,
The opening degree of the control valve 41 attached to the pipe 17 is adjusted. Instead of the control valve for adjusting the pH of the filtered water in the pH adjustment 4 to the acidic side, a pump having a mechanism for adjusting the rotation speed and stroke according to the pH value may be used.

The acidic waste water overflowing the pH adjusting tank 4 flows into the neutralizing tank 5 and is well mixed by the stirrer 37 installed in the neutralizing tank 5, while the alkali is injected from the pipe 18.
A pH meter 38 is attached to the neutralization tank 5, and the opening degree of the control valve 42 attached to the pipe 18 is adjusted so that the pH of the drainage water of the neutralization tank 5 becomes a predetermined pH near neutral. Instead of the control valve for adjusting the drainage of the neutralization tank 5 to near neutral, a pump having a mechanism for adjusting the rotation speed and stroke according to the pH value may be used.

The neutral drainage overflowing the neutralization tank 5 is stored in the storage tank 6
To monitor the pH with a pH meter 39, p
When H does not fall within a predetermined range, for example, from pH 5.8 to pH 8.6, it is returned from the pipe 43 via the pump 10 to the previous step of aggregation and precipitation. The wastewater having a pH within a predetermined range flows through a pipe 19 into a filter 7 having a filter material 32 such as sand filled therein, and is filtered again, and the filtered water passes through a pipe 20 and a pipe 21. , To the heavy metal removal tower 8. The filter 7 may be omitted in some cases. The heavy metal removal tower 8 contains 60 to 90 of the exchange groups.
Equivalent% is alkali metal type or alkaline earth metal type,
It is filled with a heavy metal removing resin 33 composed of a weakly acidic cation exchange resin of 10 to 40 equivalent% H type or a chelate resin. With this heavy metal removing resin 33, the heavy metal ions in the inflowing heavy metal-containing wastewater are almost completely adsorbed and removed, and the treated water is discharged from the pipe 22.

Next, the recycling process of the heavy metal removing resin 33 will be described. First, 5 to 10% of hydrochloric acid is introduced from the pipe 25, the heavy metal adsorbed on the heavy metal removing resin 33 is eluted through the distributor 40, all the exchange groups of the resin are changed to the H type, and the regenerated waste liquid thereof. Is discharged from the pipe 28.

After that, as a chemical liquid extrusion process, the pipe 27 is used.
More pushed water is supplied, and the chemical solution in the tower is extruded in the same line as the hydrochloric acid passage step.

Next, the heavy metal-containing waste water, which is raw water, is supplied from the pipe 21 and discharged from the pipe 28 to wash the resin 33 in the tower.

Further, in order to change all the H type resin to the Na type, 2 to 4% of caustic soda solution is supplied from the pipe 26, and the same steps as in the case of the hydrochloric acid medicine are carried out to carry out the medicine passing, extrusion and washing steps. carry out.

Generally, the amount of hydrochloric acid used as a regenerant is 2 to 7 times the total exchange capacity of the resin 33, and the amount of caustic soda is 1.0 to 1.5 times the exchange capacity of the resin. To do. In order to change a part of the exchange groups of the weakly acidic cation exchange resin or chelate resin which has become Na-form to H-form to form a mixed resin of Na-form and H-form, after the above caustic soda feed, extrusion and washing steps are completed. Into the layer of the resin 33, the amount of hydrochloric acid necessary for converting 10 to 40 equivalent% of the exchange groups of the resin 33 into the H form is introduced from the pipe 25 as a 5 to 10% aqueous solution. When the injection of the predetermined amount of hydrochloric acid is completed, the pressurizing water is supplied from the pipe 27 to extrude the injected hydrochloric acid. When the extrusion of hydrochloric acid is completed, water is removed from the inside of the tower through the pipe 28 while allowing air to enter through the pipe 30. The drainage position is usually set so that the water level in the tower is 20 to 30 cm above the resin surface. Then, supply the mixing air from the pipe 29,
The resin 33 in the tower is mixed well. Mixing time is generally 3
It may be for up to 5 minutes. Immediately after the mixing is completed, the drainage is supplied from the pipe 21, and the air in the tower is discharged from the pipe 30, and at the same time, the water in the tower is drained from the pipe 28 to fill the inside of the tower.

As another method for making a part of the resin in the column into the H type, the amount of the caustic soda to be passed is 9% of the total exchange capacity of the resin.
It may be an amount corresponding to 0 to 60 equivalent%. In this case, there is an advantage that the hydrochloric acid injection step, which is the final step, can be omitted.

[0032]

【Example】

Example 1 A chelating resin for adsorbing and removing heavy metal-containing wastewater was pretreated and regenerated. First, pretreatment was performed under the conditions shown in Table 1.

[0033]

[Table 1]

200 ml of the chelating resin (IRC-718) whose exchange group is Na type was packed in a column, and the pretreatment chemical solution shown in Table 1 was passed in a downward flow at a rate of 6 liters per hour. The solution was passed until the cadmium ion and nickel ion leaked from the lower part of the column.

After completion of the pretreatment, regeneration treatment was performed under the conditions shown in Table 2 so that the chelate resin was 100% Na type.

[0036]

[Table 2]

On the other hand, caustic soda was added to the waste water containing nickel and cadmium to adjust the pH to 12.5, and heavy metals were coagulated and precipitated in the form of hydroxide and filtered. Table 3 shows the results of analyzing the waste water after filtration.

[0038]

[Table 3]

Sulfuric acid was added to the heavy metal-containing waste water in Table 3 to obtain p
H3. The amount of sulfuric acid required for producing the acidic waste water of pH 3 was 1725 mg / L. Next, the acidic waste water was neutralized to pH 7 with caustic soda. The amount of caustic soda required for neutralization was 118 mg / L.

The neutralized waste water was passed through the column filled with the chelate resin regenerated under the conditions shown in Table 2 at a rate of 6 liters for 1 hour. When the concentrations of cadmium and nickel in the treated water flowing out from the lower part of the column were analyzed, cadmium was 0.3 to 0.6 μg Cd / L and nickel was 0.4
It was ˜0.8 μg Ni / L. The pH of the treated water is 7.
It was in the range of 5 to 9.0.

Example 2 A chelating resin for adsorbing and removing wastewater containing heavy metals was pretreated and regenerated. First, pretreatment was performed under the conditions shown in Table 4.

[0042]

[Table 4]

170 ml of the chelating resin (IRC-718) having Na as the exchange group and 30 ml of H type were mixed and packed in a column, and the pretreatment chemical solution shown in Table 4 was added at 6 liters per hour. Water was passed in a downward flow at a rate of up to until cadmium ions and nickel ions leaked from the lower part of the column.

After completion of the pretreatment, the chelate resin (IRC-7
18) was regenerated under the conditions shown in Table 5, and 80 equivalent% of the exchange group was N
A resin was prepared which was Form a and 20 equivalent% was Form H.

[0045]

[Table 5]

After the completion of extrusion III, the chelate resin was taken out from the column, mixed well, and then refilled in the column.

Sulfuric acid was added to the wastewater containing nickel and cadmium shown in Table 3 of Example 1 to adjust the pH to 3, and the acidic wastewater was neutralized to pH 7 with caustic soda.

The above neutralized waste water was passed through the column regenerated under the regeneration conditions shown in Table 5 at a rate of 6 liters per hour.
When the treated water flowing out from the bottom of the column was analyzed, cadmium was 0.2 to 0.5 μg Cd / L and nickel was 0.3 to 0.7 μg Ni / L. The pH of the treated water was in the range of 6.5 to 7.5.

Comparative Example 1 Pretreatment and regeneration treatment were carried out in the same manner as in Example 1 to prepare a column packed with a chelating resin having an Na exchange group of 100%.

The heavy metal-containing wastewater having a pH of 12.5 shown in Table 3 was neutralized to pH 7 by adding sulfuric acid without turning it to an acidic side, and water was passed through the column at a rate of 6 liters per hour. did. When the treated water flowing out from the lower part of the column was analyzed, it was found that cadmium was 3 to 13 μg Cd / L and nickel was 5 to 15 μg / L. The pH of treated water is
It was 9-10.

Comparative Example 2 CaC was used instead of the Na-type chelating resin used in Comparative Example 1.
The heavy metal-containing wastewater was treated in the same manner as in Comparative Example 1 except that the chelate resin which was made into Ca form with the l ₂ solution was used.
Cadmium in the treated water was 2 to 10 μg Cd / L, and nickel was 4 to 12 μg Ni / L. In addition, p of treated water
H was 8 to 9.2.

As described above, the heavy metal-containing waste water is once acidified, then neutralized, and treated with a chelate resin.
It can be seen that the method 2 can significantly reduce the concentration of heavy metals in the treated water as compared with the conventional methods of Comparative Examples 1 and 2 in which the heavy metal-containing wastewater is simply neutralized and treated with a chelate resin.

Example 3 A weakly acidic cation exchange resin for adsorbing and removing wastewater containing heavy metals was pretreated and regenerated. First, pretreatment was performed under the conditions shown in Table 6.

[0054]

[Table 6]

Weakly acidic cation exchange resin (IRC-76)
The exchange group of Na is 170 ml and H is 30 m
l was mixed and packed in a column, and the lead nitrate solution shown in Table 6 was passed in a downward flow of 6 liters per hour. Water flow was stopped when lead ions flowed out from the bottom of the column.

After completion of the pretreatment, the weakly acidic cation exchange resin (IRC-76) was regenerated under the conditions shown in Table 7, and 78 equivalent% of the exchange group was Na form and 22 equivalent% was H form resin. Prepared.

[0057]

[Table 7]

After the completion of the extrusion III, the weakly acidic cation exchange resin was taken out from the column, mixed well and then refilled in the column, while caustic soda was added to the lead-containing waste water to obtain a pH of 9.4.
The heavy metal was coagulated and precipitated in the form of hydroxide, and the filtered wastewater was analyzed. The analysis results are shown in Table 8.

[0059]

[Table 8]

The lead-containing waste water in Table 8 was adjusted to pH 3 with sulfuric acid.
The amount of sulfuric acid required to reach pH 3 was 104 mg / L. Then, the drainage of pH 3 is adjusted to pH 7 with caustic soda.
Neutralized. The amount of caustic soda required for neutralization was 73 mg.
Was / L.

The neutralized waste water after neutralization was passed through the column regenerated under the conditions shown in Table 7 at a rate of 6 liters for 1 hour. As a result of analyzing the treated water flowing out from the lower part of the column, the lead concentration in the treated water was 0.02 to 0.04 mg / L.
The pH of the treated water was in the range of 6.4 to 7.2.

Example 4 In accordance with Example 3, a column packed with a weakly acidic cation exchange resin which had been subjected to pretreatment and regeneration treatment was used to neutralize the acid wastewater having the lead-containing wastewater of Table 8 at pH3. Without passing water. As a result, the lead concentration in the treated water is 0.03 ~
It was 0.05 mgPb / L. Also, the pH of treated water
Was in the range of 6.3 to 6.9.

Comparative Example 3 A column of Table 6 was loaded with a Na-type cation exchange resin (IRC-7).
6) was filled with 200 ml, and the pretreatment liquid of Table 6 was added to the pretreatment liquid for 6 hours.
Water was passed at a rate of 1 liter, and water was passed until the lead ions leaked out from the lower part of the column to perform pretreatment. After the completion of the pretreatment, a regeneration treatment was performed under the conditions shown in Table 9 to make the weakly acidic cation exchange resin 100% Na type.

[0064]

[Table 9]

The lead-containing wastewater of pH 9.4 shown in Table 8 above was neutralized to pH 7 without acidification, and the neutralized wastewater was
Water was passed through the column packed with the 100% Na-form weakly acidic cation exchange resin at a rate of 6 liters per hour. When the treated water flowing out from the lower part of the column was analyzed, the lead concentration was 0.3 to 0.7 mg Pb / L.

When the treated water was further filtered through a 0.2 μm membrane filter, the lead concentration in the filtrate was
It decreased to 0.03 to 0.05 mg Pb / L.

This indicates that lead is not ionized by simply neutralizing the alkaline lead waste water and exists as a fine solid substance such as hydroxide.
The membrane filter had a large pressure loss after a few hours and caused clogging, which made filtration impossible.

Example 5 Caustic soda was added to nickel-containing wastewater to adjust the pH to 10.5.
As a result, Table 10 shows the results of analysis of the alkaline wastewater that was obtained by coagulating and precipitating heavy metals as hydroxides and filtering.

[0069]

[Table 10]

After adjusting the pH to 9.5 by adding hydrochloric acid to the alkaline nickel-containing wastewater shown in Table 10, Table 11
Then, the solution was passed through a weakly acidic cation exchange resin of 100% form H, which was pretreated and regenerated under the conditions shown in Table 12. As a result, nickel in the treated water was 0.2 to 0.5 mgNi.
/ L and the pH was 3.8-5.

[0071]

[Table 11]

[0072]

[Table 12]

Next, the chelate resin packed in the column shown in Table 13 was pretreated, and the chelated resin regenerated under the conditions shown in Table 5 was treated with the acidic treated water treated with the weakly acidic cation exchange resin. It passed.

[0074]

[Table 13]

As a result, the nickel concentration in the treated water flowing out from the bottom of the column packed with the chelate resin IRC-718 was as small as 0.2 to 0.4 μg Ni / L.
Further, the pH of the treated water was 6.3 to 7.4.

[0076]

According to the invention of claim 1, heavy metals in wastewater containing heavy metals can be significantly reduced by an extremely simple operation of pH adjustment, and the conventional heavy metal removing device can be diverted. It is a major contributor to the wastewater treatment industry.

According to the second aspect of the present invention, a weakly acidic cation exchange resin is used to adjust the pH of the alkaline wastewater to 5 or less, so that some of the heavy metal ions of the alkaline wastewater are adsorbed by the weakly acidic cation exchange resin. Therefore, the load of the chelate resin or the cation exchange resin that adsorbs heavy metal ions in the latter stage can be reduced, the treatment amount can be increased, and complicated pH control is not required, so that the treatment operation is extremely simple. There is.

The invention according to claim 3 has the effect of further enhancing the adsorption of heavy gold ions in the invention according to claim 1 or claim 2.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an apparatus for carrying out the method of the present invention.

[Explanation of symbols]

 1 Coagulation sedimentation tank 3 Filter 4 pH adjustment tank 5 Neutralization tank 6 Storage tank 7 Filter 8 Heavy metal removal tower

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication C02F 1/42 H G 1/62 Z (72) Inventor Kazuro Watanabe 5-5 Hongo, Bunkyo-ku, Tokyo No. 16 Organo Corporation (72) Inventor Koichi Soda 1-5-17 Dojima, Kita-ku, Osaka City, Osaka Prefecture Dojima Grand Building Organo Corporation, Osaka Branch

Claims (3)

[Claims] 1. A heavy metal-containing wastewater is added with an alkali to aggregate the heavy metals in the wastewater as hydroxides for solid-liquid separation, and then a chelate resin or weakly acidic cation exchange resin is used to adsorb and remove the heavy metal ions in the alkaline wastewater. In the method, the pH of the alkaline wastewater after solid-liquid separation is adjusted to 5 or less, and then 60 to 100 equivalent% of the exchange group is an alkali metal type or alkaline earth metal type and 0 to 40 equivalent% is a H type chelate resin. Alternatively, a method for treating heavy metal-containing wastewater, which comprises adsorbing and removing heavy metal ions in the wastewater with a weakly acidic cation exchange resin. 2. An alkali is added to the heavy metal-containing wastewater to aggregate the heavy metals in the wastewater as hydroxides for solid-liquid separation, and then the chelate resin or weakly acidic cation exchange resin is used to adsorb and remove the heavy metal ions in the alkaline wastewater. In the method, the alkaline wastewater after solid-liquid separation is converted into
40 equivalent% is the alkali metal form and 60-100 equivalent% is H
After passing through a weakly acidic cation exchange resin in the form of a pH of 5 or less, 60 to 100 equivalent% of the exchange groups are alkali metal or alkaline earth metal form and 0 to 40 equivalent% are H form. A method for treating heavy metal-containing wastewater, characterized by adsorbing and removing heavy metal ions in the wastewater with a chelate resin or a weakly acidic cation exchange resin. 3. A chelating resin or a weakly acidic cation exchange resin, wherein 60 to 100 equivalent% of the exchange groups are in the alkali metal form and 0 to 40 equivalent% are in the H form. 2. The method for treating wastewater containing heavy metals according to 2.