CN111266086A - A method for producing magnetic biochar from kitchen waste - Google Patents

Abstract

The invention discloses a method for preparing magnetic biochar by utilizing kitchen waste, which belongs to the technical field of biochar materials and comprises the following steps: collecting the kitchen waste, naturally drying until the water content is lower than 10%, then crushing and sieving to obtain crushed materials, putting the crushed materials into a porcelain ark, putting the porcelain ark into a tube furnace, introducing nitrogen to provide an anoxic condition, and keeping the temperature at 5-10 ℃ for min^‑1Heating to 250-600 ℃, cracking for 2-4 hours to obtain the kitchen waste biochar, and taking the kitchen waste biochar with the concentration of 40gL^‑1～100gL^‑1Kitchen waste biochar and concentration of 10mmol L^‑1～30mmolL^‑1Fe (b) of³⁺Salt and Cu²⁺Mixing with salt, and adding concentrated solution under stirringDegree of 50gL^‑1～80gL^‑1After the strong alkaline solution reacts for 6-48 hours at the temperature of 100-200 ℃, the product after hydrothermal treatment is subjected to vacuum filtration, cleaning and drying treatment to obtain the recyclable kitchen waste charcoal, so that the kitchen waste resource utilization is realized, the environmental hazard is reduced, and good social benefit and environmental benefit are achieved.

Description

A method for producing magnetic biochar from kitchen waste

technical field

The invention belongs to the technical field of biochar materials, in particular to a method for preparing magnetic biochar from kitchen waste.

Background technique

In June 2019, nine departments including the Central Agriculture Office, the Ministry of Housing and Urban-Rural Development, the Ministry of Ecology and Environment, and the Ministry of Science and Technology jointly issued the "Notice of the Ministry of Housing and Urban-Rural Development and Other Departments on Comprehensively Carrying out Domestic Waste Classification in Cities at and Above the National Prefectural Level". Since 2019, domestic waste classification has been fully launched in cities at the prefecture level and above across the country. With the full implementation of the waste classification policy, strengthening the collection, transportation and disposal of kitchen waste has become a hot issue of concern. Food waste refers to the food waste generated in the daily consumption process of public canteens, households, and catering industries, mainly including food waste during pre-meal food processing and food residue after meals. Traditional food waste disposal methods mainly include landfill and incineration. The landfill leachate and dioxins and other toxic gases produced in the incineration process are potentially harmful to the environment, and can easily lead to the outbreak of infectious diseases, which seriously affects human health. Therefore, the resource utilization of kitchen waste is of great significance. By pyrolysis of kitchen waste under hypoxic or anaerobic conditions, most of the carbon-containing organic matter in the waste cannot be converted into harmful CO ₂ , but converted into biochar, preventing CO ₂ from entering the atmosphere, which can be reduced by 21% of carbon emissions [Environmental Science and Technology, 2016, 39(S2):245-250]. In view of this, in recent years, the technology of preparing biochar by pyrolysis of kitchen waste has become increasingly active. In our previous research, it was found that biochar prepared by cracking kitchen waste as raw material can be used to improve soil properties and improve soil fertility (patent authorization number: CN104557160A), and can also effectively adsorb methylene blue in water (agricultural resources and Journal of the Environment, 2019, 36(1):115-120). However, in the process of using pure biochar powder, it is difficult to recover and separate, which may lead to waste of resources. The method of combining magnetic materials with biochar to prepare magnetic biochar can effectively solve the problem of difficult recovery of biochar.

In addition, the regeneration of adsorbed saturated biochar can not only improve the utilization rate of biochar, but also reduce its secondary pollution to the environment. The photocatalytic regeneration technology uses the generated strong oxidizing free radicals to degrade the organic matter adsorbed on the surface of the adsorbent under the irradiation of sunlight, so as to achieve the purpose of regeneration of the adsorbent. Therefore, by some means, the biochar produced by the cracking of kitchen waste is given magnetic properties, and at the same time, the regeneration of the biochar is realized by photocatalytic technology, which can not only realize the resource utilization of the kitchen waste recovered through garbage classification, reduce the number of kitchen waste The harm of garbage to the environment can also improve the important guiding significance of the biochar prepared for it in recycling and recycling.

SUMMARY OF THE INVENTION

The invention provides a method for preparing magnetic biochar from kitchen waste, which realizes the resource utilization of the kitchen waste recovered through garbage classification, reduces the harm of the kitchen waste to the environment, and at the same time realizes that the prepared biochar can be used Recycling and recycling in the process. The method adopts pyrolysis technology to prepare kitchen waste biochar, mixes it with a certain amount of Fe ³⁺ salts and Cu ²⁺ salts, and prepares iron oxides (Fe ₃ O ₄ ) through hydrothermal technology under alkaline conditions. and Fe ₂ O ₃ ) and delafossite-type CuFeO ₂ food waste magnetic biochar, of which Fe ₃ O ₄ and Fe ₂ O ₃ can provide magnetic properties for the food waste biochar to facilitate the recovery of biochar, using delafossite The photocatalytic properties of CuFeO ₂ realize the cyclic regeneration of biochar after adsorption saturation.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is as follows:

A method for preparing magnetic biochar from kitchen waste, comprising the following steps:

S1: Collect kitchen waste, air-dry to a moisture content of less than 10%, crush and sieve to obtain crushed products;

S2: the pulverized material is cracked to prepare food waste biochar, and the prepared food waste biochar is washed, dried, ground and screened for use;

S3: ultrasonically mix food waste biochar with Fe ³⁺ salt and Cu ²⁺ salt in water, and continuously add strong alkali solution under constant stirring;

S4: the above-mentioned solution is transferred to the hydrothermal reactor, and the hydrothermal cracking reaction is carried out;

S5: The product after hydrothermal cracking is vacuum filtered, washed and dried.

Preferably, the kitchen waste biochar is prepared by cracking in an inert atmosphere, the heating rate is 5-10°C min ^-1 , the cracking temperature is 250-600°C, and the cracking time is 2-4 hours.

Preferably, in step S2, dehydrated ethanol is used successively, and the concentration is 0.5-1.0 molL ^-1 hydrochloric acid, nitric acid or sulfuric acid, and deionized water for washing, and the drying temperature is 60-80 ° C, drying for 5-10 hours, using Grind in a mortar and sieve with a 300-500 mesh sieve.

Preferably, the food waste biochar content is 40 gL ^-1 to 100 gL ^-1 .

Preferably, the Fe ³⁺ salt is ferric chloride, ferric nitrate nonahydrate, ferric sulfate or ferric oxalate pentahydrate.

Preferably, the Cu ²⁺ salt is copper chloride, copper nitrate trihydrate or copper sulfate pentahydrate.

Preferably, the concentration of Fe ³⁺ salt and Cu ²⁺ salt is 10 mmolL ^-1 to 30 mmolL ^-1 .

Preferably, the strong alkali solution is sodium hydroxide or potassium hydroxide, and the concentration is 50 gL ^-1 to 80 gL ^-1 .

Preferably, the hydrothermal reaction temperature is 100-200 °C, the hydrothermal reaction time is 6-48 hours, and the product after the hydrothermal selects dehydrated ethanol, a dilute solution of hydrochloric acid, nitric acid or sulfuric acid and deionized water to rinse in turn, and the vacuum After being cleaned by suction filtration to neutrality, it is placed in an oven, and the drying temperature is 70-80°C, and drying is performed for 8-12 hours.

Preferably, the concentration of the dilute solution of hydrochloric acid, nitric acid or sulfuric acid is 0.5˜1.0 mol L ⁻¹ .

The beneficial effects of the present invention are:

1. The kitchen waste magnetic biochar of the present invention has an increased specific surface area, which realizes the resource utilization of the kitchen waste after garbage classification and recycling, and reduces the harm of the kitchen waste to the environment, which has good social and environmental benefits.

2. The kitchen waste magnetic biochar of the present invention, the kitchen waste biochar prepared by cracking is mixed with Fe ³⁺ salt and Cu ^{2 +} salt, and a series of iron oxides containing a series of iron oxides are prepared by hydrothermal under alkaline conditions. (Fe ₃ O ₄ and Fe ₂ O ₃ ) and delafossite-type CuFeO ₂ magnetic garlic straw biochar, of which Fe ₃ O ₄ and Fe ₂ O ₃ can provide magnetic properties for biochar to facilitate the recovery of biochar, using copper and iron The photocatalytic properties of ore-type CuFeO ₂ realize the cyclic regeneration of biochar after adsorption saturation.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1:

A method for preparing magnetic biochar from kitchen waste, the specific steps are as follows:

(1) Preparation of food waste biochar

Collecting kitchen waste, which includes rice, steamed bread scraps, vegetables and meat, naturally air-dried to a moisture content of less than 10%, and then crushed and sieved to obtain crushed products. Put the pulverized product into a porcelain ark and place it in a tube furnace, feed nitrogen to provide anoxic conditions, heat up to 250 °C at a heating rate of 5 °C min ^-1 , and the cracking time is 2 hours. , washed with 0.5molL ^-1 hydrochloric acid and deionized water, dried in an oven at 60°C for 5 hours, ground the dried product with a mortar, and passed through a 300-mesh sieve to obtain food waste biochar.

(2) Preparation of kitchen waste magnetic biochar

Weigh copper chloride (99.99%) and ferric chloride (99.99%) in 60 ml of deionized water at room temperature according to the Fe:Cu molar ratio of 1:1, and continue stirring until the solid is completely dissolved to obtain Fe:Cu moles Fe ³⁺ salt and Cu ²⁺ salt solution at a ratio of 1:1 and a concentration of 10 mmol L ^-1 . 2.5g of food waste biochar was added to the above solution, and then 50gL ^-1 of NaOH solution was added to provide alkaline conditions, and the stirring was continued for about 10 minutes until it was completely dissolved. The above mixed solution was transferred to a hydrothermal reactor, placed in a homogeneous reactor for hydrothermal reaction, and reacted at a temperature of 100° C. for 6 hours. After the reaction, the product after the hydrothermal treatment was successively washed with dehydrated alcohol, 0.5 ^molL of dilute nitric acid and deionized water until neutral, and the product after the centrifugation was dried in an oven at 70° C. for 12 hours. That's it.

Embodiment 2

A method for producing magnetic biochar from kitchen waste, in this example, the amount of kitchen waste biochar is 3.5g, and other steps are the same as in Example 1, as follows:

(1) Preparation of food waste biochar

The kitchen waste is collected, including rice, steamed bread scraps, vegetables and meat, etc., naturally air-dried to a moisture content of less than 10%, and then pulverized and sieved to obtain pulverized products. Put the pulverized product into a porcelain ark and place it in a tube furnace, feed nitrogen to provide anoxic conditions, and heat up to 600 °C at a heating rate of 8 °C min ^-1 , the cracking time is 4 hours, and the cracked products are sequentially selected from anhydrous ethanol , 1molL ^-1 hydrochloric acid and deionized water were washed, placed in an oven to dry at 80°C for 10 hours, the dried product was ground in a mortar and passed through a 500-mesh sieve to obtain food waste biochar.

(2) Preparation of kitchen waste magnetic biochar

Weigh Cu(NO ₃ ) ₂ ·3H ₂ O (99.99%) and Fe(NO ₃ ) ₃ ·9H ₂ O (99.99%) at room temperature according to Fe:Cu molar ratio of 1:1 and dissolve them in 60 ml of deionized water, After continuous stirring until the solid was completely dissolved, Fe ³⁺ salt and Cu ²⁺ salt solutions with Fe:Cu molar ratio of 1:1 and a concentration of 30 mmolL ⁻¹ were prepared. Add 3.5g of food waste biochar to the above solution, and then add 80gL ^-1 of potassium hydroxide solution to provide alkaline conditions, and continue to stir for 10 minutes until it is completely dissolved. The above mixed solution was transferred to a hydrothermal reactor, placed in a homogeneous reactor for hydrothermal reaction, and reacted at a temperature of 200° C. for 48 hours. After the reaction, the product after the hydrothermal treatment was successively subjected to centrifugation and washing to neutrality through absolute ethanol, ¹ molL of dilute nitric acid and deionized water, and the product after the centrifugation was dried in an oven at 80° C. for 12 hours, that is, Can.

Embodiment 3

A method for preparing magnetic biochar from kitchen waste, in this embodiment, the amount of kitchen waste biochar is 5.0g, and other steps are the same as in Example 1, and the details are as follows:

(1) Preparation of food waste biochar

The kitchen waste is collected, including rice, steamed bread scraps, vegetables and meat, etc., and is naturally air-dried to a moisture content of less than 10%, and then crushed and sieved to obtain crushed products. Put the pulverized product into a porcelain ark and place it in a tube furnace, feed nitrogen to provide anoxic conditions, heat up to 400 °C at a heating rate of 8 °C min ^-1 , and the cracking time is 3 hours. , 0.5molL ^-1 hydrochloric acid and deionized water were washed, placed in an oven and dried at 70°C for 8 hours, the dried product was ground in a mortar and passed through a 400-mesh sieve to obtain food waste biochar.

(2) Preparation of kitchen waste magnetic biochar

Weigh copper sulfate pentahydrate (99.99%) and iron oxalate pentahydrate (99.99%) at room temperature according to Fe:Cu molar ratio of 1:1, dissolve in 60 ml of deionized water, and continue stirring until the solid is completely dissolved to obtain Fe: Fe ³⁺ salt and Cu ²⁺ salt solution with Cu molar ratio 1:1 and concentration of 20 mmolL ^-1 . 5.0g of kitchen waste biochar was added to the above solution, then added to 60gL ^-1 of potassium hydroxide solution, and continued to stir for 10 minutes until it was completely dissolved. The above mixed solution was transferred to a hydrothermal reactor, placed in a homogeneous reactor for hydrothermal reaction, and reacted at a temperature of 160° C. for 24 hours. After the reaction, the product after the hydrothermal treatment was sequentially washed by dehydrated alcohol, 0.5 ^mol L of dilute nitric acid and deionized water to neutrality, and the product after the centrifugation was placed in an oven and dried at 80 ° C for 10 ℃. hours, you can. In other embodiments, ferric oxalate pentahydrate can also be replaced with ferric sulfate.

In addition, it should be understood that although this specification is described in terms of embodiments, not each embodiment only includes an independent technical solution, and this description in the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims (10)

1. A method for preparing magnetic biochar by utilizing kitchen waste is characterized by comprising the following steps:

s1: collecting the kitchen waste, air-drying until the moisture content is lower than 10%, and crushing and sieving to obtain a crushed material;

s2: cracking the crushed materials to prepare kitchen waste biochar, and washing, drying, grinding and screening the prepared kitchen waste biochar for later use;

s3: mixing kitchen waste biochar with Fe³⁺Salt and Cu²⁺Ultrasonically mixing salt in water, and continuously adding a strong alkali solution under the condition of continuous stirring;

s4: transferring the solution to a hydrothermal reaction kettle for hydrothermal cracking reaction;

s5: and (3) carrying out vacuum filtration, cleaning and drying on the product after the hydrothermal cracking to obtain the finished product.

2. The method of claim 1, wherein the kitchen waste is used as a food wasteCracking the garbage biochar in an inert atmosphere at a temperature rise rate of 5-10 ℃ for min^-1The cracking temperature is 250-600 ℃, and the cracking time is 2-4 hours.

3. The method according to claim 1, wherein the absolute ethanol is sequentially used in step S2 at a concentration of 0.5 to 1.0mol L^-1Washing with hydrochloric acid, nitric acid or sulfuric acid and deionized water, drying at 60-80 ℃ for 5-10 hours, grinding with a mortar, and sieving with a sieve of 300-500 meshes.

4. The method according to claim 1, wherein the kitchen waste biochar content is 40gL^-1～100gL^-1。

5. The method of claim 1, wherein Fe³⁺The salt is ferric chloride, ferric nitrate nonahydrate, ferric sulfate or ferric oxalate pentahydrate.

6. The method of claim 1, wherein Cu²⁺The salt is copper chloride, copper nitrate trihydrate or copper sulfate pentahydrate.

7. The method of claim 1, wherein Fe³⁺Salt and Cu²⁺The salt concentration was 10mmol L^-1～30mmolL^-1。

8. The method of claim 1, wherein the strong alkaline solution is sodium hydroxide or potassium hydroxide with a concentration of 50gL^-1～80gL^-1。

9. The method according to claim 1, wherein the hydrothermal reaction temperature is 100-200 ℃, the hydrothermal reaction time is 6-48 hours, the hydrothermal product is washed by absolute ethyl alcohol, dilute solution of hydrochloric acid, nitric acid or sulfuric acid and deionized water in sequence, and the washed product is placed in an oven after being washed to be neutral by vacuum filtration, and the oven drying temperature is 70-80 ℃ and the oven drying time is 8-12 hours.

10. The method according to claim 1, wherein the dilute solution of hydrochloric acid, nitric acid or sulfuric acid has a concentration of 0.5 to 1.0mol L^-1。