CN105129797A - Preparation method of ammoniation-activation plant activated carbon - Google Patents

Abstract

The invention discloses a preparation method of ammoniation-activation plant activated carbon, which includes following steps: (1) performing ammoniation treatment to plant raw materials with ammoniation reagents, such as urea, ammonium bicarbonate, ammonia water and the like, to obtain an ammoniated raw material; (2) mixing the ammoniated raw material with an activating agent uniformly and performing impregnation for 2-12 h, wherein the mass ratio of the ammoniated raw material to the activating agent is 1:0.5-2.0; (3) performing carbonization and activation to the impregnated raw material at 300-800 DEG C for 30-60 min to obtain activated carbon; and (4) washing and drying the activated carbon to obtain the product. The preparation method is low in production cost and simple in production process. The activated carbon is high in specific surface area and abundant in functional groups when compared with activated carbon prepared through a conventional method.

Description

A kind of preparation method of ammoniated-activated plant-based activated carbon

technical field

The invention belongs to the field of functional materials, in particular to a method for preparing ammoniated-activated plant activated carbon.

Background technique

As a common adsorbent, activated carbon is widely used in the adsorption and removal of harmful substances in gas and liquid phases. Its ability to adsorb pollutants is mainly due to the well-developed pore structure and abundant functional groups (acidic and basic functional groups such as carboxyl, lactone, and phenolic hydroxyl groups). In recent years, in order to meet the ever-expanding market demand and consumers' requirements for more efficient activated carbon, producers often improve its physical and chemical properties and adsorption performance through modification and other methods. Many studies have proved that plant-based activated carbon has the advantages of high quality and good performance. Therefore, plant-based raw materials have been widely promoted and applied in the field of activated carbon preparation. In the traditional preparation methods of plant-based activated carbon, most of the carbon precursors are pulverized and directly impregnated and activated, resulting in insufficient impregnation of the activator, low utilization rate, long impregnation time, high activation temperature, low specific surface area of activated carbon, and small number of functional groups. defect. Aiming at the deficiencies of the traditional method, a preparation method of ammoniating plant material is proposed.

After searching, the process of preparing plant-based activated carbon by ammoniation-activation method is currently a technical blank.

Contents of the invention

The invention overcomes the shortcomings of the traditional method for preparing activated carbon, and provides a process method for ammoniating and activating plant-based activated carbon. In this method, in the process of preparing activated carbon, the plant matter raw material is firstly subjected to ammonification treatment, and then activated by carbonization. Activated carbon prepared by this method has a high specific surface area and developed surface functional groups.

Technical scheme of the present invention is as follows:

A method for preparing ammoniated-activated plant matter activated carbon, comprising the following steps:

(1) using ammonification reagents such as urea, ammonium bicarbonate or ammonia water to carry out ammoniation treatment on plant matter raw materials to obtain the raw materials after ammoniation;

(2) mix the raw material after ammoniation in step (1) with the activator, soak at 20-30°C for 2-12 hours, the mass ratio of the raw material after ammoniation to the activator is 1:0.5-2.0;

(3) Carbonize and activate the impregnated raw materials at 300-800°C for 30-60 minutes to obtain activated carbon;

(4) Wash and dry the activated carbon to obtain the product.

Before the plant material raw material is subjected to ammoniation treatment, the plant material raw material is pretreated. The pretreatment method is: wash the plant material raw material, dry it, and crush it to 20-40 meshes; the advantage of pretreatment is: in order to make the ammoniated material The treatment process is more sufficient, and the reaction contact area between the ammoniation reagent and the plant material is larger, so as to reduce the ammoniation time and improve the efficiency.

In step (1), the plant material raw material is one or more mixtures of reed, reed bamboo or big-leaf grass. It has been verified by experiments that the above three plant material raw materials of reed, reed bamboo or big-leaf grass are ammoniated— The effect is the best after activation treatment, with higher specific surface area and developed functional groups.

In step (1), when the ammoniation reagent is urea or ammonium bicarbonate, the specific method of ammoniation treatment is: the mass ratio of urea or ammonium bicarbonate to the plant material is 0.03-0.08:1 and Mix urea or ammonium bicarbonate, add water to dissolve, seal, and keep at 90-100°C for 1-6 hours, preferably at 100°C.

Through experimental demonstration and analysis, it is obtained that when the mass ratio of urea or ammonium bicarbonate to plant material is 0.03-0.08:1, the effect and efficiency of ammoniation are the best, and when the ratio is high, not only waste of ammoniation reagents, It will pollute the environment, and it will cause trouble during subsequent washing; when the ratio is low, the ammoniation effect has not been fully reflected, and the activated carbon has not obtained a high specific surface area and developed functional groups.

In step (1), when the ammoniation reagent is ammonia water, the specific method of ammoniation treatment is: mix the plant matter material with ammonia water according to the mass ratio of ammonia water to plant matter material at 0.01-0.05:1, seal it, and Keep at ~30°C for 5~14d, preferably at 25°C. Preferably, the mass concentration of ammonia water is 3-15%.

Through experimental demonstration and analysis, it is obtained that when the mass ratio of ammonia water to plant raw materials is 0.01-0.05:1, the effect and efficiency of ammoniation are the best. Subsequent washing will also cause trouble; when the ratio is low, the ammoniation effect has not been fully reflected, and the activated carbon has not obtained a high specific surface area and developed functional groups.

In step (2), the activator is phosphoric acid solution or potassium hydroxide, and the mass fraction of the phosphoric acid solution is 30-55%.

In step (2), preferably, the soaking time is 2-8 hours.

According to the situation of the ammoniated plant material, soak for 2-8 hours. This soaking time can fully activate the ammoniated plant material. time and reduce efficiency.

In step (3), preferably, the temperature is 300-450° C., and the time is 30-60 min. After ammoniation treatment, the carbonization temperature and time can be significantly reduced (the carbonization temperature of the non-ammoniated plant-based activated carbon preparation method is 500-900°C, and the carbonization time is 1-4h), and the carbonization temperature and time have been verified by experiments. The carbon content standard of activated carbon.

In step (4), the activated carbon is washed until the pH value is stabilized at about 7.0 and then dried. The reason is: if the activated carbon is washed to acidic or alkaline, it may affect the reaction of the active carbon environment. For example, if the activated carbon is washed to alkaline, then May react with acids in the environment in which activated carbon is used.

For plant materials, ammoniation can destroy the chemical bonds between lignin and polysaccharides, separate cellulose and hemicellulose from lignin, change insoluble lignin into more soluble hydroxy lignin, and crystalline cellulose into Forming amorphous cellulose, causing cell expansion, making the structure of the plant material material loose; moreover, the content of crude protein in the plant material material is significantly increased during the ammoniation process, which can increase the number of amino functional groups. In the process of preparing plant-based activated carbon, ammoniating plant-based raw materials can effectively enhance the impregnation effect, increase the specific surface area of activated carbon, and increase the number of functional groups of activated carbon.

Compared with traditional preparation methods, the present invention has the following advantages:

(1) Plant materials such as straws are used as raw materials, which have the advantages of wide distribution and low cost.

(2) The amount of ammoniation reagent is small, and the pollution to the environment is small.

(3) Due to the ammonification, the usage of activator is reduced, the activation temperature is lowered, the cost is saved, the energy consumption is reduced, and the pollution is reduced.

(4) The production cost is low, the production process is simple, and the prepared activated carbon has a higher specific surface area and richer functional groups than traditional methods.

(5) Through a large number of experiments and analysis, the adsorption effect of the activated carbon obtained by the preparation method of the present invention is better than that of the activated carbon prepared by the common method.

detailed description

Below in conjunction with embodiment the present invention is further described.

Example 1

Wash, dry, and crush the reeds to 40 meshes; inject ammonia water with a weight concentration of 3% of the dry matter of the reeds, mix it evenly, seal it, and keep it at 25°C for 7 days for ammoniation treatment; the ammoniated reed powder and 45wt.% phosphoric acid solution in a mass ratio of 1:1 and impregnated at room temperature for 5 hours; the impregnated material was transferred to a crucible and placed in a muffle furnace, carbonized and activated at 300°C for 40 minutes, and naturally cooled to room temperature; the obtained activated carbon was washed with deionized water to pH 7 or so, solid-liquid separation, drying. Compared with the activated carbon prepared by the traditional method of Comparative Example 1, the specific surface area of the obtained activated carbon is increased by 20%, and the total functional group quantity is increased by 46%.

Comparative example 1

The reeds were washed, dried, and crushed to 40 mesh, and the reed powder and 45wt.% phosphoric acid solution were impregnated for 10 hours at a mass ratio of 1:2; Cool to room temperature; wash the obtained activated carbon with deionized water until the pH is about 7, separate solid and liquid, and dry.

Example 2

Wash the reeds, dry them, and crush them to 40 meshes; take urea equivalent to 7% of the weight of the dry matter of the reeds, add 2ml of water to dissolve the weight of the dry matter of the reeds per 10g, mix the aqueous urea solution with the reed powder, seal it, and keep it at 100°C 2h, carry out ammoniation treatment; soak the ammoniated reed powder and potassium hydroxide at a mass ratio of 1:2 at 30°C for 2h; transfer the impregnated material into a nickel crucible and put it in a muffle furnace, and carbonize and activate it at 650°C for 60min. Naturally cool to room temperature; wash the obtained activated carbon with deionized water until the pH is about 7, separate solid and liquid, and dry. Its specific surface area is increased by 15% compared with the traditional method Comparative Example 2, and the number of surface functional groups is increased by 50%.

Comparative example 2

The reeds were washed, dried, and crushed to 40 mesh, and the reed powder and potassium hydroxide were impregnated for 8 hours at a mass ratio of 1:2; the impregnated material was transferred into a crucible and placed in a muffle furnace, carbonized and activated at 900°C for 120 minutes, and cooled naturally to room temperature; wash the obtained activated carbon with deionized water until the pH is about 7, separate solid and liquid, and dry.

Example 3

Wash the reeds, dry them, and crush them to 40 meshes; take 5% ammonium bicarbonate of reed powder dry matter weight, add 2ml water for every 10g reed powder dry matter weight, mix the ammonium bicarbonate aqueous solution with the reed powder, seal, Keep at 100°C for 4h, carry out ammoniation treatment; soak the ammoniated reed powder and 45wt.% phosphoric acid solution at a mass ratio of 1:1.5 at 20°C for 8h; Carbonize and activate for 60 minutes, cool naturally to room temperature; wash the obtained activated carbon with deionized water until the pH is about 7, separate solid and liquid, and dry. The specific surface area is increased by 15% and the number of functional groups is increased by 18% compared with the traditional method of Comparative Example 3.

Comparative example 3

The reeds were washed, dried, and crushed to 40 mesh, and the reed powder and 45wt.% phosphoric acid solution were impregnated for 8 hours at a mass ratio of 1:1.5; Cool to room temperature; wash the obtained activated carbon with deionized water until the pH is about 7, separate solid and liquid, and dry.

Table 1: Specific surface area of activated carbon, pore size parameters and number of functional groups.

After testing, reed bamboo and Dayedi obtained the same good effect.

Example 4

The activated carbon prepared in Example 1 and Comparative Example 1 was used in domestic sewage, chemical wastewater and pharmaceutical wastewater. The experimental results of the three kinds of sewage before and after activated carbon adsorption are shown in Table 2.

The activated carbon adsorption effect of table 2 embodiment 1 and comparative example 1

The residual organic matter and residual suspended matter in the waste water are separated from the water body through the filtration and adsorption of activated carbon. It can be seen from Table 2 that the adsorption effect of the activated carbon prepared by the method of Example 1 is significantly better than that of Comparative Example 1. The adsorption effect of activated carbon.

Claims (10)

1. a preparation method of ammoniated-activated vegetable matter gac, is characterized in that, comprises the following steps: (1) Use urea, ammonium bicarbonate or ammonia ammoniation reagent to ammoniate the vegetable raw material to obtain the ammonified raw material; (2) Mix the ammoniated raw material and activator in step (1), and soak at 20~30 ^o C for 2~12 hours. The mass ratio of the ammoniated raw material to the activator is 1:0.5~ 2.0; (3) Carbonize and activate the impregnated raw materials at 300-800 ^o C for 30-60 minutes to obtain activated carbon; (4) Wash and dry the activated carbon to obtain the product. 2. The preparation method as claimed in claim 1, characterized in that: before the plant material is subjected to ammonification treatment, the plant material is pretreated, and the pretreatment method is: the plant material is washed, dried, pulverized, Crush to 20~40 mesh. 3. The preparation method according to claim 1, characterized in that: in the step (1), the plant material is one or more mixtures of reeds, reed bamboos, or Osmanthus fragrans. 4. The preparation method according to claim 1, characterized in that: in step (1), when the ammoniation reagent is urea or ammonium bicarbonate, the specific method of ammoniation treatment is: the plant material is mixed with urea or carbonic acid The mass ratio of ammonium hydrogen to vegetable raw materials is 0.03~0.08:1, mixed with urea or ammonium bicarbonate, dissolved in water, sealed, and kept at 90~100 ^o C for 1~6h. 5. The preparation method according to claim 1, characterized in that: in step (1), when the ammoniation reagent is ammonia water, the specific method of ammoniation treatment is: the plant material is mixed according to the quality of ammonia water and plant material The ratio is 0.01~0.05:1, mixed evenly with ammonia water, sealed, and kept at 18~30 ^o C for 5~14d. 6. The preparation method according to claim 5, characterized in that: the mass concentration of the ammonia water is 3-15%. 7. The preparation method according to claim 1, characterized in that: in step (2), the activator is phosphoric acid solution or potassium hydroxide. 8. The preparation method according to claim 1, characterized in that: in step (2), the soaking time is 2-8 hours. 9. The preparation method according to claim 1, characterized in that: in step (3), the temperature is 350-450 ^o C, and the time is 40-60 minutes. 10. The preparation method according to any one of claims 1-9, characterized in that: in step (4), the activated carbon is washed until the pH value is stable at about 7.0, and then dried.