CN111229165B - Method for purifying eutrophic water body, activated buckwheat hull biochar and preparation method - Google Patents
Method for purifying eutrophic water body, activated buckwheat hull biochar and preparation method Download PDFInfo
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- CN111229165B CN111229165B CN202010160414.6A CN202010160414A CN111229165B CN 111229165 B CN111229165 B CN 111229165B CN 202010160414 A CN202010160414 A CN 202010160414A CN 111229165 B CN111229165 B CN 111229165B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/34—Organic compounds containing oxygen
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/38—Organic compounds containing nitrogen
Abstract
The application relates to the field of sewage treatment, in particular to a method for purifying eutrophic water, activated buckwheat hull biochar and a preparation method. Heating the mixed solution of buckwheat hulls soaked in phosphoric acid to perform carbonization reaction to activate the buckwheat hulls, and then pulverizing the activated buckwheat hulls into powder. The powdery activated buckwheat husk biochar is mixed with the eutrophic water body for reaction so as to simultaneously adsorb blue algae, chlorophyll a and COD in the eutrophic water body. The oxygen-containing functional group with stronger polarity on the surface of the activated buckwheat husk biochar can perform electrostatic adsorption with amino in the blue algae. The activated buckwheat husk biochar has rich pore structures and extremely many mesopores, and can improve the adsorption effect in a synergistic manner. The acidic oxygen-containing functional group of the activated buckwheat husk biochar can also adsorb electronegative substances in COD, so that blue algae, chlorophyll a and COD in eutrophic water body are adsorbed simultaneously, and the adsorption efficiency is greatly improved.
Description
Technical Field
The application relates to the field of sewage treatment, in particular to a method for purifying eutrophic water, activated buckwheat hull biochar and a preparation method.
Background
In recent years, with the use and discharge of a large amount of chemical agents containing nitrogen and phosphorus elements, the problem of artificial and natural water eutrophication is becoming more serious, which not only causes the mass propagation of aquatic plants such as blue algae and the like and the reduction of water transparency, but also causes the deterioration of water quality and the death of aquatic organisms, and even damages to lake ecosystems.
At present, the methods for removing the blue algae, the chlorophyll a and the COD in the eutrophic water body mainly comprise a biological method, a chemical method and a physical method. The COD removing method mainly comprises coagulation, nanofiltration, activated carbon adsorption and other methods. However, the cultivation of plants or microorganisms in biological processes is influenced by factors such as climate and may have an effect on the biological community; the chemical method has large drug consumption and can cause secondary pollution; the physical method has higher cost and limited effect of removing small molecular organic matters. The activated carbon adsorption is a method capable of removing blue algae and COD simultaneously.
However, the main problems of the existing activated carbon adsorption method are that the removal rate of blue algae, chlorophyll a and COD by activated carbon is low and the cost of raw materials for preparing activated carbon is high.
Disclosure of Invention
The embodiment of the application aims to provide a method for purifying eutrophic water, activated buckwheat hull biochar and a preparation method.
In a first aspect, the present application provides a method for purifying an eutrophic water body, comprising:
heating the mixed solution of buckwheat hulls soaked in phosphoric acid to perform a carbonization reaction, activating the buckwheat hulls to obtain activated buckwheat hull biochar, and then crushing the activated buckwheat hull biochar into powder;
powdered activated buckwheat husk biochar is mixed with eutrophic water.
The method can simultaneously adsorb blue algae, chlorophyll a and COD in the eutrophic water body. The acidic oxygen-containing functional group of the activated buckwheat husk biochar and the amino group in the blue algae are subjected to chemical reaction to form a chemical bond. The activated buckwheat hull charcoal has rich pore structure and extremely many mesopores, and can improve the adsorption effect in a synergistic manner. The acidic oxygen-containing functional group of the activated buckwheat husk biochar can also adsorb electronegative substances in COD, so that blue algae, chlorophyll a and COD in eutrophic water body are adsorbed simultaneously, and the adsorption efficiency is greatly improved.
In a second aspect, the application provides a method for preparing activated buckwheat hull biochar capable of purifying eutrophic water, wherein a buckwheat hull mixed solution impregnated with phosphoric acid is heated to perform a carbonization reaction, so that buckwheat hulls are activated, and then the activated buckwheat hull biochar is pulverized into powder.
The method has simple preparation steps, and does not need to adjust pH value and water content when soaking buckwheat hulls with phosphoric acid. The method selects buckwheat hulls as raw materials of biomass charcoal, and has low cost and high economical efficiency. The activated buckwheat hull biochar prepared by the method can simultaneously adsorb and remove blue algae, chlorophyll a and COD in the eutrophic water body. High removing efficiency and good removing effect.
In a third aspect, the application provides an activated buckwheat hull biochar capable of purifying eutrophic water,
the activated buckwheat hull biochar is made of buckwheat hulls;
optionally, the removal effect of activated buckwheat husk biochar on chlorophyll a can reach 88.64%;
the removal effect of the activated buckwheat hull biochar on blue algae can reach 80.18 percent;
the removal effect of the activated buckwheat husk biochar on COD can reach 99.4%.
The activated buckwheat hull charcoal can simultaneously adsorb and remove blue algae, chlorophyll a and COD in eutrophic water body. High removing efficiency and good removing effect.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 is an SEM image of activated buckwheat hull biochar provided in examples 1-13 of the present application; wherein, in fig. 1: (a) buckwheat hulls (2000 x magnification); (b) activated buckwheat hull biochar (2000 times magnification); (c) buckwheat hulls (10000 times magnified); (d) activated buckwheat husk biochar (10000 times magnification).
Detailed Description
The embodiment of the application provides a method for purifying eutrophic water, which comprises the following steps:
heating the mixed solution of buckwheat hulls soaked in phosphoric acid to perform a carbonization reaction, activating the buckwheat hulls to obtain activated buckwheat hull biochar, and then crushing the activated buckwheat hull biochar into powder;
powdered activated buckwheat husk biochar is mixed with eutrophic water.
According to the method, the buckwheat hulls are selected as the biomass carbon and used for purifying the eutrophic water body, so that the cost can be effectively saved, and the environmental pollution caused by burning a large amount of waste buckwheat hulls can be reduced. The buckwheat hulls are agricultural wastes, the main components of the buckwheat hulls are cellulose, lignin and the like, and compared with the commercially available activated carbon, the buckwheat hulls have similar properties, but can greatly save the preparation cost and realize the purpose of treating wastes with wastes.
The method can simultaneously adsorb blue algae, chlorophyll a and COD in the eutrophic water body.
Specifically, buckwheat hulls are impregnated with phosphoric acid, and a phosphoric acid solution is diffused to the surfaces of the buckwheat hulls, which adsorb the phosphoric acid solution, thereby allowing the phosphoric acid solution to sufficiently adhere to the surfaces of the buckwheat hulls. Thereby ensuring the subsequent carbonization activation reaction, taking the phosphoric acid on the surface of the buckwheat hulls as an activating agent, and generating active functional groups on the surface of the buckwheat hulls in the process of heating and carbonization. The number of oxygen-containing functional groups in the active functional groups is large, the blue algae is mainly composed of a ring structure formed by a plurality of different amino acids, wherein amino groups in each amino acid can generate electrostatic adsorption with the oxygen-containing functional groups with stronger polarity on the surface of the active carbon. And other small amount of groups in the blue algae can react with oxygen-containing functional groups (phenolic hydroxyl and alcoholic hydroxyl) on the surface of the activated carbon to form chemical bonds. Meanwhile, because the buckwheat hulls are soaked by phosphoric acid, the mesopore pore volume of the buckwheat hull biochar is greatly improved, and the adsorption effect of the active buckwheat hull biochar is improved.
Furthermore, most of the surfaces of the buckwheat hull biochar activated by phosphoric acid are acidic oxygen-containing groups (carboxyl, lactone and phenolic hydroxyl) which are electron-withdrawing groups, so that pi electrons existing in a graphite state on the surface of the activated carbon can be attracted, the surface of the activated carbon is positively charged, and the adsorption of substances with electronegativity is facilitated. And the carbonyl on the surface of the activated carbon can be used as an electron donor to provide electrons for the organic matter containing the benzene ring, so that the electron donor-electron acceptor mechanism is formed to enhance the adsorption effect. Therefore, the activated buckwheat hull biochar of the present application can effectively adsorb COD, and is mainly chemisorbed.
In some embodiments of the present application, a method of purifying a eutrophic water body comprises:
step 1, preparing activated buckwheat hull charcoal powder.
Heating the mixed solution of buckwheat hulls soaked in phosphoric acid to perform carbonization reaction to activate the buckwheat hulls, and then pulverizing the activated buckwheat hulls into powder.
Further, the mixed solution of the buckwheat hulls after being soaked in the phosphoric acid is prepared by soaking the buckwheat hulls in a phosphoric acid solution at room temperature and standing for 12-24 hours.
Exemplarily, the buckwheat hulls are immersed in a phosphoric acid solution at 25 ℃ and left for 15 h; or soaking testa Fagopyri Esculenti in phosphoric acid solution at 30 deg.C, and standing for 20 hr; or soaking testa Fagopyri Esculenti in phosphoric acid solution at 26 deg.C, and standing for 22 hr.
The buckwheat hulls are soaked in the phosphoric acid solution, so that the phosphoric acid solution can be diffused to the surfaces of the buckwheat hulls, and the buckwheat hulls adsorb the phosphoric acid solution, so that the phosphoric acid solution is fully attached to the surfaces of the buckwheat hulls, and active functional groups are generated on the surfaces of the buckwheat hulls in the subsequent carbonization and activation reaction. Meanwhile, the buckwheat hulls can form a microporous structure by fully soaking, and the mesopore volume of the buckwheat hulls is improved.
Further, the buckwheat hulls are also pre-treated prior to being immersed in the phosphoric acid solution.
Illustratively, a quantity of buckwheat hulls is weighed, washed with water to remove impurities such as ash, dried, and stored in a sealed condition for further use.
Further, the mass ratio of the buckwheat hulls to the phosphoric acid is 1: 1-1: 6.
Further optionally, the weight ratio of the buckwheat hulls to the phosphoric acid is 1: 3-1: 5. Further optionally, the weight ratio of the buckwheat hulls to the phosphoric acid is 1: 3-1: 4.
Illustratively, the buckwheat hulls and the phosphoric acid are weighed according to the mass ratio of 1:3, stirred uniformly and then placed at 25 ℃ for 12 hours.
Within the mass ratio range, the full adhesion of phosphoric acid on the surface of the buckwheat hulls can be effectively ensured, so that the subsequent carbonization reaction and the mesopore pore volume of the buckwheat hull biochar are ensured.
Further, the mesopore volume of the buckwheat hull biochar after phosphoric acid impregnation is 0.5-0.8 cc/g.
Further optionally, the mesopore volume of the buckwheat hull biochar after phosphoric acid impregnation is 0.55-0.75 cc/g.
Further optionally, the mesopore volume of the buckwheat hull biochar after phosphoric acid impregnation is 0.6-0.7 cc/g.
Illustratively, according to the mass ratio of 1:3, buckwheat hulls and phosphoric acid are weighed, stirred uniformly and then placed at 25 ℃ for 12 hours, and the prepared activated buckwheat hull biochar has a mesopore volume of 0.645 cc/g.
The mesopore volume of the activated buckwheat husk biochar is in the range, so that the adsorption effect on blue algae, chlorophyll a and COD (chemical oxygen demand) can be greatly improved, and especially the adsorption effect on the blue algae and the chlorophyll a is improved.
Furthermore, the activated buckwheat hull biochar has a rich porous structure, especially has a large proportion of mesopores in total pores and a large total number of mesopores, and can greatly improve the adsorption effect on blue algae and chlorophyll a.
Further, the temperature of the carbonization reaction is 300-800 ℃, and the reaction time is 50-150 min.
Further optionally, the temperature of the carbonization reaction is 400-600 ℃, and the reaction time is 70-110 min. Further optionally, the temperature of the carbonization reaction is 400-500 ℃, and the reaction time is 85-95 min.
Illustratively, the phosphoric acid-impregnated buckwheat hull mixture is heated at 500 deg.C for 90min for carbonization activation.
In the temperature and time range, the buckwheat hulls can be effectively carbonized, and dehydration catalytic reaction, aromatic condensation and oxidation reaction are carried out at high temperature, so that acidic oxygen-containing functional groups such as phenolic hydroxyl, carboxyl, lactone group and the like are formed on the surfaces of the buckwheat hull biochar, and the adsorption effect on blue algae, chlorophyll a and COD in the water body can be improved.
Further, the step of pulverizing the activated buckwheat hull biochar into powder comprises:
and (3) crushing and sieving the activated buckwheat hull charcoal powder, and taking the powder with the diameter of 38-74 mu m.
After carbonization, crushing and sieving the activated buckwheat shell charcoal powder, and taking the powder with the diameter of 38-74 mu m to obtain the buckwheat shell-based charcoal. The method can simultaneously adsorb and remove blue algae, chlorophyll a and COD in the water body, and improve the removal efficiency.
Further optionally, pulverizing and sieving the activated buckwheat husk charcoal powder, and taking the powder with the diameter of 39-73 μm. Further optionally, the activated buckwheat husk charcoal powder is crushed and sieved, and the powder with the diameter of 40-72 μm is taken. Further optionally, the activated buckwheat husk charcoal powder is crushed and sieved, and the powder with the diameter of 41-70 μm is taken.
Further, the step of pulverizing the activated buckwheat hull biochar into powder comprises: pulverizing activated buckwheat husk biochar into powder, and washing until the pH value of the solution is neutral.
Further optionally, the rinsing is with deionized water.
By washing the activated buckwheat hull charcoal powder until the surface is neutral, residual substances on the surface can be removed, and the effect of removing blue algae, chlorophyll a and COD in the water body is improved.
Further, the washed activated buckwheat hull charcoal powder is dried.
Further optionally, the drying temperature is 100-110 ℃; the drying time is 10-15 h.
The effect of removing blue algae, chlorophyll a and COD in the water body can be further improved by drying the activated buckwheat hull charcoal powder.
And 2, removing blue algae, chlorophyll a and COD in the water body by adopting the mixing reaction of powdered activated buckwheat hull biochar and the eutrophic water body.
The powdery activated buckwheat husk biochar can simultaneously adsorb blue algae, chlorophyll a and COD in the eutrophic water body.
The acidic oxygen-containing functional group of the activated buckwheat husk biochar can adsorb amino in blue algae and chlorophyll a and carry out chemical reaction to form a chemical bond. The activated buckwheat hull charcoal has rich pore structure and extremely many mesopores, and can improve the adsorption effect in a synergistic manner. The acidic oxygen-containing functional group of the activated buckwheat husk biochar can also adsorb electronegative substances in COD, so that blue algae, chlorophyll a and COD in eutrophic water body are adsorbed simultaneously, and the adsorption efficiency is greatly improved.
Furthermore, the removal effect of the activated buckwheat husk biochar on chlorophyll a can reach 88.64%;
further, the removal effect of the activated buckwheat hull biochar on blue algae can reach 80.18%;
further, the removal effect of the activated buckwheat hull biochar on COD can reach 99.4%.
Some embodiments of the present application further provide a method for preparing activated buckwheat hull biochar capable of purifying eutrophic water, in which a mixed solution of buckwheat hulls impregnated with phosphoric acid is heated to perform a carbonization reaction, so that the buckwheat hulls are activated, and then the activated buckwheat hull biochar is pulverized into powder.
The method has simple preparation steps, and does not need to adjust pH value and water content when soaking buckwheat hulls with phosphoric acid. The method selects buckwheat hulls as raw materials of biomass charcoal, and has low cost and high economical efficiency. The activated buckwheat hull biochar prepared by the method can simultaneously adsorb and remove blue algae, chlorophyll a and COD in the eutrophic water body. High removing efficiency and good removing effect.
Some embodiments of the present application also provide an activated buckwheat hull biochar capable of purifying eutrophic water, the activated buckwheat hull biochar being made of buckwheat hulls.
Optionally, the removal effect of activated buckwheat husk biochar on chlorophyll a can reach 88.64%;
the removal effect of the activated buckwheat hull biochar on blue algae can reach 80.18 percent;
the removal effect of the activated buckwheat husk biochar on COD can reach 99.4%.
The activated buckwheat hull charcoal can simultaneously adsorb and remove blue algae, chlorophyll a and COD in eutrophic water body. High removing efficiency and good removing effect.
The features and properties of the present application will be described in detail below with reference to examples and comparative examples.
Example 1
Provides an active buckwheat husk biochar which is prepared by the following steps:
weighing a certain amount of buckwheat hulls, washing with water to remove impurities such as ash, drying, and sealing for storage. Then, weighing buckwheat hulls and an activator phosphoric acid according to a mass ratio mBuckwheat husk/mActivating agentIs put in a beaker at the ratio of 1:3, stirred evenly and placed for 12 hours at normal temperature to prepare the active buckwheat hull biochar. The active buckwheat hull charcoal has rich pore structure, large number of mesopores, and mesopore volume of 0.645 cc/g. Then the dipped mixed liquid is put into a crucible and put into a muffle furnace, the required carbonization and activation temperature is set to be 500 ℃, and the activation time is set to be 90min for carbonization and activation. And finally, taking out the prepared activated buckwheat hull biochar, grinding by using a grinder, and screening out a finished product of 38-74 micrometers. And finally, repeatedly washing the activated buckwheat hull biochar between 38 and 74 microns by using deionized water until the pH value of the solution is neutral. And (4) putting the washed sample into a drying box, drying at 105 ℃ for 12h, and taking out for later use.
Examples 2 to 6
Essentially the same procedure as in example 1, except that: the buckwheat hulls and the activator are in different mass ratios. Examples 2 to 5 wherein mBuckwheat husk/mActivating agent1:1, 1:2, 1:4, 1:5 and 1:6 in sequence.
Examples 7 to 11
The procedure was substantially the same as in example 1 except that: the activation times were different. The activation times in examples 7 to 11 were 50min, 70min, 110min, 130min, and 150min in this order.
Examples 12 to 13
The procedure was substantially the same as in example 1 except that: the activation temperature was different. In examples 12 to 13, the activation temperatures were 600 ℃ and 800 ℃.
Comparative examples 1 to 2
The procedure of example 1 was followed except that the type of activator was different and the activation temperature was different. In comparative examples 1-2, the activating agents were zinc chloride and potassium hydroxide in this order.
The activation temperature was 600 ℃.
Experimental example 1
Iodine adsorption experiments were performed using the activated buckwheat hull biochar prepared in examples 1 to 13 and comparative examples 1 to 2, and the adsorption effect was examined.
The experimental steps include: a sample is put into a conical flask with a plug and a ground opening, the sample is weighed to 0.5000g (accurately to 0.0001g) after being dried at 150 ℃, the sample is put into the conical flask with the dry 250mL ground opening, 10.0mL of hydrochloric acid (5 wt%) is accurately added to fully wet the sample, the conical flask is put on an electric furnace to be heated to boil and slightly boiled (30 +/-2 s), and after the conical flask is cooled to room temperature, 50.0mL of calibrated iodine standard solution is added. Immediately stopper the bottle, shake for 15min, filter quickly into a dry beaker. 10mL of the filtrate was pipetted into a 250mL wide-mouth flask containing 100mL of distilled water, titrated with a calibrated sodium thiosulfate standard solution, and when the solution was pale yellow, 2mL of a starch indicator was added, the solution was further assayed to become colorless, and the volume of sodium thiosulfate used was recorded. The above samples were subjected to parallel experiments and averaged.
The iodine adsorption value can indirectly represent the adsorption efficiency of the activated buckwheat hull biochar, the larger the iodine adsorption value is, the larger the pore volume and the specific surface area of the biochar are, and when the pore volume and the specific surface area are larger, the more adsorption sites are on the surface of the biochar, so that the higher the efficiency of removing blue algae, chlorophyll a and COD in the eutrophic water body by the biochar adsorption is.
The results are shown in Table 1:
TABLE 1 iodine adsorption Experimental results
| Activator type | mBuckwheat husk/mActivating agent | Activation temperature | Time of activation | Iodine adsorption number | |
| Example 1 | Phosphoric acid | 1:3 | 500℃ | 90min | 737.1mg/g |
| Example 2 | Phosphoric acid | 1:1 | 500℃ | 90min | 477.3mg/g |
| Example 3 | Phosphoric acid | 1:2 | 500℃ | 90min | 482.2mg/g |
| Example 4 | Phosphoric acid | 1:4 | 500℃ | 90min | 622.2mg/g |
| Example 5 | Phosphoric acid | 1:5 | 500℃ | 90min | 563.9mg/g |
| Example 6 | Phosphoric acid | 1:6 | 500℃ | 90min | 490.9mg/g |
| Example 7 | Phosphoric acid | 1:3 | 500℃ | 50min | 378mg/g |
| Example 8 | Phosphoric acid | 1:3 | 500℃ | 70min | 426mg/g |
| Example 9 | Phosphoric acid | 1:3 | 500℃ | 110min | 638mg/g |
| Example 10 | Phosphoric acid | 1:3 | 500℃ | 130min | 581mg/g |
| Example 11 | Phosphoric acid | 1:3 | 500℃ | 150min | 530mg/g |
| Example 12 | Phosphoric acid | 1:3 | 600℃ | 90min | 606mg/g |
| Example 13 | Phosphoric acid | 1:3 | 800℃ | 90min | 359mg/g |
| Comparative example 1 | Zinc chloride | 1:3 | 600℃ | 90min | 577mg/g |
| Comparative example 2 | Potassium hydroxide | 1:3 | 600℃ | 90min | 426mg/g |
(1) The effect of different types of activators on the adsorption effect was investigated.
From the above results, it can be seen that when the activation temperature is 600 ℃, the activation time is 90min, and the buckwheat hull to activator mass ratio is 1:3, the iodine adsorption value of the activated buckwheat hull biochar prepared using phosphoric acid as the activator is the highest (606mg/g) (example 12), followed by zinc chloride activated carbon (577mg/g) (comparative example 1), and the iodine adsorption value of the potassium hydroxide activated carbon is the lowest (426mg/g) (comparative example 2). The result shows that in the process of activating the buckwheat hull biochar by using phosphoric acid as an activating agent, because dehydration catalytic reaction, aromatic condensation and oxidation reaction are carried out at high temperature, the activated buckwheat hull biochar which is porous, large in specific surface area and high in adsorption performance is generated, and the content of oxygen-containing functional groups on the surface of the activated buckwheat hull biochar is increased, so that the adsorption capacity of the activated buckwheat hull biochar is improved. Experiments show that the buckwheat hull biochar prepared by using phosphoric acid as an activating agent has the best adsorption effect.
(2) The influence of the activation temperature on the adsorption effect was examined.
From the above results, it can be seen that when the activation time is 90min, the buckwheat hull/activator mass ratio is 1:3, and phosphoric acid is used as the activator, the iodine adsorption value of the buckwheat hull charcoal tends to increase first and then decrease as the activation temperature increases from 300 ℃ to 800 ℃. The buckwheat hull biochar has the highest iodine adsorption value (737mg/g) at an activation temperature of 500 ℃ (example 1), followed by buckwheat hull biochar having an activation temperature of 600 ℃ (606mg/g) (example 12), with the lowest iodine adsorption value (359mg/g) at an activation temperature of 800 ℃ (example 13). The result is mainly because the gas generated at high temperature can open, expand and create new holes, thereby improving the pore structure, but simultaneously because of H3PO4The addition of the active buckwheat husk biochar can obviously reduce the carbonization temperature of the active buckwheat husk biochar, so that the active buckwheat husk biochar with a developed pore structure can be prepared at a lower temperature (400-500 ℃), and the adsorption effect is optimal. The activation temperature is 400-600 ℃ and the adsorption effect is good.
(3) The influence of the activation time on the adsorption effect was examined.
From the above results, it can be seen that the buckwheat hull biochar prepared using phosphoric acid as an activator has the highest iodine adsorption value (737mg/g) at 90min (example 1), followed by 110min (638mg/g) (example 9), and followed by 130min (581mg/g) (example 10) when the activation temperature is 500 ℃ and the buckwheat hull to activator mass ratio is 1: 3; 150min of activated carbon prepared (530mg/g) (example 11); activated carbon prepared for 70min (426mg/g) (example 8); the iodine adsorption value of activated carbon at 50min was the lowest (378mg/g) (example 7). This is mainly due to the incomplete activation of buckwheat hulls when the time is below 90 min; and when the time exceeds 90min, the high temperature causes the surface functional groups to be destroyed and the adsorption efficiency to be reduced. When the activation time is more than 70min and less than or equal to 110min, the adsorption effect is better. The activation time is 90min, and the adsorption effect is optimal.
(4) The influence of the quality ratio of the buckwheat hulls and the activating agent on the adsorption effect is examined.
According to the results, phosphoric acid is used as an activating agent, the activating time is 90min, the activating temperature is 500 ℃, and the mass ratio of the buckwheat hulls to the activating agent is 1: 1-1: the iodine adsorption value at 6 was 477.3mg/g (example 2), 482.2mg/g (example 3), 737.1mg/g (example 1), 622.2mg/g (example 4), 563.9mg/g (example 5), 490.9mg/g (example 5). The weight ratio of the buckwheat hulls to the activating agent is 1: when the ratio is 3-1: 5, the adsorption effect is good.
Experimental example 2
The activated buckwheat hull biochar prepared in the above examples 1-13 is used for purifying eutrophic water.
The steps for purifying the eutrophic water body comprise:
and (3) inspecting the removal effect of the pollutants in the artificial lake by adopting a static adsorption method. Firstly, 0.01g, 0.02g, 0.05g, 0.1g and 0.2g of activated buckwheat hull biochar are weighed and put into a 50mL conical flask filled with two artificial lake water samples to be sealed, then the conical flask is placed in a constant-temperature oscillation box to oscillate for 24 hours at 25 ℃, mixed liquid is taken out and filtered by a 0.45-micrometer mixed fiber filter membrane, and finally the concentration of pollutants such as blue algae, COD and the like in the filtered water sample is measured. Each group of static experiments are provided with parallel experiments, and the error can be controlled within the range of 3-5%.
The experimental results are as follows: the activated buckwheat hull biochar prepared in the embodiments 1-13 can adsorb and remove blue algae, chlorophyll a and COD in the eutrophic water body. Among them, the removal effect of example 1 was the highest, and the removal rate of chlorophyll a was 88.64%; the blue algae removal rate is 80.18 percent; the COD removal rate is 99.4%.
According to the experimental results, the activated buckwheat hull biochar provided by the embodiment of the application can simultaneously adsorb and remove blue algae, chlorophyll a and COD in the eutrophic water body, and has high removal efficiency.
Experimental example 3
(1) The activated buckwheat hull biochar prepared in examples 1 to 13 was subjected to elemental analysis using an elemental analyzer (variao MACRO CHNS). The results are shown in Table 2:
TABLE 2 elemental analysis results of activated buckwheat husk biochar
As can be seen from table 2, the carbon content (60.500%), the oxygen content (35.247%), and the nitrogen content (1.119%) of the buckwheat hull biochar after phosphoric acid activation. It is presumed that the activated buckwheat hull biochar has a large number of oxygen-containing functional groups. The result is mainly related to the activation mode of the activated carbon, and the activated buckwheat hull biochar is mainly subjected to dehydration activation by a phosphoric acid method, so that the pore volume and the oxygen-containing functional group content of the activated carbon surface can be increased after activation.
(2) Oxygen-containing functional groups of the activated buckwheat hull biochar prepared in examples 1-13 were detected by means of Bohm titration. The results are shown in Table 3:
TABLE 3 oxygen-containing functional groups of activated buckwheat hull biochar
As can be seen from Table 3, the content of acidic functional groups (phenolic hydroxyl group, carboxyl group and lactone group) of the activated buckwheat hull biochar was 0.633 mmol.g-1Wherein the content of phenolic hydroxyl group is 0.351 mmol/g-1The carboxyl group content is 0.062 mmol.g-1The lactone group content is 0.220 mmol.g-1(ii) a The content of alkaline functional group in activated buckwheat husk charcoal is 0.336 mmol/g-1。
(3) The surface morphology of the activated buckwheat hulls biochar of examples 1-13 was observed and analyzed by imaging with a scanning electron microscope (MERLIN VP Compact). The result is shown in the attached figure 1 of the specification. Wherein, in fig. 1: (a) buckwheat hulls (2000 x magnification); (b) activated buckwheat hull biochar (2000 times magnification); (c) buckwheat hulls (10000 times magnified); (d) activated buckwheat husk biochar (10000 times magnification).
In order to study the apparent morphology characteristics of the activated buckwheat husk biochar, two groups of scanning electron microscope analyses were performed on the buckwheat husk and the buckwheat husk-based biochar, with the magnification of 2000 times and 10000 times in sequence. As can be seen from fig. 1, the surface of the buckwheat hull raw material exhibits a zigzag fiber structure without a pore structure [ fig. 1 (a), fig. 1 (c) ]; the modified activated buckwheat hull-based biochar has a flat surface and a certain amount of pore channels and pore structures, as shown in fig. 1 (b) and fig. 1 (d). This is mainly due to the rich pore structure of buckwheat hulls produced by high temperature activation of phosphoric acid, which provides a large specific surface area and thus provides more adsorption sites for subsequent adsorption.
Thus, the activated buckwheat husk biochar prepared by the method is proved to have high oxygen content and the acidic oxygen-containing functional groups on the surface mainly comprise phenolic hydroxyl, carboxyl and lactone groups; certain pore structures appear on the surface of the activated buckwheat husk biochar, so that the specific surface area is increased, and more adsorption sites are generated.
Experimental example 4
The specific surface area and pore volume and pore diameter of the activated buckwheat hull biochar prepared in examples 1 to 13 were measured.
The BET specific surface area and pore volume and pore size of the activated buckwheat hull biochar were measured using an Autosorb-iQ instrument (Quantachrome, USA). The measurement range of the porous material is that the porosity is 0.35 nm-500 nm, and the specific surface area is more than 0.0005m2(ii)/g; the micro-porous material has accurate micro-porous analysis capability, and the ultimate high vacuum can reach 10-10 mmHg; the pressure can reach 2.5 multiplied by 10- 7mmHg. Nitrogen is used as adsorbate, helium or hydrogen is used as carrier gas, and the two gases are mixed according to a certain proportion. When the sample tube is put into liquid nitrogen for heat preservation, the sample physically adsorbs nitrogen in the mixed gas, the carrier gas is not adsorbed, and an adsorption peak appears on the screen. When the liquid nitrogen was taken away, the sample tube was again at room temperature and a desorption peak appeared on the screen. By changing the mixing ratio of nitrogen gas and carrier gas, the adsorption amount at relative pressures of several nitrogen gases can be measured, and the specific surface area can be calculated according to the BET formula.
The experimental results are as follows:
the activated buckwheat hull biochar prepared in examples 1-13 all had abundant pore structures, wherein the pore structure of example 1 was the most abundant, the total pore volume was 0.666cc/g, the mesopore volume was 0.645cc/g, and the specific surface area was 785.293(m2/g)。
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (16)
1. A method for purifying a eutrophic water body, comprising:
heating the mixed solution of the buckwheat hulls soaked by the phosphoric acid to perform a carbonization reaction, activating the buckwheat hulls to obtain activated buckwheat hull biochar, and then crushing the activated buckwheat hull biochar into powder;
mixing powdered activated buckwheat hull biochar with eutrophic water;
the removal effect of the activated buckwheat hull biochar on chlorophyll a can reach 88.64%;
the removal effect of the activated buckwheat hull biochar on blue algae can reach 80.18%;
the removal effect of the activated buckwheat hull biochar on COD can reach 99.4%.
2. The method for purifying an eutrophic water body according to claim 1,
the temperature of the carbonization reaction is 300-800 ℃.
3. The method for purifying an eutrophic water body according to claim 2,
the temperature of the carbonization reaction is 400-600 ℃.
4. The method for purifying an eutrophic water body according to claim 2,
the temperature of the carbonization reaction is 400-500 ℃.
5. The method for purifying the eutrophic water body according to claim 1, wherein the carbonization reaction time is 50-150 min.
6. The method for purifying an eutrophic water body according to claim 5,
the carbonization reaction time is 70-110 min.
7. The method for purifying an eutrophic water body according to claim 5,
the carbonization reaction time is 90 min.
8. The method for purifying a eutrophic water body according to claim 1 or 2,
the weight ratio of the buckwheat hulls to the phosphoric acid is 1: 1-1: 6.
9. The method for purifying an eutrophic water body according to claim 8,
the weight ratio of the buckwheat hulls to the phosphoric acid is 1: 3-1: 5.
10. The method for purifying an eutrophic water body according to claim 3,
the mixed solution of the buckwheat hulls after being soaked in the phosphoric acid is prepared by soaking the buckwheat hulls in a phosphoric acid solution at room temperature and standing for 12-24 hours.
11. The method for purifying an eutrophic water body according to claim 4,
the mesopore volume of the buckwheat hulls after phosphoric acid impregnation is 0.5-0.8 cc/g.
12. The method for purifying an eutrophic water body according to claim 1,
the step of pulverizing the activated buckwheat hull biochar into powder comprises the following steps:
and (3) crushing and sieving the activated buckwheat hull charcoal powder, and taking the powder with the diameter of 38-74 mu m.
13. The method for purifying an eutrophic water body according to claim 1,
the step of pulverizing the activated buckwheat hull biochar into powder comprises the following steps:
pulverizing activated buckwheat husk biochar into powder, and washing until the pH value of the solution is neutral.
14. A method for the purification of an eutrophic water body according to claim 13, where the rinsing is performed with deionized water.
15. The method for purifying an eutrophic water body according to claim 13,
drying the washed activated buckwheat hull charcoal powder.
16. The method for purifying an eutrophic water body according to claim 15, wherein,
drying at 100-110 ℃; the drying time is 10-15 h.
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| CN110015745A (en) * | 2019-04-28 | 2019-07-16 | 哈尔滨工业大学 | A method of removal water pollutant is acted on using charcoal enhanced oxidation agent |
| CN110339812A (en) * | 2019-07-09 | 2019-10-18 | 四川大学 | Modification biological charcoal and its application in absorption VOCs |
| CN110681350A (en) * | 2019-09-19 | 2020-01-14 | 天津大学 | Preparation method of phosphoric acid modified enteromorpha biological carbon and application of phosphoric acid modified enteromorpha biological carbon in removal of heavy metal cadmium |
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| CN104923153A (en) * | 2015-05-07 | 2015-09-23 | 浙江大学 | Preparation method for Canna biological carbon capable of simultaneously adsorbing ammonia nitrogen and cadmium |
| CN110015745A (en) * | 2019-04-28 | 2019-07-16 | 哈尔滨工业大学 | A method of removal water pollutant is acted on using charcoal enhanced oxidation agent |
| CN110339812A (en) * | 2019-07-09 | 2019-10-18 | 四川大学 | Modification biological charcoal and its application in absorption VOCs |
| CN110681350A (en) * | 2019-09-19 | 2020-01-14 | 天津大学 | Preparation method of phosphoric acid modified enteromorpha biological carbon and application of phosphoric acid modified enteromorpha biological carbon in removal of heavy metal cadmium |
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