CN111495322A - Rambutan peel modified charcoal and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of waste recycling, and particularly relates to rambutan peel modified charcoal and a preparation method and application thereof. The invention relates to a preparation method of rambutan peel modified charcoal, which comprises the step of adding MgCl₂The modification method under the ultrasonic condition is combined with thermal cracking modification, a large number of surface functional groups of the rambutan peel are reserved, other oxygen-containing groups and pore channels are introduced, and an MgO coating is embedded in the pore channels. The adsorption capacity of the rambutan peel modified charcoal prepared by the method is obviously enhanced, and the rambutan peel modified charcoal has a good adsorption effect on various cationic dyes.

Description

Rambutan peel modified charcoal and preparation method and application thereof

Technical Field

The invention belongs to the technical field of waste recycling, and particularly relates to rambutan peel modified charcoal and a preparation method and application thereof.

Background

The dye industry plays an important role in national economy, and products of the dye industry cover various fields such as textile, printing ink, coating, rubber, leather, medicine, food and the like. Methylene Blue (MB), malachite green, crystal violet, rhodamine and other cationic dyes are used as common dyes in the printing and dyeing industry and are widely applied to the industries of textile, printing, leather, paper making and the like. Because a plurality of chemicals which are harmful to human bodies and the environment are adopted in the dyeing process of the cationic dye, waste water, waste gas and other wastes generated in the dyeing process must be treated before being discharged.

The biochar is a carbon-rich substance obtained by cracking biomass under the anoxic or anaerobic condition, has the characteristics of rich surface functional groups, high carbon content, multiple pore structures and the like, and is expected to be used as a novel adsorbent for adsorbing cationic dyes instead of activated carbon.

Rambutan (nephium lappaceum L.) is an evergreen arbor of the genus nephridae, is also a famous tropical rare fruit, is originally produced in malaysia and indonesia, and is widely distributed in asia areas such as thailand, burma, india, vietnam, singapore and the like at present in 1960, the research institute of the tropical crops in south-hai province is introduced from malaysia for pilot planting, and China starts to popularize and plant in a large scale in 1995, currently, the planting area is nearly 2 ten thousand acres, the planting area is mainly concentrated in the areas such as the county and the city of west-san city in south-hai province, and the rambutan peel is a byproduct with extremely low economic benefit, is mostly discarded, and is not fully utilized.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides rambutan peel modified charcoal and a preparation method and application thereof.

The technical scheme of the invention is realized as follows:

a preparation method of rambutan peel modified charcoal comprises the following steps:

(1) drying and crushing the rambutan peel to obtain rambutan peel powder;

(2) putting the rambutan peel powder into a magnesium chloride aqueous solution, mixing, performing ultrasonic treatment, and removing water from the mixed solution to obtain rambutan peel modified powder;

(3) and carrying out thermal cracking on the rambutan peel modified powder, cooling, washing and drying to obtain the rambutan peel modified charcoal.

Further, in the step (1), the rambutan peel is dried at 50-70 ℃ after being cleaned, and is sieved by a 60-mesh sieve after being crushed.

Further, in the step (2), MgCl is added to the magnesium chloride aqueous solution₂·6H₂The content of O is 50 g/L, and 50g of rambutan peel powder is added into L per 1000m of magnesium chloride aqueous solution.

Further, the ultrasonic treatment condition is ultrasonic treatment for 2h at 25000 Hz.

Further, in the step (2), the moisture is removed by drying at 70-80 ℃.

Further, in the step (3), the pyrolysis conditions are as follows: heating at the speed of 5 ℃/min under the nitrogen atmosphere, and carrying out thermal cracking for 1h at the constant temperature of 200-400 ℃.

Further, in the step (3), after cooling to 15-30 ℃, washing with deionized water until the filtrate is colorless.

The rambutan peel modified charcoal is prepared by the preparation method.

The application of the rambutan pericarp modified charcoal prepared by the preparation method in dye adsorption.

Further, the dye is a cationic dye.

Further, the cationic dye is methylene blue, T safranine, malachite green, crystal violet and/or rhodamine B.

Further, in the application shown, the rambutan peel modified charcoal is used under neutral or alkaline conditions.

Has the advantages that:

the invention relates to a preparation method of rambutan peel modified charcoal, which comprises the step of adding MgCl₂The modification method under the ultrasonic condition is combined with thermal cracking modification, a large number of surface functional groups of the rambutan peel are reserved, other oxygen-containing groups and pore channels are introduced, and an MgO coating is embedded in the pore channels.

Adsorption experiments on other cationic dyes prove that the erysipelas peel modified charcoal prepared by the method has a good adsorption effect on the cationic dyes generally.

Drawings

FIG. 1 is a methylene blue standard curve;

FIG. 2 is a comparison of the surface morphology of MBC-300 and BC-300, wherein (a) MBC-300; (b) BC-300;

FIG. 3 is a comparison of MBC-300 and BC-300 infrared spectra, wherein (a) MBC-300; (b) BC-300;

FIG. 4 is Zeta potentials for MBC and BC at different pH values;

FIG. 5 is a graph of the adsorption amounts of samples at different pyrolysis temperatures;

FIG. 6 is a graph showing the effect of pH on methylene blue adsorption performance;

FIG. 7 is the effect of adsorption time on MB adsorption performance;

FIG. 8 is a quasi-first order kinetic fit of MBC-300 to MB adsorption;

FIG. 9 is a quasi-first order kinetic fit of BC-300 to MB adsorption;

FIG. 10 is a quasi-second order kinetic fit of MBC-300 to MB adsorption;

FIG. 11 is a quasi-second order kinetic fit of BC-300 to MB adsorption;

FIG. 12 is a graph showing the effect of initial MB concentration on the adsorption capacity of different adsorbent materials;

FIG. 13 is an L angmuir fit of MBC-300 to MB adsorption;

FIG. 14 is an L angmuir fit of BC-300 to MB adsorption;

FIG. 15 is a Freundlich fit of MBC-300 to MB adsorption;

FIG. 16 is a Freundlich fit of BC-300 to MB adsorption;

FIG. 17 is a T safranine standard curve;

FIG. 18 is a malachite green standard curve;

FIG. 19 is a crystal violet standard curve;

FIG. 20 is a rhodamine B standard curve;

FIG. 21 shows the adsorption effect of different cationic dyes.

Detailed Description

The invention will be better understood from the following description of specific embodiments with reference to the accompanying drawings. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications.

In the following examples, rambutan was purchased from Hainan Baotion Li nationality Miao county. All chemicals include HCl, NaOH, MgCl₂MB (1200 mg/L) was prepared and diluted to the desired concentration (25-1200 mg/L). 2 mol/L HCl or NaOH solution to adjust the pH of the solution.

Example 1

Preparation of rambutan pericarp modified charcoal (MBC)

Washing the rambutan peel with tap water, drying at 50-70 deg.C, cutting into small pieces, pulverizing, and sieving with 60 mesh sieve to obtain rambutan peel powder. 50g of MgCl were taken₂·6H₂Dissolving O (analytically pure) in a 1L beaker by adding 1000m of L ultrapure water, adding 50g of the erysipelas peel powder into a magnesium chloride solution, carrying out ultrasonic treatment for 2h at 25000Hz, drying the obtained mixed solution in an oven at 70-80 ℃ to obtain erysipelas peel modified powder, adding the obtained erysipelas peel modified powder into a ceramic crucible, and placing the ceramic crucible into a vacuum tube furnace (QSH-VGF-RTF-1700T, Quanshuo, Shanghai) for thermal cracking to prepare the erysipelas peel modified biochar, wherein the thermal cracking conditions are that the heating is carried out at the speed of 5 ℃/min to 200 ℃ in a nitrogen atmosphere, and the thermal cracking is carried out at the constant temperature of 200 ℃ for 1 h.Then cooled to room temperature and the sample was washed with deionized water until the filtrate was colorless. And then drying at 60 ℃ to obtain the modified biochar (MBC-200). The same method is used to prepare the modified biochar (MBC-300, MBC-400, MBC-500 and MBC-600) with the thermal cracking temperature of 300 ℃, 400 ℃, 500 ℃ and 600 ℃. The dried modified biochar was ground to a powder (no apparent lumpy solids) for more complete contact with the wastewater.

Example 2

Preparation of rambutan pericarp modified charcoal (BBC)

Washing the rambutan peel with tap water, drying at 50-70 deg.C, cutting into small pieces, pulverizing, and sieving with 60 mesh sieve to obtain rambutan peel powder. 50g of MgCl were taken₂·6H₂Dissolving O (analytically pure) in a 1L beaker by adding 1000m of L ultrapure water, adding 50g of the erysipelas peel powder into a magnesium chloride solution, soaking for 2h, drying the obtained mixed solution in an oven at 70-80 ℃ to obtain erysipelas peel modified powder, adding the obtained erysipelas peel modified powder into a ceramic crucible, placing the ceramic crucible into a vacuum tube furnace (QSH-VGF-RTF-1700T, Quanshu, Shanghai) for thermal cracking to prepare the erysipelas peel modified biochar, wherein the thermal cracking conditions are that the erysipelas peel modified biochar is heated to 300 ℃ at the rate of 5 ℃/min under the nitrogen atmosphere, the temperature is constant for 1h at 200 ℃ for thermal cracking, then the temperature is cooled to room temperature, the sample is washed by deionized water until the filtrate is colorless, then the sample is dried at 60 ℃ to obtain the erysipelas peel modified biochar (BBC-200), the thermal cracking temperature is respectively 300 ℃, 400 ℃, 600 ℃ modified biochar (BBC-300, BBC-400, BBC-500 ℃ and BBC-500 ℃ for standby, BBC-500 ℃ for drying, and the block-shaped biochar powder (BBC-200) is ground into.

Example 3

Preparation of rambutan pericarp modified charcoal (PBC)

Washing the rambutan peel with tap water, drying at 50-70 deg.C, cutting into small pieces, pulverizing, and sieving with 60 mesh sieve to obtain rambutan peel powder. And putting the obtained rambutan peel powder into a vacuum tube furnace (QSH-VGF-RTF-1700T, Quanshuo, Shanghai) for thermal cracking to prepare the rambutan peel modified charcoal. Conditions of thermal crackingComprises the following steps: heating to 200 deg.C at a rate of 5 deg.C/min under nitrogen atmosphere, and performing thermal cracking at 300 deg.C for 1 h. Then cooled to room temperature and the sample was washed with deionized water until the filtrate was colorless. And then drying at 60 ℃ to obtain the rambutan pericarp biochar. 50g of MgCl were taken₂·6H₂Dissolving O (analytically pure) in a 1L beaker by adding 1000m of L ultrapure water, adding 50g of the rambutan pericarp biochar into a magnesium chloride solution, soaking for 2h, drying the obtained mixed solution in an oven at 70-80 ℃, cleaning to obtain rambutan pericarp modified biochar (PBC-300), preparing the modified biochar (PBC-300, PBC-400, PBC-500 and PBC-600) with thermal cracking temperatures of 300 ℃, 400 ℃, 500 ℃ and 600 ℃ respectively by the same method, and grinding the dried modified biochar into powder (without obvious blocky solids) for later use.

Comparison of adsorption effects of biochar prepared by different modification methods

(1) Preparation of rambutan pericarp biochar

The rambutan peel powder prepared in example 1 was put into a ceramic crucible and placed in a vacuum tube furnace (QSH-VGF-RTF-1700T, Quanshuo, Shanghai) for thermal cracking to prepare rambutan biochar. Heating to 200 deg.C at a rate of 5 deg.C/min under nitrogen atmosphere, and performing thermal cracking at 200 deg.C for 1 h. Then cooled to room temperature and the sample was washed with deionized water until the filtrate was colorless. Drying at 60 deg.C to obtain rambutan peel biochar (BC-200). Biochar (BC-300, BC-400, BC-500, BC-600) was prepared in the same manner at 300 deg.C, 400 deg.C, 500 deg.C, 600 deg.C. The dried biochar was ground to a powder (no apparent lumpy solids) for use.

(2) Batch adsorption experiment

2.1 Standard Curve transfer of a certain amount of methylene blue stock solution (1000 mg/L) to prepare a series of standard solutions with mass concentrations of 0, 1, 2, 3, 4 and 5 mg/L at lambda_maxThe absorbance was measured at 665nm and a standard curve was plotted (see fig. 1). The regression equation is: y 0.2484x + 0.0137. R2 ═ 0.999, where y is the absorbance (Abs) and x is the mass concentration C of methylene blue_b(mg/L)。

2.2 methods of measurement

20mg of the sample and 40m of L MB of the aqueous solution were put into a conical flask sealed with a rubber stopper, and the resulting mixture was shaken at a fixed temperature in a constant-temperature rotary shaker for a desired time at 180r/min, then the solid was filtered off, and the absorbance thereof was measured at 665nm wavelength with an ultraviolet spectrophotometer, and the adsorption amount (mg/g) was calculated as follows:

q＝(c₀－c_e)V/M(1)

in the formula c₀(mg/L) -initial mass concentration of MB solution,

c_e(mg/L) -mass concentration at adsorption equilibrium of the MB solution,

v (L) -MB solution volume

M (g) -mass of sample

2.3 the adsorption effect of the biochar prepared and modified by different pyrolysis temperatures is explored.

BC-200, BC-300, BC-400, BC-500, BC-600, MBC-200, MBC-300, MBC-400, MBC-500, MBC-600 samples were taken from 3 groups each, and 400 mg/L MB solution was adsorbed for 24 hours at 25 ℃ under 180 r/min.

2.4 influence of solution pH on the adsorption effect of charcoal.

100 mg/L MB solution is taken, the pH value of the solution is adjusted to 3, 4, 5, 6, 7, 8, 9 and 10, and the adsorption experiment is carried out at 25 ℃ by using BC-300 and MBC-300 as adsorbents.

2.5 adsorption kinetics study

Adsorption experiments were performed at 50 mg/L, 100 mg/L, 150 mg/L MB solutions at 25 ℃ for different time intervals (1, 2, 4, 7, 11, 16, 22, 29, 37, 48h) at BC-30025 ℃ and adsorption experiments were performed at 300 mg/L, 400 mg/L, 500 mg/L MB solutions at 25 ℃ for different time intervals (1, 2, 4, 7, 11, 16, 22, 29, 37, 48h) at BC-30025 ℃.

2.6 adsorption isotherms and thermodynamic studies

In the isothermal adsorption experiment, 25, 50, 75, 100, 150, 200, 250, 300 and 400 mg/L MB solutions are used for carrying out adsorption experiments at different temperatures by BC-300, wherein the adsorption time is 72 hours, the temperatures are respectively 15 ℃, 25 ℃, 35 ℃ and 45 ℃, in the isothermal adsorption experiment, 300, 350, 400, 450, 500, 600, 700, 800, 1000 and 1200 mg/L MB solutions are used for carrying out adsorption experiments at different temperatures by MBC-300 as an adsorbent, the adsorption time is 72 hours, and the temperatures are respectively 15 ℃, 25 ℃, 35 ℃ and 45 ℃.

2.7 characterization

Surface area and pore structure were measured on a surface area and porosity analyzer (ASAP 2460 analyzer Micromeritics, USA). The biochar was degassed in vacuo and passed through N at 77K₂And (5) performing characterization by adsorption. The surface area was calculated by the Brunauer-Emmett-Teller (BET) method. The biochar particle size was analyzed by a particle size analyzer (Mastersizer2000, Malvern, UK). Zeta Potential (ZP) was recorded on a Zeta potential analyzer (Zetasizer NANO ZS, Malvern, UK) in water at pH 4.0 to 10.0, with pH adjusted by NaOH or HCl solution and determined by pH test strips. The surface morphology was observed with a Scanning Electron Microscope (SEM) instrument (SU1510, Hitachi, Japan). The functional groups were analyzed by Fourier Transform Infrared (FTIR) spectrometer (Bruker Tensor 27). Powdered biochar was mixed with KBr at a ratio of 1:500wt, tabletted and recorded at 400-4000cm^-1In the meantime. The total elemental composition including C, O, N, H and S was measured by an elemental analyzer (Thermo Scientific Flash 2000CHNS/O, America). The Mg content was analyzed by Inductively Coupled Plasma (ICP) elemental analyzer (Agilent ICPOES 730, USA).

(3) Results and analysis

3.1 characterization

3.1.1 SEM characterization

FIG. 2 is the surface morphology of MBC-300 and BC-300 under SEM magnification of 14500 times. As can be seen from fig. 2 (a): the MBC-300 pore channel is dredged well, the light-color small-block-shaped solid embedded in the pore channel is MgO particles, the MgO particles are well embedded on the surface of the biochar, and the BC-300 in the figure 2(b) has a flat surface and the pore channel is blocked. From the surface structure, MBC-300 is significantly more readily adsorbed than BC-300, indicating that the modification was successfully achieved.

3.1.2 BET analysis

TABLE 1 Physics and Chemicals parameters of rambutan pericarp biochar and modified biochar

As shown in Table 1, the pore diameter, the pore volume and the specific surface area of the MBC-300 are far larger than those of the BC-300; while the average particle size of MBC-300 biochar is significantly smaller than BC-300, which may be due to Mg filling into the pores or pore collapse, which is advantageous for adsorption. The BET analysis results showed that the physical properties of rambutan pericarp modified biochar were improved by modification with magnesium chloride under ultrasound.

3.1.3 elemental analysis

TABLE 2 element contents of rambutan pericarp biochar and modified biochar thereof

As shown in Table 2, both MBC-300 and BC-300 are composed of C, O, H, N and S elements. MBC has a lower C, N content than BC; and H, O is higher than BC. The content of O in the product is increased from 21.63% to 33.11%, the content is obviously increased, and the increase of oxygen-containing groups is favorable for the adsorption of cations. Through modification of magnesium chloride ultrasound, an Mg element is introduced into the MBC-300, and the Mg element can be attributed to MgO coated on the surface of the MCB.

3.1.4 Infrared analysis

As shown in FIG. 3, both MBC-300 and BC-300 are 3550-3400cm^-1、2930-2920cm^-1、1640-1540cm^-1、1450-1340cm^-1And 1320-1210cm^-1Absorption peaks are shown in the positions corresponding to O-H bonds in-OH, C-O stretching of methyl, carbonyl, carboxyl and carboxylic acids and O-H in-plane bending vibration respectively, which indicates that the biochar contains a large number of organic functional groups. After modification, the magnesium modified biochar is increased by 2364.27cm compared with the original biochar^-1、1567.99cm^-1、1120～1030cm^-1And 1075 and 1000cm^-1The absorption peaks corresponding to carbon-carbon triple bond, carbonyl and hydroxyl respectively show that the number of functional groups of carbonyl and hydroxyl in the magnesium modified biochar is increased, and the increase of oxygen-containing groups is beneficial to adsorption.

3.1.5 Zeta potential analysis

As shown in FIG. 4, the Zeta potential of MBC-300 and BC is negative betweenpH 4 andpH 10, and the negative value increases with increasing pH, and the Zeta potential of BC-300 is always higher than that of MBC. This means that MBC-300 has more negative surface charge. This is probably due to the introduction of other oxygen-containing species groups and the bonding of MgOX to the surface of MBC-300. The generally negatively charged surface facilitates the adsorption of cations by electrostatic interactions^[20]。

3.2 Effect of adsorption conditions

3.2.1 adsorption Effect of different samples

As shown in FIG. 5, the adsorption effect of MBC is significantly better than that of BC at the same thermal cracking temperature, wherein the adsorption effect of MBC-300 is significantly optimal at 300 ℃, and BC-300 and MBC-300 are used as the control samples in the following experiments.

3.2.2 adsorption experiments at different pH

As shown in FIG. 6, the equilibrium adsorption capacity of the two biochar to methylene blue is similar to the change rule of pH, both of the biochar and the methylene blue increase with the increase of the pH value, and the adsorption capacity of MBC-300 is far higher than that of BC-300. MB is a cationic dye, and at lower pH, more H is present in solution⁺It competes with methylene blue cation for active adsorption sites on the surface of the charcoal, thus resulting in a decrease in the amount of adsorption.

pH is an important parameter affecting the adsorption capacity of biochar to MB, as it affects the surface charge and functional group ionic state of biochar and the ionization degree of MB. The adsorption efficiency of BC and MBC increased with increasing pH (fig. 6), which is consistent with the law of increasing surface negative charge (fig. 4). Although the adsorption amount of BC and MBC is larger under alkaline condition, the amplification is not much compared with the adsorption amount under neutral condition, and the dye waste water of MB is not too high in concentration generally, so that the dye waste water is more close to neutral, and the subsequent experiments are all selected to be carried out under the condition ofpH 7 in consideration of practical application.

3.2.3 kinetic experiments

Since the kinetic progress of the adsorption reaction is closely related to the contact time, the experiment investigated the change law of the adsorption amount of two samples to MB with time, as shown in fig. 7. Obviously, the adsorption rate of MBC and BC on MB is increased gradually with the increase of time, the adsorption of MB is nearly balanced in 48h, the equilibrium adsorption capacity of MBC is far greater than that of BC, and the adsorption capacity of MBC and BC is increased with the increase of MB concentration. We fit the experimental data with quasi-primary and quasi-secondary kinetic models, respectively.

A quasi-first order kinetic model:

ln(Q_e-Q_t)＝ln Q_e-k₁t

a quasi-second order kinetic model:

wherein t is adsorption time (min), Q_tThe amount of adsorption at time t (mg. g)^-1)，k₁(min^-1) And k₂(g·mg^-1min^-1) Are respectively a quasi-first and a quasi-second adsorption rate constant, Q_eTo balance the adsorption amount (mg. g)^-1). The quasi-first and second order kinetic fits for MB adsorption are shown in FIGS. 8-11, with relevant parameters listed in Table 3.

TABLE 3 kinetic fitting parameters

From Table 3, it can be seen that the regression coefficients R of MBC-300 and BC-300 were fitted with quasi-second order kinetics²The quasi first-order power fitting is closer to 1, and the expected equilibrium adsorption quantity Q_eAlso with the experimentally obtained Q_maxMore closely, the quasi-first order kinetic model fits with poorer results. Indicating that the quasi-second order fit is more consistent with the adsorption process. It was shown that adsorption of MB by MBC-300 and BC-300 is dominated by chemisorption.

3.2.4 thermodynamic experiments

FIG. 12 is an adsorption isotherm of MBC-300 and BC-300, with the abscissa being the concentration of the MB solution and the ordinate being the equilibrium adsorption capacity at different temperatures for that concentration, it is clear that the equilibrium adsorption value of the sample to MB gradually increases with increasing concentration and eventually reaches a saturation value, the maximum equilibrium adsorption capacity of MBC-300 and BC-300 both increases with increasing temperature due to the opening of the porous structure at high temperature, wherein the maximum equilibrium adsorption capacity of MBC-300 does not change much with temperature, demonstrating the better adsorption effect of modified biochar MBC-300 at different temperatures, and the thermodynamic fit of L angmuir and Freundlich is performed for MB adsorption below.

The L angmuir model equation can be expressed as:

the Freundlich model equation can be expressed as:

in the formula, C_eMass concentration of residual MB in solution after equilibration for adsorption (mg L)^-1)，Q_eAdsorption amount of MB onto the adsorbent (mg g) after equilibrium for adsorption^-1)，Q_maxTo theoretically saturate the adsorption capacity (mg. g)^-1)，K_LIs adsorption equilibrium constant (L. mg)^-1)。K_FFreundlich constant (mg)^1-n·Lⁿ·g^-1) And n represents the degree of adsorption dependent on the equilibrium concentration.

The thermodynamic fit of L angmuir and Freundlich to MB adsorption is shown in fig. 13-16, with relevant parameters in table 4.

TABLE 4 thermodynamic fitting parameters

As can be seen from Table 4, the fitting parameter was higher in the L angMuir model than in the Freundlich model, and the maximum equilibrium adsorption Q was fitted_maxValue and experimentally determined Q_e，maxClose to each other, so that the adsorption process of MB can be better described, and the maximum adsorption quantity of MBC-300 reaches about 850mg/g, which is higher than the adsorption value of the biochar reported by most of documents and patents, the high fitness of L angmuir model indicates that the adsorption of MB-300 and BC-300 belongs to single-layer adsorption.

3.3 comparison of the adsorption amounts of the samples of different examples

TABLE 5 comparison of the adsorption amounts of the samples of the different examples

As shown in Table 5, the adsorption capacity of the biochar MBC modified by the method in example 1 is obviously better than that of BBC and PBC modified by the methods in examples 2 and 3, the maximum adsorption capacity of MBC-300 reaches 683.756mg/g, and the BBC-300 and PBC-300 with the maximum adsorption capacities in examples 2 and 3 only have 604.046mg/g and 445.370mg/g respectively. Namely, the modification method of firstly soaking by ultrasonic magnesium chloride and then thermally cracking is superior to the modification method of directly soaking by magnesium chloride and then thermally cracking and firstly thermally cracking and then soaking by ultrasonic magnesium chloride.

3.4 adsorption Properties for other cationic dyes

Referring to the drawing method of the methylene blue standard curve, adsorption standard curves of different cationic dyes are respectively drawn, as shown in FIGS. 17 to 20. The adsorption amounts of different cationic dyes by MBC-300 and BC-300 were measured under adsorption conditions of 25 ℃, 180r/min and 48h, respectively, and the results are shown in FIG. 21.

As shown in FIG. 14, MBC-300 has good adsorption effect on different cationic dyes, and the adsorption amount is obviously better than that of BC-300, and the specific data are shown in the following table.

TABLE 6 adsorption Effect of biochar on different cationic dyes

The adsorption capacity of BC-300 to the rest of cations is small, especially the adsorption capacity to T safranine and rhodamine B is almost zero, and is only 3.509mg/g and 2.249mg/g, which is difficult to be observed in FIG. 14. In addition to the good adsorption effect of the MBC-300 on various cationic dyes, the MBC-200 and MBC-400 have good adsorption capacity on various cationic dyes, and the adsorption capacity of the MBC-400 on the malachite green reaches 694.913mg/g, which is better than that of the MBC-300.

The embodiments of the present invention have been described in detail, but the embodiments are merely examples, and the present invention is not limited to the embodiments described above. Any equivalent modifications and substitutions to those skilled in the art are also within the scope of the present invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.

Claims (10)

1. A preparation method of rambutan peel modified charcoal is characterized by comprising the following steps:

(1) drying and crushing the rambutan peel to obtain rambutan peel powder;

(2) putting the rambutan peel powder into a magnesium chloride aqueous solution, mixing, performing ultrasonic treatment, and removing water from the mixed solution to obtain rambutan peel modified powder;

(3) and carrying out thermal cracking on the rambutan peel modified powder, cooling, washing and drying to obtain the rambutan peel modified charcoal.

2. The method for preparing rambutan pericarp modified biochar as claimed in claim 1, wherein in step (1), rambutan pericarp is washed, dried at 50-70 ℃, pulverized and sieved with a 60-mesh sieve.

3. The method for preparing rambutan pericarp modified biochar as claimed in claim 1, wherein in step (2), MgCl is added to the aqueous solution of magnesium chloride₂·6H₂The content of O is 50 g/L, 50g of rambutan peel powder is added into L per 1000m of magnesium chloride aqueous solution, and the ultrasonic treatment condition is ultrasonic treatment for 2h at 25000 Hz.

4. The method for preparing the rambutan pericarp modified biochar as claimed in claim 1, wherein in the step (3), the pyrolysis conditions are as follows: heating at the speed of 5 ℃/min under the nitrogen atmosphere, and carrying out thermal cracking for 1h at the constant temperature of 200-400 ℃.

5. The method for preparing rambutan pericarp modified biochar as claimed in claim 1, wherein in the step (2), the moisture is removed by drying at 70-80 ℃; and (3) after cooling to 15-30 ℃, washing with deionized water until the filtrate is colorless.

6. A rambutan pericarp modified charcoal prepared by the preparation method of any one of claims 1-5.

7. The application of the rambutan pericarp modified charcoal in dye adsorption is characterized in that the rambutan modified charcoal is prepared by the preparation method of any one of claims 1-5.

8. The use of claim 6, wherein: the dye is a cationic dye.

9. The use of claim 8, wherein: the cationic dye is methylene blue, T safranine, malachite green, crystal violet and/or rhodamine B.

10. Use according to claim 8 or 9, characterized in that: the rambutan peel modified charcoal is used under neutral or alkaline conditions.

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