CN113842881B

CN113842881B - Oyster shell powder enhanced biochar for removing seawater culture water body micro-plastics and preparation method and application thereof

Info

Publication number: CN113842881B
Application number: CN202111144011.3A
Authority: CN
Inventors: 陈斌
Original assignee: Xiamen University Tan Kah Kee College
Current assignee: Xiamen University Tan Kah Kee College
Priority date: 2021-09-28
Filing date: 2021-09-28
Publication date: 2023-09-05
Anticipated expiration: 2041-09-28
Also published as: CN113842881A

Abstract

The invention relates to a preparation method of oyster shell powder enhanced biochar for removing seawater culture water body microplastic, which comprises the following steps: pulverizing biomass material to obtain a pulverized raw material having a particle size in the range of 10 mesh to 50 mesh; placing the crushed raw materials into an alkaline ferric salt aqueous solution for hydrothermal reaction; freezing the crushed raw material obtained after the hydrothermal reaction by liquid nitrogen, and sequentially vacuum freeze-drying at-40 ℃ to-65 ℃ and-10 ℃ to-25 ℃; placing the freeze-dried crushed raw materials into a processor which is insulated from oxygen, is filled with protective gas and is sealed, and performing high-temperature treatment in at least three stages, wherein the high-temperature treatment in the first stage is 680-720 ℃, the high-temperature treatment in the second stage is 400-420 ℃, and the high-temperature treatment in the third stage is 580-640 ℃; ball milling is carried out on the prepared biochar, and calcined oyster shell powder is added in the ball milling process to be mixed to form the enhanced biochar. The enhanced biochar provided by the invention can be well applied to the removal of micro plastics and heavy metals in water body cultivation.

Description

Oyster shell powder enhanced biochar for removing seawater culture water body micro-plastics and preparation method and application thereof

Technical Field

The invention relates to the technical field of biological environmental protection, in particular to oyster shell powder enhanced biochar for removing seawater culture water body microplastic, and a preparation method and application thereof.

Background

The Biochar (English: biochar) is formed by pyrolysis and carbonization of biomass in a complete or partial anoxic state, has high carbon content, rich pore structure and strong adsorption capacity, has a highly aromatic structure, developed pore structure and rich carbon content, can help plant growth, can be applied to agricultural application and carbon collection and storage, purifies water quality, and is favorable for reducing the use of chemical fertilizers, and is different from the traditional charcoal which is generally used for fuels.

The traditional method for preparing the biochar is to stack biomass, cover thin-layer soil, ignite smoke at a sealing position or heat the biomass in a kiln mode, so that the biomass is burnt and cracked in an anoxic environment to form the biochar, but the method has the defects of poor production conditions, long period, serious environmental pollution and the like, so more and more students are devoted to researching the biochar preparation method with higher feasibility, and the application is thermal cracking.

According to different pyrolysis technologies, the current preparation methods of the biochar can be divided into carbonization technology, liquefaction technology, gasification technology, microwave pyrolysis technology and the like, and along with the continuous development and perfection of a biomass preparation biochar technology system, the application of the biochar in various fields is more mature, and more waste biomass can be effectively utilized.

Especially in the current increasingly scarce water resources, the comprehensive treatment of polluted water bodies and the attention of water environment restoration are increased year by year; wherein, due to overuse of nitrogenous fertilizer in agricultural production and random discharge of sewage in daily life and industrial production, the pollution of micro plastics, foam plastics, heavy metals, persistent organic pollution, antibiotics and the like in groundwater and surface water bodies is increasingly serious, and serious harm is caused to natural environment and organisms.

Disclosure of Invention

Aiming at the problems existing in the prior art, the invention provides a preparation method of oyster shell powder enhanced biochar for removing micro-plastics in a seawater culture water body, which comprises the following steps:

pulverizing biomass material to obtain a pulverized raw material having a particle size in the range of 10 mesh to 50 mesh;

placing the crushed raw materials into an alkaline ferric salt aqueous solution for hydrothermal reaction;

freezing the crushed raw material obtained after the hydrothermal reaction by liquid nitrogen, and sequentially vacuum freeze-drying at-40 ℃ to-65 ℃ and-10 ℃ to-25 ℃;

placing the crushed raw materials after freeze drying into a processor which is insulated and is sealed by protective gas, and performing high-temperature treatment of at least three stages, wherein the high-temperature treatment of the first stage is to quickly raise the temperature from the freeze drying temperature to 680-720 ℃, the high-temperature treatment of the second stage is to lower the temperature from the final temperature of the first stage to 400-420 ℃, and the high-temperature treatment of the third stage is to raise the temperature from the final temperature of the second stage to 580-640 ℃ at a speed of 30-45 ℃/min to obtain biochar;

Ball milling is carried out on the prepared biological carbon, and calcined oyster shell powder is added in the ball milling process to be mixed to form the oyster shell powder reinforced biological carbon for removing the micro plastics in the seawater culture water body.

In some embodiments, the weight ratio of the biomass material to the ferric salt added in the ferric salt aqueous solution is (4-8): (0.5-1).

In some embodiments, the hydrothermal reaction comprises at least two stages, the first stage is to mix the crushed raw material with the ferric salt aqueous solution at 45-55 ℃ and sufficiently stir for 0.5-2 h, and the second stage is to raise the final temperature of the first stage to 60-65 ℃ under a reaction pressure of 1-1.5 MPa, and react for 12-24 h.

In some embodiments, the iron salt comprises ferric nitrate, ferric sulfate, and ferric chloride;

wherein the weight ratio of the ferric nitrate to the ferric sulfate to the ferric chloride is (1-2): 1-3): 0.5-1.

In some embodiments, the method of making further comprises: and performing ultraviolet modification on the oyster shell powder reinforced biochar subjected to ball milling and removed of the seawater culture water body microplastic.

In some embodiments, the freeze-drying comprises a first stage at-40 ℃ to-65 ℃ and a second stage at-10 ℃ to-25 ℃, and the liquid cooled frozen product is placed in a time ratio of (1-2) between the first stage and the second stage, respectively: (2-4).

The invention provides oyster shell powder enhanced biochar for removing marine culture water body microplastic, which is prepared by the preparation method of oyster shell powder enhanced biochar for removing marine culture water body microplastic.

The invention provides an application of oyster shell powder enhanced biochar for removing seawater culture water microplastic in culture water purification.

Based on the above, compared with the prior art, the oyster shell powder enhanced biochar for removing the microplastic in the seawater culture water body has high aperture and high specific surface area, and can be well applied to removing the microplastic and heavy metal in the water body culture. In the using process, through the combination of calcined oyster shell powder biochar, the calcined oyster shell powder reacts with water to form local heat release, so that water molecules more fully circularly flow into the gaps of the oyster shell powder reinforced biochar for removing the seawater culture water body micro-plastics, and the purifying effect is better.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments; the technical features designed in the different embodiments of the invention described below can be combined with each other as long as they do not conflict with each other; all other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs and are not to be construed as limiting the present invention; it will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The respective steps of the charcoal preparation method of the present application will be explained in more detail below.

It should be understood that regardless of the manner in which the individual product amounts are present herein, they should be interpreted as precisely referring to the last two decimal places. Thus, 50 wt% means 50.00 wt%, and similarly, 0.3 wt% means 0.30 wt%.

For the purposes of the present application, the term "biochar" shall be given its broadest possible meaning and shall include any solid material obtained from pyrolysis, hydrothermal carbonization, gasification or any other thermal and/or chemical conversion of biomass, wherein the biochar comprises at least 55 wt% carbon. Pyrolysis is generally defined as the thermochemical decomposition of organic materials at high temperatures in the absence of oxygen or with a reduced oxygen content.

As used herein, unless otherwise indicated, room temperature is 25 ℃. Standard temperatures and pressures were 25 ℃ and 1 atmosphere. Unless otherwise indicated, in general, the term "about" is intended to include a variance or range of ±10%, experimental or instrumental errors associated with obtaining the values, and preferably includes the larger of these.

The application provides a preparation method of oyster shell powder enhanced biochar for removing seawater culture water body microplastic, which comprises the following steps:

Step one: the biomass material is pulverized to obtain a pulverized raw material having a particle size in the range of 10 mesh to 50 mesh.

Biochar can be prepared from essentially any carbon source, for example, from hydrocarbons (e.g., petroleum-based materials, coal, lignite, peat) and from biomass materials (e.g., wood, hardwood, softwood, waste paper, coconut shell, manure, chaff, food waste, etc.). Combinations and variations of these starting materials, as well as various and different members of each group of starting materials, may be and are used. Thus, a large number of very different starting materials results in biochar with different properties.

However, in order to make the effect of the present application more remarkable, the raw material for preparing biochar used in the present application is preferably limited to biomass materials such as wood, hardwood, cork, waste paper, coconut husk, manure, chaff, food waste, etc., and furthermore, a large amount of waste fruit wood in the local area can be utilized to realize pollution control with waste.

For such a pulverization treatment of biomass material, in order to make the effect of the present application more remarkable, it is considered to control the particle size range of the biomass material to be used to a size of 10 to 50 mesh, or 10 to 40 mesh, or 10 to 30 mesh, or 10 to 20 mesh, or more in smaller mesh number. It will be appreciated that control of the above particle size ranges is not necessary, but merely to enable better selection of the properties of the subsequent material preparation, and that the desired particle size and particle size distribution will vary depending on the intended effect to be achieved in the preparation step. In the present application, in view of the fact that it is difficult for the particle size of a general biomass material to meet the above conditions, it is preferable that the biomass material is pulverized to obtain a pulverized raw material when the particle size of the biomass material does not meet the above conditions. The pulverizing method of the biomass material is not particularly limited, and may be any pulverizing method known to those skilled in the art.

Step two: the powder is prepared by placing the crushed raw materials into alkaline ferric salt aqueous solution for hydrothermal reaction.

Taking biomass materials as an example, the biomass materials generally contain natural pore structures, and crushed raw materials obtained after crushing are fully immersed in an aqueous solution, so that the pore structures of the biomass materials are filled with the aqueous solution.

However, the pore size of the pore structure of the biomass material is generally relatively small, for this purpose, as a preferred scheme, the ferric salt aqueous solution contains one or more iron-containing soluble salts, such as ferric nitrate, ferrous nitrate, ferric sulfate, ferrous sulfate, ferric chloride or ferrous chloride, etc., the biomass material and the ferric salt aqueous solution are subjected to low-temperature mixed permeation at 45-55 ℃, and slow reaming is realized through the slow transpiration of the aqueous solution at the temperature;

alternatively, the reaction pressure may be controlled at 1 to 1.5MPa, preferably 1.1 to 1.3MPa, while the above-mentioned slow transpiration is carried out, and the alkali solution is dropwise added to the solution so as to be alkaline, for example, sodium hydroxide solution (5 mol/L); in order to make reaming more obvious and make biomass material and ferric salt solution fully mixed, micro-nano bubbles can be introduced in the whole process of the hydrothermal reaction to carry out low-temperature mixed permeation so as to increase hydrothermal uniformity, and then hydrothermal reaction is carried out at 60-65 ℃ for 12-24 hours, and based on the method provided by the embodiment of the invention, iron ions can be effectively and uniformly dispersed on the surface of the biomass material with a porous structure, thereby improving the utilization rate of the iron ions and simultaneously reducing the manufacturing cost;

Optionally, slow transpiration is preferably continued for a period of time, for example, for 0.5-2 hours, or 0.5-1 hour, etc., so that the pore size is stabilized, and then hydrothermal reaction is performed, which is beneficial to the densification of the pore structure under freezing in the subsequent step.

Alternatively, in a preferred version of this step, the weight ratio of the biomass material to the addition of the iron-containing soluble salt may be (4-8): (0.5-1), according to the method provided by the embodiment of the invention, the addition of a smaller amount of the iron-containing soluble salt can be realized, so that the recycling of the purified biochar material can be satisfied, and the manufacturing cost is further reduced.

Optionally, in a preferred scheme of the step, in order to further expand the pore structure, the iron-containing soluble salt may be combined with at least one other iron-containing soluble salt in addition to ferric chloride, and in the experimental process, it is found that, in addition to the foregoing technical effects, a combination of ferric nitrate, ferric sulfate and ferric chloride is adopted, which is beneficial to enhancing the magnetism of the finally prepared oyster shell powder for removing the micro plastics of the seawater culture water body, and in the case that the weight ratio of the ferric nitrate, the ferric sulfate and the ferric chloride is (1-2): 1-3): 0.5-1, the magnetic level is most obvious when the weight ratio of the same biomass material and the iron-containing soluble salt is added, and in the combined case, on one hand, the content of ferric ions is controlled sufficiently, and the reaming effect of the biomass material is also beneficial.

Step three: freezing the crushed raw material obtained after the hydrothermal reaction by liquid nitrogen, and sequentially vacuum freeze-drying at-40 ℃ to-65 ℃ and-10 ℃ to-20 ℃;

the biomass material filled with the aqueous solution in the pore structure is placed in an environment below 0 ℃, the aqueous solution is gradually changed from a liquid state to a solid state to be condensed into ice, so that the pore diameter enlarged in the previous step is further expanded under the action of expansion force, the specific surface area is increased, and the expanded pore structure is stabilized.

Specifically, under normal atmospheric pressure, the temperature of the low temperature environment can be 0 to-5 ℃, or-5 to-10 ℃, or-10 to-25 ℃, or-25 to-40 ℃, or-40 to-65 ℃, or-100 to-200 ℃; in consideration of the subsequent application to water body culture filtration, a low-temperature environment with gradually reduced temperature is preferably adopted, for example, after liquid nitrogen is rapidly frozen, the liquid nitrogen is sequentially placed in a low-temperature environment of minus 40 ℃ to minus 65 ℃ and minus 10 ℃ to minus 25 ℃ and below for freezing, so that a pore structure with more uniform dispersion and compact quality is obtained.

In some embodiments, the liquid nitrogen is frozen for a period of time ranging from 1 to 4 hours, and the total time of freeze drying is from 4 to 18 hours, preferably from 8 to 12 hours; in order to make the effect of the application more remarkable, in some embodiments provided by the application, after liquid nitrogen is rapidly frozen, the liquid nitrogen is respectively placed at-60 ℃ to-65 ℃ and at-10 ℃ to-15 ℃ in sequence, and the pore distribution of the front side and the rear side of the porous structure is more uniform and the consistency of the pore sizes is better; in other embodiments provided by the application, after liquid nitrogen is rapidly frozen, the liquid nitrogen is respectively placed at-40 ℃ to-45 ℃ and at-20 ℃ to-25 ℃ in sequence, and the pore size distribution of one side of the front side and the rear side of the porous structure is finer and more uniform, and the pore size of the other side is obviously different and slightly larger than that of the front side, so that the integral multi-level purification is realized. It will be appreciated that depending on the temperature selection, the products obtained at different pore sizes may be varied depending on the particular application in which the biochar is intended to be used. In other embodiments, the two stages involved in the freeze drying are a first stage at-40 ℃ to-65 ℃ and a second stage at-10 ℃ to-25 ℃, respectively, and the time ratio of the first stage to the second stage may be (1-2): (2-4).

In addition, in another embodiment provided by the invention, the crushed raw material obtained after the hydrothermal reaction is frozen by liquid nitrogen and then sequentially placed at-5 ℃ to-10 ℃ and at-60 ℃ to-65 ℃ for vacuum freeze drying, and the integral pore size is larger, and the internal combination of the structure is more loose, so that the porosity is improved. Step four: placing the crushed raw materials after freeze drying into a processor which is insulated and is sealed by protective gas, and performing high-temperature treatment of at least three stages, wherein the high-temperature treatment of the first stage is to quickly raise the temperature from the freeze drying temperature to 680-720 ℃, the high-temperature treatment of the second stage is to lower the temperature from the final temperature of the first stage to 400-420 ℃, and the high-temperature treatment of the third stage is to raise the temperature from the final temperature of the second stage to 580-640 ℃ at a speed of 15-30 ℃/min.

Biochar is most commonly produced by pyrolysis of biomass materials; while many different pyrolysis or carbonization methods may be and are used to produce biochar. Typically, these methods involve heating the starting material under positive pressure, reduced pressure, vacuum, inert atmosphere, or flowing inert atmosphere through one or more heating cycles in which the temperature of the material typically reaches above about 250 ℃ and may be in the range of about 250 ℃ to about 900 ℃. For example, the external thermal pyrolysis method is an internal thermal pyrolysis method in which a high-temperature heat carrier is used as a heat source for heating, or a hybrid heating method in which an external thermal type and an internal thermal type are simultaneously used. Generally, the faster the heating rate, and the higher the final temperature, the lower the coke yield. Conversely, in general, the slower the heating rate or lower the final temperature, the higher the coke yield. Higher final temperatures also result in changing the properties of the coke due to changing the inorganic mineral composition, which in turn changes the properties of the coke.

Raw or untreated biochar is typically made by: biomass is subjected to a uniform or varying pyrolysis temperature (e.g., 250 ℃ to 550 ℃ to 750 ℃ or higher) in an anoxic environment for a predetermined period of time. The process may be run rapidly with high reactor temperatures and short residence times, slowly with lower reactor temperatures and longer residence times, or in between. For better results, the biomass used to obtain the coke may be freed of impurities such as bark, leaves and branches first, although this is not required.

Moreover, at present, hydrothermal carbonization technology is attracting more and more attention in realizing efficient conversion application of biomass resources due to economy and environmental friendliness. While the hydrothermal charcoal technology adopts water as a reaction solvent, biomass as a raw material, and synthesizes a carbon-rich solid product in a sealed pressure vessel at a temperature of less than 375 ℃ (usually 150-280 ℃). Because of the participation of subcritical water medium, the product obtained through hydrothermal carbonization treatment has a plurality of inherent advantages such as uniform size, regular morphology, good physical and chemical stability, and the surface is rich in a large amount of oxygen-containing functional groups.

Furthermore, by using biochar derived from different biomass materials (e.g., pine, oak, hickory, birch, and coconut shells from different regions), the biochar can be enhanced based on the initial properties of the biomass material and the preparation steps under the inventive concept to tailor the subtleties of the individual steps in the process and ultimately produce treated oyster shell meal depleted of marine body microplastics of the contemplated physical and chemical properties as claimed herein.

However, in order to make the effect of the present application more remarkable, in some embodiments of the present application, only pyrolysis is selected; namely, when the crushed raw material obtained after freeze drying is rapidly placed in a processor which is insulated from oxygen and is filled with protective gas and is sealed, and is respectively subjected to three stages of high-temperature treatment, the high-temperature treatment in the first stage is to rapidly raise the temperature from the freeze drying temperature to 680 ℃ to 720 ℃ and maintain for 0.5 to 2 hours, the rapid temperature raising speed can be 60 ℃ to 120 ℃/min, the crushed raw material subjected to the freeze treatment is maintained by rapidly raising the temperature and ensuring that the crushed raw material is not sufficiently recovered to a pore structure state at normal temperature at high temperature, and the high-temperature treatment in the second stage is to slowly lower the final temperature of the first stage to 400 ℃ to 420 ℃ and maintain for 1 to 4 hours, the cooling speed from the final temperature of the first stage to the second stage can be reduced under the condition of 5-20 ℃/min, and the high temperature environment of the first stage exists, so that compared with the conventional high temperature treatment at the temperature below 300 ℃ for the first stage, the temperature of the second stage used by the method avoids the influence on the porous density degree caused by excessive temperature change on one hand, and on the other hand, the high temperature treatment of the third stage is to maintain 1-4 h from the final temperature of the second stage to 580-640 ℃ at the speed of 30-45 ℃/min, the obtained biochar realizes high-temperature rapid charcoal formation and ensures that the adsorption effect of the biomass material after the biochar is formed is stronger, and particularly the adsorption effect on spherical microplastic is stronger.

And fifthly, ball milling the prepared biochar, and adding oyster shell powder in the ball milling process to mix to form the oyster shell powder reinforced biochar for removing the seawater culture water microplastic.

In the step, ball milling is carried out on the prepared biochar, the particles of the prepared biochar can reach the nanometer level under the action of mechanical force, the reduction of the particle size promotes the increase of the specific surface area, and meanwhile, the internal pore structure of the prepared biochar is more developed under the action of mechanical force.

In the ball milling process, calcined oyster shell powder is fully mixed with biochar by adding calcined oyster shell powder into the biochar, and when the ball milling process is used, the calcined oyster shell powder is used, the main component of the calcined oyster shell powder is calcium oxide (CaO), the calcined oyster shell powder is more alkaline and is easier to carry out precipitation reaction with heavy metals and the like in water, meanwhile, the surface of the calcined oyster shell powder is more than a lot of tiny gaps than the surface of the uncalcined oyster shell powder, after the ball milling process is carried out, the calcined oyster shell powder with smaller size is formed, after the calcined oyster shell powder is put into water, the calcined oyster shell powder is subjected to adsorption effect and is easier to react with the heavy metals to generate hydroxide precipitation, the formed local heat is released, nearby water is promoted to flow under the influence of temperature, so that the water body is more fully circulated to the oyster shell powder for reinforcing the biochar and the pores of the oyster shell powder for removing seawater culture water micro plastics, the multiple purification of the oyster shell powder is realized, and the combined evolution effect is better.

Specifically, the oyster shell powder may be pulverized and ground to a smaller particle size range, for example, 1 to 50 μm, or 1 to 25 μm, or 1 to 15 μm, or 1 to 5 μm, etc., before calcination; and then calcining for 3-8 hours in a calciner at 700-900 ℃ to obtain calcined oyster shell powder. Optionally, in the ball milling process, the mass ratio of the biochar to the calcined oyster shell powder is (5-10): (0.5-1).

Alternatively, the ball milling time may last from 8 to 16 hours.

Optionally, after ball milling is completed, the formed oyster shell powder enhanced biochar for removing the micro plastics in the marine culture water body is modified by ultraviolet light to induce the surface of the biochar to perform oxidation reaction, so that the number of functional groups such as carboxyl, hydroxyl and the like in the biochar is increased, and the adsorption capacity of metal particles in the water body is further increased; specifically, the illumination intensity of the ultraviolet light is 5-15 mW/cm ² ；

In order to make the effect of the application more outstanding, experiments show that the oyster shell powder enhanced biochar for removing the seawater culture water body microplastic prepared by the method has the advantages that after ball milling, the oyster shell powder enhanced biochar for removing the seawater culture water body microplastic formed by ball milling has larger specific surface area, ultraviolet light modification is carried out, besides the increase of the content of oxygen-containing functional groups, the pore structure of the oyster shell powder enhanced biochar for removing the seawater culture water body microplastic is further enhanced, and the comprehensive adsorption capacity in the water body is improved.

In general, biochar can have a very broad range of particle sizes and distributions, which are generally reflected in the sizes that occur in the input biomass. In addition, the biochar may be ground, sieved, strain treated (strained) or crushed after pyrolysis to further alter particle size. To address most basic water farming applications, it is desirable to use biochar particles having the following particle sizes: such as 50 mesh to 200 mesh, or 50 mesh to 150 mesh, or 50 mesh to 100 mesh. It should be understood that the desired particle size and particle size distribution may vary depending on the particular application for which the biochar is intended.

As used herein, unless otherwise indicated, the terms "porosity", "porous structure" and "porous morphology" and the like should be given their broadest possible meaning and shall include materials having open cells, closed cells and combinations of open and closed cells and shall also include large, medium and micro cells and combinations, variations and continuum of these morphologies. Unless otherwise indicated, the term "pore volume" is the total volume occupied by the pores in a particle or collection of particles; the term "inter-particle void volume" is the volume that exists between a collection of particles; the term "solid volume or volume of solid entity" is the volume occupied by the solid material and does not include any free volume that may be related to the pore or inter-particle void volume; and the term "bulk volume" is the apparent volume of the material that includes the volume of particles, the volume of inter-particle voids, and the volume of internal pores.

The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

Step 1: washing the waxberry branches with deionized water, drying at 105 ℃ to constant weight, and crushing to 10 meshes to obtain a crushed raw material;

step 2: placing the crushed raw material prepared in the step 1 into a reaction container containing an iron salt aqueous solution, introducing micro-nano bubbles into the reaction container, controlling the temperature in the reaction container to be 45 ℃ for 0.5h, controlling the reaction pressure to be 1.1MPa, and heating to 60 ℃ for reaction for 12h;

wherein the weight ratio of the biomass material to the iron-containing soluble salt is 8:0.5, wherein the iron-containing soluble salt comprises ferric nitrate, ferric sulfate and ferric chloride, and the weight ratio of the ferric nitrate to the ferric sulfate to the ferric chloride is 1:2:1;

step 3: rapidly transferring the product obtained by the final reaction in the step 2 into liquid nitrogen for freezing for 1h, and then performing freeze drying treatment, wherein the freeze drying treatment is respectively performed for 3h and 6h at minus 60 ℃ and minus 10 ℃ in sequence;

Step 4: placing the product obtained after the step three of freeze drying into an anaerobic environment, introducing protective gas into a sealed processor, and performing three-stage high-temperature treatment, wherein the first-stage high-temperature treatment is to quickly raise the temperature from the freeze drying temperature to 680 ℃ at a heating rate of 60 ℃/min and maintain the temperature for 0.5h, the second-stage high-temperature treatment is to lower the final temperature of the first stage to 400-420 ℃ at a speed of 10 ℃/min and maintain the temperature for 1h, and the third-stage high-temperature treatment is to raise the temperature from the final temperature of the second stage to 580-640 ℃ at a speed of 15-30 ℃/min and maintain the temperature for 1h, so as to obtain the biochar;

step 5: ball milling the prepared biochar for 12 hours, adding calcined oyster shell powder in the ball milling process, mixing to form oyster shell powder reinforced biochar for removing the seawater culture water body micro-plastics, and controlling the granularity of the oyster shell powder reinforced biochar for removing the seawater culture water body micro-plastics after ball milling to be 50-100 meshes;

the preparation method of the calcined oyster shell powder is as follows:

washing and drying oyster shell powder with deionized water, grinding to a particle size ranging from 10 mu m to 15 mu m, and calcining in a calciner at 800 ℃ for 5 hours to obtain calcined oyster shell powder;

The mass ratio of the biochar to the calcined oyster shell powder is 5:0.8.

Example 2

Step 1: washing the waxberry branches with deionized water, drying at 105 ℃ to constant weight, and crushing to 40 meshes to obtain a crushed raw material;

step 2: placing the crushed raw materials obtained in the step 1 into a reaction container containing an iron salt aqueous solution, introducing micro-nano bubbles into the reaction container, controlling the temperature in the reaction container to be 50 ℃ for 1h, controlling the reaction pressure to be 1.3MPa, and heating to 60 ℃ for reaction for 18h;

wherein the weight ratio of the biomass material to the iron-containing soluble salt is 6:0.8, wherein the iron-containing soluble salt comprises ferric nitrate, ferric sulfate and ferric chloride, and the weight ratio of the ferric nitrate to the ferric sulfate to the ferric chloride is 1.5:2:1;

step 3: rapidly transferring the product obtained by the final reaction in the step 2 into liquid nitrogen for freezing for 1.5 hours, and then performing freeze drying treatment, wherein the freeze drying treatment is respectively performed for 4 hours and 4 hours at the temperature of-63 ℃ and the temperature of-13 ℃ in sequence;

step 4: placing the product obtained after the freeze drying in the step three into an anaerobic environment, introducing protective gas and sealing the processor, and performing three-stage high-temperature treatment, wherein the first-stage high-temperature treatment is to quickly raise the temperature from the freeze drying temperature to 700 ℃ at a heating rate of 90 ℃/min and maintain the temperature for 0.5h, the second-stage high-temperature treatment is to lower the temperature from the final temperature of the first stage to 410 ℃ at a speed of 10 ℃/min and maintain the temperature for 2h, and the third-stage high-temperature treatment is to raise the temperature from the final temperature of the second stage to 610 ℃ at a speed of 25 ℃/min and maintain the temperature for 2h, so that biochar is obtained;

Step 5: ball milling the prepared biochar for 12 hours, adding calcined oyster shell powder in the ball milling process, mixing to form oyster shell powder reinforced biochar for removing the seawater culture water body micro-plastics, and controlling the granularity of the oyster shell powder reinforced biochar for removing the seawater culture water body micro-plastics after ball milling to be 50-150 meshes;

the preparation method of the calcined oyster shell powder is as follows:

washing and drying oyster shell powder with deionized water, grinding to a particle size ranging from 5 μm to 10 μm, and calcining in a calciner at 800 ℃ for 6 hours to obtain calcined oyster shell powder;

the mass ratio of the biochar to the calcined oyster shell powder is 7:0.5.

Example 3

Step 1: washing the waxberry branches with deionized water, drying at 105 ℃ to constant weight, and crushing to 30 meshes to obtain a crushed raw material;

step 2: placing the crushed raw material prepared in the step 1 into a reaction container containing an iron salt aqueous solution, introducing micro-nano bubbles into the reaction container, controlling the temperature in the reaction container to be 55 ℃ for 2 hours, controlling the reaction pressure to be 1.4MPa, and heating to 65 ℃ for reaction for 24 hours;

wherein the weight ratio of the biomass material to the iron-containing soluble salt is 4:1, the iron-containing soluble salt comprises ferric nitrate, ferric sulfate and ferric chloride, and the weight ratio of the ferric nitrate to the ferric sulfate to the ferric chloride is 1:1:1;

Step 3: rapidly transferring the product obtained by the final reaction in the step 2 into liquid nitrogen for freezing for 3 hours, and then performing freeze drying treatment, wherein the freeze drying treatment is respectively performed for 4 hours and 4 hours at the temperature of minus 65 ℃ and minus 15 ℃ in sequence;

step 4: placing the product obtained after the freeze drying in the step three into an anaerobic environment, introducing protective gas and sealing the processor, and performing three-stage high-temperature treatment, wherein the first-stage high-temperature treatment is to quickly raise the temperature from the freeze drying temperature to 720 ℃ at a heating rate of 120 ℃/min and maintain the temperature for 0.5h, the second-stage high-temperature treatment is to lower the temperature from the final temperature of the first stage to 420 ℃ at a speed of 10 ℃/min and maintain the temperature for 3h, and the third-stage high-temperature treatment is to raise the temperature from the final temperature of the second stage to 640 ℃ at a speed of 30 ℃/min and maintain the temperature for 3h, so that biochar is obtained;

the preparation method of the calcined oyster shell powder is as follows:

the mass ratio of the biochar to the calcined oyster shell powder is 5:1.

Example 4

step 3: rapidly transferring the product obtained by the final reaction in the step 2 into liquid nitrogen for freezing for 1.5 hours, and then performing freeze drying treatment, wherein the freeze drying treatment is respectively performed for 4 hours and 4 hours at the temperature of-43 ℃ and the temperature of-23 ℃ in sequence;

the preparation method of the calcined oyster shell powder is as follows:

the mass ratio of the biochar to the calcined oyster shell powder is 7:0.5.

Example 5

Step 3: rapidly transferring the product obtained by the final reaction in the step 2 into liquid nitrogen for freezing for 1.5 hours, and then performing freeze drying treatment, wherein the freeze drying treatment is respectively performed for 4 hours and 4 hours at the temperature of minus 40 ℃ and minus 25 ℃ in sequence;

the preparation method of the calcined oyster shell powder is as follows:

the mass ratio of the biochar to the calcined oyster shell powder is 7:0.5.

Comparative example 1

Commercially available conventional biochar was used.

Comparative example 2

step 3: rapidly transferring the product obtained in the final reaction of the step 2 into liquid nitrogen for freezing for 1.5 hours, and then performing freeze drying treatment, wherein the freeze drying treatment is performed for 8 hours at the temperature of minus 13 ℃;

the preparation method of the calcined oyster shell powder is as follows:

the mass ratio of the biochar to the calcined oyster shell powder is 7:0.5.

Comparative example 3

Step 3: treating the product obtained by the final reaction in the step 2, and respectively freeze-drying at-63 ℃ and-13 ℃ for 5h and 4.5 h;

the preparation method of the calcined oyster shell powder is as follows:

The mass ratio of the biochar to the calcined oyster shell powder is 7:0.5.

Comparative example 4

Step 5: ball milling the prepared biochar for 12 hours, and controlling the granularity of the oyster shell powder reinforced biochar for removing the seawater culture water microplastic to be between 50 and 150 meshes.

Comparative example 5

the preparation method of the calcined oyster shell powder is as follows:

the mass ratio of the biochar to the calcined oyster shell powder is 5:1.5.

Comparative example 6

the preparation method of the calcined oyster shell powder is as follows:

the mass ratio of the biochar to the calcined oyster shell powder is 12:0.5.

Comparative example 7

step 4: placing the product obtained after the freeze drying in the step three into an anaerobic environment, introducing protective gas into a sealed processor, and performing two-stage high-temperature treatment, wherein the first-stage high-temperature treatment is to quickly raise the temperature from the freeze drying temperature to 410 ℃ at a heating rate of 90 ℃/min and maintain the temperature for 2.5 hours, and the second-stage high-temperature treatment is to raise the temperature from the final temperature of the first stage to 610 ℃ at a heating rate of 25 ℃/min and maintain the temperature for 2 hours, so as to obtain biochar;

the preparation method of the calcined oyster shell powder is as follows:

the mass ratio of the biochar to the calcined oyster shell powder is 7:0.5.

Example 8

The remaining procedure is as in example 2, except that the ratio of the iron-containing soluble salt is changed to 1:1:1.1.

Example 9

The remaining procedure is as in example 2, except that the ratio of the iron-containing soluble salt is changed to 2:3:0.4.

Example 10

The remaining procedure is identical to example 2, except that the iron-containing soluble salts are changed from three to 2, i.e. iron nitrate, iron sulfate are included in a weight ratio of 1.5:2.

the oyster shell powder-reinforced biochar prepared in the above examples 1-5 and comparative examples 1-10, from which the microplastic of the seawater culture water body was removed, was subjected to one or more of the following tests;

(1) Testing of the microplastic removal effect:

the oyster shell powder enhanced biochar for removing the seawater culture water body microplastic is tested for the removal effect of PE, PP, PS, PVC, PET five common microplastics, and specifically comprises the following steps:

step 1: taking culture seawater which is not polluted by micro-plastics, adding micro-plastics of polyethylene (PE, 6.5 mu m), polypropylene (PP, 6.5 mu m), polystyrene (PS, 13 mu m), polyvinyl chloride (PVC, 13 mu m) and polyethylene terephthalate (PET, 6.5 mu m) with the same mass and different sizes;

the concentration of the microplastic of the obtained solution is 0.20mg/L, pH which is 8.2 and simulates the cultivation seawater polluted by the microplastic;

step 2: taking three beakers, respectively marking as A, B, C, respectively adding 2L of prepared simulated water sample into each beaker, respectively stirring the simulated water sample in the beakers A, B, C at 120r/min for 5min through magnetic stirring, adding 300mg oyster shell powder for removing microplastic in the seawater culture water body to strengthen biochar, continuously stirring at 60r/min for 10min, and then respectively standing for 30min, 60min and 300min, and then testing the residual microplastic in the simulated water sample.

Of course, the peak area of the chromatogram can also be obtained by measuring the solution supernatant after the experiment by using a fluorescence spectrophotometer and recording the peak area. The comparison of the adsorption performance of the oyster shell powder enhanced biochar for removing the seawater culture water body micro-plastics on different kinds of plastic microspheres can be intuitively understood from the result graph.

(2) Testing of heavy metal removal effect:

oyster shell powder enhanced biochar for removing seawater culture water body microplastic from culture seawater ²⁺ 、 Pb ²⁺ The removal effect of (2) is tested, which comprises the following steps:

step 1: taking culture seawater which is not polluted by micro plastics, and adding Cd in a simulated water sample ²⁺ 、Pb ²⁺ The concentration of the total amount reaches 200mg/L;

step 2: taking three beakers, respectively marking as A, B, C, respectively adding 2L of prepared simulated water sample into each beaker, respectively stirring the simulated water sample in the beakers A, B, C at 120r/min for 5min by magnetic stirring, adding 200mg oyster shell powder for removing microplastic in the seawater culture water body to enhance biochar, continuously stirring at 60r/min for 10min, and then respectively standing for 30min, 60min and 300min to perform Cd in the simulated water sample ²⁺ 、Pb ²⁺ Testing of concentration.

(3) And (5) recycling and testing the purifying material.

The specific test results are shown in the following table:

table 1 example test results list

Table 2 list of test results for examples and comparative examples

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Table 3 comparative test results list

Table 4 comparative test results list

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Through the embodiment and the comparative example, the biological carbon with a certain proportion and the calcined oyster shell powder have a certain complementary effect, so that the efficiency of removing the micro-plastics and the heavy metals can be effectively improved. Meanwhile, the efficiency of removing the micro plastic and heavy metal can be further improved through specific freezing treatment and stage high-temperature treatment in the preparation method steps. It can also be seen from examples 1-3 and examples 4-5 that the pore size distribution formed in examples 4-5 provides better removal in the simulated water body case due to the size differences in the microplastic added during the experimental process during the stage freeze drying process.

Meanwhile, experiments also find that when the ferric salt solution prepared by the invention is adopted, the 7-day recovery efficiency of the ferric salt solution prepared by the invention can reach 97.22%, 98.13%, 95.69%, 97.92% and 98.04% respectively when the purification material is recovered after the water body purification is finished in the examples 1-5, and the recovery efficiency of the ferric chloride prepared by the invention can reach 80.13%, 72.37% and 65.56% respectively in the comparative examples 8-10, so that ferric nitrate and ferric sulfate in the hydrothermal reaction are easier to reduce and effectively adhere to biochar after the ferric chloride undergoes slow transpiration in the step 2.

It should be noted that the specific parameters or some common reagents in the above embodiments are specific embodiments or preferred embodiments under the concept of the present invention, and are not limited thereto; and can be adaptively adjusted by those skilled in the art within the concept and the protection scope of the invention.

In addition, it should be understood by those skilled in the art that although many problems exist in the prior art, each embodiment or technical solution of the present invention may be modified in only one or several respects, without having to solve all technical problems listed in the prior art or the background art at the same time. Those skilled in the art will understand that nothing in one claim should be taken as a limitation on that claim.

Although terms such as biochar, pore size, carbonization, etc. are more used herein, the possibility of using other terms is not precluded. These terms are used merely for convenience in describing and explaining the nature of the invention; they are to be interpreted as any additional limitation that is not inconsistent with the spirit of the present invention; the terms first, second, and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims

1. The preparation method of the oyster shell powder enhanced biochar for removing the seawater culture water body micro-plastics is characterized by comprising the following steps:

placing the crushed raw materials into an alkaline ferric salt aqueous solution for hydrothermal reaction; the hydrothermal reaction comprises at least two stages, wherein the first stage is to mix and fully stir the crushed raw materials and an iron salt aqueous solution for 0.5-h h at the temperature of 45-55 ℃, and the second stage is to increase the final temperature of the first stage to 60-65 ℃ and react for 12-24 h under the reaction pressure of 1-1.5 MPa;

2. The method for preparing oyster shell powder enhanced biochar for removing micro-plastics from a seawater culture water body according to claim 1, which is characterized in that: the weight ratio of the biomass material to the ferric salt added in the ferric salt aqueous solution is (4-8): (0.5-1).

3. The method for preparing oyster shell powder-enhanced biochar for removing micro-plastics from a seawater culture water body according to claim 1 or 2, wherein the method comprises the following steps: the ferric salt comprises ferric nitrate, ferric sulfate and ferric chloride;

4. The method for preparing oyster shell powder enhanced biochar for removing micro-plastics from a seawater culture water body according to claim 1, which is characterized in that: the preparation method further comprises the following steps: and performing ultraviolet modification on the oyster shell powder reinforced biochar subjected to ball milling and removed of the seawater culture water body microplastic.

5. The method for preparing oyster shell powder enhanced biochar for removing micro-plastics from a seawater culture water body according to claim 1, which is characterized in that: freeze drying comprises a first stage at-40 ℃ to-65 ℃ and a second stage at-10 ℃ to-25 ℃, and the time ratio of the first stage to the second stage after liquid nitrogen freezing is (1-2): (2-4).

6. An oyster shell powder-enhanced biochar for removing micro-plastics of a seawater culture water prepared by the method for preparing an oyster shell powder-enhanced biochar for removing micro-plastics of a seawater culture water according to claim 1 to claim 5.

7. Use of oyster shell powder enhanced biochar for removing micro-plastics from a seawater aquaculture water according to claim 6 for purifying aquaculture water.