Compound heavy metal chelating agent containing dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer

Abstract

A compound heavy metal chelating agent, which relates to the field of chemical and environmental protection technology, includes dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and alkylene diamine-N,N′-sodium bisdithiocarboxylate with a molar ratio in a range of 1:1.0 to 1:10.0. The two different structural types of components have the synergistic positive effect. While chelating heavy metals, the compound heavy metal chelating agent alternately combine with heavy metals to form insoluble chelating super-molecular deposits, which has both chelation and flocculation functions. The compound heavy metal chelating agent meets the standard for treating heavy metal wastewater, and low concentration heavy metal wastewater. It has a wide adaptability range, and does not need to add coagulant. Moreover, it is simple in preparation method, easily available for raw materials, low in cost, and easy to be industrialized.

Claims

1. A compound heavy metal chelating agent, which comprises dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and alkylene diamine-N,N′-sodium bisdithiocarboxylate, wherein: the dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer has a chemical formula of C[CH.sub.2OCH.sub.2CH.sub.2OCOCH.sub.2CH.sub.2N(CSSM)(CH.sub.2).sub.n NHCSSM].sub.4; the alkylene diamine-N,N′-sodium bisdithiocarboxylate has a chemical formula of (MSSC).sub.2N(CH.sub.2).sub.nN(CSSM).sub.2, here n is a positive integer between 2 and 12, M is Na.sup.+, K.sup.+ or NH.sub.4.sup.+; a molar ratio of the dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and the alkylene diamine-N,N′-sodium bisdithiocarboxylate is in a range from 1:1.0 to 1:10.0.

2. A preparation method of a compound heavy metal chelating agent, wherein: the compound heavy metal chelating agent comprises dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and alkylene diamine-N,N′-sodium bisdithiocarboxylate, wherein: the dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer has a chemical formula of C[CH.sub.2OCH.sub.2CH.sub.2OCOCH.sub.2CH.sub.2N(CSSM)(CH.sub.2).sub.n NHCSSM].sub.4; the alkylene diamine-N,N′-sodium bisdithiocarboxylate has a chemical formula of (MSSC).sub.2N(CH.sub.2).sub.nN(CSSM).sub.2, here n is a positive integer between 2 and 12, M is Na.sup.+, K.sup.+ or NH.sub.4.sup.+; a molar ratio of the dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and the alkylene diamine-N,N′-sodium bisdithiocarboxylate is in a range from 1:1.0 to 1:10.0; the preparation method comprises steps of: (1) performing a first addition reaction, which comprises adding a first low-carbon alcohol solution drop by drop into a second low-carbon alcohol solution at 20-25° C. under nitrogen protection, wherein the first low-carbon alcohol solution contains ethoxylated pentaerythritol tetraacrylate (EPTA), the second low-carbon alcohol solution contains excessive alkylenediamine (ADA) with a chemical formula of H.sub.2N(CH.sub.2).sub.n NH.sub.2, here n is a positive integer between 2 and 12; and then obtaining a mixed low-carbon alcohol solution which contains (N-(n-aminoalkylene))-3-aminopropionate hyperbranched polymer and unreacted alkylenediamine by stirring for 20-48 h at 20-35° C.; and (2) performing a second addition reaction, which comprises adding alkaline aqueous solution and carbon disulfide drop by drop after cooling the mixed low-carbon alcohol solution obtained by the step (1) to 10-25° C., stirring for 3-8 h at 20-35° C., standing at room temperature for 3-24 h, precipitating a solid product, filtering and drying to obtain the compound heavy metal chelating agent, wherein: a molar ratio of the EPTA, the ADA, the alkali and the carbon disulfide is in a range of 1: (5.0-14.0): (10.0-28.0): (10.0-28.0).

3. The preparation method according to claim 2, wherein each of the first low-carbon alcohol and the second low-carbon alcohol in the step (1) is one member selected from the group consisting of methanol, ethanol, propanol, ethylene glycol and propylene glycol.

4. The preparation method according to claim 2, wherein the step (1) of performing the first addition reaction comprises adding the first low-carbon alcohol solution containing ethoxylated pentaerythritol tetraacrylate into the second low-carbon alcohol solution containing excessive alkylenediamine at 20-25° C. under nitrogen protection drop by drop, and then stirring for 4-8 h both of which are repeated for 1 to 10 times, and then obtaining the mixed low-carbon alcohol solution which contains N-(n-aminoalkylene))-3-aminopropionate hyperbranched polymer and unreacted alkylenediamine by stirring for 20-48 h at 20-35° C.

5. The preparation method according to claim 2, wherein the alkali in the step (2) is one member selected from the group consisting of sodium hydroxide, potassium hydroxide and ammonia.

6. A method for treating heavy metal wastewater comprising applying a compound heavy metal chelating agent wherein the compound heavy metal chelating agent comprises dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and alkylene diamine-N,N′-sodium bisdithiocarboxylate, wherein: the dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer has a chemical formula of C[CH.sub.2OCH.sub.2CH.sub.2OCOCH.sub.2CH.sub.2N(CSSM)(CH.sub.2).sub.n NHCSSM].sub.4; the alkylene diamine-N,N′-sodium bisdithiocarboxylate has a chemical formula of (MSSC).sub.2N(CH.sub.2).sub.nN(CSSM).sub.2, here n is a positive integer between 2 and 12, M is Na.sup.+, K.sup.+ or NH.sub.4.sup.+; a molar ratio of the dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and the alkylene diamine-N,N′-sodium bisdithiocarboxylate is in a range from 1:1.0 to 1:10.0.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(1) The compound heavy metal chelating agent containing dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer provided by the present invention will be described in detail with reference to embodiments as below, but these embodiments are unable to be understood as limiting the protective scope of the present invention.

First Embodiment

(2) Preparation of dithiocarboxylate functionalized pentaerythritol core hyperbranched polymer and di sodium N,N′-bis-(dithiocarboxy) ethylenediamine compound heavy metal chelating agent:

(3) Under nitrogen protection, add 36.00 g (0.60 mol) of ethylenediamine (EDA) and 36.00 g of methanol to a round-bottomed flask with a stirrer, a reflux condenser, a constant pressure dropping funnel and a thermometer, stir at 25° C.; and then add 52.80 g (0.10 mol) of ethoxylated pentaerythitol tetraacrylate (EPTA) and 52.80 g of methanol to the constant pressure dropping funnel to obtain an intermediate mixture, divide the intermediate mixture into three equal parts, add the three equal parts to the round-bottomed flask drop by drop in sequence every 6 hours; and then react for 28 h at 25° C., obtain a mixed methanol solution of ((N-(2-aminoalkylene))-3-aminopropionate) hyperbranched polymer and ethylenediamine; and then cool to 20° C., add 96.00 g (1.20 mol, 50%) of sodium hydroxide aqueous solution and 91.20 g (1.20 mol) of carbon disulfide drop by drop; and then react for 5 h at 25° C., precipitate a solid product, filter and dry under vacuum to obtain 188.22 g of a white product with a yield of 91.19%, namely, the compound heavy metal chelating agent containing dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer (EPTA/EDA/DTC) and disodium N,N′-bis-(dithiocarboxy) ethylenediamine (EDA/DTC), wherein a molar ratio of the EPTA/EDA/DTC and the EDA/DTC is 1:2.

(4) Chemical shifts of the characteristic absorption peak of .sup.13C nuclear magnetic resonance spectrum (D.sub.2O) of the white product are respectively: 34,23, 39.98, 41.19, 45.56, 46.92, 59.39, 66.01, 68.24, 69.03, 174.89, 210.76, 212.31 and 213.94 ppm, which shows that the compound heavy metal chelating agent is a mixture of dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer (EPTA/EDA/DTC) and disodium N,N′-bis-(dithiocarboxy) ethylenediamine (EDA/DTC) with a structural formula of

(5) ##STR00006##

Second Embodiment

(6) Preparation of dithiocarboxylate functionalized pentaerythritol core hyperbranched polymer and 1,4-butanediamine-N,N′-sodium bisdithiocarboxylate compound heavy metal chelating agent:

(7) Under nitrogen protection, add 52.80 g (0.60 mol) of 1,4-butanediamine (BDA) and 52.80 g of ethanol to a round-bottomed flask with a stirrer, a reflux condenser, a constant pressure dropping funnel and a thermometer, stir at 25° C.; and then add 52.80 g (0.10 mol) of ethoxylated pentaerythitol tetraacrylate (EFTA) and 52.80 g of ethanol to the constant pressure dropping funnel to obtain an intermediate mixture, divide the intermediate mixture into three equal parts, add the three equal parts to the round-bottomed flask drop by drop in sequence every 6 hours; and then react for 28 h at 25° C., obtain a mixed ethanol solution of ((N-(4-aminoalkylene))-3-aminopropionate) hyperbranched polymer and 1,4-butanediamine; and then cool to 20° C., add 96.00 g (1.2.0 mol, 50%) of sodium hydroxide aqueous solution and 91.20 g (1.20 mol) of carbon disulfide drop by drop; and then react for 5 h at 25° C., precipitate a yellowish solid product, filter and dry under vacuum to obtain 209.18 g of a white product with a yield of 93.72%, namely, the compound heavy metal chelating agent containing dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer (EPTA/BDA/DTC) and 1,4-butanediamine-N,N′-sodium bisdithiocarboxylate (BDA/DTC), wherein a molar ratio of the EPTA/BDA/DTC and the BDA/DTC is 1:2.

(8) Chemical shifts of the characteristic absorption peak of .sup.13C nuclear magnetic resonance spectrum (D.sub.2O) of the white product are respectively: 25.24, 26.98, 27.21, 31.26, 45.61, 45.98, 50.25, 53.24, 65.32, 68.38, 70.90, 47.03, 172.32, 211.98, 212.18 and 213.36 ppm, which shows that the compound heavy metal chelating agent is a mixture of dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer (EPTA/BDA/DTC) and 1,4-butanediamine-N,N′-sodium bisdithiocarboxylate (BDA/DTC) with a structural formula of

(9) ##STR00007##

Third Embodiment

(10) Preparation of dithiocarboxylate functionalized pentaerythritol core hyperbranched polymer and 1,6-hexanediamine-N,N′-sodium bisdithiocarboxylate compound heavy metal chelating agent:

(11) Under nitrogen protection, add 81.20 g (0.70 mol) of 1,6-hexanediamine (HDA) and 81.20 g of ethanol to a round-bottomed flask with a stirrer, a reflux condenser, a constant pressure dropping funnel and a thermometer, stir at 20° C.; and then add 52.80 g (0.10 mol) of ethoxylated pentaerythitol tetraacrylate (EPTA) and 52.80 g of ethanol to the constant pressure dropping funnel to obtain an intermediate mixture, divide the intermediate mixture into two equal parts, add one of the two equal parts to the round-bottomed flask drop by drop, stir for 4 h, add another of the two equal parts drop by drop; and then react for 24 h at 25° C., obtain a mixed ethanol solution of ((N-(6-aminoalkylene))-3-aminopropionate) hyperbranched polymer and 1,6-hexanediamine; and then cool to 20° C., add 112.00 g (1.40 mol, 50%) of sodium hydroxide aqueous solution and 106.40 g (1.40 mol) of carbon disulfide drop by drop; and then react for 5 h at 25° C., precipitate a yellowish solid product, filter and dry under vacuum to obtain 244.26 g of a white product with a yield of 90.07%, namely, the compound heavy metal chelating agent containing dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and 1,6-hexanediamine-N,N′-sodium bisdithiocarboxylate with a molar ratio of 1:3.

(12) Chemical shifts of the characteristic absorption peak of .sup.13C nuclear magnetic resonance spectrum (D.sub.2O) of the white product are respectively: 25.68, 25.98, 26.42, 29.34, 29.93, 30.56, 33.74, 43.28, 48.28, 49.26, 50.28, 53.84, 67.94, 68.82, 71.06, 174.92, 211.16, 212.06 and 212.98 ppm, which shows that the compound heavy metal chelating agent is a mixture of dithiocarboxylate functionalized ethoxylated pentaerythritol core hyperbranched polymer and 1,6-hexanediamine-N,N′-sodium bisdithiocarboxylate with a structural formula of

(13) ##STR00008##

First Control Example

(14) Commercially available sodium diethyldithiocarbamate solid

Second Control Example

(15) Commercially available disodium N,N′-bis-(dithiocarboethylenediamine

Fourth Embodiment

(16) Treatment of copper-containing electroplating wastewater

(17) The compound heavy metal chelating agents obtained by the first embodiment, the second embodiment and the third embodiment, and the traditional chelating agents provided by the first control example and the second control example are used to treat heavy metal wastewater (pH 3.7, Cu .sup.2+ 16.12 mg.Math.L.sup.−1 and Ni.sup.2+ 5.68 mg.Math.L.sub.−1) from a circuit board factory in Shanghai, China respectively.

(18) A treatment method comprises steps of: (1) adjusting a pH value of the heavy metal wastewater to 7.0 with NaOH; (2) taking 500 mL of the heavy metal wastewater, stirring at 150 rpm for 10 min with a stirrer, simultaneously adding a chelating agent on a base of dry basis; (3) performing a next step for the compound heavy metal chelating agents provided by the first embodiment, the second embodiment and the third embodiment, or adding a polyacrylamide (PAM) aqueous solution with a mass concentration of 0.1% and a density of 50 mg.Math.L.sup.−1 to the traditional chelating agents provided by the first control example and the second control example, stirring at 50 rpm for 5 min; and (4) standing for 30 min, filtering and determining a heavy metal content with ICP-MS (7700, Agilent). Determination results are shown in Table 1.

(19) TABLE-US-00001 TABLE 1 Result comparison of treatment on heavy metal wastewater (Cu.sup.2+ 16.12 mg .Math. L.sup.−1) Heavy metals Whether in water Chelating Concentration PAM is (mg .Math. L.sup.−1) agent (mg .Math. L.sup.−1) added Cu.sup.2+ Ni Precipitation First 120 No 1.09 0.98 Large particles, dense, fast Embodiment 130 No 0.23 0.11 settling, easy separation, 140 No 0 0.07 less sludge Second 120 No 2.25 1.45 Large particles, dense, fast Embodiment 130 No 0.18 0.09 settling, easy separation, 140 No 0 0.01 less sludge Third 120 No 2.34 1.25 Large particles, dense, fast Embodiment 130 No 0.29 0.43 settling, easy separation, 140 No 0.06 0.08 less sludge First Control 120 Yes 2.93 1.97 Fine particles, slow settling, Example 150 Yes 1.01 0.98 need PAM for coagulation, 200 Yes 1.02 0.98 and large amount of sludge Second 120 Yes 1.61 1.73 Small particles, slow Control 130 Yes 0.48 1.28 settling, need PAM to help Example 150 Yes 0.27 1.29 coagulation, and large 200 Yes 0.373 0.12 amount of sludge Special heavy metal emission limit 0.3 0.1 — standards in Table 3 of “Emission Standards of Electroplating Pollutant (GB21900-2008)”

(20) It is able to be seen from Table 1 that the composite heavy metal chelating agents provided by the present invention has a good removal effect on Cu.sup.2+, and the concentration of Cu.sup.2+ after treatment is lower than special heavy metal emission limit standards in Table 3 of “Emission Standards of Electroplating Pollutant (GB21900-2008)”. Judging from the morphology of the deposit formed by the compound heavy metal chelating agents with heavy metals, the floc deposits formed by the compound heavy metal chelating agents, which are provided by the first embodiment, the second embodiment and the third embodiment of the present invention, with the heavy metals are large and dense in particles, and have a fast settling speed, do not need PAM to help coagulation, so the sludge is less. However, the floc deposits, formed by sodium diethyldithiocarbamate of the first control example with heavy metals, are small in particles, have a slow settling speed, need PAM to help coagulation, so the sludge is much, which is unable to meet special heavy metal emission limit standards in Table 3 of “Emission Standards of Electroplating Pollutant (GB21900-2008)”. The floc deposits, formed by disodium N,N′-bis-(dithiocarboxy) ethylenediamine of the second control example with heavy metals, are small in particles, have a slow settling speed, need PAM to help coagulation, so the sludge is much, which is also unable to meet special heavy metal emission limit standards in Table 3 of “Emission Standards of Electroplating Pollutant (GB21900-2008)”.

Fifth Embodiment

(21) Treatment of mercury-containing wastewater

(22) The compound heavy metal chelating agent obtained by the first embodiment, and the traditional chelating agents provided by the first control example and the second control example are used to treat blast furnace washing water (pH 1.65, Hg.sup.2+ 1.566 mg.Math.L.sup.−1, Ni.sup.2+ 0.828 mg.Math.L.sup.−1 and Pb.sup.2+ 1.029 mg.Math.L.sup.−1) from an enterprise in Shanghai, China respectively.

(23) A treatment method comprises steps of: (1) adjusting a pH value of the blast furnace washing water to 7.0 with NaOH; (2) taking 500 mL of the blast furnace washing water, stirring at 150 rpm for 10 min with a stirrer, simultaneously adding a chelating agent on a base of dry basis; (3) stirring at 50 rpm for 30 min; (4) standing for 30 min, filtering and determining a heavy metal content with ICP-MS (7700, Agilent), Determination results are shown in Table 2.

(24) TABLE-US-00002 TABLE 2 Result comparison of treatment on blast furnace washing water Heavy metals in water Concentration (mg .Math. L.sup.−1) Serial No. (mg .Math. L.sup.−1) Hg.sup.2+ Ni.sup.2+ Pb.sup.2+ Precipitation Raw water 1.566 0.828 1.029 First 10 0.001 0.013 0.035 Flocs are embodiment produced Second 10 0.001 0.011 0.033 Flocs are embodiment produced Third 10 0.002 0.009 0.026 Flocs are embodiment produced First control 10 1.566 0.828 1.029 example 20 1.566 0.828 1.029 No floc is 30 1.566 0.828 1.029 produced Second control 10 1.566 0.828 1.029 example 20 1.566 0.828 1.029 No floc is 30 1.566 0.828 1.029 produced Shanghai Local Standard 0.005 0.1 0.1 — “Comprehensive Emission Standard DB31/199-2018”

(25) The treatment of low-concentration heavy metal wastewater is an industry problem. It is able to be seen from Table 2 that the compound heavy metal chelating agents provided by the present invention has a good removal effect on low-concentration heavy metal wastewater. Because the heavy metal chelating agent containing hyperbranched polymer is synergized with the micromolecular disodium N,N′-bis-(dithiocarboxy) ethylenediamine, and alternately chelated with heavy metals to form larger chelate deposits, thereby producing macroscopic floc deposits, which is able to satisfy Shanghai Local Standard “Comprehensive Emission Standard DB31/199-2018” after filtration. However, the sodium diethyldithiocarbamate solid provided by the first control example, and the disodium N,N′-bis-(dithiocarboxy) ethylenediamine provided by the second control example are unable to produce floc deposits, and unable to effectively treat the low-concentration heavy metal wastewater.

(26) It is able to be seen from the above embodiments that the hyperbranched polymer compound heavy metal chelating agent provided by the present invention has a wide application range while processing heavy metals, does not need to add coagulant, has a good processing effect, and has both chelation and flocculation functions. Therefore, it is able to effectively treat low-concentration wastewater.

(27) The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications are able to be made. These improvements and modifications should also be regarded as the protective scope of the present invention.