阅读说明：本技术 一种制备活性炭负载纳米零价纯铁粉生产方法及应用 (Production method and application for preparing activated carbon loaded nano zero-valent pure iron powder ) 是由 李成威 刘谦 亢淑梅 金辉 刘帅 刘宏伟 于 2021-07-22 设计创作，主要内容包括：本发明涉及一种制备活性炭负载纳米零价纯铁粉生产方法及应用,制备方法包括活性炭微米粉体和微纳米铁红粉体分别高能研磨及再混合研磨,得到前驱体粉体。然后将前驱体粉体在还原气氛下进行中温还原,待还原结束后,得到活性炭负载纳米零价纯铁粉。制备的活性炭负载纳米零价纯铁粉可用于降解土壤或水中的重金属或有机类污染物等。活性炭和铁氧化物来源广泛、成本低廉,采用气相还原法避免了生产过程中纯净水的大量使用和化学还原剂所造成的污染,本发明的工艺方法更适合批量生产。本发明所制得的活性炭负载纳米零价纯铁粉粒度达到纳米级别,分散性好,提高了对水体中Cr(Ⅵ)的去除效率。(The invention relates to a production method and application of active carbon loaded nano zero-valent pure iron powder. And then, carrying out medium-temperature reduction on the precursor powder in a reducing atmosphere, and obtaining the activated carbon loaded nano zero-valent pure iron powder after the reduction is finished. The prepared activated carbon loaded nano zero-valent pure iron powder can be used for degrading heavy metals or organic pollutants and the like in soil or water. The source of the active carbon and the iron oxide is wide, the cost is low, the gas phase reduction method is adopted to avoid the pollution caused by the large use of purified water and chemical reducing agent in the production process, and the process method is more suitable for batch production. The active carbon loaded nano zero-valent pure iron powder prepared by the method has the advantages that the granularity reaches the nano level, the dispersibility is good, and the removal efficiency of Cr (VI) in a water body is improved.)

1. A production method for preparing activated carbon loaded nano zero-valent pure iron powder is characterized by comprising the following steps:

1) pretreating raw materials, namely grinding iron oxide red by a high-energy grinder to obtain iron oxide red micro-nano powder;

2) drying the activated carbon in a protective atmosphere, and grinding the dried activated carbon in the protective atmosphere by using a high-energy grinder to obtain activated carbon micron powder;

3) mixing the powder treated in the steps 1) and 2), adding a grinding aid and grinding balls, and then grinding in a high-energy grinder to obtain precursor powder of iron oxide red powder distributed on the activated carbon powder;

4) and (3) putting the precursor powder obtained in the step 3) into a reduction furnace, carrying out medium-temperature reduction in a reducing atmosphere, and cooling to room temperature in a water cooling manner in a protective atmosphere after the reduction is finished to obtain the activated carbon loaded nano zero-valent pure iron powder.

2. The production method of the activated carbon-supported nano zero-valent pure iron powder of claim 1, wherein in the step 1), the iron oxide red is ultrafine ferric oxide powder obtained by spray drying the pickling solution for steel rolling, and has a chemical purity of 99.0% and a particle size of-5 μm.

3. The production method for preparing the activated carbon loaded nano zero-valent pure iron powder according to claim 1, wherein in the step 1), the iron red grinding time is 3-6 h, and the ball-to-material ratio is 4-12: 1, the granularity D50 of the obtained iron red micro-nano powder is less than 0.3 mu m, and D90 is less than 0.8 mu m.

4. The production method for preparing activated carbon-supported nano zero-valent pure iron powder as claimed in claim 1, wherein in the step 2), the activated carbon is wood activated carbon or fruit shell activated carbon which is commercially available, is granular or powdery, and has a particle size of-150 μm.

5. The production method for preparing the activated carbon-loaded nano zero-valent pure iron powder according to claim 1, characterized in that in the step 2), the drying temperature is 90-120 ℃, the time is 1-3 h, the protective atmosphere is nitrogen, and the flow rate of nitrogen during drying is 10-20 NL/min; the grinding time is 1-3 h, and the ball material ratio is 3-10: 1, the nitrogen flow during grinding is 5-10 NL/min, and the granularity of the obtained activated carbon micron powder is as follows: d50 is less than 30 μm, and D90 is less than 50 μm.

6. The production method for preparing the activated carbon-supported nano zero-valent pure iron powder according to claim 1, wherein in the step 3), the mass ratio of the iron oxide red to the activated carbon is 1: 3-7; the grinding aid is stearate, the stearate is one or two of zinc stearate or lithium stearate, and the addition amount of the stearate is 0.8-1.5 percent of the total mass of the mixture of the iron oxide red and the active carbon; the ball material ratio is 4-12: 1, the grinding time is 1-4 h.

7. The production method for preparing the activated carbon-supported nano zero-valent pure iron powder according to claim 1, wherein in any one of the steps 1), 2) and 3), the high-energy grinding mill is one of a planetary ball mill, a vibration ball mill, a roller ball mill and a stirring ball mill; the grinding ball used by the high-energy grinding machine is one of a carbon steel ball, a stainless steel ball and a zirconia ball; the diameter specification of the grinding balls is 6mm, 8mm and 10mm, wherein the grinding balls with the diameter of 10mm account for 10-20% of the total mass ratio of the grinding balls, the grinding balls with the diameter of 8mm account for 21-30% of the total mass ratio of the grinding balls, and the grinding balls with the diameter of 6mm account for 50-70% of the total mass ratio of the grinding balls.

8. The production method for preparing activated carbon-loaded nano zero-valent pure iron powder according to claim 1, wherein in the step 4), the reduction furnace is a tube furnace reduction furnace or a steel strip reduction furnace; heating the reducing furnace at a heating rate of 15-20 ℃/min, controlling the temperature of the reducing furnace at 550-750 ℃, keeping the temperature for 30-50 min, and controlling the flow of the reducing atmosphere at 20-100 NL/min; the reducing atmosphere is a mixed gas of hydrogen and nitrogen, the volume percentage of the hydrogen is 75-80%, and the volume percentage of the nitrogen is 20-25%; the protective atmosphere is nitrogen, and the flow rate is 10-30 NL/min; the granularity of the activated carbon loaded nano zero-valent pure iron powder is D50: < 0.1 μm, D90: less than 0.3 μm.

9. The activated carbon-supported nano zero-valent pure iron powder obtained by the preparation method according to any one of claims 1 to 8.

10. The use of the activated carbon-supported nano zero-valent pure iron powder according to claim 9 for degrading Cr (VI).

Technical Field

The invention relates to the technical field of nano material preparation and environmental chemistry, in particular to a production method and application for preparing activated carbon loaded nano zero-valent pure iron powder.

Background

Cr plays an important role in industries such as plating, printing, and leather, and accompanying the development of the industries, Cr contamination is a prominent problem. Cr exists mainly in the forms of Cr (VI) and Cr (III), wherein the Cr (VI) is far more toxic than Cr (III), and can cause various body diseases or teratogenesis and carcinogenesis after long-term contact.

The nano zero-valent iron has excellent adsorption and reduction capabilities due to high reaction activity and large specific surface area, has wide raw material sources, and has reduction or degradation effects on heavy metals, dyes, pesticides, organic matters and the like in industrial sewage, so the nano zero-valent iron has wide attention in the field of environmental remediation.

Although nano zero-valent iron has the advantage of high reactivity due to its small size, it has the problem of easy agglomeration and oxidation in specific applications. In order to improve the dispersibility and the oxidation resistance of the nano zero-valent iron, researchers at home and abroad explore various modification methods for many years, such as treating the nano zero-valent iron by using a surfactant or a polymer to enhance the inter-particle repulsion force, or adding an inactive metal to improve the oxidation resistance of the nano zero-valent iron, and loading the nano zero-valent iron on materials such as graphene, bentonite and montmorillonite to improve the dispersibility and the oxidation resistance of the nano zero-valent iron. The patent: CN 111530414A, discloses a spherical-milled biochar-loaded vulcanized nano zero-valent iron composite material and a preparation method and application thereof; patent CN 111687426 a discloses a preparation method of slow-release nano zero-valent iron particles; patent CN 110918060A, disclosureA pyrolytic carbon loaded zero-valent iron composite material and a preparation method and application thereof. The methods improve the utilization rate of the nano zero-valent iron and the efficiency of treating pollutants, but have some limitations, such as: in the preparation process, water or (ethanol and acetone) is used as a solvent to combine the ferric salt and the carbon material, and then the mixture is washed for many times, so that the waste and pollution of water resources are inevitably caused; or a toxic reducing agent NaBH is used in the reduction process₄Especially, ferric chloride, ferrous sulfate and the like are used as raw materials to generate a large amount of by-products and waste water with strong corrosivity, and secondary pollution is generated in the preparation process of the nano zero-valent iron. The patent: CN 105833850A, discloses a method for preparing Fe/C composite porous structure material by limonite; the patent: CN105925742A discloses a Fe/C composite porous structure material prepared from oolitic hematite and a preparation method thereof. The method adopts the direct carbonization of wood materials such as straws and shells to bring impurities such as ash, sulfur, phosphorus and the like into the iron source, and the main iron source adopts iron ore powder with low purity and large granularity as the raw material, so that the high-purity nano zero-valent iron powder cannot be obtained although the cost is low.

Disclosure of Invention

The invention aims to solve the technical problem of providing a production method and application of preparing activated carbon loaded nano zero-valent pure iron powder, which has the advantages of simple process flow, no secondary pollution in the preparation process, cheap and easily available raw materials, low equipment requirement and capability of meeting the requirement of large-scale production.

In order to achieve the purpose, the invention adopts the following technical scheme:

a production method for preparing activated carbon loaded nano zero-valent pure iron powder specifically comprises the following steps:

1) pretreating raw materials, namely grinding iron oxide red by a high-energy grinder to obtain iron oxide red micro-nano powder;

2) drying the activated carbon in a protective atmosphere, and grinding the dried activated carbon in the protective atmosphere by using a high-energy grinder to obtain activated carbon micron powder;

3) mixing the powder treated in the steps 1) and 2), adding a grinding aid and grinding balls, and then grinding in a high-energy grinder to obtain precursor powder of iron oxide red powder distributed on the activated carbon powder;

4) and (3) putting the precursor powder obtained in the step 3) into a reduction furnace, carrying out medium-temperature reduction in a reducing atmosphere, and cooling to room temperature in a water cooling manner in a protective atmosphere after the reduction is finished to obtain the activated carbon loaded nano zero-valent pure iron powder.

Further, in the step 1), the iron oxide red is the superfine ferric oxide powder obtained by spray drying the steel rolling acid washing solution, the chemical purity is 99.0%, and the particle size is-5 mu m.

Further, in the step 1), the grinding time of the iron oxide red is 3-6 hours, and the ball-material ratio is 4-12: 1, granularity D50 of the obtained iron red micro-nano powder: < 0.3 μm, D90: 0 is less than 0.8 mu m.

Further, in the step 2), the activated carbon is commercially available wood activated carbon or fruit shell activated carbon, is in the form of particles or powder, and has a particle size of-150 μm.

Further, in the step 2), the drying temperature is 90-120 ℃, the time is 1-3 h, the protective atmosphere is nitrogen, and the flow rate of nitrogen during drying is 10-20 NL/min.

Further, in the step 2), the grinding time is 1-3 h, the ball-to-material ratio is 3-10: 1, the nitrogen flow during grinding is 5-10 NL/min, and the granularity of the obtained activated carbon micron powder is D50: < 30 μm, D90: < 50 μm.

Further, in the step 3), the mass ratio of the iron oxide red to the activated carbon is 1: 3 to 7.

Further, in the step 3), the grinding aid is stearate, the stearate is one or two of zinc stearate and lithium stearate, and the addition amount of the stearate is 0.8-1.5% of the total mass of the mixture of the iron oxide red and the activated carbon.

Further, in the step 3), the ball-material ratio is 4-12: 1, the grinding time is 1-4 h.

Further, in any one of the steps 1), 2) and 3), the high-energy grinding mill is one of a planetary ball mill, a vibration ball mill, a roller ball mill and a stirring ball mill; the grinding ball used by the high-energy grinding machine is one of a carbon steel ball, a stainless steel ball and a zirconia ball; the diameter specification of the grinding balls is 6mm, 8mm and 10mm, wherein the grinding balls with the diameter of 10mm account for 10-20% of the total mass ratio of the grinding balls, the grinding balls with the diameter of 8mm account for 21-30% of the total mass ratio of the grinding balls, and the grinding balls with the diameter of 6mm account for 50-70% of the total mass ratio of the grinding balls.

Further, in the step 4), the reduction furnace is a tube furnace reduction furnace or a steel strip reduction furnace; heating the reducing furnace at a heating rate of 15-20 ℃/min, controlling the temperature of the reducing furnace at 550-750 ℃, keeping the temperature for 30-50 min, and controlling the flow of the reducing atmosphere at 20-100 NL/min; the reducing atmosphere is a mixed gas of hydrogen and nitrogen, wherein the volume percentage of the hydrogen is 75-80%, and the volume percentage of the nitrogen is 20-25%.

Further, in the step 4), the protective atmosphere is nitrogen, and the flow rate is 10-30 NL/min. The granularity of the obtained activated carbon loaded nano zero-valent pure iron powder is D50: < 0.1 μm, D90: less than 0.3 μm.

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

the method has the advantages of simple process flow, no secondary pollution in the preparation process, cheap and easily-obtained raw materials and low equipment requirement, and can meet the requirement of large-scale production. The obtained product has good dispersibility, large contact area with wastewater, easy reduction reaction and excellent degradation effect on Cr (VI) or other heavy metals and organic pollutants in the wastewater or soil.

(1) The invention combines the iron oxide red and the active carbon by a high-energy grinding method, and compared with a liquid phase deposition method, the invention does not need water as a medium and does not cause waste and pollution to water resources; the iron oxide red is reduced by using hydrogen as a reducing agent, no toxic reducing agent or other chemical reagents need to be added, the preparation process is green and pollution-free, the sources of the used raw materials are wide, and the equipment is simple.

(2) The active carbon loaded nano zero-valent pure iron powder prepared by the method is in a nano level, and because the active carbon and the stearate are added to play a role in loading a carrier and a grinding aid, the grinding efficiency is improved, and the particle size is reduced. The zero-valent iron particles are fixed on the activated carbon in the gas-phase reduction process or are separated by the activated carbon to cause the particles not to contact, and the growth of the contact fusion of the particles is inhibited.

(3) The activated carbon loaded nano zero-valent pure iron powder prepared by the method has good dispersibility, high reaction activity and good fluidity, can be used for degrading Cr (VI) or other heavy metals and organic matters in water or soil, and can be produced and applied in a large scale.

Drawings

FIG. 1 is an SEM image of a precursor powder prepared in example 1.

Fig. 2 is an SEM image of the activated carbon-supported nano zero-valent pure iron powder prepared in example 1.

FIG. 3 is a graph showing the effect of example 1 on Cr (VI) degradation in water;

in fig. 3: BM&GPR nZVI-AC represents the activated carbon loaded nano zero-valent pure iron powder prepared in example 1, t (min) is reaction time, and C/C₀Is the ratio of the Cr (VI) content after the reaction to the initial Cr (VI) content.

Detailed Description

The following further illustrates embodiments of the invention:

a production method for preparing activated carbon loaded nano zero-valent pure iron powder comprises the steps of respectively grinding activated carbon micron powder and micro-nano iron red powder at high energy and then mixing and grinding to obtain precursor powder. And then, carrying out medium-temperature reduction on the precursor powder in a reducing atmosphere, and obtaining the activated carbon loaded nano zero-valent pure iron powder after the reduction is finished.

Example 1

A production method for preparing activated carbon loaded nano zero-valent pure iron powder specifically comprises the following steps:

(1) pretreatment of raw materials: grinding 50g of iron oxide red powder with the particle size of less than 4 mu m in a planetary ball mill, wherein the ball-material ratio is 10: 1, selecting a carbon steel ball as a grinding ball material, wherein the total weight of the carbon steel ball is 500g, the grinding time is 3h, and the grinding ball material is 100g for 10mm, 125g for 8mm and 275g for 6 mm. The granularity D50 of the obtained iron red micro-nano powder is as follows: 0.2 μm, D90: 0.7 μm.

(2) 50g of wood activated carbon powder with the particle size of 100 meshes is dried under the nitrogen atmosphere, the nitrogen flow is 10NL/min, the drying temperature is 90 ℃, and the drying time is 2 h. Then grinding in a planet ball mill under the protection of nitrogen atmosphere, wherein the nitrogen flow is 5NL/min, and the ball-material ratio is 8: 1, selecting a carbon steel ball as a ball milling ball material, wherein the ball milling ball material is 500g, 100g of 10mm grinding ball, 110g of 8mm grinding ball and 300g of 6mm grinding ball, and the grinding time is 1 h. The granularity of the obtained activated carbon micron powder is D50: 13 μm, D90: 28 μm.

(3) According to the mass ratio of 1: 3, weighing 10g of iron oxide red powder and 30g of wood activated carbon powder which are ground in the steps (1) and (2), adding a mixture of 40g into a ball milling tank, weighing 0.45g of zinc stearate, and adding the zinc stearate into the ball milling tank, wherein the ball-to-material ratio is 10: weighing 400g of carbon steel grinding balls, wherein 40g of 10mm grinding balls, 85g of 8mm grinding balls and 280g of 6mm grinding balls, grinding in a planetary ball mill for 3h to obtain precursor powder (shown in figure 1) of iron oxide red powder distributed on activated carbon powder after grinding is finished.

(4) Intermediate-temperature gas-phase reduction: and (4) transferring the precursor powder prepared in the step (3) into a corundum burning boat, putting the corundum burning boat into a heating section of a tubular reduction furnace, raising the temperature to 650 ℃ according to the temperature rise rate of 15 ℃/min, starting timing when the temperature rises to 650 ℃, and keeping the temperature for 40 min. And continuously introducing a mixed gas of hydrogen and nitrogen (75% by volume of hydrogen and 25% by volume of nitrogen) as a reducing atmosphere in the temperature rising process, wherein the flow rate of the reducing atmosphere is 20 NL/min. And (3) closing a heating button after heat preservation is finished, changing to introduce protective atmosphere nitrogen, wherein the nitrogen flow is 15NL/min, pushing the burning boat to a water cooling section for accelerated cooling when the temperature is reduced to 280 ℃, and cooling to room temperature to obtain the activated carbon loaded nano zero-valent pure iron powder (shown in figure 2), wherein the particle size is D50: 60nm, D90: 100 nm. Vacuum packaging is adopted for convenient storage and transportation of the product.

Example 2

A production method for preparing activated carbon loaded nano zero-valent pure iron powder specifically comprises the following steps:

(1) pretreatment of raw materials: 200kg of iron oxide red powder with the particle size of-5 mu m is ground in a stirring ball mill, and the ball-material ratio is 5: 1, selecting a stainless steel ball as a grinding ball material, wherein the ball loading amount of the stainless steel grinding ball is 1t, 100kg of 10mm grinding balls, 200kg of 8mm grinding balls and 700kg of 6mm grinding balls, and the grinding time is 4 hours. The particle size of the obtained iron oxide red powder D50: 0.2 μm, D90: 0.6 μm. And producing for later use in multiple batches.

(2): 200kg of wood activated carbon with the particle size of 75 mu m is dried under the nitrogen atmosphere, the nitrogen flow is 15NL/min, the drying temperature is 100 ℃, and the drying time is 2 h. Then grinding in a roller ball mill under the protection of nitrogen atmosphere, wherein the flow rate is 8NL/min, and the ball-material ratio is 5: 1, selecting a stainless steel ball as a grinding ball material, wherein the ball loading amount of the stainless steel grinding ball is 1t, 150kg of 10mm grinding balls, 250kg of 8mm grinding balls and 600kg of 6mm grinding balls, and the grinding time is 2 h. The particle size of the obtained activated carbon powder is D50: 12 μm, D90: 39 μm. And producing for later use in multiple batches.

(3) Preparing a precursor: according to the mass ratio of 1: and 3, taking 100kg of iron oxide red powder and 300kg of wood activated carbon powder which are ground in the steps (1) and (2), adding a mixture of 400kg into a roller ball mill, and then adding 4.5kg of zinc stearate into the roller ball mill, wherein the ball-to-material ratio is 4: 1, loading the stainless steel grinding balls with the ball loading of 1.6t, wherein 320kg of 10mm grinding balls, 480kg of 8mm grinding balls and 800kg of 6mm grinding balls are subjected to high-energy grinding in a roller ball mill for 3h to obtain precursor powder of iron oxide red powder distributed on the activated carbon powder after grinding; and producing for later use in multiple batches.

(4) Intermediate-temperature gas-phase reduction: and (4) transferring the precursor powder prepared in the step (3) to a steel belt type reduction furnace, controlling the speed of the steel belt and the heating speed, heating to 710 ℃ at 18 ℃/min, and keeping the temperature for 40 min. And continuously introducing mixed gas of hydrogen and nitrogen (75% by volume of hydrogen and 25% by volume of nitrogen) into the temperature rising section and the heat preservation section to serve as reducing atmosphere, wherein the flow rate of the reducing atmosphere is 50 NL/min. And (3) introducing nitrogen into the water cooling section at the flow rate of 20NL/min, and cooling to room temperature to obtain the activated carbon loaded nano zero-valent pure iron powder with the particle size of D50: 37nm, D90: 85 nm. In order to facilitate the storage and transportation of the product, vacuum packaging is adopted.

Application example

Example 1 the specific steps of the Cr (vi) removal experiment for preparing the activated carbon-supported nano zero-valent pure iron powder are as follows:

by K₂Cr₂O₇The water solution simulates wastewater containing Cr (VI), the preparation concentration is 20mg/L, the solution volume is 100ml, and the reaction is carried out in a 100ml conical shapeThe reaction was carried out in a flask, the pH was 3, the dosage of the activated carbon-supported nano zero-valent pure iron powder prepared in example 1 was 0.4g/L, and the flask was placed in a constant temperature oscillator to carry out the reaction, and the temperature was set at 25 ℃. After the reaction is carried out for 10min, 20min, 30min, 50min, 80min and 120min, the solution is extracted and filtered by a filter membrane of 0.1 mu m, and the concentration of Cr (VI) is detected by a spectrophotometer, and the experimental result is shown in figure 3.

The activated carbon loaded nano zero-valent pure iron powder prepared in the example 1 has a balanced reaction when the reaction is carried out for 50min, and the balanced removal rate of Cr (VI) reaches 99.4%. The activated carbon loaded nano zero-valent pure iron powder can be used for degrading heavy metals or organic pollutants in soil or water.

The active carbon loaded nano zero-valent pure iron powder prepared by the method has the advantages that the granularity reaches the nano level, the dispersibility is good, and the removal efficiency of Cr (VI) in a water body is improved.

It will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the principles of the invention, and these modifications and variations also fall within the scope of the invention as defined in the appended claims. The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and their concepts should be equivalent or changed within the technical scope of the present invention.