JPH03231921A - Metal scavenger and metal collection - Google Patents

Abstract

PURPOSE:To obtain a metal scavenger which is blended with flying ash, etc., immobilizes, collects and removes heavy metals, by mixing a specific polyamine derivative and a polyethyleneimine derivative which contain a dithiocarboxyl group or a salt thereof as an N-substituent group. CONSTITUTION:A polyamine derivative which is obtained by reacting a polyamine (e.g. ethylenediamine) having <=500, preferably 60-250 molecular weight with carbon disulfide and contains one or more dithiocarboxyl groups or a salt thereof as an N-substituent group is blended with a polyethyleneimine derivative which is obtained by reacting a polyethyleneimine having >=5,000, preferably 20,000-150,000 average molecular weight and contains one or more dithiocarboxyl groups or a salt thereof as an N-substituent group in a ratio of preferably 9-7:1-3 to give a metal scavenger which firmly immobilizes heavy metals and prevents outflow thereof.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a metal collecting agent and a metal collecting method.

[Conventional technology and Problems that the invention seeks to solve]

In recent years, as the pollution of rivers, oceans, etc. by wastewater from factories has become a problem, regulations to prevent pollution from wastewater have been strengthened, and it is now mandatory to keep metals contained in wastewater below a specified concentration. There is.

In addition, slag discharged from mines, fly ash generated during garbage incineration at garbage incinerators, sludge generated as industrial waste during neutralization coagulation sedimentation treatment and sedimentation treatment using flocculants during wastewater treatment, and further pollution. Soil, etc. contains various heavy metals, and these heavy metals are washed away and are disposed of in groundwater, rivers, etc.
Contamination of these metals into seawater has become a problem, and establishing a treatment method for these metals is an urgent issue. In particular, strict regulations are placed on heavy metals that are harmful to the human body, such as mercury, cadmium, lead, zinc, copper, and chromium. For this reason, various methods have been proposed for removing metals in wastewater treatment.
This type of method includes methods such as ion flotation, ion exchange, electrolytic flotation, electrodialysis, and reverse osmosis, as well as adding an alkali neutralizing agent such as calcium hydroxide or sodium hydroxide to A known method is a neutralization coagulation-sedimentation method in which the hydroxide is converted into a hydroxide, and then removed by coagulation and precipitation using a polymer flocculant.

However, the ion flotation method, ion exchange method, electrolytic flotation method, electrodialysis method, and reverse osmosis method have problems such as the removal rate of heavy metals, operability, and running cost, and are only applicable to some special wastewater treatments. The current situation is that it is not being used. In addition, the neutralization coagulation-sedimentation method generates a large amount of metal hydroxide sludge, and these hydroxide sludges have poor dewatering properties and large sludge volumes, making it difficult to transport. It is also extremely difficult to remove wastewater below the wastewater standard value. Moreover, depending on how these sludges are disposed of, they may be redissolved and cause secondary pollution.

On the other hand, wastewater treatment using metal scavengers can solve the above problems, so metal scavengers have been widely used in recent years. As this type of metal scavenger, a metal scavenger made of a polyamine derivative having a dithiocarboxylic group as a functional group is known, and various wastewater treatment methods using this metal scavenger have also been proposed (for example, Kosho 56-393
No. 58, Special Publication No. 60-57920, Special Publication No. 1983-35
No. 49, JP-A No. 62-65788, etc.).

The above-mentioned polyamine derivatives have excellent metal collection efficiency, and the flocs produced by collecting metal ions are large, and the sedimentation rate is also high, so they remove metal ions from wastewater more efficiently than conventional methods. but still chrome (
(2), the adsorption properties for nickel, cobalt, and manganese were not sufficient. In addition, the cake obtained by separating and removing the flocs produced by metal binding to metal scavengers and solidifying them is treated by incineration or hardening with concrete, but when using conventional metal scavengers, In some cases, the water content in the cake is relatively high, which causes problems such as excessive energy being required to incinerate the cake, and the bulk of the cake increasing, requiring more effort and expense than necessary for processing. There was a case.

In addition, conventional methods for disposing of fly ash, sludge, slag, and metals in soil were to solidify them with cement and then bury them or dump them in the ocean, but metals leaked through cement walls. It cannot be said that this is a safe method, as there is a risk of this occurring, and a complete treatment method was required.

The present invention was made to solve the above-mentioned problems, and furthermore, it is possible to efficiently collect and remove various metal ions in wastewater, and the water content in the cake can be reduced compared to conventional methods, making it possible to reduce the amount of water contained in the cake. The purpose of the present invention is to provide a metal scavenger that can also improve the efficiency of metal trapping. Also, fly ash containing heavy metals,
When solidifying sludge, slag, soil, etc. with cement and disposing of it by ocean dumping, landfilling, etc., by treating it with the metal scavenger of the present invention, the volume of bete cake can be reduced compared to conventional cement. It is possible to reduce the amount of metal, making it easier to dispose of in landfills, etc., and also to firmly immobilize heavy metals contained in fly ash, sludge, slag, soil, etc., and prevent metals from flowing out. The purpose is to provide a metal collection method.

[Means for Solving the Problems] That is, the present invention provides a polyamine having at least one dithiocarboxy group or a salt thereof as an N-substituent substituted with an active hydrogen of the polyamine per molecule of a polyamine having a molecular weight of 500 or less. Polyamine derivative and average molecular weight 50
A metal scavenger comprising a polyethyleneimine derivative having at least one dithiocarboxy group or a salt thereof as an N-substituent substituted with the active hydrogen of the polyethyleneimine, per molecule of polyethyleneimine having a molecular weight of 00 or more. The main points are as follows.

The metal collecting agent of the present invention can be applied to a metal collecting method in which heavy metals in fly ash, sludge, slag, soil, etc. are added and kneaded to immobilize the heavy metals therein.

The polyamine derivatives and polyethyleneimine derivatives used in the present invention have an active hydrogen bonded to the nitrogen atom of a polyamine molecule having a primary and/or secondary amino group or a polyethyleneimine molecule having a primary and/or secondary amino group. As the substituted N□i substituent, at least one dithiocarboxymini-C35H or a salt thereof, such as an alkali metal salt such as a sodium salt or a potassium salt, an alkaline earth metal salt such as a calcium salt, an ammonium salt, etc. (hereinafter referred to as A dithiocarboxy group and its salts are collectively referred to simply as a dithiocarboxy group). These polyamine derivatives and polyethyleneimine derivatives can be obtained, for example, by reacting polyamine or polyethyleneimine with carbon disulfide. Alternatively, by performing the above reaction in the presence of an alkali, the active hydrogen at the terminal of the dithiocarboxy group can be replaced with an alkali metal, an alkaline earth metal, ammonium, or the like. The reaction between polyamines, polyethyleneimines and carbon disulfide is carried out in a solvent, preferably water or alcohol, at 30 to 100°C for 1 to 10 hours, especially at 40°C.
Preferably, the reaction is carried out at ~70°C for 2 to 5 hours.

As the polyamine forming the skeleton of the polyamine derivative constituting the metal scavenger of the present invention, a polyamine having a molecular weight of 500 or less, particularly preferably a molecular weight of 60 to 250, is used. The above polyamines include ethylene diamine, propylene diamine, butylene diamine, hexamethylene diamine, diethylene triamine, dipropylene triamine, diethylene triamine, triethylene tetramine, tripropylene tetramine, tributylene tetramine, tetraethylene pentamine, tetrapropylene pentamine, and tetrabutylene pentaamine. amine, pentaethylene hexamine [
-Formula, H-(Nl(-CHzCHzCH)mNH-C
HzCHz-NH-(CHzCHzCHz-Nl()n
-4! (However, m and n are integers, m+n=l~8
Polyalkylene polyamines such as phenylene diamine, o-, m-, xylene diamine, iminobispropylamine, monomethylaminopropylamine, methyliminobispropylamine, 1,3-bis( aminomethyl)cyclohexane, 1
, 3 diaminopropane, 1,4-diaminobutane, 3,
Examples include 5-diaminochlorobenzene, melamine, 1-aminoethylpiperazine, piperazine, 3,3'-dichlorobenzidine, diaminophenyl ether, tolidine, m-tolylenediamine, and the like. These can be used not only alone, but also in combination of two or more.

The polyethyleneimine forming the skeleton of the polyethyleneimine derivative which is the other component of the metal scavenger of the present invention has an average molecular weight of 5000 or more, preferably an average molecular weight of 1.
0000 to 200000, particularly preferably average molecular weight 2
0000 to 150000 is used.

The above polyamine and polyethyleneimine (hereinafter, polyamine and polyethyleneimine may be collectively referred to as polyamines) may have an alkyl group, an acyl group, or a β-hydroxyalkyl group as an N-substituent. In order to introduce an alkyl group as an N-substituted alkyl group, the above-mentioned polyamines (or polyamines into which a dithiocarboxy group has been introduced as a substituent) and an alkyl halide may be reacted. In addition, to introduce an acyl group as an N-substituent,
The above polyamines (or polyamines into which a dithiocarboxy group has been introduced as a substituent) and fatty acids may be reacted. Furthermore, in order to introduce a β-hydroxyalkyl group as an N-substituent, polyamines (or polyamines into which a dithiocarboxy group has been introduced as a substituent) and an epoxyalkane may be reacted. The N-substituted alkyl group preferably has 2 to 18 carbon atoms, and the N-substituted acyl group preferably has 2 to 30 carbon atoms.

Further, as the N-substituted β-hydroxyalkyl group, an alkyl group having 2 to 35 carbon atoms is preferable.

The metal scavenger of the present invention is a mixture of the polyamine derivative having a dithiocarboxy group and the polyethyleneimine derivative having a dithiocarboxy group, and the mixing ratio of the polyamine derivative and the polyethyleneimine derivative is by weight, and the polyamine derivative: Polyethyleneimine derivative-9~
7:1-3 is preferred.

The metal scavenger of the present invention adsorbs metals to form large flocs, and the flocs have a high sedimentation rate, so even if the metal scavenger of the present invention is used as is, it can efficiently capture metals in wastewater. Although it can be collected and removed, if it is used in combination with at least one of sodium sulfides such as sodium monosulfide, sodium polysulfide, and sodium hydrogen sulfide, the sedimentation rate of flocs can be further increased, resulting in more efficient treatment. As the sodium polysulfide, sodium disulfide, sodium trisulfide, sodium tetrasulfide, and sodium trisulfide are used. When the metal scavenger of the present invention and the above-mentioned sodium sulfides are mixed and used, the mixing ratio of both is 1:99 to 99 by weight.
:1 range may be adopted, but especially 20:80 to 98:2
is preferred. When using a mixture of the two, the metal scavenger of the present invention and sodium sulfides may be mixed in advance and added to the wastewater, or they may be added separately, but it is preferable to mix the two in advance and add them. preferable. Incidentally, when adding them separately, the effect will be the same regardless of which one is added first.

The amount of the metal scavenger of the present invention added to wastewater is 0.8 to 0.8 of the amount of metal ions in the wastewater when only the metal scavenger is used.
1.4 molar equivalents, particularly preferably 0.9 to 132 molar equivalents, and when used in combination with sodium sulfides, the total amount of both is 0.8 to 1.4 molar equivalents of the amount of metal ions in the wastewater. , particularly preferably 0.9 to 1.2 molar equivalents.

The metal collector of the present invention can effectively collect metal ions in wastewater having a pH in the range of 3 to 10, but it is particularly preferable to adjust the pH in the range of 4 to 9. The acid or alkali used to adjust the pH of wastewater may be any acid or alkali that does not inhibit the formation of flocs.2 Hydrochloric acid, sulfuric acid, nitric acid, etc. are usually used as the acid, and sodium hydroxide, water, etc. are used as the alkali. Potassium oxide etc. are used.

Furthermore, in order to fix heavy metals in fly ash, sludge, slag, and soil using the metal scavenger of the present invention, 1. 2-3.0
An aqueous solution containing double the amount of metal scavenger is mixed into fly ash, sludge, slag,
A method of adding it to soil and kneading it is adopted, but water may also be added to make the kneading process easier. In addition, since a pH range of 3 to 10 is preferable for capturing heavy metals in slag, the pH should be within the above range when kneading with the above-mentioned acid or alkali and adding a metal scavenger. It is preferable to adjust to

The metal collector of the present invention includes mercury, cadmium, lead, zinc, copper,
Metal ions such as chromium (■), arsenic, gold, silver, platinum, vanadium, and thallium can be collected and removed as efficiently as or more efficiently than conventional metal collectors, and can be removed by conventional metal collectors. Metal ions such as chromium (nickel, cobalt, manganese, etc.) that were difficult to collect can also be efficiently collected and removed.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 8, Comparative Examples 1 to 4 First, polyamine derivatives and polyethyleneimine derivatives were synthesized by the method shown below.

To 333.3 parts by weight of a 30% aqueous solution of polyethyleneimine having an average molecular weight of 10,000, 400 parts by weight of a 10% aqueous sodium hydroxide solution was added, and while stirring, the temperature of the solution was adjusted to 40°C. 76 parts by weight of carbon sulfide were gradually added. After the addition was completed, the reaction was continued at 45°C for 15 hours to obtain polyethyleneimine derivative 1.

Bo. To 500 parts by weight of a 30% aqueous solution of polyethyleneimine having an average molecular weight of 70,000, add 1 part by weight of a 10% aqueous sodium hydroxide solution.
Add 120 parts by weight and add 2 parts by weight of carbon disulfide in the same manner as above.
Polyethyleneimine derivative 2 was obtained by reacting 12 parts by weight.

Polyethyleneimine 30% of polyethyleneimine with an average molecular weight of 100,000
Add 1400 parts by weight of a 10% sodium hydroxide aqueous solution to 500 parts by weight of the aqueous solution, and add 2 parts by weight of carbon disulfide in the same manner as above.
Polyethyleneimine derivative 3 was obtained by reacting 65 parts by weight.

Bo1 Ethyleneimine 4 Add 500 parts by weight of a 30% aqueous solution of polyethyleneimine with a human average molecular weight of 1200 to 14 parts of a 10% aqueous sodium hydroxide solution.
00 parts by weight was added, and 265 g of carbon disulfide was reacted in the same manner to obtain polyethyleneimine derivative 4.

Ethylenediamine (molecular weight 60) 4 in a four-eyed flask
0g and 536g of 20% sodium hydroxide aqueous solution were added, and while stirring vigorously at 40°C, 203.7g of carbon disulfide was added dropwise from the dropping funnel.After the addition was completed, the mixture was aged for 4 hours at the same temperature. 5 Polyamine derivative 1 was obtained.

Polyamine droplet Triethylenetetramine (molecular weight 146) was added to the same device as No. 2.
101 g and 464 g of 20% aqueous sodium hydroxide solution were charged, and 176.3 g of carbon disulfide was reacted in the same manner as above to obtain polyamine derivative 2.

Diethylenetriamine (molecular weight 103) 4
8.5 g and 384 g of water were charged, heated to 60°C, 145.9 g of carbon disulfide was added dropwise from the dropping funnel, and after the addition was completed, aging was carried out at the same temperature for 4 hours. Next, the temperature of the reaction solution was raised to 70 to 75°C, 384 g of a 20% aqueous sodium hydroxide solution was added, and the reaction was carried out for 1.5 hours to obtain polyamine derivative 3.

, Jun-hi 1'' 711 mouths (Niji 9-hui 戊N-propyltriethylenetetramine (molecular weight 188)
90.2 g and 640 g of a 15% aqueous sodium hydroxide solution were charged, and 172.8 g of carbon disulfide was reacted in the same manner as in the synthesis method for polyamine derivative 1 to obtain polyamine derivative 4.

, Hirojo 1'' 1 ■■ (LΔHei) 91.5 g of β-hydroxypropylpentaethylene hexamine (molecular weight 290) and 296 g of a 20% aqueous sodium hydroxide solution were prepared in the same manner as the synthesis method of polyamine derivative 1. Polyamine derivative 5 was obtained by reacting 112.5 g of carbon disulfide.

A metal scavenger obtained by mixing the polyethyleneimine derivative (solid content) and polyamine derivative (solid content) obtained above and, if necessary, sodium sulfide (solid content) in the proportions shown below (however, compared to In Example 1.2, 4 types of aqueous solutions were treated using 4 types of aqueous solutions.

Example 1 Polyethyleneimine derivative 3 1.3% by weight Polyamine derivative 1 8.7% by weight Example 2 Polyethyleneimine derivative 2 2.8% by weight Polyamine derivative 2 7.2% by weight Example 3 Polyethyleneimine derivative 1 2% by weight Polyamine derivative 3 8% by weight Example 4 Polyethyleneimine derivative 2 1.5% by weight Polyamine derivative 4 8.5% by weight Example 5 Polyethyleneimine derivative 3 2.5% by weight Polyamine derivative 5 7. 5% by weight Example 6 Metal scavenger of Example 1 8.0% by weight - Sodium sulfide 2.0% by weight Example 7 Metal scavenger of Example 3 9.0% by weight Sodium pentasulfide 1.0% by weight % Example 8 Metal scavenger of Example 5 8.5% by weight Sodium hydrogen sulfide 1.5% by weight Comparative example 1 Using polyethyleneimine derivative 2 alone Comparative example 2 Using polyamine derivative 1 alone Comparative example 3 Polyethylene Imine derivative 4 1.3% by weight Polyamine derivative 1 8.7% by weight Comparative example 4 Metal scavenger of Comparative example 3 8.0% by weight - Sodium sulfide 2.0% by weight The aqueous solution used for the treatment was a nickel aqueous solution. Nickel (II) ion content 50 ppm, pl (=6.8), manganese aqueous solution (
Manganese (II) ion content 50 ppm, pH=
5.6), cobalt aqueous solution (cobalt (II) ion content 50 ppm, pH = 4.6), chromium aqueous solution (chromium (I[[) ion content 50 ppm, p)
I=4.0).

The treatment method is the aqueous solution to be treated 11! After adding 70 μm of metal scavenger to the mixture and stirring for 5 minutes, the mixture was allowed to stand and the time required for the formed flocs to precipitate was measured. Next, the generated flocs were filtered, and the remaining metal ion concentration in the filtrate was measured by atomic absorption spectrometry. Table 1 shows the measurement results of the floc precipitation time, the amount of flocs produced, the moisture content of the cake formed by filtering the flocs, and the concentration of residual metal ions in the filtrate. The moisture content of the cake was expressed as the amount of water evaporated by infrared irradiation in weight percent.

Example 9 Lead 950ppm, cadmium 1251)I)lll, zinc 5300ppm, total chromium i3oppm, mercury 13p
1 g of the same metal scavenger used in Example 2 was added as an aqueous solution diluted with water Log to 50 g of fly ash produced by garbage incineration containing 160 ppm of copper and 4 pl of nickel) ffl at a temperature of 65 to 70 ml. Mix well for 20 minutes at °C. An elution test (Environmental Agency Notification No. 13) was conducted on the treated ash (room temperature) and untreated ash after kneading, and the amount of eluted metal and the bulk density of the fly ash before and after treatment were measured. The results are shown in Table 2.

Example 10 In Example 1, 50 g of sludge (water content 82%) obtained from the wastewater treatment of a garbage incinerator, containing mercury (25 pI) Ill, lead 1108 pp, cadmium 2 ppHl, zinc 160 pp111, and nickel 3 pp111, was obtained from the wastewater treatment of a garbage incinerator. 0.1 g of the same metal scavenger used was added, mixed well for 20 minutes, filtered, and the metal concentration in the filtrate was measured.
Mercury was 0.002 ppm, lead was 0.3 ppm, and cadmium, nickel, and zinc were not detected.

Comparative Example 5 0.1 g of polyethyleneimine derivative 2 was added to 50 g of the same sludge as in Example 10, and after thoroughly kneading for 20 minutes, the metal concentration in the filtered filtrate was measured, and it was found that mercury was 0.0
3ppm, lead 1.2ppm, cadmium 0.5ppm
, zinc 20 ppm, nickel 2 PI) III.

Example 11 Mercury Q, 014111) III as metals, 330 ppm cadmium, 220 ppm lead, 0.7 ppm chromium
0.5 g of the same metal scavenger used in Example 5 dissolved in 5 g of water was added to 50 g of slag containing 10 ppm of m-copper, and the mixture was thoroughly kneaded for 20 minutes. An elution test was conducted on the treated slag after kneading and the amount of metal elution was measured, and the results were 0.001 ppm of mercury and 0.19 prn of cadmium.

Lead Q was 2 ppm, copper was 0.3 ppm, and chromium was not detected.

24 [Effects of the Invention] As explained above, the metal scavenger of the present invention has a molecular weight of 50
A polyamine derivative having as a functional group a dithiocarboxy group substituted with the active hydrogen of a polyamine having an average molecular weight of 5000 or less, and a polyethyleneimine derivative having as a functional group a dithiocarboxy group substituted with the active hydrogen of a polyethyleneimine having an average molecular weight of 5000 or less. By making it a mixture,
The flocs formed by collecting metals are large and the sedimentation rate of the flocs is high, so metal ions in wastewater can be efficiently collected and removed. Moreover, when the metal scavenger of the present invention is used, the entanglement of water in the flocs is less than when conventional metal scavengers are used. can reduce the water content of
The cake can be easily processed. Furthermore, the metal scavenger of the present invention has excellent adsorption properties for metal ions such as chromium (■), nickel, cobalt, and manganese, which were not so well adsorbed by conventional metal scavengers. Since a wide variety of metal ions can be efficiently collected, the range of wastewater to be treated can be expanded.

Furthermore, according to the metal collection method of the present invention, heavy metals contained in fly ash, sludge, slag, soil, etc. are firmly fixed, so even if they are solidified with cement and disposed of by ocean dumping, landfill, etc. There is no risk of metal flowing out through the cement wall, and furthermore, when treated with the method of the present invention, the volume of the treated material after treatment is small, so the volume at the time of disposal can be reduced, so the amount of cement used for solidification can be reduced. This also has the effect of making it easier to handle during disposal.

Claims (5)

[Claims] (1) A polyamine derivative having at least one dithiocarboxy group or its salt as an N-substituent substituted with the active hydrogen of the polyamine per molecule of polyamine having a molecular weight of 500 or less, and a polyethyleneimine having an average molecular weight of 5000 or more. A metal scavenger comprising a polyethyleneimine derivative having at least one dithiocarboxy group or a salt thereof per molecule as an N-substituent substituted with the active hydrogen of the polyethyleneimine. (2) A method for collecting metals, which comprises adding the metal collecting agent according to claim 1 to fly ash containing heavy metals and kneading the mixture to immobilize the heavy metals in the fly ash. (3) A method for collecting metals, which comprises adding the metal collecting agent according to claim 1 to slag containing heavy metals and kneading the mixture to immobilize the heavy metals in the slag. (4) A method for collecting metals, which comprises adding the metal collecting agent according to claim 1 to soil containing heavy metals and kneading the mixture to immobilize the heavy metals in the soil. (5) A method for collecting metals, which comprises adding the metal collecting agent according to claim 1 to sludge containing heavy metals and kneading the mixture to immobilize the heavy metals in the sludge.