阅读说明：本技术 一种重金属捕集剂n-甲基-n-苯基氨基二硫代甲酸钠的合成方法及应用 (Synthesis method and application of heavy metal trapping agent N-methyl-N-phenyl amino sodium dithioformate ) 是由 郭祥荣 杨荣华 王璀 郭彦恺 于晓晗 刘瑞鹏 于 2020-05-26 设计创作，主要内容包括：本发明提供了一种重金属捕集剂N-甲基-N-苯基氨基二硫代甲酸钠的合成方法,及其在含重金属废水处理以及飞灰中重金属去除的应用。本发明提供的合成方法以N-甲基苯胺、氢氧化钠、二硫化碳为原料,根据反应物料的物理化学性质、反应机理和反应条件,分阶段控制反应温度,采用三个不同反应温度实现反应完全,缩短了反应时间、提升了产物收率,通过调整反应物配比,制备的成品无含硫无机物的臭味,无二硫化碳分解产生的细小的碳颗粒,产品贮存稳定性高,工艺操作简单,反应过程便于控制,生产过程中无“三废”产生,对环境无污染,操作安全。(The invention provides a method for synthesizing a heavy metal trapping agent N-methyl-N-phenyl amino sodium dithioformate and application thereof in heavy metal-containing wastewater treatment and heavy metal removal in fly ash. The synthesis method provided by the invention takes N-methylaniline, sodium hydroxide and carbon disulfide as raw materials, controls the reaction temperature by stages according to the physicochemical properties, reaction mechanism and reaction conditions of reaction materials, adopts three different reaction temperatures to realize complete reaction, shortens the reaction time, improves the product yield, and has the advantages that the prepared finished product has no odor of sulfur-containing inorganic substances and no fine carbon particles generated by decomposition of the carbon disulfide by adjusting the proportion of reactants, the product has high storage stability, the process operation is simple, the reaction process is convenient to control, no three wastes are generated in the production process, no pollution is caused to the environment, and the operation is safe.)

1. A method for synthesizing a heavy metal trapping agent N-methyl-N-phenyl amino sodium dithioformate is characterized by comprising the following steps:

step 1, preparing materials: respectively measuring water and a sodium hydroxide solution, then sucking the water and the sodium hydroxide solution into a first reaction kettle in vacuum, and starting stirring to form a sodium hydroxide diluent;

metering N-methylaniline, and sucking into a first reaction kettle in vacuum;

pressing carbon disulfide from a storage tank into a carbon disulfide metering tank by using compressed air;

step 2, primary reaction: introducing refrigerating fluid into a first reaction kettle jacket, when the temperature in the kettle is reduced to 5-10 ℃, dropwise adding carbon disulfide, reacting the carbon disulfide with N-methylaniline and sodium hydroxide, and controlling the dropwise adding speed of the carbon disulfide to keep the reaction temperature at 15-25 ℃ until the primary reaction is finished;

step 3, secondary reaction: after the dropwise addition of the carbon disulfide is finished, pressing the material from the first reaction kettle to the second reaction kettle by using compressed air, introducing refrigerating fluid into a shell pass of a condenser connected with the second reaction kettle, introducing steam into a kettle jacket after the material is transferred, raising the temperature to 30-45 ℃ within 10-20 minutes, and then reacting for 10-20 minutes;

and 4, carrying out three reactions: after the secondary reaction is finished, opening a large steam valve, heating the kettle to 60-70 ℃ within 10-20 minutes, continuing the reaction for 20-30 minutes, finally, cooling the temperature in the second reaction kettle to below 30 ℃, and sampling and analyzing;

and 5, adding water into the second reaction kettle according to the analysis result to adjust the concentration of the prepared sodium N-methyl-N-phenylamino-dithionate, and warehousing after the detection is qualified.

2. The synthesis method of the sodium N-methyl-N-phenyl amino-dithioformate as the heavy metal trapping agent according to claim 1, wherein the molar ratio of materials in the synthesis method is that N-methylaniline: carbon disulfide: 100% NaOH: water 1: (1.0-1.03): (1.0-1.2): (13.8-17.9).

3. The method for synthesizing sodium N-methyl-N-phenyl amino dithioformate as a heavy metal trapping agent according to claim 2, wherein the material is a uniform liquid without layering after one reaction in step 2.

4. The method for synthesizing sodium N-methyl-N-phenyl amino dithioformate as a heavy metal trapping agent according to claim 3, wherein the carbon disulfide is added dropwise within 30-50 minutes in the step 2, and the reaction is completed.

5. The method for synthesizing sodium N-methyl-N-phenylaminodithioformate as a heavy metal trapping agent according to claim 4, wherein the concentration of the sodium hydroxide diluent is 12% or more after the sodium hydroxide solution is mixed with water in the step 1.

6. The method for synthesizing sodium N-methyl-N-phenyl-amino-dithiocarbamate as heavy metal trapping agent according to claim 4, wherein the concentration of the sodium hydroxide diluent is 12-20% after the sodium hydroxide is mixed with water in the step 1.

7. The method for synthesizing sodium N-methyl-N-phenylamino-dithioate as heavy metal trapping agent according to claim 5 or 6, characterized in that the weight percentage of the solution of hydrogen hydroxide in step 1 is 30%.

8. An application of a heavy metal trapping agent N-methyl-N-phenyl amino sodium dithioformate in treating waste water containing heavy metals and removing heavy metals in fly ash.

Technical Field

The invention belongs to the technical field of environment functional materials, and particularly relates to a synthesis method and application of a heavy metal trapping agent N-methyl-N-phenyl amino sodium dithioformate.

Background

With the development of socioeconomic, the acceleration of urbanization process, the high development of urbanization and the improvement of physical life of people in China, the yield of domestic garbage is greatly increased, the annual production amount of municipal domestic garbage in China reaches more than 1.5 hundred million tons, and the annual production rate is increased by 8-10%. The incineration treatment is regarded as the best means for treating the garbage in China with remarkable reduction, harmlessness and resource advantages, however, a large amount of fly ash is generated in the incineration process, and the fly ash contains heavy metals with higher leaching concentration, such as Pb²⁺、Cr³⁺、Cd²⁺、Cu²⁺、Hg²⁺And Zn²⁺Etc., and is therefore classified as a hazardous waste (HW 18). Especially the very complex components and toxic and harmful substances in the fly ash cause great pollution to the living environment. Therefore, the fly ash is subjected to harmless treatment, and the significance of reduction control is very great. The medicament stabilization is a more common fly ash harmless treatment technology, and the chelating group of the metal chelating agent captures and chelates various heavy metals in the fly ash, so that the heavy metals in the fly ash can be converted into a complex which is difficult to dissolve and migrate, heavy metal ions are fixed, and secondary pollution is avoided.

Heavy metal ions such as Cu generated in industrial, agricultural, etc. production activities²⁺，Pb²⁺And the like have high toxicity and nondegradable property, and once entering the organism from the water body, the heavy metal-containing wastewater can not only be gradually accumulated, but also can cause serious consequences such as diseases and even death, and the like, so that the high-efficiency treatment of the heavy metal-containing wastewater becomes an important problem in the field of global environmental protection. At present, the treatment methods commonly used for heavy metal ions in wastewater include chemical precipitation, chelation precipitation, membrane separation, ion exchange, adsorption, electrodialysis and other removal methods, and among them, chelation precipitation is recognized as a heavy metal removal method capable of efficiently and massively treating heavy metal wastewater due to its advantages of simplicity, rapidness and low cost.

Dithiocarbamates (DTCs for short), which are widely used as chelating agents for effectively removing heavy metal ions due to their strong binding to metal ions, have been used for inorganic analysis and heavy metal trapping agents, and the DTC class of chelating agents can be roughly classified into two classes according to their molecular structures: one is a high molecular weight chelating agent with a DTC group grafted on a high molecular matrix; another class is small molecule DTC chelators. The large molecular weight chelating agent has good flocculation and sedimentation performance, but the high molecular chain has steric hindrance, so that the chelating efficiency of a DTC group and heavy metal is low, and the matrix cost is high; the micromolecule DTC chelating agent has high chelating efficiency with heavy metal, but the formed floc is small and the sedimentation performance is poor. N-methylaniline and its series derivatives are used as important intermediates in N-alkyl arylamine series, and are widely applied to the fields of rubber, petroleum, agriculture, mining industry, medicine, environmental protection, analytical chemistry and the like as a plurality of series products of N-phenyl-N-alkyl sodium dithiocarbamate synthesized with carbon disulfide and sodium hydroxide. The N-methyl-N-phenyl amino sodium dithioformate has unique advantages in the aspects of removing complex copper and nickel ions and the like due to the characteristics of molecular structure and the characteristics of surface charge distribution of functional groups and heavy metal complexes, and the chelating agent has more surface charges of the functional groups, is easier to polarize and deform to generate an electric field and destroy complex bonds, thereby adsorbing cations to generate chelate bonds and removing complex heavy metals, and has high chelating capacity for partial heavy metals compared with other trapping agents used in the industry at present.

The prior domestic research results related to the synthesis of the sodium N-methyl-N-phenyl amino dithiocarbamate mainly comprise: yanzhengning et al, published in 2006, study of PVC membrane silver ion selective electrode using bis (N-methyl-N-phenyl amino dithioformic acid) 1, 4-butanediol ester as carrier, and proposed a method for preparing sodium N-methyl-N-phenyl amino dithioformate by using ethanol as solvent and reacting carbon disulfide, sodium hydroxide and N-methylaniline, but the yield is only 70%, and the obtained sodium N-methyl-N-phenyl amino dithioformate has high impurity content and is limited in use even if ethyl acetate is used for washing for a plurality of times in the subsequent process. In the thesis of hu yuan (university of south-central province, 2013) on the synthesis of dithiocarbamate and the flotation performance of dithiocarbamate on lead-zinc sulfide ore, the hu yuan proposes a method of synthesizing by adding carbon disulfide and N-methylaniline into a sodium hydroxide aqueous solution for a plurality of times by using water as a solvent, and although the yield of the product sodium N-methyl-N-phenylaminodithiocarbamate reaches 88%, the operation is still complicated, the carbon disulfide and the N-methylaniline are required to be added for a plurality of times respectively, and the reaction endpoint is difficult to determine; the loss of carbon disulfide is large, the reaction is incomplete, and the yield of inorganic salt is large, so that the obtained N-methyl-N-phenyl amino sodium dithioformate has low purity and the like. The Chen Chaoyang Shuozhi paper 'preparation and performance research of novel dialkyl dithiocarbamate' (Zhongnan university, 2003) proposes an operation of mixing sodium hydroxide with a concentration of 45% with N-methylaniline and then dropwise adding carbon disulfide into the mixed solution, wherein the average yield of the product sodium N-methyl-N-phenyl amino dithiocarbamate reaches 96%, the reaction time is 100-plus-120 min, the reaction is incomplete, both the raw materials N-methylaniline and carbon disulfide have residues, the reaction solution is layered (the upper layer is N-methylaniline, and the bottom is provided with carbon disulfide liquid drops), and the reaction solution has a hydrogen sulfide smell; improper reaction temperature selection, unreasonable carbon disulfide dropping temperature and reaction temperature setting value after dropping, and the like.

The prior synthesis process of the sodium N-methyl-N-phenyl amino dithioformate has the following main problems:

(1) the reaction time is long and the production operation period is long due to unreasonable reaction temperature setting and temperature rise gradient;

(2) the reasonable use of carbon disulfide is not fully considered in process design, the carbon disulfide loss is more, and the environment is polluted;

(3) the inorganic salt generated by the reaction of the carbon disulfide and NaOH has a large amount, so that the carbon disulfide and the main raw material N-methylaniline have insufficient reaction, and the conversion rate of the main raw material N-methylaniline is low;

(4) the reaction is incomplete, carbon disulfide liquid drops are distributed and more in finished product materials discharged from the bottom of the reactor, and insoluble oily substances sometimes appear on the upper part of reaction liquid.

Therefore, on the basis of the existing synthesis process, research is carried out with the purposes of mainly preparing a target product for removing heavy metal ions, improving the product yield, improving the conversion rate of N-methylaniline and shortening the reaction time, and the method has important theoretical value and practical significance of industrial production.

Disclosure of Invention

The existing synthesis process of sodium N-methyl-N-phenyl amino dithioformate has the problems of unreasonable raw material proportion, unreasonable reaction temperature setting and temperature gradient, long reaction time, low conversion rate of N-methylaniline, poor product storage stability, insufficient reaction and the like, and in order to solve the problems, the following points are needed to be considered:

(1) preparing a target product for removing heavy metal ions in wastewater and fly ash, wherein the product is required to be an aqueous solution for the purposes of convenient use and environmental protection;

(2) adjusting reaction conditions to ensure that N-methylaniline fully reacts with NaOH and carbon disulfide, the molar ratio of the carbon disulfide to the N-methylaniline is generally more than 1.05 during feeding in the prior art, and excessive carbon disulfide does not completely react or generates side reaction or is lost from a reaction system;

(3) the loss of carbon disulfide is reduced, and during the synthesis of the existing small-scale technology, the carbon disulfide is easy to decompose and can generate black fine particles;

(4) determining reasonable reaction temperature and reaction time;

(5) the storage period and the stability of the product are prolonged.

In order to achieve the results, the invention provides a synthesis method and application of a heavy metal trapping agent N-methyl-N-phenyl amino sodium dithioformate. Firstly, the invention provides a new synthesis method; meanwhile, the synthesized sodium N-methyl-N-phenyl amino dithioformate is used as a heavy metal trapping agent for heavy metal-containing wastewater treatment and a heavy metal removal experiment in fly ash, and the effect of removing heavy metals is determined. The technical scheme of the invention is as follows:

the first purpose of the invention is to provide a method for synthesizing a heavy metal trapping agent sodium N-methyl-N-phenyl amino dithioformate, which comprises the following steps:

step 1, preparing materials: respectively measuring water and a sodium hydroxide solution, then sucking the water and the sodium hydroxide solution into a first reaction kettle in vacuum, and starting stirring to form a sodium hydroxide diluent;

metering N-methylaniline, and sucking into a first reaction kettle in vacuum;

pressing carbon disulfide from a storage tank into a carbon disulfide metering tank by using compressed air;

step 2, primary reaction: introducing refrigerating fluid into a first reaction kettle jacket, when the temperature in the kettle is reduced to 5-10 ℃, dropwise adding carbon disulfide, reacting the carbon disulfide with N-methylaniline and sodium hydroxide, and controlling the dropwise adding speed of the carbon disulfide to keep the reaction temperature at 15-25 ℃ until the primary reaction is finished;

step 3, secondary reaction: after the dropwise addition of the carbon disulfide is finished, pressing the material from the first reaction kettle to the second reaction kettle by using compressed air, introducing refrigerating fluid into a shell pass of a condenser connected with the second reaction kettle, introducing steam into a kettle jacket after the material is transferred, raising the temperature to 30-45 ℃ within 10-20 minutes, and then reacting for 10-20 minutes;

and 4, carrying out three reactions: after the secondary reaction is finished, opening a large steam valve, heating the kettle to 60-70 ℃ within 10-20 minutes, continuing the reaction for 20-30 minutes, finally, cooling the temperature in the second reaction kettle to below 30 ℃, and sampling and analyzing;

and 5, adding water into the second reaction kettle according to the analysis result to adjust the concentration of the prepared sodium N-methyl-N-phenylamino-dithionate, and warehousing after the detection is qualified.

Preferably, the molar ratio of the materials in the synthesis method is N-methylaniline: carbon disulfide: 100% NaOH: water 1: (1.0-1.03): (1.0-1.2): (13.8- -17.9).

Preferably, the material is a uniform liquid without layering when the primary reaction in step 2 is completed.

More preferably, in the step 2, the carbon disulfide is dripped within 30-50 minutes, and the reaction is completed.

Preferably, the concentration of the sodium hydroxide diluent in step 1 after mixing the sodium hydroxide with water is 12% or more.

More preferably, the concentration of the sodium hydroxide diluent after the sodium hydroxide is mixed with water in the step 1 is 12 to 20 percent.

More preferably, the mass fraction of the solution of hydrogen oxidation in step 1 is 30%.

In order to verify the influence of different process conditions on the synthesis effect, the embodiment of the invention also provides comparison for experiments by changing the process conditions, and the comparison shows that the reaction temperature is reduced, the reaction is incomplete, the reaction temperature is increased, black fine particles exist in materials generated after the reaction is finished, and the N-methylaniline conversion rate is possibly low.

The second purpose of the invention is to provide the application of the heavy metal trapping agent sodium N-methyl-N-phenyl amino dithioformate in the treatment of heavy metal-containing wastewater and the removal of heavy metals in fly ash. In order to verify the effect of removing heavy metal, the embodiment of the invention respectively provides a test for removing single-component heavy metal ions, a test for removing multi-component heavy metal ions coexisting in the solution and a test for removing heavy metal ions in the waste incineration fly ash.

In the test of removing single-component heavy metal ions, Cu is respectively prepared²⁺,Zn²⁺,Cd²⁺,Pb²⁺,Ni²⁺Simulating a heavy metal water sample, adding 100mg/L of the synthesized heavy metal trapping agent, stirring for reaction for 10min at 200r/min, standing and filtering, taking supernate to determine the concentration of heavy metal ions, and detecting results show that the product of the invention can be used for treating free Cu²⁺The heavy metal ions have good removal effect.

In the test for removing the coexisting multi-component heavy metal ions in the solution, the electroplating wastewater of a certain company is selected and the Cu in the electroplating wastewater is measured²⁺、Zn²⁺、Mn²⁺、Pb²⁺、Ni²⁺Adding a certain amount of the synthesized heavy metal trapping agent, stirring at the speed of 200r/min, reacting and stirring for 10min, standing and filtering, taking supernate to measure the concentration of the five metal ions, and detecting results show that the concentration of the five metal ions in the heavy metals is differentUnder the coexistence environment of ions, the product of the invention still has good removal effect on various heavy metal ions.

In the test for removing heavy metal ions in the fly ash from the waste incineration, fly ash in the normal operation period of a certain domestic waste incineration power plant is selected, the synthesized heavy metal collecting agent is used, the heavy metal collecting agent, the fly ash and water are mixed and stirred for a certain time in a mixer according to a certain proportion, then the fly ash block is maintained for three days, the well-maintained fly ash solidified block is taken out, the concentration of heavy metals in the leachate of the fly ash solidified block is detected, and the result shows that the content of heavy metals in the treated fly ash reaches the national identification standard of dangerous wastes and the standard requirement of the landfill entrance of domestic garbage.

Compared with the prior art, the invention has the beneficial effects that:

1. the reaction time is shortened. Controlling the reaction temperature in stages according to the physicochemical properties, the reaction mechanism and the reaction conditions of reaction materials, adopting three different reaction temperatures to realize complete reaction, and reducing the reaction time (including the carbon disulfide dripping time and the heat preservation reaction time) from 200 minutes of the current pilot plant technical level to 120 minutes which is only needed by industrial scale production;

2. the yield of the sodium N-methyl-N-phenyl amino dithioformate is improved, and the product yield is improved to 98.2 percent of industrial scale production from 96 percent of the current pilot plant technical level;

3. the proportion of reaction materials is adjusted, the molar ratio of the carbon disulfide to the N-methylaniline is reduced to be below 1.03, and the prepared finished product has no odor of sulfur-containing inorganic substances and no fine carbon particles generated by decomposition of the carbon disulfide;

4. the storage stability of the product is improved, the product is sampled and analyzed after being placed for one and a half years, the content of the product obtained by industrial production is only reduced by 0.1 to 0.3 percent, and the appearance of the product is not obviously changed by visual inspection;

5. the product prepared by the invention is mainly used as a heavy metal trapping agent, the formed process is simple to operate, the reaction process is convenient to control, three wastes are not generated in the production process, the environment is not polluted, and the operation is safe;

6. the product is used in various fields such as heavy metal ion-containing wastewater treatment, waste incineration fly ash treatment and the like.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.