RU2565194C2 - Method of producing carbon-based sorbent - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to sorbents made from nutshells. Production of carbon sorbent with pore mean size of 2.2 nm, pore mean volume of 0.14 cm³/g and specific surface of 1336.96 m²/g consists in minced nutshell carbonizing in muffler with air access at 700-800°C for two hours.

EFFECT: higher sorption properties of the product.

4 dwg

Description

The invention relates to a method for producing a sorbent based on natural carbon material, which can be used in medicine, veterinary medicine, pharmacy and for solving environmental problems due to the high sorption activity.

Of particular interest are carbon sorbents obtained on the basis of plant materials and possessing unique physical and chemical properties. Currently, walnuts are widely used in the manufacture of confectionery and in pharmacy to produce valuable nutty oil with biological activity. The result was a new source of natural raw materials - shell, which was previously considered waste. Thus, the processing of walnut shells solves the problems of rational use of all parts of the walnut.

As a rule, the process of producing active carbon consists of two stages:

Stage 1 - processing of carbon-containing raw materials at high temperatures, for example, pyrolysis or carbonization;

Stage 2 - activation by water vapor, a mixture of water vapor with carbon dioxide or chemical reagents.

A known method of producing carbon material from fruit seeds or nutshells (Patent RU No. 2064429, "CARBON SORBENT AND METHOD FOR ITS PRODUCTION", published. 07.27.1996), including preliminary processing of fruit seeds and / or nutshells with alkali or acid solution, carbonization, heat treatment, activation to obtain a carbon carrier and its modification. Carbonization is carried out by pyrolysis at 260-900 ° C for 0.5-120 hours, activation is carried out in a stream of water vapor and / or flue gases at 700-900 ° C.

RU patent No. 2154603 “Method for producing activated carbon” (published on 08.20.2000) describes a method for producing activated carbon from pine nutshell shells, including heat treatment at a temperature of 750-850 ° C and activation with water vapor.

Patent RU No. 2166990 "Method for producing a carbon sorbent" (published May 20, 2001) includes carbonization of stone raw materials at a temperature of 750 ° C, activation by a mixture of water vapor with carbon dioxide at a temperature of 900-1000 ° C, and washing by magnetic separation.

The method of producing activated carbon from pine nutshell (Patent RU No. 2196732, published. 01.20.2003) is characterized in that the pyrolysis and activation are carried out simultaneously in an atmosphere of water vapor at a temperature of 600-700 ° C for 1-3 hours. The disadvantage is that this method is intended for processing raw materials from pine nutshells, and a low yield of the finished product (up to 30%).

Patent RU No. 2228293 A METHOD FOR PRODUCING ACTIVE COAL FROM NUTS CORLUP (published on 02/10/2009) describes a method for producing crushed activated carbon, including carbonization of coconut shells, activation, cooling and sieving of a finished product, characterized in that carbonization is heat treated without access after carbonization air at a temperature of 780-850 ° C for 15-24 hours, after which the uncooled product is supplied for activation with water vapor at 920-1050 ° C with a steam flow rate of 8.5-12.0 kg / kg of coal. The disadvantage is the use of only coconut shells as a raw material and the narrow focus on the use of the finished product: only for low molecular weight substances, such as ammonia.

A known method of producing a sorbent (patent RU No. 2329948 "Method for producing oxidized coal from vegetable raw materials for wastewater treatment from copper ions", published. 07.27.2008), which consists in calcining a pine nut shell in air at a temperature of 290-300 ° C to obtain carbon material, followed by treatment with nitric acid or hydrogen peroxide. The disadvantage of this method is that it is intended for the processing of raw materials from the shell of pine nuts and multi-stage processing, as well as the insufficiently high efficiency of sorption on copper.

A known method of producing a sorbent (Patent of the Russian Federation 2172209, publ. 08/20/2001), which consists in grinding the shell of walnuts to 0.8 cm, processing with hydrochloric acid for 15 hours, washing the shell until neutral, processing with a concentrated solution of sodium hydroxide, followed by washing grinding and drying. The disadvantage of this method is the length of the process and the use of aggressive chemical compounds.

The closest in its features and in the raw materials adopted for the prototype is patent RU No. 2111923 (publ. 05/27/1998), including crushing fruit seeds or nutshells, including walnuts, carbonization in a stream of carbon dioxide in the temperature range 400- 750 ° C, cooling of the carbonizate, re-carbonization at 750-900 ° C, gas-vapor activation and sieving of the finished product, characterized by a large volume of micropores with a predominant size X = 0.5-0.7 nm, which ensures a high degree of absorption of such organic substances - pollution water bodies like acetone and acetic acid. The disadvantages of this method are multi-stage processing, complex hardware design, the finished product yield is less than 50% and the narrow focus of the use of the finished product.

The task of the invention is to eliminate the disadvantages of the prototype, including a higher yield of sorbent with a high specific surface area.

The technical result consists in the fact that the method provides the sorbent from the walnut shell with high sorption properties due to the fact that:

- on the surface of the sorbent increases the number of pores and active sites: the average pore size of 2.2 nm, the average pore volume of 0.14 cm ³ / g;

- the specific surface area of the obtained sorbent according to methylene blue (MG), determined according to GOST 4453-74, is 1336.96 m ² / g, which is comparable to the specific surface area of activated carbon used for medical purposes (500-1500 m ² / g);

- yield of finished product over 60%.

Moreover, the specified technical result is achieved in one stage, which provides a significant reduction in the duration of the process, in addition, the implementation of the method does not require additional equipment for supplying carbon dioxide.

The problem is solved by the proposed method for producing a carbon sorbent from a walnut shell, including chopping the shell and carbonization, which differs from the prototype in the following ways:

- carbonization is carried out in one stage with access of air,

- carbonization is carried out at a temperature of 700-800 ° C for 2 hours.

As a result of the implementation of the proposed method receive a sorbent with the following characteristics:

- the specific surface area of the obtained sorbent for methylene blue (MG) is 1336.96 m ² / g, which is comparable to the specific surface area of activated carbon used for medical purposes (500-1500 m ² / g),

- the average pore size of the sorbent 2.2 nm, the average pore volume of 0.14 cm ³ / year

No technical solutions have been found from the prior art that use carbonization of walnut shells in one step with air access at a temperature of 700-800 ° C for two hours to obtain a carbon sorbent, which suggests that the claimed method meets the condition of "novelty" and the condition of "inventive step", because obtained by the proposed method, the sorbent not only preserves the sorption properties of analogues, but also surpasses them in this indicator.

The method is characterized by the following graphic materials:

- figure 1 presents a graph of the influence of the processing temperature on the change in the mass of the walnut shell, i.e. the dependence of the mass loss of the feedstock on temperature,

- figure 2 presents images confirming a change in the surface structure of the samples depending on the temperature treatment: 2a - treatment at 250 ° C, 2b - treatment at 400 ° C, 2c - treatment at 700 ° C, 2g - treatment at 1200 ° C . Pictures taken using a HITACHISU1510 scanning microscope,

- figure 3 shows the results of energy dispersive analysis of the elemental composition of the obtained sorbent: the carbon material consists of 77.86% carbon and 21.70% oxygen, and there are also trace amounts of Al, K, Ca, Fe, Cu. The content of K and Ca in the obtained carbon sorbent indicates its plant origin. Data obtained on a Quanta 3D instrument,

- figure 4 illustrates the sorption of methylene blue (MG) according to GOST 4453-74 on a sample obtained by carbonization at a temperature of 700 ° C.

During carbonization, the surface of the samples is structured, with the formation of particles of various morphologies characteristic of plant fiber. A temperature of 700-800 ° C is the optimum carbonization temperature, which is confirmed by the graph in figure 1 and the image in figure 2. The graph (figure 1) shows that up to a temperature of 450 ° C there is a loss of chemisorbed water; with a further increase in temperature, the mass decreases due to carbon burnout, and at a temperature of 700 ° C the mass loss ceases, since the carbon dioxide formed reacts with the hot carbon, resulting in the formation of a carbonized product. Above 800 ° C, the carbonization curve reaches a plateau and a further increase in temperature is impractical. A carbonization time of less than 2 hours does not provide complete burnout and the required development of the pore system, and more than 2 hours is not economically feasible.

On figa visible intact plant fibers after carbonization at t = 250 ° C. The difference between the sample obtained at a temperature of 400 ° C (Fig.2b) and the sample at a temperature of 700 ° C (Fig.2c) is clearly visible. As a result of the treatment, the lignin burned out and the number of micro-, meso- and macropores increased. The high processing temperature t = 1200 ° C leads to "sintering" of the surface, the number of micro- and mesopores decreases (Fig.2g).

An example of the method

Example 1. The walnut shell was subjected to grinding in a mechanical mill, then the resulting mass was transferred to corundum crucibles. Carbonization was carried out in a muffle furnace with air access at a temperature of 700 ° C for 2 hours.

The surface of the obtained sorbent is characterized by the presence of a large number of micro-, meso- and macropores; the average pore size of 2.2 nm, the specific surface area (MG) is 1336.96 m ² / year The yield of the finished product is 61.8%.

Example 2. The walnut shell was subjected to grinding in a mechanical mill, then the resulting mass was transferred to corundum crucibles. Carbonization was carried out in a muffle furnace with air access at a temperature of 800 ° C for 2 hours. The surface of the obtained sorbent is characterized by the presence of a large number of micro-, meso- and macropores; the average pore size of 2.2 nm, the specific surface area (MG) is 1336.96 m ² / year The yield of the finished product is 61.8%.

The high sorption activity of the obtained sorbent is confirmed by experimental data: sorption for cadmium (87.06%), lead (87.69%) and copper (88.24%).

Thus, the task of creating a less laborious method of obtaining an effective sorbent from the walnut shell with a higher yield of the finished product is solved. The surface of the obtained sorbent is characterized by the presence of a large number of micro-, meso- and macropores; the average pore size of 2.2 nm, the specific surface area (MG) is 1336.96 m ² / year Such characteristics of the sorbent suggest the possibility of its widespread use in pharmacy, medicine and veterinary medicine as an antidote, and high sorption on cadmium (87.06%), lead (87.69%) and copper (88.24%) allows the use of the obtained sorbent for water purification from heavy metals.

Claims (1)

A method of producing a carbon sorbent having an average pore size of 2.2 nm, an average pore volume of 0.14 cm ³ / g and a specific surface area of 1336.96 m ² / g, which consists in the carbonization of crushed walnut shells in a muffle furnace with air access at a temperature 700-800 ° C for 2 hours

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