JPH0468035B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a novel polymeric heavy metal scavenger. Conventional techniques and their problems Conventionally, the methods for removing harmful heavy metals contained in waste water from garbage disposal, waste water from garbage incinerators, etc. include (1) neutralization coagulation precipitation method, (2) soda sulfide method, (3) Chelate resin methods and the like are known. Among these methods, the neutralization coagulation-sedimentation method is suitable in terms of running costs and maintenance management, but is not suitable for removing mercury. In addition, the soda sulfide method poses a problem of secondary pollution due to the generation of hydrogen sulfide, which is a harmful gas. In addition, the chelate resin method also adsorbs organic matter present in wastewater, reducing the capture efficiency of heavy metals.Furthermore, it requires a large amount of highly concentrated mineral acids for regeneration, resulting in high treatment costs. Disadvantages include that there is a risk of secondary contamination and that regeneration is difficult. On the other hand, in recent years, a polymeric heavy metal scavenger method has been attracting attention as a method that can overcome the drawbacks of the above treatment methods. This method is characterized in that a water-soluble polymeric heavy metal scavenger captures heavy metals through neutralization, chelation, adsorption reactions, etc., becomes insoluble, and can be removed by precipitation out of the system. It is considered that almost all aspects are satisfactory. By the way, sodium dithiocarbamate of polyethyleneimine, sodium cellulose xanthate, sodium polyglutamate, etc. are known as the scavengers used in the polymer heavy metal scavenger method, but all of them have poor scavenging ability and sedimentation separation properties. The problem is that it is not sufficient. Means for Solving the Problems The present invention aims to overcome the drawbacks of conventional polymeric heavy metal scavengers. That is, it is an object of the present invention to provide a polymeric heavy metal scavenger that is excellent in heavy metal scavenging ability, sedimentation separability, etc., which are the performance requirements of a polymeric heavy metal scavenger, and is also satisfactory in terms of cost. In order to achieve the above object, the present inventors conducted intensive studies on molecular design, focusing on a Hofmann rearrangement product of polyacrylamide, which is known as a paper strength agent and a polymer flocculant. As a result, all of the above problems could be solved for the first time by reacting carbon disulfide with a polymer having a primary amino group such as the rearranged product to form a chelate with the heavy metal and introducing a dithiocarbamate group that exhibits a scavenging action. The present inventors have discovered that it is possible to obtain a polymeric heavy metal scavenger that absorbs water, and have completed the present invention. That is, the present invention is based on the formula The active ingredient is an alkali metal dithiocarbamate obtained by reacting a high molecular weight polymer containing 5 to 100 mol% of the structural unit represented by the above as a constituent component of the polymer with carbon disulfide. The present invention relates to a characteristic polymeric heavy metal scavenger. It is essential that the high molecular weight polymer serving as a starting material in the present invention contains 5 to 100 mol% of the structural unit of the formula [] as a structural component of the polymer. That is, if the content of the structural unit is less than 5 mol %, the heavy metal trapping ability will be insufficient, which is not preferable. The content of the structural unit is preferably 40 to 100 mol%, particularly preferably 60 to 100 mol%, from the viewpoint of heavy metal trapping ability. The molecular weight of the high molecular weight polymer is not particularly limited, but usually its weight average molecular weight is 1000 to 1000.
10,000,000, preferably 5,000 to 4,000,000. If the molecular weight is less than 1,000, the sedimentation separation property will be low, and if it exceeds 1,000,000, the viscosity of the aqueous solution of the scavenger will be excessive, resulting in a decrease in handling efficiency, which are both unfavorable. As a method for producing a high molecular weight polymer containing the structural unit of the formula [] as a constituent component of the polymer, polyacrylamide or a copolymer of acrylamide and an α,β-unsaturated monomer (hereinafter referred to as acrylamide) is used. It is preferable to employ a method in which a material (referred to as a polymer) is used as a raw material and subjected to a Hofmann rearrangement reaction.
Alternatively, it may be produced by polymerizing N-vinylphthalimide, N-vinylformamide or N-vinylacetamide and then hydrolyzing the polymer. As α,β-unsaturated monomers that can be copolymerized with acrylamide in the production of the above-mentioned acrylamide-based polymers, various monomers such as methacrylamide, lower alkyl esters of acrylic acid, acrylic acid, and methacrylic acid can be used. I can give an example. The amount of the monomer used is determined by the content of the structural unit of formula [] in the resulting polymer, and is usually 95 mol% or less, preferably 60 mol% or less, particularly preferably 40 mol%. The following should be used. The polymer containing a predetermined amount of the structural unit of the formula [] obtained by the above method is then reacted with carbon disulfide in the presence of an alkali to form an alkali metal dithiocarbamate salt of the polymer. It can be made into a polymeric heavy metal scavenger of the invention. Here, examples of the alkali metal include sodium, potassium, and lithium. In this reaction, it is a matter of course that the reaction product of the polymer production can be used as it is or after being isolated and produced as the polymer.
In addition, when using a Hofmann rearrangement reaction product, hydrogen peroxide can also be used to decompose unreacted hypohalite used as a reaction reagent during the Hofmann rearrangement reaction. The reaction for introducing a dithiocarbamate group can be represented by the following reaction formula. (In the formula, R represents the main chain of the polymer containing the structural unit of the formula [], and M represents a monovalent cation of an alkali metal.) The alkali used in the reaction is:
Hydroxides of alkali metals such as sodium, potassium, and lithium are preferred. In addition, the molar ratio of carbon disulfide to the primary amino groups in the polymer should originally be stoichiometric, but usually
It can be used in an amount of about 0.05 to 10 mol, preferably 0.5 to 2 mol. If the amount is less than 0.05 mol, the amount of carbamate groups produced will be too small and the performance of the resulting polymeric heavy metal scavenger (especially heavy metal scavenging ability and sedimentation separation property) will be insufficient. In either case, there is no point in using it in excess and it becomes uneconomical. The above reaction usually proceeds at room temperature, but in order to complete the reaction in a short time, it is preferable to heat it to reflux at about 40°C. The reaction time is not particularly limited;
The time period can be determined as appropriate, usually from about 1 to 24 hours, preferably from 2 to 8 hours. By employing these reaction conditions, dithiocarbamic acid groups can be easily introduced in an amount of about 1 to 90 mol%, usually 5 to 40 mol%, based on the total amount of side chain primary amino groups. The polymeric heavy metal scavenger of the present invention contains as an active ingredient the alkali metal dithiocarbamate of the specific polymer obtained by the above-mentioned method, and usually can exhibit excellent performance by itself. However, sodium sulfide, sodium polysulfide,
This does not preclude the use of sulfides such as sodium hydrosulfide in combination. In addition, when the concentration of the metal ion to be captured is extremely dilute, if necessary, a known polymer flocculant such as a carboxylic acid-based anionic polymer flocculant, an acrylamide-based nonionic polymer flocculant, It goes without saying that a polyamine-based cationic polymer flocculant can be used in combination to further enhance the sedimentation separation properties. The polymeric heavy metal scavenger of the present invention is usually used in the form of an aqueous solution of about 5% by weight or less, and the amount used varies depending on the amount of heavy metals present in the treated wastewater, but it is usually expressed in terms of weight. Content of 0.1~
It may be used in an amount of about 20 times, preferably in a range of 0.5 to 10 times. Effects of the Invention The polymeric heavy metal scavenger of the present invention simultaneously satisfies all of the performance requirements of the scavenger, such as heavy metal capture ability, sedimentation separability, product price, running cost, and prevention of secondary pollution. It is something to be gained;
It is superior in performance compared to the above-mentioned performances of conventional polymeric heavy metal scavengers. Therefore, the polymeric heavy metal scavenger of the present invention can be widely applied to various wastewaters containing harmful heavy metals, such as wood wastewater, municipal waste incinerator flue gas treatment wastewater, and industrial wastewater from dry cell manufacturers. That is, it has the advantage that various heavy metals present in these wastewaters can be efficiently captured and, as a result, insolubilized substances are formed, so that they can be easily separated by sedimentation. Furthermore, the polymeric heavy metal trapping agent of the present invention has the advantage of being able to efficiently trap and remove substances that are subject to particularly strict regulations under the Water Pollution Control Act, such as water metal, copper, cadmium, and lead. be. Examples Hereinafter, the present invention will be described in more detail with reference to Examples, Comparative Examples, and Test Examples, but the present invention is not limited to these Examples. In each example, all parts and percentages are based on weight unless otherwise specified. Example 1 90.8 parts of an aqueous sodium hypochlorite solution (1.67 mol/Kg) was placed in a reaction apparatus equipped with a stirring device, and 5.3 parts of 95% sodium hydroxide was added thereto and dissolved with stirring. The temperature inside the reaction system was cooled to about -10℃, and then polyacrylamide (weight average molecular weight 10,000) was added.
60 parts of an 18.9% aqueous solution of was added dropwise over 10 minutes, and the reaction temperature was maintained at -5°C during this time. Subsequently, 41.2 parts of a 48% aqueous sodium hydroxide solution was added dropwise over 10 minutes, and the mixture was then kept at 0° C. for 4 hours and then returned to room temperature. To this was added 10 parts of 6% hydrogen peroxide solution, and after stirring at room temperature for 1 hour, 11.2 parts of carbon disulfide was added dropwise over 10 minutes. After stirring at room temperature for 1 hour, the temperature was raised to 40° C. and maintained at the same temperature for 3 hours to obtain an aqueous solution of dithiocarbamate sodium salt of a polymer which is a Hofmann rearrangement product of polyacrylamide. This heavy metal scavenger has a reddish-brown appearance and a polymer concentration of
It was 5.45%. Other properties are shown in Table 1. Examples 2 to 7 Same procedure as in Example 1 except that at least one of the molecular weight of the raw material polyacrylamide, the amination rate of polyacrylamide, and the amount of carbon disulfide used was changed as shown in Table 1. The reaction was carried out to obtain an aqueous solution of a sodium dithiocarbamate salt of a polymer which is a Hofmann rearrangement product of various polyacrylamides. The properties of these heavy metal scavengers are shown in Table 1.

[Table] Comparative Example 1 50 parts of a 30% aqueous solution of polyethyleneimine (weight average molecular weight 70,000) was placed in a reaction apparatus equipped with a stirring device and a cooling tube, and 10% sodium hydroxide was added to it.
42 parts were added and stirred. The mixture was then heated to 40°C and 26.5 parts of carbon disulfide was added dropwise over 1 hour. Thereafter, the solution was maintained at the same temperature for 4 hours to obtain an aqueous solution of polyethyleneimine dithiocarbamate sodium salt. The amount of dithiocarbamate groups in the polymer is
The amount was 35.0 mol% based on the total amino groups including primary, secondary and tertiary amino groups. The polymer concentration of this heavy metal scavenger was 23.6%. Test Example 1 Take 100 ml of an aqueous solution containing 7.2 ppm Hg ²⁺ in a beaker, and add a second solution of the heavy metal scavenger obtained in Examples 1 to 7 diluted with water to a concentration of 0.1%.
Add and stir as shown in the table. After standing for 10 minutes, 0.2 ml of a 1% ferric chloride aqueous solution was added as a reagent to speed up coprecipitation in an experiment, and the pH was adjusted to 8 with 2N sodium hydroxide. After another 10 minutes, 1 ml of a 0.04% aqueous solution of an anionic polymer flocculant (manufactured by Kyoritsu Organic Industrial Research Institute, trade name "Himoloku SS-120A") was added, stirred for 10 minutes, and then left to stand for another 10 minutes. passed. The residual Hg ²⁺ concentration in the liquid was measured by reduction vaporization atomic absorption spectrometry. The results are shown in Table 2.

【table】

[Table] Test Example 2 Take 100 ml of municipal garbage incinerator smoke wash wastewater (Hg ²⁺ concentration: 667 ppb) obtained from M factory into a beaker and collect PH.
was adjusted to 7. A solution prepared by diluting the heavy metal scavenger obtained in Examples 1 to 7 with water to a concentration of 0.1% was added to the solution as shown in Table 3, and the mixture was stirred. After leaving for 10 minutes, add 0.2ml of 1% ferric chloride aqueous solution, then add 2N
The pH was adjusted to 8 with sodium hydroxide. 10 more
After a few minutes, 1 ml of the 0.04% aqueous solution of the anionic polymer flocculant was added, stirred for 10 minutes, and then allowed to stand for an additional 10 minutes. The residual Hg ²⁺ concentration in the liquid was measured by reduction vaporization atomic absorption spectrometry. The results are shown in Table 3.

【table】

[Table] Comparative Test Example 1 Various Huffmann rearrangement reactants obtained at the intermediate stage in Examples 1 to 3, polyacrylamide (weight average molecular weight 10,000), and the heavy metal scavenger obtained in Comparative Example 1 were all mixed at 0.1%. The residual Hg ²⁺ concentration was measured as an aqueous solution in the same manner as in Test Example 1.
The progress is shown in Table 4.

[Table] Test Example 3 Take 100 ml of an aqueous solution containing 50 ppm Cu ²⁺ in a beaker, and add the solution prepared by diluting the heavy metal scavenger obtained in Examples 1 to 7 with water to a concentration of 1% as shown in Table 5. and stirred. After standing for 10 minutes, 1 ml of the 0.2% aqueous solution of the anionic polymer flocculant was added, stirred for 10 minutes, and then left standing for an additional 10 minutes. The residual Cu ²⁺ concentration in the liquid was measured by atomic absorption spectrometry.
The results are shown in Table 5.

【table】

[Table] Comparative Test Example 2 Various Hofmann rearrangement reactants obtained at the intermediate stage in Examples 1 to 3, polyacrylamide (weight average molecular weight 10,000), and the heavy metal scavenger obtained in Comparative Example 1 were all added at 1%. Test example 3 as an aqueous solution
The residual Cu ²⁺ concentration was measured using the same procedure as above.
The results are shown in Table 6.

【table】

Claims (1)

[Scope of Claims] 1. Dithiocarbamine of a polymer obtained by reacting a polymer containing 5 to 100 mol% of the structural unit represented by the formula [formula] as a constituent component of the polymer with carbon disulfide. A polymeric heavy metal scavenger characterized by containing an acid alkali metal salt as an active ingredient. 2. The scavenger according to claim 1, wherein the high molecular weight polymer is a Hofmann rearrangement product of polyacrylamide. 3 The weight average molecular weight of the high molecular weight polymer is 1000 or more.
10,000,000, the scavenger according to claim 1 or 2. 4. The scavenger according to claim 1, wherein the high molecular weight polymer contains 40 to 100 mol% of the structural unit. 5. The scavenger according to claim 4, wherein the high molecular weight polymer contains 60 to 100 mol% of the structural unit.