CN115970643A - Recyclable magnetic biochar and preparation method and application thereof - Google Patents
Recyclable magnetic biochar and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to the technical field of environment restoration materials, in particular to a recyclable magnetic biochar and a preparation method and application thereof. The invention has the following advantages and effects: the silicate composite calcium-based magnetic biochar particle loaded with titanium dioxide prepared by the invention can effectively solve the problems that the common biochar can not simultaneously remove cadmium and arsenic pollution and iron oxide agglomeration; the gap of the biochar is combined with titanium dioxide, so that secondary pollution is avoided; meanwhile, the titanium dioxide-loaded magnetic calcium-based biochar granulated by the ordinary portland cement has better magnetism, sufficient physical strength and excellent hydraulic performance due to the formation of the C-S-H gel fiber and the hydrated calcium sulphoaluminate while improving the adsorption capacity of cadmium and arsenic, and provides a plurality of recovery ways to solve the problem of difficult recovery.
Description
Technical Field
The invention relates to the technical field of environment restoration materials, in particular to a recyclable magnetic biochar and a preparation method and application thereof.
Background
Cadmium (Cd) and arsenic (As) in sewage pose a health hazard to humans through the food chain and drinking water due to their toxicity and bioaccumulation properties. Cadmium causes severe damage to the kidneys and bones, and arsenic causes gastrointestinal symptoms, cardiovascular and nervous system dysfunction and even carcinogenicity. Wherein As (III) and As (V) are the main forms of arsenic in contaminated water and soil, and the toxicity of As (III) is 60 times higher than that of As (V) compared with As (V). Due to the wide pollution and high toxicity of Cd and As, development is urgently needed, and an economic and effective technology is used for simultaneously restoring water bodies polluted by Cd and As so As to prevent the Cd and As from harming human health.
However, the chemical properties of arsenic and cadmium in water bodies are quite different. Arsenic is present predominantly as anions and cadmium is present predominantly as cations, so that materials that adsorb to remove cadmium often cannot simultaneously remove arsenic. Therefore, the simultaneous removal of the heavy metals of anions and cations in the water body becomes one of the bottleneck problems in the remediation of the heavy metal pollution of the water body.
The biochar is an economic carbon skeleton material, and can effectively remove cationic heavy metals including Cd (II), pb (II), cr (VI) and the like due to large specific surface area, high pH value, abundant charges on the surface, high porosity and abundant oxygen-containing functional groups. However, since the cation and the anion have opposite Zeta potentials and pH dependencies, biochar cannot remove As. Meanwhile, because the biochar is generally powdery, the biochar has the problems of difficult recovery and separation, easy secondary pollution and the like. The adsorption efficiency needs to be improved, the adsorbable metal species needs to be increased, and the recovery problem needs to be solved through modified biochar.
Iron oxides have been shown to have a strong adsorption capacity for As. Meanwhile, the iron oxide is widely existed in natural environment, has the excellent characteristics of high storage capacity, low cost, small influence on environment and the like, and is often used as modified biochar to simultaneously repair various heavy metal pollutions. Biochar is modified with iron salts as in patent publication CN 104941583A to adsorb cadmium and arsenic simultaneously in solution; the patent of publication No. CN 114797779A uses ferrihydrite to modify the biochar prepared by high-temperature pyrolysis of reed straws, and can repair heavy metals of arsenic, lead and cadmium in the polluted soil. However, higher iron loading causes acidification of the adsorbent material, which inhibits the adsorption performance of the obtained adsorbent material on cationic metal pollutants, and moreover, most of biochar modified by iron does not have good hydraulic performance and is changed along with the erosion of aqueous solution. Meanwhile, although the materials can simultaneously remove arsenic and cadmium in water bodies, the removal capability is low, the magnetism of the materials is not endowed, and the materials cannot be conveniently recycled.
Titanium dioxide has been shown to have a good adsorption effect on a variety of heavy metals including arsenic. The method comprises the following steps of independently using titanium dioxide to repair arsenic, such as: in the patent publication No. CN 102107907A, a porous nano hydrated titanium dioxide is used for removing arsenic. Modification with titanium dioxide has also been used to enhance arsenic removal, such as nano titanium dioxide enhanced microalgae arsenic removal (publication No. CN 108439603A). However, titanium dioxide generally has difficulties in recycling and causing secondary pollution due to its small particles.
Aiming at the bottleneck problems of low capacity, poor physical properties and incapability of recycling of the existing material for removing arsenic and cadmium, the material disclosed by the invention further introduces titanium dioxide and a magnetic iron material, so that the arsenic and cadmium pollution of a water body can be simultaneously removed, and meanwhile, the adsorbing material is strong in removing capacity, stable in treatment effect and capable of being recycled, thereby greatly reducing the use cost.
Disclosure of Invention
The invention aims to provide a recyclable magnetic biochar and a preparation method and application thereof, which effectively solve the agglomeration of iron oxide, avoid the problem of secondary pollution due to the combination of titanium dioxide with the gaps of the biochar, have better magnetism, sufficient physical strength and excellent hydraulic performance due to the generation of C-S-H gel fibers and hydrated calcium sulphoaluminate and provide a plurality of recycling ways to solve the problem of difficult recycling.
The technical purpose of the invention is realized by the following technical scheme: the preparation method comprises the steps of preparing an adsorption material precursor, titanium dioxide-loaded magnetic calcium-based biochar and titanium dioxide-loaded silicate composite calcium-based magnetic biochar particles, wherein the preparation of the adsorption material precursor comprises the following steps:
s1: preparing fresh phyllostachys pubescens into dry bamboo powder, immersing the dried dry bamboo powder into a Fe2+ solution, adjusting the pH to 12, continuously stirring in a constant-temperature water bath, filtering after reaction to obtain a biomass-magnetite mixture, and drying in vacuum to obtain a dried biomass-magnetite mixture;
s2: adding calcium carbonate powder into the dried biomass-magnetite mixture in the S1, and uniformly stirring to obtain a mixture;
s3: putting the mixture in the S2 into a muffle furnace, heating up for pyrolysis, cooling to obtain a pyrolysis product, grinding, crushing and sieving to obtain an adsorption material precursor, namely calcium-based magnetic biochar;
the preparation method of the titanium dioxide loaded calcium-based magnetic biochar comprises the following steps:
s4: respectively adding the calcium-based magnetic biochar and deionized water in the step S3 into a reactor, and performing ultrasonic reaction and vacuum filtration separation to obtain calcium-based magnetic biochar subjected to ultrasonic treatment;
s5: mixing and stirring butyl titanate and ethanol, then adding the calcium-based magnetic biochar subjected to ultrasonic treatment in the step S4 into the mixed solution, mixing and stirring again, filtering to obtain a precipitate, washing the precipitate with water and ethanol, and then drying and sieving in vacuum to obtain the magnetic calcium-based biochar loaded with titanium dioxide;
the preparation method of the titanium dioxide loaded silicate composite calcium-based magnetic charcoal particles comprises the following steps:
s6: and (3) mixing the titanium dioxide-loaded magnetic calcium-based biochar in the step (S5) with ordinary portland cement, then introducing the mixture into a disc granulator for granulation, and screening to obtain the titanium dioxide-loaded silicate composite calcium-based magnetic biochar granules.
The invention is further provided with: and (4) compacting the mixture in the S3, wrapping the aluminum foil paper, placing the mixture into a muffle furnace, blowing the mixture by introducing nitrogen until the mixture is full of a hearth, heating to 400 ℃ at 20-1 ℃, maintaining the temperature at 400 ℃ for pyrolysis for 120min, naturally cooling to obtain a pyrolysis product, grinding and crushing the pyrolysis product, and sieving the ground pyrolysis product with a 100-mesh sieve to obtain an adsorption material precursor, namely the calcium-based magnetic charcoal.
The invention is further provided with: the ultrasonic reaction in the S4 is carried out under the constant condition of 28KHZ and the temperature of 25 ℃ for 15 minutes.
The invention is further provided with: and the times of water washing and alcohol washing in the S5 are respectively at least 2 times.
The invention is further provided with: the molar concentration of Fe & lt 2+ & gt solution in S1 is 0.1mol L-1, the molar ratio of ferric chloride to ferrous sulfate in the Fe2 & lt + & gt solution is 1.
The invention is further provided with: the calcium carbonate powder in S2 accounts for 2-4% of the weight of the dry biomass-magnetite mixture.
The invention is further provided with: the volume ratio of the butyl titanate to the ethanol in the S5 is 1.
The invention is further provided with: the mass ratio of the magnetic calcium-based biochar loaded with titanium dioxide in S6 to ordinary portland cement is 1.
The invention is further provided with: a recyclable magnetic biochar is prepared by a preparation method of the recyclable magnetic biochar.
The invention is further configured as follows: an application of recoverable magnetic biochar in remediation of heavy metal polluted water.
The invention has the beneficial effects that:
1. the invention provides a titanium dioxide-loaded silicate composite magnetic calcium-based biochar particle and a preparation method and application thereof. Through gradual modification, iron oxide, calcium carbonate and bamboo powder are pyrolyzed together to obtain magnetic calcium-based biochar, titanium dioxide is loaded on the magnetic calcium-based biochar after ultrasonic treatment, and portland cement is used for granulation. Because the iron oxide can efficiently adsorb arsenic and cadmium, the functional groups on the biochar can efficiently combine cadmium, and the titanium dioxide enhances the adsorption effect of cadmium and arsenic and simultaneously solves the difficulty that the iron oxide has poor adsorption effect on arsenic when the pH value is less than 3. The invention solves the problem that the concentration of cadmium is increased to reduce the arsenic adsorption capacity in the competitive adsorption of cadmium and arsenic in most materials through various modification ways, so the product of the invention has larger adaptability.
2. The invention solves the technical difficulty that the common biochar can only remove Cd but can not remove As. In the preparation process, volatile blockage formed in the pyrolysis process of the biochar is removed through ultrasonic treatment, and the surface area and the pore volume of the biochar are increased. This facilitates the transfer and diffusion of ions during loading of the titania and during adsorption, as well as the loading of more selectively adsorbed particles within the channels. The iron oxide and the titanium dioxide are loaded on the charcoal, so that arsenic can be efficiently adsorbed, and cadmium can be further adsorbed. Meanwhile, silicate is added in the granulation stage, more-OH functional groups are introduced into the biochar, and SiO 32-capable of reacting with Cd < 2+ > is also introduced, so that the adsorption effect of the biochar on cadmium is greatly enhanced.
3. The magnetic biochar particles prepared by the method have better physical and hydraulic properties, do not generate secondary pollution, and are environment-friendly materials. The magnetic calcium-based biochar loaded with titanium dioxide is combined with silicate granulation, so that the magnetic calcium-based biochar has excellent pressure resistance and hydraulic performance, the problem of over dispersion of a powdery adsorbent is solved, and the shape of a material cannot be changed along with the erosion of a solution; on the contrary, as the charcoal granules can continuously generate the C-S-H gel fibers in the solution, the charcoal granules soaked in the water are more tightly combined, so that the charcoal granules have enough physical strength and excellent hydraulic performance, and the continuous adsorption effect on the heavy metals in the polluted water body is obviously enhanced.
4. The combination of various materials can effectively solve the agglomeration of the iron oxide, and the combination of the biological carbon and the titanium dioxide in the gaps can also avoid the problem of secondary pollution.
5. The product of the invention can be recovered by various recovery modes, has high recovery rate and is easy to store. The product has magnetism, and can separate the adsorption material by a magnetic recovery method; in addition, because the product has good physical properties, the material can be recovered by the technologies of filtering, sieving and the like, a plurality of recovery ways are provided, and the problem of difficult recovery is solved.
6. The main raw materials of the phyllostachys pubescens and the ordinary portland cement used in the invention are low in price and convenient to obtain. The obtained product particles have strong anti-crushing capability, convenient storage, easy transportation and difficult secondary pollution, and are a safe and effective repair material for underground water, surface water and industrial wastewater, which is easy to use.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of a manufacturing method of the present invention.
Fig. 2 is a graph showing the effect of removing cadmium and arsenic from the titanium dioxide-loaded silicate composite calcium-based magnetic biochar particles prepared by the example.
FIG. 3 shows the effect of the concentration of As (III) and Cd (II) on the ability of the charcoal granules to adsorb Cd (II) and As (III) simultaneously when the pH value is 6, a shows the effect of the addition of As (III) with different concentrations on the adsorption capacity of Cd (II), b shows the effect of the addition of Cd (II) with different concentrations on the adsorption capacity of As (III), c shows the effect of the addition of As (III) with different concentrations on the adsorption capacity of Cd (II), and d shows the effect of the addition of Cd (II) with different concentrations on the adsorption capacity of As (III).
FIG. 4 is a graph showing the effect of pH on biochar pellets to remove cadmium arsenic simultaneously in the examples.
Fig. 5 is a picture of the morphology of the titanium dioxide-loaded silicate composite calcium-based magnetic biochar particles prepared by the example, wherein the magnification of the picture a is 1000 times, and the magnification of the picture b is 20000 times.
Fig. 6 is EDX spectrum information of the element types and contents of the titanium dioxide supported silicate composite calcium-based magnetic biochar particles prepared by the example.
Detailed Description
The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
The embodiment is as follows:
1. preparation of adsorbent Material precursor
S1: pulverizing fresh Phyllostachys pubescens with a pulverizer to obtain 0.15mm powder, cleaning bamboo powder, and oven drying at 50 deg.C; then, 1kg of dry bamboo powder is immersed into 20L of 0.1mol L-1Fe2+ solution, the pH value of the mixed solution is adjusted to 12 by using 5mol L-1NaOH, the suspension is continuously stirred for 2h in a water bath at 60 ℃, the suspension is reacted for 24h in a beaker covered with a preservative film, the mixture is filtered to obtain a biomass-magnetite mixture, and the mixture is dried for 24h in vacuum at 50 ℃ to obtain a dry biomass-magnetite mixture;
s2: adding 3% of calcium carbonate powder into the dried biomass-magnetite mixture, and uniformly stirring to obtain a mixture;
s3: and putting the mixture into a ceramic crucible, compacting, wrapping aluminum foil paper, putting into a muffle furnace, blowing by nitrogen until the furnace hearth is filled, closing the furnace door, heating to 400 ℃ according to the temperature of 20-1 min, maintaining the temperature of 400 ℃ for pyrolysis for 120min, naturally cooling to obtain a pyrolysis product, grinding and crushing the product, and sieving by a 100-mesh sieve to obtain an adsorption material precursor, namely the calcium-based magnetic charcoal.
2. Preparation of titanium dioxide-loaded magnetic calcium-based biochar
S4: adding 20L of deionized water into a 50L reactor, adding 1kg of calcium-based magnetic biochar, performing ultrasonic reaction at 25 ℃ under a constant condition of 28KHZ for 15 minutes, and performing vacuum filtration and separation to obtain the calcium-based magnetic biochar subjected to ultrasonic treatment.
S5: slowly adding 1L of butyl titanate into 3L of ethanol, simultaneously fully mixing and violently stirring by using a magnetic stirrer, adding the calcium-based magnetic biochar subjected to ultrasonic treatment into the violently stirred solution, keeping stirring for 2 hours, filtering the product after 2 hours, sequentially washing with ethanol and water for 2 times, carrying out vacuum drying at 100 ℃ for 6 hours, and sieving with a 100-mesh sieve to obtain the titanium dioxide-loaded magnetic calcium-based biochar.
3. Preparation of titanium dioxide-loaded silicate composite magnetic calcium-based biochar particles
S6: uniformly mixing titanium dioxide-loaded magnetic calcium-based biochar with ordinary portland cement according to the proportion of 1; and (3) after rotating and granulating for 3-6 minutes, screening out granules with the particle size of 4-6.00 mm, naturally drying in the air, monitoring the quality after drying in the air, and obtaining the titanium dioxide-loaded silicate composite calcium-based magnetic biochar granules after the granules are qualified.
In the embodiment, the average size of the titanium dioxide loaded silicate composite magnetic calcium-based biochar particles is about 4.86mm, and the average compressive strength is higher than 170N.
Comparative example:
the comparative example provides a preparation method of common phyllostachys pubescens biochar:
1. pulverizing fresh Phyllostachys pubescens with a pulverizer to obtain 0.15mm powder, cleaning bamboo powder, and oven drying at 50 deg.C.
2. Putting 1kg of dry bamboo powder into a ceramic crucible, compacting, wrapping aluminum foil paper, putting into a muffle furnace, blowing with nitrogen until the furnace hearth is filled, closing the furnace door, heating to 400 ℃ according to 20 ℃ min-1, maintaining the temperature at 400 ℃ for pyrolysis for 120min, and naturally cooling to obtain a pyrolysis product.
3. And (3) grinding and crushing the pyrolysis product obtained in the step (2), and sieving the crushed material with a 100-mesh sieve to obtain the phyllostachys pubescens biochar.
1. The effect of the titanium dioxide-loaded silicate composite calcium-based magnetic biochar particles for simultaneously removing cadmium (Cd (II)) and arsenic (As (III)) is determined
(1) Preparing a mother solution: dissolving Cd (NO 3) 2.4H2O and As2O3 in deionized water, separately preparing stock solutions of 2000mgL-1Cd (II) and 2000mgL-1As (III), wherein the pH of Cd is 2.0, mixing the stock solution of 2000mgL-1As (III) with a large amount of Cd solution with the concentration of 2000mgL-1 according to the volume ratio of 1.
(2) Preparation of a measurement solution: the stock solution in (1) was used to prepare a solution having a Cd (II) concentration of 500mg L-1 and an As (III) concentration of 50mg L-1, and the pH was adjusted to 6 using 1M NaOH and 1M HCl. (ii) a
(3) 2.5g of the titanium dioxide loaded silicate composite magnetic calcium-based biochar particles obtained in the embodiment of the invention and 2.5g of biochar in the comparative example are weighed and respectively added into a beaker with the capacity of 2L, and three parallel samples are arranged on different materials;
(4) Pouring 1L of the solution in the step (2) into the step (3), and stirring the solution for 24 hours by using an electric stirrer at the rotating speed of 90r/min;
(5) The experimental environment is as follows: room temperature is 25 ℃;
(6) And (5) measuring the concentrations of Cd (II) and As (III) in the solution after the reaction is finished (4).
The results of the measurement were as follows:
fig. 2 shows that the effect of the biological carbon granules for efficiently removing cadmium (Cd (II)) and arsenic (As (III)) is simultaneously achieved, and As can be seen from fig. 2, the titanium dioxide-loaded silicate composite magnetic calcium-based biological carbon granules of the present invention have a good effect of removing cadmium and arsenic. Compared with the original charcoal, the adsorption effect of the titanium dioxide-loaded silicate composite magnetic calcium-based charcoal particles on cadmium is improved by 474.8%; the original biochar has no substantial removal effect on arsenic (As (III)) (BC removal rate =1.33 +/-0.18%), and the adsorption efficiency of the titanium dioxide-loaded silicate composite magnetic calcium-based biochar particles on arsenic reaches 84.54%. The result shows that the finished product prepared by the invention has the capability of repairing the cadmium-arsenic heavy metal polluted water body at the same time.
Through observation by a scanning electron microscope and scanning analysis of an EDS (electron-dispersive spectroscopy) spectrum of the adsorbing material in the embodiment, and as shown in the figures 5a and 5b, the surface morphology of the adsorbing material in the embodiment 1 is shown, it can be found that the particles with small and dense surfaces of the adsorbing material are iron oxide particles, the size is about 1-10nm, the surface of the biochar is large, the size is about 2um, and the size is about 2 um. Meanwhile, the CSH gel fiber with a fish scale lamellar structure can be observed to be generated by combining the silicate and the biochar through a granulation process. The presence of aqueous calcium sulphoaluminate hydrate (CSAH, also known as ettringite) characterized by a needle-like structure is also evident, which proves the effectiveness of stepwise modification using various modification methods in different preparation stages. The EDX element composition analysis in FIG. 6 can further prove that the added CaCO3, ferric oxide and TiO2 are successfully loaded into BC step by step. The elemental contents of Ca, fe and Ti after granulation were 4.07%,6.70% and 3.70%, respectively, which is a direct evidence of the success of the modification.
2. Determination of influence of different cadmium and arsenic concentrations on removal of cadmium (Cd (II)) and arsenic (As (III)) from charcoal granules simultaneously
(1) The mother liquor in experiment (1) was assayed for the effect of simultaneously removing cadmium (Cd (II)) arsenic (As (III)) using titanium dioxide-loaded silicate composite calcium-based magnetic biochar pellets, 16 sets of solutions of different cadmium and arsenic concentrations were prepared, with 4 concentrations of cadmium Cd (II) (including 100, 200, 300, and 600 mg/L) and 4 concentrations of arsenic As (III) (including 20, 40, 60, and 120 mg/L), and the pH of the solution was adjusted to 6 using 1M NaOH, 1M HCl.
(2) Weighing 0.5g of the titanium dioxide loaded silicate composite magnetic calcium-based biochar particles obtained in the embodiment of the invention, adding the weighed particles into a 500ml conical flask, and arranging three parallel samples for different materials;
(3) 250mL of each solution in the step (1) is poured into the step (2), and the mixture is put into a shaking table, the shaking time is 24h, and the rotating speed is 180r/min.
(4) And (3) determining the concentrations of Cd (II) and As (III) in the solution after the reaction is finished.
The results of the measurement were as follows:
FIG. 3 shows the effect of the concentration of As (III) and Cd (II) on the ability of the biochar to adsorb Cd (II) and As (III) simultaneously.
FIGS. 3a and 3c show the effect of the initial As (III) concentration on the Cd (II) adsorption capacity of the biochar pellets, from which it can be seen that the addition of As (III) reduces the Cd (II) adsorption capacity; when the As (III) concentration is 20mg/L, the adsorption amount of Cd (II) by the biochar granules is maximum (FIG. 3 a). The adsorption amount of the biochar particles to Cd (II) is the most dropping when the concentration of As (III) is 60mg/L, and then the adsorption amount of the biochar particles to Cd (II) is increased As the addition amount of As (III) is increased (FIG. 3 b).
FIGS. 3b and 3d show the effect of the initial Cd (II) concentration on the ability of the biochar pellets to adsorb As (III). The adsorption capacity of the biochar granules to As (III) can be improved by adding Cd (II) (fig. 3 b), when the concentration of Cd (II) is 100-300mg/L, the adsorption capacity of As (III) is improved along with the increase of the addition amount of Cd (II), the adsorption capacity of As (III) reaches a peak value when the addition amount of Cd (II) is 300mg/L, and the adsorption capacity of arsenic is slightly reduced along with the increase of the addition amount of Cd (II) and is still higher than the adsorption capacity of arsenic added with the lowest cadmium (fig. 3 d).
The above experimental results show that: the silicate composite magnetic calcium-based biochar particles loaded with titanium dioxide can effectively remove Cd (II) pollution in most natural cadmium-arsenic composite polluted environments, and the capacity of removing arsenic (As (III)) is improved along with the existence of cadmium Cd (II).
3. Determination of effect of biochar granules in removing cadmium (Cd (II)) and arsenic (As (III)) simultaneously at different pH values
(1) The mother liquor in the experiment (1) is measured by using the effect of removing cadmium (Cd (II)) and arsenic (As (III)) from titanium dioxide-loaded silicate composite calcium-based magnetic biochar particles, mixed solutions of Cd (II) and As (III) with the concentrations of 200mg L-1 and 20mg L-1 are prepared, and the pH values are respectively adjusted to 2,3,4,5,6 and 7 by using 1M NaOH and 1M HCl;
(2) Weighing 0.5g of the titanium dioxide loaded silicate composite magnetic calcium-based biochar particles obtained in the embodiment of the invention and 0.5g of biochar prepared in the comparative example, respectively adding the weighed materials into a 500ml conical flask, and setting three parallel samples for different materials;
(3) Pouring 250mL of the solution in the step (1) into the step (2), and putting the solution in a shaking table, wherein the shaking time is 24h and the rotating speed is 180r/min;
(4) And (3) determining the concentrations of Cd (II) and As (III) in the solution after the reaction is finished.
The results of the measurement were as follows:
fig. 4 shows the effect of different pH on the simultaneous removal of cadmium (Cd (II)) and arsenic (As (III)) from the biochar pellets, and it can be seen from fig. 4 that the titanium dioxide-loaded silicate composite magnetic calcium-based biochar pellets still have good effect of simultaneously removing cadmium and arsenic under the low pH condition (pH = 2), compared with the original biochar having substantially no effect of removing cadmium and arsenic under this condition. And the removal rate of the titanium dioxide loaded silicate composite magnetic calcium-based biochar particles to cadmium and arsenic is rapidly increased along with the increase of pH to 3, and the removal rate is over 80 percent. This shows that the titanium dioxide-loaded silicate composite magnetic calcium-based biochar particles have a repair effect of more than 60% in a strong acidic environment.
4. Determination of hydraulic performance of charcoal granules
(1) Introducing ordinary portland cement into a laboratory disc granulator, starting the granulator, setting the speed to be 20 rpm, and spraying a small amount of distilled water while rotating the granulator to obtain a mixture;
(2) And (3) rotating and granulating for 3-6 minutes, screening out granules with the particle size of 4-6.00 mm, naturally drying in the air, and obtaining the common silicate cement granules after drying in the air.
(3) The compressive strength of the titanium dioxide-loaded silicate composite magnetic calcium-based biochar particles obtained in the example of the present invention and the compressive strength of the ordinary silicate cement particles obtained in (2) were measured, respectively.
(4) Respectively putting the titanium dioxide-loaded silicate composite magnetic calcium-based biochar particles obtained in the embodiment of the invention and the common silicate cement particles obtained in the step (2) into water, soaking for 3 days, taking out, and respectively measuring the compressive strength of the soaked wet material.
TABLE 1 compressive strength before and after the titanium dioxide-loaded silicate composite magnetic calcium-based biochar particle material
As can be seen from Table 1, the titanium dioxide-loaded silicate composite magnetic calcium-based biochar granules prepared by the embodiment of the invention have better physical resistance, and the compressive strength is improved by 24.5% compared with that of common silicate cement granules. Meanwhile, the titanium dioxide-loaded silicate composite magnetic calcium-based biochar particles in the embodiment 1 have better hydraulic capacity, and the compression resistance is improved by 12.1% after soaking, because unreacted C3S and beta-C2S in the soaked OPC can continuously react with each other to generate more C-S-H gel, the combination of the biochar is tighter, and the hydraulic capacity is further improved. The better hydraulic capacity of the biochar granules indicates that the biochar granules cannot cause structural erosion due to erosion of aqueous solution. In addition, the hydraulic performance is generally directly related to the recovery rate of the biochar, and the better water conservancy capacity of the biochar granules indicates better recovery rate.
Claims (10)
1. A preparation method of recyclable magnetic biochar is characterized by comprising the following steps: the preparation method comprises the steps of preparing an adsorption material precursor, titanium dioxide-loaded magnetic calcium-based biochar and titanium dioxide-loaded silicate composite calcium-based magnetic biochar particles, wherein the preparation of the adsorption material precursor comprises the following steps:
s1: preparing dry bamboo powder from fresh Phyllostachys pubescens, and soaking the dried dry bamboo powder in Fe 2+ In the solution, adjusting the pH value to 12, continuously stirring in a constant-temperature water bath, filtering after reaction to obtain a biomass-magnetite mixture, and drying in vacuum to obtain a dry biomass-magnetite mixture;
s2: adding calcium carbonate powder into the dried biomass-magnetite mixture in the S1, and uniformly stirring to obtain a mixture;
s3: putting the mixture in the S2 into a muffle furnace, heating up for pyrolysis, cooling to obtain a pyrolysis product, grinding, crushing and sieving to obtain an adsorption material precursor, namely calcium-based magnetic biochar;
the preparation method of the titanium dioxide-loaded calcium-based magnetic biochar comprises the following steps:
s4: respectively adding the calcium-based magnetic biochar and deionized water in the step S3 into a reactor, and performing ultrasonic reaction and vacuum filtration separation to obtain calcium-based magnetic biochar subjected to ultrasonic treatment;
s5: mixing and stirring butyl titanate and ethanol, then adding the calcium-based magnetic biochar subjected to ultrasonic treatment in S4 into the mixed solution, mixing and stirring again, filtering to obtain a precipitate, washing the precipitate with water and alcohol, and performing vacuum drying and sieving to obtain titanium dioxide-loaded magnetic calcium-based biochar;
the preparation method of the titanium dioxide loaded silicate composite calcium-based magnetic charcoal particles comprises the following steps:
s6: and (3) mixing the titanium dioxide-loaded magnetic calcium-based biochar in the step (S5) with ordinary portland cement, then introducing the mixture into a disc granulator for granulation, and screening to obtain the titanium dioxide-loaded silicate composite calcium-based magnetic biochar granules.
2. The method for preparing recyclable magnetic biochar particles according to claim 1, wherein the method comprises the following steps: compacting the mixture in the S3, wrapping the aluminum foil paper, putting the aluminum foil paper into a muffle furnace, introducing nitrogen gas, blowing till the furnace hearth is full of the mixture, and performing heating at 20 ℃ for min -1 Heating to 400 ℃, keeping the temperature at 400 ℃ for pyrolysis for 120min, naturally cooling to obtain a pyrolysis product, grinding and crushing, and then sieving with a 100-mesh sieve to obtain an adsorption material precursor, namely the calcium-based magnetic charcoal.
3. The method for preparing recyclable magnetic biochar particles as claimed in claim 2, wherein the method comprises the following steps: the ultrasonic reaction in the S4 is carried out under the constant condition of 28KHZ and the temperature of 25 ℃ for 15 minutes.
4. The method for preparing recyclable magnetic biochar particles according to claim 3, wherein the method comprises the following steps: and the times of water washing and alcohol washing in the S5 are respectively at least 2 times.
5. The method for preparing recyclable magnetic biochar particles according to claim 4, wherein the method comprises the following steps: fe in S1 2 + The molar concentration of the solution is 0.1mol L -1 ，Fe 2+ The molar ratio of ferric chloride to ferrous sulfate in the solution is 1.
6. The method for preparing recyclable magnetic biochar particles according to claim 5, wherein the method comprises the following steps: and the calcium carbonate powder in the S2 accounts for 2-4% of the weight of the dry biomass-magnetite mixture.
7. The method for preparing recyclable magnetic biochar particles according to claim 6, wherein the method comprises the following steps: the volume ratio of the butyl titanate to the ethanol in the S5 is 1.
8. The method for preparing recyclable magnetic biochar particles as claimed in claim 7, wherein the method comprises the following steps: the mass ratio of the magnetic calcium-based biochar loaded with titanium dioxide in S6 to ordinary portland cement is 1.
9. A recoverable magnetic biochar is characterized in that: the recyclable magnetic biochar is prepared by the preparation method of the recyclable magnetic biochar as claimed in any one of claims 1 to 8.
10. The application of the recyclable magnetic biochar according to any one of claims 1 to 8 in remediation of heavy metal polluted water.
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