阅读说明：本技术 一种高效提升生物炭电子交换能力的方法 (Method for efficiently improving electronic exchange capacity of biochar ) 是由 吕凡 卢学敏 何品晶 李莎莎 章骅 邵立明 于 2020-10-19 设计创作，主要内容包括：本发明公开了一种高效提升生物炭电子交换能力的方法,属于环境工程材料技术领域。本发明方法包括以下步骤：首先,将待活化的原料生物炭清洗干燥,然后球磨至一定粒径范围；其次,将上述处理后的生物炭与设计质量比的活化剂加水混合,加热搅拌直至形成黑色胶体状泥浆,再将泥浆恒温热解,热解过程中持续通入惰性气体以保证无氧气氛；最后,将泥浆恒温热解后用酸浸洗,然后清洗干燥,即可获得活化生物炭。本发明方法可使低品级的原料生物炭的电子交换能力得到显著提升从而得到高品级的活化生物炭,其中,相比未活化生物炭原料,活化生物炭的供电子能力最大可提升约50倍,得电子能力最大可提升30余倍。(The invention discloses a method for efficiently improving the electronic exchange capacity of biochar, and belongs to the technical field of environmental engineering materials. The method comprises the following steps: firstly, cleaning and drying raw material biochar to be activated, and then ball-milling the biochar to a certain particle size range; secondly, adding water into the treated charcoal and an activating agent with a designed mass ratio, mixing, heating and stirring until black colloidal slurry is formed, pyrolyzing the slurry at constant temperature, and continuously introducing inert gas in the pyrolysis process to ensure an oxygen-free atmosphere; finally, pyrolyzing the slurry at constant temperature, washing with acid, and then cleaning and drying to obtain the activated biochar. The method can obviously improve the electron exchange capacity of the low-grade raw biochar so as to obtain the high-grade activated biochar, wherein the electron supply capacity of the activated biochar can be improved by about 50 times to the maximum extent and the electron obtaining capacity can be improved by more than 30 times to the maximum extent compared with the raw biochar without being activated.)

1. A method for efficiently improving the electronic exchange capacity of biochar is characterized by comprising the following steps:

(1) cleaning and drying raw material biochar to be activated, and then ball-milling to a certain particle size range;

(2) adding water into the biochar treated in the step (1) and an activating agent with a designed mass ratio for mixing, heating and stirring until black colloidal slurry is formed, pyrolyzing the slurry at constant temperature, and continuously introducing inert gas in the pyrolysis process to ensure an oxygen-free atmosphere;

(3) and (3) pyrolyzing the slurry in the step (2) at constant temperature, washing with acid, and then cleaning and drying to obtain the activated charcoal.

2. The method of claim 1, wherein the activated biochar has an electron donating ability of not less than 0.5mmol/g, an electron donating ability of not less than 1.8mmol/g, a BET specific surface area of not less than 1000m²/g。

3. The method of claim 1, wherein the raw biochar is biochar produced by the pyrolytic charring of agricultural and garden waste.

4. The method as claimed in claim 1, wherein the washing and drying in step (1) is carried out by immersing raw biochar in water for 10min according to a solid-liquid volume ratio of 1:3, filtering out water, repeating the above steps three times, and drying the biochar in air at 105 ℃ for 12 h; and (3) the cleaning and drying in the step (3) means that the biochar after acid leaching is cleaned by water until the filtrate is neutral, and then the biochar is dried in the air at 105 ℃ for 12 hours.

5. The method of claim 1, wherein the particle size in step (1) is in the range of 25 to 75 microns.

6. The method of claim 1, wherein the mass ratio of the activating agent to the biochar in the step (2) is (2-12): 1.

7. The method of claim 1, wherein the activating agent in the step (2) is solid potassium hydroxide with the purity of not less than 85%, and the heating and stirring temperature is 75-85 ℃.

8. The method of claim 1, wherein the pyrolysis temperature in step (2) is 700 ℃ and the pyrolysis time is 1 h.

9. The method of claim 1, wherein nitrogen is continuously introduced during the pyrolysis in step (2) so that the oxygen concentration is less than 10ppm to ensure an oxygen-free atmosphere.

10. The method of claim 1, wherein the pickling with acid in step (3) is performed by soaking with a 3mol/L HCl solution for 12 hours.

Technical Field

The invention relates to a method for efficiently improving the electronic exchange capacity of biochar, and belongs to the technical field of environmental engineering materials.

Background

In recent years, biochar has been used as an electron donor, an electron acceptor, or an electron transfer channel in processes of contaminant degradation, metal (ion) immobilization/transfer, nutrient conversion, soil remediation, and the like in biological and non-biological fields. Multiple researches find that the electron exchange capacity, especially the electron supply capacity, of the biochar is a key factor influencing the application effect. However, the electron exchange capacity of the biochar is influenced by the raw materials for preparing the biochar and the parameters (such as pyrolysis temperature and time) of the pyrolysis process, and the electron exchange capacity of the biochar obtained in each research is obviously different. Besides optimizing the raw material proportion and the pyrolysis process parameters to obtain the raw material biochar, the selection of a proper activation method to activate the raw material biochar is also a key technology for producing and utilizing the biochar with high electron exchange capacity. How to activate raw material biochar and directionally and efficiently improve the electron exchange capacity of the biochar so as to increase the application value of the biochar is still a great technical problem in the research and application of the biochar at present.

At present, a series of activation methods for carbon materials have been explored and researched at home and abroad, and the activation methods mainly include a physical activation method and a chemical activation method. Physical activation processes typically use oxidizing gases such as CO₂Or activating the carbon material by steam and the like at high temperature (800-over 1000 ℃), wherein the chemical activation method comprises the steps of firstly loading a chemical activating agent on the surface of the carbon material, and then carbonizing and pyrolyzing the carbon material loaded with the activating agent at high temperature (450-900 ℃). The strong alkali compound KOH is one of the most commonly used activating agents in the chemical activation method, and the loading mode is mostly a method of soaking in solution and then carrying out solid-liquid separation and drying. At present, the activation research is mainly to increase the specific surface area of the carbon material to improve the adsorption capacity or adsorption selectivity of the carbon material to pollutants, and few activation processes are currently performed from the viewpoint of improving the electron exchange capacity of the carbon materialAnd (5) research of optimization.

There are some published articles and patents that focus on the research of technical means for improving the electron exchange capacity of biochar. For example, the chinese patent publication No. CN 111363573a improves the electron exchange capacity of raw biochar by optimally matching biomass raw materials and regulating the corresponding pyrolysis temperature, but the method still has limited improvement range of the electron exchange capacity of biochar, and does not reach the difference of magnitude order; a paper (Chacon, F.J., et al, Engineering biochar redox properties through Engineering Journal,2020,395) researches various biochar activation methods to improve the electron exchange capability of raw biochar, wherein KOH is also used as an activator, but the method only loads the biochar on the surface, does not carry out subsequent pyrolysis treatment, has no remarkable improvement effect and can only reach 2-3 times of the biochar before activation.

Disclosure of Invention

The method comprises the steps of cleaning and drying raw biochar, grinding the biochar to a certain particle size, then uniformly loading an activating agent on the biochar in a loading mode of adding water into the biochar and mixing the biochar with the activating agent, heating and stirring, and pyrolyzing at high temperature, so that the electron exchange capacity of the activated biochar can be efficiently improved, compared with the raw biochar which is not activated, the electron supply capacity of the activated biochar can be improved by about 50 times to the maximum, and the electron supply capacity can be improved by more than 30 times to the maximum.

In order to achieve the technical purpose, the technical scheme of the invention is as follows:

a method for efficiently improving the electronic exchange capacity of biochar comprises the following steps:

(1) cleaning and drying raw material biochar to be activated, and then ball-milling to a certain particle size range;

(2) adding water into the biochar treated in the step (1) and an activating agent with a designed mass ratio for mixing, heating and stirring until black colloidal slurry is formed, pyrolyzing the slurry at constant temperature, and continuously introducing inert gas in the pyrolysis process to ensure an oxygen-free atmosphere;

(3) and (3) pyrolyzing the slurry in the step (2) at constant temperature, washing with acid, and then cleaning and drying to obtain the activated charcoal.

Preferably, the electron donating ability of the activated biochar is not less than 0.5mmol/g, the electron donating ability is not less than 1.8mmol/g, and the BET specific surface area is not less than 1000m²/g。

Preferably, the raw material biochar is biochar prepared by pyrolyzing and carbonizing agricultural and garden wastes.

Preferably, the cleaning and drying in the step (1) refers to soaking the raw material biochar in water according to the solid-liquid volume ratio of 1:3 for 10min, then filtering the water, repeating the process for three times, and then drying the biochar in the air at 105 ℃ for 12 h; and (3) the cleaning and drying in the step (3) means that the biochar after acid leaching is cleaned by water until the filtrate is neutral, and then the biochar is dried in the air at 105 ℃ for 12 hours.

Preferably, the particle size in step (1) is in the range of 25-75 microns.

Preferably, the mass ratio of the activating agent to the biochar in the step (2) is (2-12): 1.

Preferably, the activating agent in the step (2) is solid potassium hydroxide, the purity is not lower than 85%, and the heating and stirring temperature is 75-85 ℃. .

Preferably, the pyrolysis temperature in the step (2) is 700 ℃ and the pyrolysis time is 1 h.

Preferably, nitrogen is continuously introduced during the pyrolysis in the step (2) so that the oxygen concentration is less than 10ppm to ensure an oxygen-free atmosphere.

Preferably, the pickling with acid in the step (3) refers to soaking for 12 hours with a HCl solution with a concentration of 3 mol/L.

From the above description, it can be seen that the present invention has the following advantages:

(1) according to the invention, by improving the activator loading method, the activator KOH can be more uniformly loaded on the surface of the biochar, the contact area between the biochar and the activator is increased, and the activation effect is improved more under the condition of the same amount of the activator, so that the consumption of an activation agent and the discharge of secondary pollutants are reduced, and better clean production and green production benefits are obtained.

(2) The method can obviously improve the electron exchange capacity of the low-grade raw biochar so as to obtain the high-grade activated biochar, wherein the electron supply capacity of the activated biochar can be improved by about 50 times to the maximum extent and the electron obtaining capacity can be improved by more than 30 times to the maximum extent compared with the raw biochar without being activated, so that the application value of the biochar in the biological and non-biological fields is greatly improved, and higher economic benefit is obtained.

(3) The activating agent KOH adopted by the invention is a conventional chemical raw material, is easy to obtain and low in price, has low environmental risk, does not involve high pressure and high temperature in the reaction, and is safe and reliable in the activating process and easy to operate and implement.

Drawings

FIG. 1 is the electron donating ability of the resulting activated biochar at different KOH/biochar mass ratios in example 1;

FIG. 2 is the electron-yielding capacity of the activated biochar obtained in example 1 at different KOH/biochar mass ratios;

Detailed Description

The features of the invention will be further elucidated by the embodiments described below, without limiting the scope of the invention in any way.

Example 1

(1) Pyrolyzing pine wood at 400 ℃ for 15h to obtain raw biochar to be activated, wherein the electron supply capacity of the raw biochar is 0.0217mmol/g, the electron supply capacity is 0.1679mmol/g, and the BET specific surface area is 3.8m²/g；

(2) Soaking raw material biochar to be activated in water for 10min according to the solid-liquid volume ratio of 1:3, filtering the water, repeating the process for three times, placing the biochar in the air, drying at 105 ℃ for 12h, and then performing ball milling to enable the particle size of the biochar to be 25-75 micrometers;

(3) mixing the biochar treated in the step (2) with solid potassium hydroxide with the purity not lower than 85% by adding water, wherein the mass ratio of an activating agent to the biochar is (2-12) to 1, heating and stirring at 80 ℃ after mixing until black colloidal slurry is formed, pyrolyzing the slurry at the constant temperature of 700 ℃ for 1h, and continuously introducing nitrogen in the pyrolysis process to ensure an oxygen-free atmosphere;

(4) and (4) pyrolyzing the slurry in the step (3) at constant temperature, soaking the slurry in HCl solution with the concentration of 3mol/L for 12h, then washing the slurry with water until the filtrate is neutral, and then drying the slurry in air at 105 ℃ for 12h to obtain the activated charcoal. As shown in figure 1 and figure 2, the activated charcoal obtained under the condition that the mass ratios of the activating agent KOH to the biochar treated by the step (2) are respectively 2, 4, 6, 8, 10 and 12 has electron supply capacities of 0.5214, 0.5641, 0.8040, 0.9944, 1.0742 and 0.8471mmol/g, electron capacities of 2.2975, 1.8804, 5.2290, 4.8907, 3.9821 and 3.4281mmol/g, BET specific surface areas of 1213, 2573, 2953, 3733, 3200 and 3224m²/g。

Example 2

Activated charcoal was prepared in the same manner as in example 1, except that the raw material charcoal to be activated was obtained by pyrolyzing oak at 800 ℃ for 5 hours, the electron donating ability of the raw material charcoal was 0.0197mmol/g, the electron donating ability was 0.1496mmol/g, the BET specific surface area was 11m²/g。

When the mass ratio of the activating agent KOH to the biochar treated in the step (2) is 2, 4, 6, 8, 10 and 12, respectively, the electron donating ability of the activated biochar obtained by the method of the embodiment is 0.6645, 0.5267, 0.8429, 0.8937, 0.9472 and 0.8092mmol/g, the electron donating ability is 1.8354, 2.7869, 5.1752, 4.8356, 4.7358 and 3.8922mmol/g, the BET specific surface area is 1065, 1976, 2681, 3183, 2985 and 3041m²/g。

Example 3

Activated charcoal was prepared in the same manner as in example 1, except that the raw material charcoal to be activated was obtained by pyrolysis of the cut branches of olive tree at 500 ℃ for 2 hours, the electron donating ability of the raw material charcoal was 0.0247mmol/g, the electron donating ability was 0.1827mmol/g, the BET specific surface area was 2.4m²/g。

When the mass ratio of the activating agent KOH to the biochar treated in the step (2) is 2, 4, 6, 8, 10 and 12, respectively, the electron donating capability of the activated biochar obtained by the method of the embodiment is 0.5023, 0.5513, 0.8946, 1.0090 and 1.182, respectively3 and 0.7519mmol/g, the electron obtaining capacity is 2.3324, 3.9975, 5.9133, 4.2917, 4.9980 and 3.6301mmol/g respectively, the BET specific surface area is 1633, 2224, 2598, 3564, 3035 and 2836m respectively²/g。

Example 4

Activated charcoal was prepared in the same manner as in example 1, except that the raw material charcoal to be activated was obtained by pyrolyzing corn stover at 500 ℃ for 2 hours, the raw material charcoal had an electron donating ability of 0.0158mmol/g, an electron donating ability of 0.0874mmol/g, and a BET specific surface area of 18.4m²/g。

When the mass ratios of the activating agent KOH and the biochar treated in the step (2) are respectively 2, 4, 6, 8, 10 and 12, the electron donating capacities of the activated biochar obtained by the method are 0.5139, 0.5614, 0.6281, 0.7167, 0.7935 and 0.6834mmol/g, the electron obtaining capacities are 1.9866, 2.8767, 3.2583, 2.9756, 2.5647 and 2.1937mmol/g, the BET specific surface areas are 1337, 2359, 2812, 2925, 3023 and 2789m²/g。

It should be understood that the detailed description of the invention is merely illustrative of the invention and is not intended to limit the invention to the specific embodiments described. It will be appreciated by those skilled in the art that the present invention may be modified or substituted equally as well to achieve the same technical result; as long as the use requirements are met, the method is within the protection scope of the invention.