CN104525119B - A functional carbon adsorption material of g-C3N4/ZnO/activated carbon and its preparation method - Google Patents

Abstract

The invention discloses a g-C ₃ N ₄ /ZnO/activated carbon functional carbon adsorption material and a preparation method thereof. The main raw materials are biomass (wood or bamboo), melamine, and zinc acetate, and the carbonization, impregnation, and activation , high-temperature polycondensation and other reactions to prepare g‑C ₃ N ₄ /ZnO/activated carbon functional carbon adsorption materials. In the present invention, the activated carbon precursor is combined with the g-C ₃ N ₄ precursor and the ZnO precursor, and zinc acetate is used as the activator for preparing the activated carbon to obtain g-C ₃ N ₄ /ZnO/activated carbon functional carbon The adsorption material is firmly combined and not easy to lose, has a long service life, and can be regenerated by in-situ photocatalysis.

Description

A functional carbon adsorption material of g-C3N4/ZnO/activated carbon and its preparation method

technical field

The invention belongs to the field of preparation of functional carbon adsorption materials, in particular to a gC ₃ N ₄ /ZnO/activated carbon functional carbon adsorption material and a preparation method thereof.

Background technique

Activated carbon is widely used in food industry, chemical industry, environmental protection and other fields because of its developed pore structure, strong adsorption capacity, rich surface functional groups, high mechanical strength, and chemical inertness. However, due to the lack of activated carbon varieties, low technical content, and lack of functional high-quality special activated carbon, my country's activated carbon industry is restricted from moving towards a higher level of application. Modification of activated carbon to develop functional activated carbon that can efficiently and deeply purify pollutants is an effective way to reduce the cost of activated carbon, expand its scope of use, and improve its utilization efficiency. It is an important direction for the future development of the activated carbon industry.

Since the adsorption of pollutants by activated carbon is mainly based on micropore filling, the adsorption capacity is limited, and the adsorption saturation can be reached in a short time and the adsorption capacity is lost. The saturated activated carbon becomes a secondary pollution source and must be regenerated before it can be reused. use. At present, the activated carbon regeneration methods can be generally divided into two categories: one is to try to desorb the adsorbate, that is, by creating conditions corresponding to the low load (introducing substances or energy to weaken or disappear the force between the adsorbate molecules and the activated carbon). ), to remove the adsorbate; the second is to rely on thermal decomposition or redox reaction to destroy the structure of the adsorbate and remove the adsorbate. Traditional regeneration methods mainly include thermal regeneration, chemical regeneration, solvent regeneration, biological regeneration, etc., but due to their defects such as low efficiency, high cost, harsh operating conditions, and complicated processes, traditional regeneration methods can no longer meet the needs of current industrial development. . Therefore, developing a regeneration method at normal temperature, normal pressure, low consumption, high efficiency, and simple operation process has become a hot research topic at home and abroad.

In 2009, Chinese scientists cooperated with German and Japanese scientists to discover a metal-free conjugated polymer graphitic carbon nitride (gC ₃ N ₄ ) visible light photocatalytic material, and used density functional theory (DFT) and Using electrochemical methods, the energy band structure of carbon nitride was studied, and it was found that gC ₃ N ₄ has a typical semiconductor energy band structure, and the sp ² hybridized N ² p orbital constitutes the highest occupied molecular orbital (HOMO) of gC ₃ N ₄ , The C ² p hybrid orbital constitutes its lowest unoccupied molecular orbital (LUMO), with a band gap of about 2.7eV and a specific surface area of 10 m ² /g. Under the induction of λ > 387 nm visible light, it can catalyze redox reactions . However, gC ₃ N ₄ polymers still have some problems as photocatalysts, such as small specific surface area, high exciton binding energy for generating photogenerated carriers, low quantum efficiency and large forbidden band width ( λ <460 nm) and cannot Effective use of sunlight, etc. In response to these problems, scientists have carried out a lot of research work around gC ₃ N ₄ to improve the specific surface area of gC ₃ N ₄ catalysts, the absorption range of the spectrum, and the separation efficiency of photogenerated carriers.

Contents of the invention

The purpose of the present invention is to provide a functional carbon adsorption material of gC ₃ N ₄ /ZnO/activated carbon and its preparation method, and the functional carbon adsorption material of gC ₃ N ₄ /ZnO/activated carbon has high pollutant removal ability , not easy to deactivate, long service life, and in-situ photocatalytic regeneration.

To achieve the above object, the present invention adopts the following technical solutions:

A gC ₃ N ₄ /ZnO/activated carbon functional carbon adsorption material has a ZnO content of 2-5wt.%, and a gC ₃ N ₄ content of 3-8wt.%.

The preparation method comprises the following steps:

(1) Crushing, screening and drying wood or bamboo raw materials;

(2) Take 10g of the dried raw material and heat it up to 400~450℃ at a rate of 5℃/min under the protection of high-purity nitrogen, keep it warm for 1-2h, and cool it down to room temperature naturally;

(3) Add 1g~3g of zinc acetate to 50 mL of distilled water under stirring condition, and react for 20 minutes, then add 1.5~5g of melamine, continue to stir and react for 30 minutes, fully mix with the material prepared in step (2), and soak for 24 hours , drying at 80°C;

(4) The material prepared in step (3) was raised from room temperature to 500°C at a rate of 10°C/min under the protection of high-purity nitrogen, kept at a constant temperature for 2 hours, and then raised to 530°C at a rate of 0.2°C/min. And keep the temperature for 5 hours, then naturally cool to room temperature, and then obtain the functional carbon adsorption material of gC ₃ N ₄ /ZnO/activated carbon.

The notable advantages of the present invention are: the functional carbon adsorption material of gC ₃ N ₄ /ZnO/activated carbon prepared by the present invention has high ability to remove pollutants, is not easy to deactivate, has a long service life, and can be regenerated by photocatalysis in situ. It has great potential application value in the deep treatment of organic polluted water bodies.

Description of drawings

Figure 1 is the XRD spectrum of gC ₃ N ₄ /ZnO/AC.

Figure 2 is the N ₂ adsorption-desorption curves of gC ₃ N ₄ /ZnO/AC and AC.

Figure 3 shows the removal of phenol by gC ₃ N ₄ /ZnO/AC and AC under light and dark adsorption conditions.

Figure 4 shows the removal effect of gC ₃ N ₄ /ZnO/AC and AC repeated 6 times on phenol under light conditions.

Figure 5 shows the photocatalytic regeneration effect of gC ₃ N ₄ /ZnO/AC, gC ₃ N ₄ /AC and AC. 1. gC ₃ N ₄ /ZnO/AC, 2. gC ₃ N ₄ /AC, 3. AC.

detailed description

Example 1

A preparation method of a functional carbon adsorption material of gC ₃ N ₄ /ZnO/activated carbon comprises the following steps:

(1) Crushing, screening and drying wood or bamboo raw materials;

(2) Take 10g of the dried raw material and heat it up to 400°C at a rate of 5°C/min under the protection of high-purity nitrogen, keep it warm for 2h, and cool it down to room temperature naturally;

(3) Add 1g of zinc acetate to 50 mL of distilled water under stirring conditions, and react for 20 minutes, then add 1.5g of melamine, continue to stir and react for 30 minutes, and fully mix with the material prepared in step (2), dip for 24 hours, 80 °C down drying;

(4) The material prepared in step (3) was raised from room temperature to 500°C at a rate of 10°C/min under the protection of high-purity nitrogen, kept at a constant temperature for 2 hours, and then raised to 530°C at a rate of 0.2°C/min. And constant temperature 5h, naturally cool to room temperature, promptly obtain the functional carbon adsorption material of described gC ₃ N ₄ /ZnO/activated carbon, the content of ZnO in the functional carbon adsorption material is 2wt.%, the content of gC ₃ N ₄ is 3wt.%.

Example 2

A preparation method of a functional carbon adsorption material of gC ₃ N ₄ /ZnO/activated carbon comprises the following steps:

(1) Crushing, screening and drying wood or bamboo raw materials;

(2) Take 10g of the dried raw material and heat it up to 420°C at a rate of 5°C/min under the protection of high-purity nitrogen, keep it warm for 1h, and cool it down to room temperature naturally;

(3) Add 3g of zinc acetate to 50 mL of distilled water under stirring conditions, and react for 20 minutes, then add 5g of melamine, continue stirring and reacting for 30 minutes. drying;

(4) The material prepared in step (3) was raised from room temperature to 500°C at a rate of 10°C/min under the protection of high-purity nitrogen, kept at a constant temperature for 2 hours, and then raised to 530°C at a rate of 0.2°C/min. And constant temperature 5h, naturally cool to room temperature, promptly get the functional carbon adsorption material of described gC ₃ N ₄ /ZnO/activated carbon, the content of ZnO in the functional carbon adsorption material is 5wt.%, the content of gC ₃ N ₄ is 8wt.%.

Example 3

A preparation method of a functional carbon adsorption material of gC ₃ N ₄ /ZnO/activated carbon comprises the following steps:

(1) Crushing, screening and drying wood or bamboo raw materials;

(2) Take 10g of the dried raw material and heat it up to 450°C at a rate of 5°C/min under the protection of high-purity nitrogen, keep it warm for 1.5h, and cool it down to room temperature naturally;

(3) Add 2g of zinc acetate to 50 mL of distilled water under stirring conditions, and react for 20 minutes, then add 3g of melamine, continue stirring and reacting for 30 minutes, fully mix with the material prepared in step (2), dip for 24 hours, at 80 drying;

(4) The material prepared in step (3) was raised from room temperature to 500°C at a rate of 10°C/min under the protection of high-purity nitrogen, kept at a constant temperature for 2 hours, and then raised to 530°C at a rate of 0.2°C/min. And keep the temperature for 5h, and naturally cool to room temperature to obtain the functional carbon adsorption material of gC ₃ N ₄ /ZnO/activated carbon. The content of ZnO in the functional carbon adsorption material is 3.5wt.%, and the content of gC ₃ N ₄ is 5wt.%.

Figure 1 is the XRD spectrum of gC ₃ N ₄ /ZnO/AC. It can be seen from the figure that there are two phases of gC ₃ N ₄ and ZnO in gC ₃ N ₄ /ZnO/activated carbon, and the spectrum is 13.2 ^o and 27.6 The diffraction peaks at ^o correspond to the (100) crystal plane and (002) crystal plane diffraction peaks of gC ₃ N ₄ , respectively. The diffraction peaks at 31.7 ^o , 34.4 ^o , 36.2 ^o , 47.5 ^o , and 56.5 ^o in the spectrum correspond to the (100) crystal plane, (002) crystal plane, (101) crystal plane, (102) crystal plane, Diffraction peaks of (110) crystal plane.

Fig. 2 is the N ₂ adsorption-desorption curve of gC ₃ N ₄ /ZnO/AC. It can be seen from the figure that the adsorption isotherm of gC ₃ N ₄ /ZnO/AC presents type IV (IUPAC classification) adsorption-desorption isotherm and hysteresis loop. When the relative pressure is low, the adsorption amount gradually increases with the increase of the relative pressure. At this time, _N2 molecules are adsorbed on the inner surface of the pores in a single layer or multiple layers; when the relative pressure is 0.1, the adsorption equilibrium is basically reached; then with The adsorption amount increases slowly with the increase of relative pressure, and when the relative pressure of N ₂ is 0.95, the adsorption amount jumps, which is caused by the capillary condensation of N ₂ in the mesoporous channels. It can be seen that the gC ₃ N ₄ /ZnO/AC is dominated by micropores and some mesopores exist.

Figure 3 shows the removal of phenol by gC ₃ N ₄ /ZnO/AC and AC under light and dark adsorption conditions. It can be seen from the figure that the gC ₃ N ₄ /ZnO/AC prepared by this process not only has the function of adsorption, but also has the function of photocatalysis. Under dark adsorption conditions, the adsorption capacity of gC ₃ N ₄ /ZnO/AC was slightly less than that of AC; however, the removal efficiency of gC ₃ N ₄ /ZnO/AC was significantly higher than that of AC under light conditions.

Figure 4 is the experiment of the removal effect of gC ₃ N ₄ /ZnO/AC and AC for 6 times of repeated use of phenol under light conditions. It can be seen from the figure that the removal effect of gC ₃ N ₄ /ZnO/AC on phenol is significantly better than that of AC, under the same conditions, the removal rate of phenol was 91.6% after gC ₃ N ₄ /ZnO/AC was reused for 6 times. However, AC has almost no removal effect on phenol after repeated use for 3 times.

After mixing activated carbon with melamine and fully grinding the sample, under the protection of high-purity nitrogen, the temperature was raised to 480°C at a rate of 2°C/min, and after holding for 2 hours, the temperature was raised to 520°C at a rate of 1°C/min, and kept for 2 hours. Naturally cooled to room temperature to obtain gC ₃ N ₄ /AC. Figure 5 shows the photocatalytic regeneration effect experiment of gC ₃ N ₄ /ZnO/AC, gC ₃ N ₄ /AC and AC under the light after adsorption and saturation under the light-proof parts (experiment method: gC ₃ N ₄ /ZnO/AC, gC After ₃ N ₄ /AC and AC are adsorbed and saturated under dark conditions, centrifuge to separate gC ₃ N ₄ /ZnO/AC, add gC ₃ N ₄ /AC and AC to distilled water respectively, and regenerate under sunlight. Afterwards, gC ₃ N ₄ /ZnO/AC is separated by centrifugation, gC ₃ N ₄ /AC and AC are put into water with a certain concentration of pollutants to adsorb pollutants). It can be seen from the figure that gC ₃ N ₄ /ZnO/AC has the best effect under the same conditions, followed by gC ₃ N ₄ /AC, and AC has almost no regenerative effect.

Purification effect experiments on pollutants under light and dark conditions:

The photocatalytic reaction was carried out in a self-made quartz/glass jacketed reactor (250 ml), with a built-in 350 W spherical xenon lamp ( _λML = 450 nm) in the quartz/glass tube, and a glass filter tube was used to filter out _λML < 400 nm Light) is a visible light source. Cooling water was passed into the outer jacket of the reactor to maintain the reaction temperature at (25±1)°C. The outer layer of the reactor was covered with aluminum foil to avoid other light interference. Before the photocatalytic reaction, magnetically stir for 120 min in the dark to make the surface adsorption of the catalyst reach equilibrium, and 60 ml/min air is introduced to stir and replenish dissolved oxygen, and the catalyst dosage is 1.0 g/L. After reacting for a certain period of time, samples are taken, and the concentration of the substance to be tested is detected by chromatography.

Purification effect experiment on pollutants under sunlight:

Weigh 0.1 g of catalyst and pour it into a petri dish with a diameter of 15 cm, add 100 ml of 0.05 g/L pollutant solution to be tested, absorb under magnetic stirring for 120 min, then seal the petri dish with plastic wrap, and put it under sunlight . After the light is finished, a sample is taken, and the concentration of the substance to be tested is detected by chromatography.

Application example 1

Table 1 is the experiment of the purification effect of gC ₃ N ₄ /ZnO/AC, gC ₃ N ₄ /AC and AC on the wastewater containing nitrobenzene under sunlight. It can be seen from the table that the purification effect of gC ₃ N ₄ /ZnO/AC on p-nitrobenzene is obviously better than that of gC ₃ N ₄ /AC and AC on p-nitrobenzene.

Table 1 Purification effect of gC ₃ N ₄ /ZnO/AC, gC ₃ N ₄ /AC and AC on wastewater containing nitrobenzene

Application example 2

Table 2 is the experiment of the purification effect of gC ₃ N ₄ /ZnO/AC, gC ₃ N ₄ /AC and AC on the wastewater containing o-chlorotoluene under sunlight. It can be seen from the table that the purification effect of gC ₃ N ₄ /ZnO/AC on o-chlorotoluene is significantly better than that of gC ₃ N ₄ /AC and AC on o-chlorotoluene.

Table 2 Purification effect of gC ₃ N ₄ /ZnO/AC, gC ₃ N ₄ /AC and AC on wastewater containing o-chlorotoluene

Application example 3

Table 3 shows the purification effect experiments of gC ₃ N ₄ /ZnO/AC, gC ₃ N ₄ /AC and AC on aniline-containing wastewater under sunlight. It can be seen from the table that the purification effect of gC ₃ N ₄ /ZnO/AC on aniline is obviously better than that of gC ₃ N ₄ /AC and AC on the purification of aniline.

Table 3 Purification effect of gC ₃ N ₄ /ZnO/AC, gC ₃ N ₄ /AC and AC on aniline-containing wastewater

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (2)

1. a g-C₃N₄The preparation method of the functional charcoal sorbing material of/ZnO/ activated carbon, it is characterised in that: in functional charcoal sorbing material, the content of ZnO is 2 ~ 5wt.%, g-C₃N₄Content be 3 ~ 8wt.%；Its preparation method comprises the following steps:

(1) carry out pulverizing, sieve and drying by wooden or bamboo raw material；

(2) take the raw material after 10g is dried under high pure nitrogen is protected with the ramp of 5 DEG C/min to 400 ~ 450 DEG C, and be incubated 1 ~ 2h, naturally cool to room temperature；

(3) under agitation toward addition 1g ~ 3g zinc acetate in 50 mL distilled water, after reaction 20min, add 1.5 ~ 5g melamine, continue stirring reaction 30min, after the material prepared with step (2) is sufficiently mixed, impregnate 24h, dry at 80 DEG C；

(4) material that step (3) prepares is risen to 500 DEG C with the speed of 10 DEG C/min by room temperature under high pure nitrogen is protected, constant temperature 2 h, then rise to 530 DEG C, and constant temperature 5h with the speed of 0.2 DEG C/min, naturally cool to room temperature, obtain described g-C₃N₄The functional charcoal sorbing material of/ZnO/ activated carbon.

2. the g-C that a preparation method as claimed in claim 1 prepares₃N₄The application of the functional charcoal sorbing material of/ZnO/ activated carbon, it is characterised in that: described g-C₃N₄/ ZnO/ activated carbon is used for administering organic pollution aquifer.