阅读说明：本技术 一种过渡金属锌掺杂硫化钼复合催化粉体材料及其制备与应用 (Transition metal zinc-doped molybdenum sulfide composite catalytic powder material and preparation and application thereof ) 是由 姚运金 郑宏达 尹红玉 高梦雪 张阳洋 胡欢欢 张宇 于 2020-05-18 设计创作，主要内容包括：本发明公开了一种过渡金属锌掺杂硫化钼复合催化粉体材料及其制备与应用,该复合催化粉体材料是一种过渡金属锌掺杂硫化钼的粉体材料。本发明的复合催化材料具有性能优异、比表面积大、重复利用率高、分散性好等优点,基于其构建的一体化甲酸耦合还原反应装置可高效还原重金属六价铬污染物；同时本发明的制备工艺流程简单、操作可控,具有安全、高效、绿色环保等优点,适合大规模生产。(The invention discloses a transition metal zinc-doped molybdenum sulfide composite catalytic powder material, and a preparation method and application thereof. The composite catalytic material has the advantages of excellent performance, large specific surface area, high repeated utilization rate, good dispersibility and the like, and the integrated formic acid coupling reduction reaction device constructed based on the composite catalytic material can efficiently reduce heavy metal hexavalent chromium pollutants; meanwhile, the preparation process is simple in flow, controllable in operation, safe, efficient, green and environment-friendly, and the like, and is suitable for large-scale production.)

1. A preparation method of a transition metal zinc-doped molybdenum sulfide composite catalytic powder material is characterized by comprising the following steps:

step 1, adding ammonium molybdate tetrahydrate and metal zinc salt into deionized water, stirring for 2-4 hours, adding a sulfur source, and continuously stirring for 1-3 hours to obtain a mixed solution;

step 2, carrying out hydrothermal reaction on the mixed solution obtained in the step 1 at the temperature of 100-200 ℃ for 10-20 h;

and 3, drying and fully grinding the product obtained in the step 2, placing the product in a tubular furnace, heating to 600-700 ℃ under the protection of inert gas, reacting at a constant temperature for 1-3 hours, and cooling to room temperature after the reaction is finished to obtain the transition metal zinc-doped molybdenum sulfide composite catalytic powder material.

2. The method of claim 1, wherein: in the step 1, the using amount ratio of ammonium molybdate tetrahydrate, the metal zinc salt and the sulfur source is 10-30 mmol: 0.1-0.3 mol: 0.1 to 0.5 mol.

3. The production method according to claim 1 or 2, characterized in that: in the step 1, the metal zinc salt is one of water-soluble salts of metal zinc; the sulfur source is at least one of thiourea, sulfur and ammonium tetrathiomolybdate.

4. The production method according to claim 1 or 2, characterized in that: in the step 3, the drying is carried out for 10-30 h at the temperature of 60-80 ℃.

5. The production method according to claim 1 or 2, characterized in that: in the step 3, the inert gas is argon or nitrogen, and the flow rate of the inert gas is 0.1-5 mL/min.

6. The production method according to claim 1 or 2, characterized in that: in the step 3, the temperature rise rate of the temperature rise is controlled to be 5-10 ℃/min.

7. A transition metal zinc-doped molybdenum sulfide composite catalytic powder material prepared by the preparation method of any one of claims 1 to 6.

8. The use of the transition metal zinc-doped molybdenum sulfide composite catalytic powder material of claim 7 in the reduction of hexavalent chromium as a heavy metal.

9. A method for reducing heavy metal hexavalent chromium by using the transition metal zinc-doped molybdenum sulfide composite catalytic powder material of claim 7, which is characterized by comprising the following steps: constructing a reduction reaction device which comprises a hexavalent chromium sewage storage tank, a formic acid storage tank, a catalytic reactor and a sedimentation tank;

a water inlet is formed in the top of the catalytic reactor; the bottom outlet of the hexavalent chromium sewage storage pool and the bottom outlet of the formic acid storage pool are communicated to the water inlet through a water inlet pump and a throttle valve respectively;

a catalyst bed layer containing a plurality of transition metal zinc-doped molybdenum sulfide composite catalytic powder materials is fixed in the catalytic reactor;

a reacted water outlet is formed in the bottom of the catalytic reactor and communicated to a water inlet in the top of the sedimentation tank through a water outlet pump and a throttle valve; the top of the sedimentation tank is also provided with a sodium hydroxide inlet, the side surface of the sedimentation tank is provided with a water outlet, and the bottom of the sedimentation tank is provided with a chromium hydroxide sludge outlet;

a blower is connected in the catalytic reactor;

the method for reducing the heavy metal hexavalent chromium by using the reduction reaction device comprises the following steps:

loading hexavalent chromium sewage to be treated into a hexavalent chromium sewage storage tank, loading formic acid into a formic acid storage tank, respectively introducing the hexavalent chromium sewage into a catalytic reactor through corresponding water inlet pumps, and regulating the flow through corresponding throttle valves; mixing hexavalent chromium sewage and formic acid, slowly flowing from top to bottom through the composite catalytic powder material, performing catalytic reduction reaction to achieve the degradation effect, and increasing the reaction speed through a blower; introducing the solution after reaction into a sedimentation tank through a water outlet pump, and adding sodium hydroxide into the sedimentation tank for sedimentation treatment; discharging the chromium hydroxide sludge generated after precipitation, leading out the residual solution after treatment from a water outlet, and detecting: if the treated solution reaches the discharge standard, directly discharging; if the treated solution does not meet the discharge standard, the solution is reintroduced into the hexavalent chromium sewage storage pool to form circulation.

10. The method of claim 9, wherein: in the catalytic reactor, the molar ratio of formic acid to hexavalent chromium is 1.2-4: 1.

Technical Field

The invention relates to the technical field of inorganic catalyst preparation, in particular to a transition metal zinc-doped molybdenum sulfide composite catalytic powder material, and preparation and application thereof.

Background

Heavy metal pollution has been a long-standing environmental concern in countries around the world due to its non-degradable nature. Hexavalent chromium is a common water pollutant and is widely produced in the industrial fields of electroplating, metal processing, tanning, dyes, steel, chemical industry and the like. If the treatment is improper, the ground water is polluted, and the environment and the human health are seriously harmed. In aqueous environments, chromium is present predominantly in the form of hexavalent chromium and trivalent chromium. The two oxidation states of chromium have significantly different chemical properties and different toxicity to the human body. Hexavalent chromium has high mobility and toxicity, and has teratogenic and carcinogenic effects on human bodies. Trivalent chromium is not easy to migrate, has lower toxicity and is an essential trace element related to human health and life. The maximum concentration of hexavalent chromium specified by the domestic drinking water standard of China does not exceed 50 mug/L. Therefore, there is a need to remediate hexavalent chromium contamination in the environment to avoid the severe environmental and health problems caused by hexavalent chromium.

The existing hexavalent chromium treatment methods mainly comprise an electric flocculation method, a membrane separation method, an ion exchange method, an adsorption method and a chemical reduction method. Among them, the chemical reduction method is favored by most researchers because of its advantages such as low cost, high efficiency, and environmental friendliness. The chemical reduction method is to reduce hexavalent chromium into trivalent chromium, and then add alkali to adjust the pH value so as to further precipitate and remove the trivalent chromium. Commonly used reducing agents include ferrous sulfate, sulfur dioxide, sulfites, polyaluminum ferric chloride, and the like. However, the use of these conventional reducing agents introduces other impurity ions, making subsequent separation difficult. Formic acid is a green chemical substance produced by utilizing renewable biomass resources, has the characteristics of low price, strong reducing capability and the like, and is directly mineralized into water and carbon dioxide under the activation of a metal catalyst without generating any toxic intermediate. The formic acid is used as a reducing agent for converting hexavalent chromium into trivalent chromium, and has a great application prospect. It has been found that various noble metal catalysts having high surface energy (e.g., Au, Ag, Pd, and Pt) have been used for the reduction of hexavalent chromium. However, these noble metal-based catalysts have a high investment cost. This limitation has prompted efforts to develop highly efficient non-noble metal catalysts. Molybdenum disulfide is a naturally occurring layered solid that has been used in many areas of catalysis for hydrogen evolution reactions, electrochemical intercalation, hydrogen storage, and coating materials in lithium batteries due to its unique electronic properties. In the chemical reduction method, the theory and experiment that the molybdenum disulfide catalyst is verified is one of the most potential non-noble metal catalysts.

At present, the improvement of the catalytic activity of molybdenum sulfide is mainly realized by means of phase change engineering, defect engineering, impurity element doping and the like. In-plane defect engineering and doping of hetero elements are effective means for activating molybdenum sulfide, increasing the number of active sites and improving catalytic activity. Therefore, finding a cheap means to obtain the molybdenum sulfide material with ultra-small size, element doping and a large amount of in-plane sulfur vacancies has important significance for promoting the progress of the environment. The metal zinc is a typical transition metal, has low price and excellent performance, and shows good compatibility when being combined with molybdenum sulfide, so that zinc ions can easily enter a crystal lattice structure of the molybdenum sulfide after a zinc element is doped into the molybdenum sulfide, the number of surface active sites of the molybdenum sulfide can be effectively increased, the surface activity of the molybdenum sulfide is enhanced, hexavalent chromium is efficiently reduced, and the reaction efficiency is improved. Patent CN109378267A discloses a method for preparing molybdenum sulfide material, which comprises obtaining a photo-etching pattern by a photo-etching method, depositing a molybdenum-based film layer by a film coating process, and finally obtaining a target product by a high-temperature heating method. Patent CN 103641171A discloses Zn²⁺Regulation and control of synthetic MoS₂The material is prepared with Mo source, S source and reductant as material and through adding Zn²⁺The morphology of the product is regulated and controlled, and MoS is synthesized₂Materials, butThe catalyst prepared by the method has the technical defects of easy inactivation, agglomeration, considerable ion leaching, easy secondary pollution of water, difficult recovery and the like. Patent CN110614104A discloses a method for preparing molybdenum sulfide photocatalytic material for treating sewage, which adopts hydrothermal method and in-situ precipitation method to prepare target product for treating sewage, but the conditions for treating sewage require illumination, and sewage cannot be treated simply and rapidly, and the ultraviolet light absorption range is narrow, the light energy utilization rate is low, the energy consumption is large, and the reduction rate of sewage is not high.

In conclusion, the previous reports have the problems of low activity, high cost and the like in the aspects of material preparation process, product performance and a method for reducing hexavalent chromium pollutants. Therefore, the preparation of a catalytic material with low cost, simple operation and excellent performance and a simple, efficient and rapid hexavalent chromium reduction method are in urgent need of discovery.

Disclosure of Invention

The invention aims to provide a transition metal zinc-doped molybdenum sulfide composite catalytic powder material and preparation and application thereof aiming at the defects of the prior art, and the technical problems to be solved are that: the method solves the problems that the material preparation process is complicated, complicated experimental conditions are required, large-scale production cannot be realized, the prepared catalyst is poor in structural stability, low in dispersity and difficult to recover, and secondary pollution is caused to a water body, and the technical problem of how to simply, efficiently and quickly reduce hexavalent chromium pollutants is solved.

In order to solve the technical problems, the invention adopts the following technical scheme:

a preparation method of a transition metal zinc-doped molybdenum sulfide composite catalytic powder material comprises the following steps:

step 1, adding ammonium molybdate tetrahydrate and metal zinc salt into deionized water, stirring for 2-4 hours, adding a sulfur source, and continuously stirring for 1-3 hours to obtain a mixed solution;

step 2, carrying out hydrothermal reaction on the mixed solution obtained in the step 1 at the temperature of 100-200 ℃ for 10-20 h;

and 3, drying and fully grinding the product obtained in the step 2, placing the product in a tubular furnace, heating to 600-700 ℃ under the protection of inert gas, reacting at a constant temperature for 1-3 hours, and cooling to room temperature after the reaction is finished to obtain the transition metal zinc-doped molybdenum sulfide composite catalytic powder material.

Further, in the step 1, the use amount ratio of ammonium molybdate tetrahydrate, transition metal salt and sulfur source is 10-30 mmol: 0.1-0.3 mol: 0.1 to 0.5 mol.

Further, in step 1, the metal zinc salt is one of water-soluble salts of metal zinc, and the sulfur source is at least one of thiourea, sulfur and ammonium tetrathiomolybdate.

Further, in the step 3, the drying is carried out for 10-30 hours at the temperature of 60-80 ℃.

Further, in the step 3, the inert gas is argon or nitrogen, and the flow rate of the inert gas is 0.1-5 mL/min.

Further, in the step 3, the temperature rise rate of the temperature rise is controlled to be 5-10 ℃/min.

The invention also discloses the application of the transition metal zinc-doped molybdenum sulfide composite catalytic powder material prepared by the preparation method in reducing heavy metal hexavalent chromium. The method for reducing the heavy metal hexavalent chromium by using the transition metal zinc-doped molybdenum sulfide composite catalytic powder material comprises the following steps: and constructing a reduction reaction device which comprises a hexavalent chromium sewage storage tank, a formic acid storage tank, a catalytic reactor and a sedimentation tank.

A water inlet is formed in the top of the catalytic reactor; the bottom outlet of the hexavalent chromium sewage storage pool and the bottom outlet of the formic acid storage pool are communicated to the water inlet through a water inlet pump and a throttle valve respectively;

a catalyst bed layer containing a plurality of transition metal zinc-doped molybdenum sulfide composite catalytic powder materials is fixed in the catalytic reactor;

a reacted water outlet is formed in the bottom of the catalytic reactor and communicated to a water inlet in the top of the sedimentation tank through a water outlet pump and a throttle valve; the top of the sedimentation tank is also provided with a sodium hydroxide inlet, the side surface of the sedimentation tank is provided with a water outlet, and the bottom of the sedimentation tank is provided with a chromium hydroxide sludge outlet;

a blower is connected in the catalytic reactor;

the method for reducing the heavy metal hexavalent chromium by using the reduction reaction device comprises the following steps:

loading hexavalent chromium sewage to be treated into a hexavalent chromium sewage storage tank, loading formic acid into a formic acid storage tank, respectively introducing the hexavalent chromium sewage into a catalytic reactor through corresponding water inlet pumps, and regulating the flow through corresponding throttle valves; mixing hexavalent chromium sewage and formic acid, slowly flowing from top to bottom through the composite catalytic powder material, performing catalytic reduction reaction to achieve the degradation effect, and increasing the reaction speed through a blower; introducing the solution after reaction into a sedimentation tank through a water outlet pump, and adding sodium hydroxide into the sedimentation tank for sedimentation treatment; discharging the chromium hydroxide sludge generated after precipitation, leading out the residual solution after treatment from a water outlet, and detecting: if the treated solution reaches the discharge standard, directly discharging; if the treated solution does not meet the discharge standard, the solution is reintroduced into the hexavalent chromium sewage storage pool to form circulation.

Further, in the catalytic reactor, the molar ratio of formic acid to hexavalent chromium is 1.2-4: 1.

further, the optimal pH condition of the reaction of the hexavalent chromium sewage and formic acid is 2-3, and a pH regulator inlet is arranged at the top of the catalytic reactor and used for adding a pH value regulator such as hydrochloric acid or sodium hydroxide to regulate the pH value of the reaction system.

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

(1) the whole preparation process related by the invention is simple and convenient, does not need complex experimental conditions, has good repeatability and is environment-friendly, and the industrial production of the transition metal zinc-doped molybdenum sulfide composite catalytic powder material is realized.

(2) The transition metal zinc used in the invention is cheap and easy to obtain, has good compatibility in the molybdenum sulfide matrix, and can effectively increase the number of active sites on the surface of the molybdenum sulfide, thereby enhancing the surface activity of the molybdenum sulfide and improving the reaction efficiency. According to the invention, the content of sulfur vacancy in the surface of the nanoparticle is effectively regulated and controlled by doping the transition metal zinc and the molybdenum sulfide, so that the catalytic performance of the nanoparticle is regulated and controlled, and a new material is provided for hexavalent chromium reduction.

(3) The composite catalytic powder material prepared by the invention has large reaction contact area and high repeated utilization rate, and is coupled with formic acid for degrading and reducing heavy metal hexavalent chromium pollutants for the first time, the reduction rate reaches 100 percent, and a new method is provided for the field of reducing hexavalent chromium. In addition, the catalyst has high purity, uniform granularity and good dispersibility, and solves the problems of poor dispersibility, easy activation and poisoning, easy aggregation and the like of the traditional powder catalytic material.

(4) Based on the obtained transition metal zinc-doped molybdenum sulfide composite catalytic powder material, the invention also constructs a related reduction reaction device for reducing the heavy metal hexavalent chromium pollutants for the first time. The device can realize large-scale application of reducing hexavalent chromium, and provides a new idea for the field of reducing hexavalent chromium.

Drawings

FIG. 1 is an XRD diagram of a transition metal zinc-doped molybdenum sulfide composite catalytic powder material prepared in example 1 of the present invention;

FIG. 2 is an SEM image of a transition metal zinc-doped molybdenum sulfide composite catalytic powder material prepared in example 1 of the present invention;

FIG. 3 is a schematic view of a reduction reaction apparatus constructed according to the present invention.

Detailed Description

The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.