CN110694591A

CN110694591A - Preparation method and application of Fe-GO/Cs composite microspheres

Info

Publication number: CN110694591A
Application number: CN201910838461.9A
Authority: CN
Inventors: 单慧媚; 赵超然; 彭三曦; 罗林波; 王少培; 曾春芽
Original assignee: Wuhan East Lake Kechuang Test Base Technology Co ltd; Guilin University of Technology
Current assignee: Wuhan East Lake Kechuang Test Base Technology Co ltd; Guilin University of Technology
Priority date: 2019-09-05
Filing date: 2019-09-05
Publication date: 2020-01-17

Abstract

The invention discloses a preparation method of Fe-GO/Cs composite microspheres, which comprises the following steps: ultrasonically stirring and mixing acetic acid aqueous solution and graphene oxide, adding chitosan, ultrasonically stirring and mixing to obtain graphene oxide/chitosan mixed solution, namely GO/Cs mixed solution, and standing and curing; dripping the cured GO/Cs mixed solution into an alkaline aqueous solution while stirring, standing and curing to obtain microspheres after the dripping is finished, filtering, washing the microspheres until the pH of a washing solution is neutral, and adding 5 wt% of glutaric acidStirring, filtering, washing and drying a methanol solution of aldehyde to obtain GO/Cs spheres; adding GO/Cs spheres into FeCl₂Heating the water solution to dryness, washing and drying to obtain Fe-GO/Cs composite microspheres; also discloses the application of the Fe-GO/Cs composite microspheres as an adsorbent. The invention has better effect on removing As (III) in water.

Description

Preparation method and application of Fe-GO/Cs composite microspheres

Technical Field

The present invention relates to the field of inorganic materials. More specifically, the invention relates to a preparation method and application of Fe-GO/Cs composite microspheres.

Background

The magnetic polymer composite microspheres are polymer microspheres containing magnetic metal or metal oxide and having magnetic response performance. On one hand, the magnetic polymer microsphere not only has the characteristics of the common polymer microsphere, for example, a new functional group can be endowed to the magnetic polymer microsphere through means of surface modification, copolymerization crosslinking and the like; on the other hand, the polymer microsphere can reach a directional area or be separated under the action of an external magnetic field due to the unique magnetic responsiveness, so that the polymer microsphere has a great prospect in the fields of biomedicine, bioengineering, cytology and the like.

Graphene Oxide (GO) has a large specific surface area, is a good conductor of electrons and an excellent modified base material, but contains a plurality of hydrophilic oxygen functional groups, so that GO is easily dissolved in water, and therefore, the GO needs to be modified to obtain a better performance effect.

Disclosure of Invention

An object of the present invention is to solve at least the above problems and to provide at least the advantages described later.

The invention also aims to provide a preparation method of the Fe-GO/Cs composite microspheres and application of the Fe-GO/Cs composite microspheres, and the Fe-GO/Cs composite microspheres have a good effect on removing As (III) in water.

To achieve these objects and other advantages in accordance with the present invention, there is provided a method for preparing Fe-GO/Cs composite microspheres, comprising the steps of:

step one, carrying out ultrasonic stirring and mixing on 1.5% (V/V) acetic acid aqueous solution and graphene oxide, adding chitosan, carrying out ultrasonic stirring and mixing to obtain graphene oxide/chitosan mixed solution, namely GO/Cs mixed solution, standing and curing;

step two, dropwise adding the cured GO/Cs mixed solution into an alkaline aqueous solution while stirring, standing and curing to obtain microspheres after the dropwise adding is finished, filtering, washing the microspheres until the pH of a washing solution is neutral, adding a 5 wt% methanol solution of glutaraldehyde, stirring, filtering, washing and drying to obtain GO/Cs spheres;

step three, taking GO/Cs spheres and adding FeCl₂Heating the water solution to dryness, washing and drying to obtain the Fe-GO/Cs composite microspheres.

Preferably, the dropping in the second step is carried out by using a syringe at a dropping rate of 1 drop/s.

Preferably, the alkaline aqueous solution in the second step is a 2 wt% aqueous solution of sodium hydroxide.

Preferably, the washing in the third step is washed by deionized water until the conductivity of the washing liquid is less than 30us/cm and the conductivity is not changed.

Also provides the application of the Fe-GO/Cs composite microspheres as an adsorbent.

The invention at least comprises the following beneficial effects: takes graphene oxide and chitosan as precursors and FeCl₂As a modifier, the iron-loaded graphene oxide/chitosan composite microspheres (Fe-GO/Cs) are researched and prepared by a heating evaporation method, and the Fe-GO/Cs composite microspheres have a good effect on the adsorption removal of As (III) in water.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1 is a schematic flow chart of the preparation of Fe-GO/Cs composite microspheres according to an embodiment of the present invention;

FIG. 2 is an FTIR spectrum of Fe-GO/CS composite microspheres of an embodiment of the present invention;

FIG. 3 is an SEM image of GO/Cs spheres before and after loading iron in an embodiment of the invention;

FIG. 4 shows the removal rate of As (III) from Fe-GO/Cs composite microspheres under different iron-loading conditions according to an embodiment of the present invention;

FIG. 5 is a graph showing the change of adsorption capacity of Fe-GO/Cs composite microspheres to As (III) with pH according to an embodiment of the present invention;

FIG. 6 is Zeta zero potential of Fe-GO/Cs composite microspheres according to an embodiment of the present invention;

FIG. 7 is a curve showing the change of the adsorption capacity of Fe-GO/Cs composite microspheres to As (III) with time according to the embodiment of the present invention.

Detailed Description

The present invention is further described in detail below with reference to the drawings and examples so that those skilled in the art can practice the invention with reference to the description.

It is to be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified.

Example 1

The embodiment provides a preparation method of an Fe-GO/Cs composite microsphere, which comprises the following steps as shown in FIG. 1:

step one, carrying out ultrasonic stirring and mixing on 100ml of 1.5% (V/V) acetic acid aqueous solution and 0.025g of Graphene Oxide (GO), then adding 4.0g of Chitosan (Chitosan, Cs), carrying out ultrasonic stirring and mixing to obtain graphene oxide/Chitosan mixed solution, namely GO/Cs mixed solution, standing and curing;

step two, dropwise adding the cured GO/Cs mixed solution into a 2% wt sodium hydroxide aqueous solution according to the volume ratio of 2:5, stirring while dropwise adding, dropwise adding by using an injector at the dropping speed of 1 drop/s, standing and solidifying for 24 hours after dropwise adding is completed to obtain microspheres, filtering, washing the microspheres with deionized water until the pH of a washing solution is neutral, adding a 5% wt methanol solution of glutaraldehyde, stirring, filtering, washing with deionized water, and drying to obtain GO/Cs spheres;

step three, taking 1g of GO/Cs spheres and adding 100mL of 0.1M FeCl₂Heating and evaporating the water solution to dryness, washing the water solution with deionized water until the conductivity of the washing solution is less than 30us/cm and the conductivity is unchanged, and drying the washed water solution to obtain the Fe-GO/Cs composite microspheres.

Example 2

The embodiment provides a preparation method of Fe-GO/Cs composite microspheres, which comprises the following steps:

step one, carrying out ultrasonic stirring and mixing on 200ml of 1.5% (V/V) acetic acid aqueous solution and 0.05g of Graphene Oxide (GO), then adding 8.0g of Chitosan (Chitosan, Cs), carrying out ultrasonic stirring and mixing to obtain a Graphene oxide/Chitosan mixed solution, namely a GO/Cs mixed solution, and standing and curing;

step two, dropwise adding the cured GO/Cs mixed solution into a 2% wt sodium hydroxide aqueous solution according to the volume ratio of 2:5, stirring while dropwise adding, dropwise adding by using an injector at the dropwise adding speed of 3 drops/s, standing and solidifying for 24 hours after dropwise adding is completed to obtain microspheres, filtering, washing the microspheres with deionized water until the pH of a washing solution is neutral, adding a 5% wt methanol solution of glutaraldehyde, stirring, filtering, washing and drying to obtain GO/Cs spheres;

step three, taking 2g of GO/Cs spheres and adding 200mL of 0.1M FeCl₂Heating and evaporating the water solution to dryness, washing the water solution with deionized water until the conductivity of the washing solution is less than 30us/cm and the conductivity is unchanged, and drying the washed water solution to obtain the Fe-GO/Cs composite microspheres.

Example 3

step one, carrying out ultrasonic stirring and mixing on 150ml of 1.5% (V/V) acetic acid aqueous solution and 0.038g of Graphene Oxide (GO), then adding 6.0g of Chitosan (Chitosan, Cs), carrying out ultrasonic stirring and mixing to obtain graphene oxide/Chitosan mixed solution, namely GO/Cs mixed solution, and standing and curing;

step two, dropwise adding the cured GO/Cs mixed solution into a 2% wt sodium hydroxide aqueous solution according to the volume ratio of 2:5, stirring while dropwise adding, dropwise adding by using an injector at the speed of 2 drops/s, standing and solidifying for 24 hours after dropwise adding is completed to obtain microspheres, filtering, washing the microspheres by using deionized water until the pH of a washing solution is neutral, adding a 5% wt methanol solution of glutaraldehyde, stirring, filtering, washing and drying to obtain GO/Cs spheres;

step three, taking 1.5g of GO/Cs spheres and adding 150mL of 0.1M FeCl₂Heating and evaporating the water solution to dryness, washing the water solution with deionized water until the conductivity of the washing solution is less than 30us/cm and the conductivity is unchanged, and drying the washed water solution to obtain the Fe-GO/Cs composite microspheres.

The embodiment also provides the application of the Fe-GO/Cs composite microspheres as an adsorbent.

(1) Adsorption experiments

Adding Fe-GO/Cs composite microspheres into an aqueous solution containing As (III);

equilibrium adsorption capacity Q for As (III)_eAnd the removal rate R is calculated by the following formula:

in the formula, C₀、C_e- -As (III) concentration at the initial time and at equilibrium, mg. L^-1(ii) a V- -volume of As (III) solution added, mL, m- -added mass of adsorbent, g.

(2) Adsorption model calculation

The research on the kinetics of the adsorption process of Fe-GO/Cs on As (III) and the isothermal adsorption characteristics can better describe the reaction rate of the adsorbent adsorption and the solute adsorption.

Common models for dynamic process research include primarily pseudo-primary and pseudo-secondary kinetic models. The method comprises the following specific steps:

the pseudo first order kinetic model assumes that adsorption is primarily physical adsorption, and the equation is as follows:

non-linearity:

linearity:

the pseudo-second order kinetic model assumes that the adsorption is mainly chemisorption, and the equation is as follows:

non-linearity:

linearity:

wherein Q is_eAnd Q_t(mg/g) represents the adsorption amounts of As (III) at the equilibrium time and t-time, K₂(g·mg^-1·min^-1) Is the rate constant of the second order kinetics.

Common models for studying isothermal adsorption characteristics include the Langmuir and Freundlich models. Among them, the Langmuir model assumes that the adsorbent has a uniform surface structure, mainly single-layer adsorption, and its binding sites have the same adsorption tendency and no interaction occurs. The Freundlich model assumes that the adsorbent surface has non-uniformity, and is considered to be dominated by multi-layer adsorption. The specific expression is as follows:

Langmuir：

Freundlich：Q_e＝K_FC_e ^1/n

wherein Q is_e(mg·g^-1) And Ce (mg. L)^-1) Respectively represents the adsorption capacity of Fe-GO/Cs adsorption equilibrium and the equilibrium concentration of As (III), Q_m(mg/g) is the maximum adsorption capacity of As (III); k_LIs the Langmuir adsorption equilibrium constant and is related to the strength of the adsorption interaction. K_FAnd 1/n are the adsorption equilibrium constant and the adsorption strength constant of the Freundlich equation, respectively, and the smaller the 1/n, the better the adsorption capacity.

(3) Adsorption effect

a) Characteristics of change of material structure before and after reaction

FTIR graphs of As (III) adsorbed by the Fe-GO/Cs composite microspheres before and after the reaction are shown in FIG. 2. From fig. 2 it can be found that: at 3438cm^-1A broadband characteristic peak appears and is at 1671cm^-1The appeared characteristic peaks respectively belong to a-OH stretching vibration peak and a C-OH bending vibration absorption peak of a water molecule; at 2947cm^-1The characteristic peak is a C-H stretching vibration peak; at 1719cm^-1The position is a stretching vibration peak of C ═ O on the carboxyl of the graphene oxide; at 1380cm^-1May be-CH₃A characteristic peak; at 1061cm^-1The peak is the vibration absorption peak of C-O-C. The Fe-GO/Cs found before and after the comparison reaction is 2947cm^-1、1671cm^-1The C-H, C-OH before and after adsorption is changed in position, which shows that the functional group is mainly involved in the adsorption removal of arsenic.

Comparing the SEM images of GO/Cs spheres before and after loading iron, as shown in FIG. 3, the left side of FIG. 3 is before loading iron, and the right side of FIG. 3 is after loading iron, and a large number of needles are formed on the surface of the GO/Cs sphere material after loading iron, which greatly increases the surface area of the material.

b) Effect of iron-carrying conditions on removal of As (III) from GO/Cs

Respectively using FeCl with different concentrations₂、FeCl₃The removal effect of the modified GO/Cs on 2mg/LAs (III) is shown in FIG. 4. As a result, it was found that: (1) fe²⁺The removal rate of modified GO/Cs to As (III) is obviously higher than that of Fe³⁺Modified GO/Cs composite microspheres; (2) fe with increasing iron concentration²⁺The removal rate of As (III) by the modified GO/Cs is reduced and then increased, and when the concentration of iron carrier is 0.1mol/L, Fe²⁺The removal rate of GO/Cs to As (III) is as high as 95%.

c) Influence of pH on removal of As (III) from Fe-GO/Cs composite microspheres

The adsorption capacities (solid-to-liquid ratio of 1g/L) of GO/Cs and Fe-GO/Cs to 2mg/LAs (III) at

pH

3, 5, 7, 9, 11 are shown in FIG. 5. The results show that: the adsorption capacity of the GO/Cs composite microspheres to As (III) is sharply reduced along with the increase of the pH value of the water environment, while the adsorption capacity of the Fe-GO/Cs composite microspheres to As (III) is firstly reduced and then increased along with the increase of the pH value, and the adsorption capacity is the minimum when the pH value is 9. This is because the zeta zero potential of the Fe-GO/CS spheres is 9.18, as shown in FIG. 6, whenWhen the pH value of the solution is about 9, the surface of the material is not charged, so that the electrostatic adsorption effect is reduced, and the adsorption capacity is reduced. The adsorption capacity of the Fe-GO/Cs composite microspheres to As (III) is maximum at the pH value of 11, because As (III) is mainly H in the alkaline environment₂AsO₃ ^-、HAsO₃ ^2-Exists in an anionic form and is very easy to be combined with adsorption sites on the surface of the material.

d) Effect of reaction time on removal of As (III) from Fe-GO/Cs

The adsorption capacity of Fe-GO/Cs versus 2mg/las (iii) at different reaction times under reaction conditions of 20 ℃ and pH 11 is shown in fig. 7. From fig. 7 it can be found that: with the prolonging of the reaction time, the adsorption capacity of Fe-GO/Cs to As (III) gradually increases (0-1200 min), and finally tends to be stable (>1200 min). When the reaction reaches the equilibrium, the adsorption capacity of Fe-GO/Cs to As (III) is up to 0.955 mg/g.

Pseudo first-order and pseudo second-order kinetic models are adopted to fit the adsorption process of the Fe-GO/Cs composite microspheres to As (III), and the fitting result is shown in figure 7 and table 1. From fig. 7 and table 1 it can be found that: the pseudo first-stage adsorption model and the pseudo second-stage model have high fitting degree on the dynamic process of adsorbing As (III) by the Fe-GO/Cs composite microspheres, and R is²>0.98, but relatively speaking, the theoretical value (0.942mg/g) of Qe obtained by using a pseudo-first order kinetic model is closer to the experimental value (0.955mg/g), so the kinetic process of adsorbing As (III) by the Fe-GO/Cs composite microspheres is more consistent with the pseudo-first order kinetic model, and the adsorption is mainly physical adsorption.

TABLE 1 kinetic model fitting parameters

e) Isothermal adsorption characteristics

When the equilibrium concentration is in the range of 0-10 mg/L, the result of the isothermal adsorption model fitting is shown in Table 2, and the results can be found in Table 2: the Langmuir and Freundlich models have high fitting degree on the isothermal adsorption process of Fe-GO/Cs composite microsphere pairs As (III) (R is²>0.96), which means that the adsorption of the Fe-GO/Cs composite microspheres to As (III) is a ratioA more complicated process. On one hand, a large amount of iron (hydrogen) oxide is carried on the surface of the Fe-GO/Cs composite microsphere, and meanwhile, the rich carboxyl on GO and a large amount of amino on Cs can undergo amidation reaction through self-assembly to form amido bond-CONH-, so that the adsorption of As (III) can be influenced by a plurality of factors such as iron (hydrogen) oxide, carboxyl, amino, amido bond-CONH-and the like.

TABLE 2 fitting parameters of isothermal adsorption model

In summary, the Fe-GO/Cs composite microspheres prepared in this example found:

(1)Fe²⁺the adsorption capacity of the modified GO/Cs composite microspheres to As (III) is higher than that of Fe³⁺Modified GO/Cs composite microspheres;

(2) the equilibrium adsorption capacity of the Fe-GO/Cs composite microspheres to a 2mg/LAs (III) solution under the condition of pH 11 is 0.955 mg/g;

(3) the Langmuir model fitting result shows that Fe is in the equilibrium concentration range of 0-10 mg/LAs (III)²⁺The maximum equilibrium adsorption quantity of GO/CS composite microspheres to As (III) is 3.15 mg/g;

(4) the removal of As (III) by the Fe-GO/Cs composite microspheres is mainly carried out by physical adsorption, and because a large amount of iron (hydrogen) oxide is carried on the surfaces of the Fe-GO/Cs composite microspheres, and simultaneously carboxyl groups rich in GO and a large amount of amino groups rich in Cs can undergo amidation reaction through self-assembly to form amido bond-CONH-, the adsorption mechanism of the Fe-GO/Cs composite microspheres to As (III) is relatively complex and is possibly influenced by a plurality of factors such as iron (hydrogen) oxide, carboxyl groups, amino groups, amido bond-CONH-, and the like.

While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable to various fields of endeavor for which the invention may be embodied with additional modifications as would be readily apparent to those skilled in the art, and the invention is therefore not limited to the details shown and described herein without departing from the generic concept as defined by the claims and their equivalents.

Claims

A preparation method of Fe-GO/Cs composite microspheres is characterized by comprising the following steps:

step one, carrying out ultrasonic stirring and mixing on 1.5% (V/V) acetic acid aqueous solution and graphene oxide, adding chitosan, carrying out ultrasonic stirring and mixing to obtain graphene oxide/chitosan mixed solution, namely GO/Cs mixed solution, standing and curing;

step two, dropwise adding the cured GO/Cs mixed solution into an alkaline aqueous solution while stirring, standing and curing to obtain microspheres after the dropwise adding is finished, filtering, washing the microspheres until the pH of a washing solution is neutral, adding a 5 wt% methanol solution of glutaraldehyde, stirring, filtering, washing and drying to obtain GO/Cs spheres;

step three, taking GO/Cs spheres and adding FeCl₂Heating the water solution to dryness, washing and drying to obtain the Fe-GO/Cs composite microspheres.
2. The method for preparing Fe-GO/Cs composite microspheres of claim 1, wherein the dropwise addition in the second step is performed by using a syringe.
3. The method for preparing Fe-GO/Cs composite microspheres according to claim 1, wherein the alkaline aqueous solution in step two is a 2 wt% aqueous solution of sodium hydroxide.
4. The method for preparing Fe-GO/Cs composite microspheres according to claim 1, wherein the washing in step three is performed with deionized water until the conductivity of the washing solution is less than 30us/cm and the conductivity is not changed.
5. Use of the Fe-GO/Cs composite microspheres according to any one of claims 1 to 4 as an adsorbent.