阅读说明：本技术 三维层状CoAl双金属氢氧化物纳米材料的制备方法及其在水体重金属离子检测中的应用 (Preparation method of three-dimensional layered CoAl bimetal hydroxide nano material and application of three-dimensional layered CoAl bimetal hydroxide nano material in detection of heavy metal ions ) 是由 李丽 林崇 潘清江 史克英 刘志 张雪影 于 2019-06-04 设计创作，主要内容包括：本发明提供了一种三维层状CoAl双金属氢氧化物纳米材料的制备方法及其在水体重金属离子检测中的应用,首先通过用氢氧化钠水解法制备了层状双金属氢氧化物前驱体,然后再经过过滤、干燥等步骤制得三维层状CoAl双金属氢氧化物纳米材料,本发明提供的制备方法简单,所制得的三维层状CoAl双金属氢氧化物纳米材料具有丰富的层结构,层与层组成花状结构,使其具有更大的比表面积,更有利于对水体中重金属离子的捕集,提高了检测灵敏度。(The invention provides a preparation method of three-dimensional layered CoAl bimetal hydroxide nano materials and application thereof in detection of heavy metal ions in water bodies.)

1, three-dimensional layered CoAl bimetal hydroxide nanometer materials, which is characterized in that the nanometer materials are prepared by raw materials comprising cobalt salt, aluminum salt and surfactant.

2. The material according to claim 1, wherein the cobalt salt is selected from or two of cobalt nitrate, cobalt chloride, cobalt sulfate and cobalt carbonate, preferably, the cobalt salt is cobalt nitrate;

the aluminum salt is or two selected from aluminum nitrate, aluminum chloride, aluminum sulfate and aluminum carbonate, preferably, the aluminum salt is aluminum nitrate.

3. The material according to claim 1 or 2, wherein the surfactant is selected from anionic surfactants and nonionic surfactants selected from at least of alkylphenol ethoxylates, higher fatty alcohol ethoxylates and sucrose esters;

the anionic surfactant is selected from sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, α -sodium alkenyl sulfonate, sodium lignin sulfonate and sodium secondary alkyl sulfonate, and the preferred step is .

4. The material of claim 1, wherein the raw material further comprises a precipitant selected from kinds of sodium hydroxide solution, potassium hydroxide solution and ammonia water, preferably sodium hydroxide solution.

5. The material of claim 1, wherein the XRD spectrum thereof has distinct diffraction peaks at 11.528 °, 23.205 °, 34.604 °, 38.783 ° and 60.024 °.

A process for the preparation of three-dimensional layered CoAl double hydroxide nanomaterials, preferably for the preparation of the materials of claims 1 to 5, wherein said process comprises the steps of:

step 1, adding cobalt salt, aluminum salt and a precipitator into a solvent, and uniformly mixing;

step 2, reacting at room temperature;

and 3, filtering, washing and drying to obtain the three-dimensional layered CoAl bimetal hydroxide nano material.

7. The method according to claim 6, wherein, in step 1,

the cobalt salt is selected from or two of cobalt nitrate, cobalt chloride, cobalt sulfate and cobalt carbonate, preferably, the cobalt salt is cobalt nitrate;

the aluminum salt is selected from or two of aluminum nitrate, aluminum chloride, aluminum sulfate and aluminum carbonate, and preferably, the aluminum salt is aluminum nitrate;

the molar ratio of the cobalt salt to the aluminum salt is (0.5-8): 1, preferably (1-4): 1;

the precipitant is selected from sodium hydroxide solution, potassium hydroxide solution and ammonia water, preferably sodium hydroxide solution.

8. The method according to claim 6, wherein a surfactant selected from the group consisting of anionic surfactants and nonionic surfactants is further added in step 1; preferably, the surfactant is selected from anionic surfactants.

9. The preparation method according to claim 6, wherein in the step 2, the reaction temperature is 15-40 ℃, preferably 20-35 ℃; the reaction time is 12-36 h;

and 3, filtering to obtain a precipitate, washing the precipitate obtained by filtering with deionized water until the pH value of a washing liquid is neutral, then washing with absolute ethyl alcohol for 2-3 times, and finally drying the precipitate in a drying box.

10. Use of the material according to claims 1 to 5 or the material prepared by the method of the method of claims 6 to 9 for the detection of heavy metal ions in a body of water, preferably the heavy metal ions comprise Cd (ii), Pb (ii), Cu (ii), Hg (ii).

Technical Field

The invention relates to the technical field of nano materials, in particular to a preparation method of three-dimensional layered CoAl bimetal hydroxide nano materials and application thereof in detection of heavy metal ions in a water body.

Background

Heavy metal pollution becomes a global environmental problem, particularly, heavy metal pollution to water bodies has the characteristics of concealment, irreversibility and long-term property, can directly influence the ecological environment, and can influence the health of human bodies or animals through skin contact, breath inhalation and food chains, so that the caused consequences are very serious.

Due to the existence of abundant laminate cations and interlayer anions in the unique layer structure of the layered hydroxide, the layered hydroxide provides abundant active sites and electron transfer channel advantages for the layered hydroxide, and through long-term research and development, the layered hydroxide is widely applied to industries such as environment, food, medical treatment, home decoration and the like by .

Layered Double Hydroxides (LDH) are novel inorganic materials with abundant layer structures, and have the characteristics of acid-base property, thermal stability, interlaminar anion exchangeability, structure memory effect and the like, which are widely used as catalysts, anion exchange materials, flame retardants, adsorbents, drug delivery agents and the like, but the application of the LDH as a heavy metal detection material in water is rarely reported.

At present, materials for detecting heavy metals in water bodies are mainly graphene composite materials, and the time and cost of the preparation process are higher than those of LDH.

Therefore, there is a need to research and provide a preparation method of three-dimensional layered CoAl-based composite oxide (CoAl) bimetallic hydroxide materials which can be used for detecting heavy metals in water, have a larger adsorption surface area and can provide more active sites to trap heavy metal ions.

Disclosure of Invention

Firstly, preparing a three-dimensional layered double hydroxide precursor by a simple sodium hydroxide coprecipitation method, and then preparing the three-dimensional layered CoAl double hydroxide by filtering, washing, drying and other steps.

The object of the present invention is to provide the following:

, the invention provides three-dimensional layered CoAl bimetal hydroxide nanometer materials, which are prepared by raw materials comprising cobalt salt, aluminum salt and surfactant.

In a second aspect, the invention also provides a preparation method of three-dimensional layered CoAl double metal hydroxide nano materials, preferably used for preparing the material of the aspect, wherein the preparation method comprises the following steps:

step 1, adding cobalt salt, aluminum salt and a precipitator into a solvent, and uniformly mixing;

step 2, reacting at room temperature;

and 3, filtering, washing and drying to obtain the three-dimensional layered CoAl bimetal hydroxide nano material.

In a third aspect, the use of the material of the above or the material prepared by the method of the second aspect for detecting heavy metal ions in a water body, preferably the heavy metal ions comprise Cd (II), Pb (II), Cu (II), and Hg (II).

According to the preparation of the three-dimensional layered CoAl bimetal hydroxide nano materials and the application thereof in the detection of heavy metals in water bodies, the beneficial effects are as follows:

(1) the three-dimensional layered CoAl bimetal hydroxide has rich layer structures, the layers form a flower-shaped structure, the specific surface area of the flower-shaped layered bimetal hydroxide is larger, more active sites can be provided to trap heavy metal ions, and pores are formed between the flower-shaped layered bimetal hydroxide layers, so that heavy metal ions can be trapped, and an electron transmission channel is increased;

(2) the three-dimensional layered CoAl bimetal hydroxide nano material has good heavy metal detection effect, can improve the detection sensitivity and reduce the detection limit, has short detection time, can detect single heavy metal ions, and can also detect mixed solution of various heavy metal ions, wherein the heavy metal ions include but are not limited to Cd (II), Pb (II), Cu (II) and Hg (II);

(3) the fine and high XRD diffraction peak of the three-dimensional layered CoAl bimetal hydroxide nano material shows that the crystallinity of the material is good and the material is a pure layered compound, so that the performance of the material is more stable;

(4) the three-dimensional layered double-metal hydroxide precursor is prepared by a simple sodium hydroxide hydrolysis method, and the preparation method is simple; the cost of cobalt nitrate, aluminum nitrate or sodium dodecyl sulfate used for preparing the three-dimensional layered CoAl bimetal hydroxide nano material is far lower than that of a graphene composite material, so that the cost is low.

Drawings

Figure 1 shows the XRD pattern of the sample of example 1;

FIG. 2 shows an SEM image of a sample of example 1;

FIGS. 3, 4 and 5 illustrate Cd²⁺The detection data result of the ions;

FIG. 6, FIG. 7 and FIG. 8 show Pd²⁺The detection data result of the ions;

FIGS. 9, 10 and 11 show Cu²⁺The detection data result of the ions;

fig. 12, 13 and 14 show Hg²⁺The detection data result of the ions;

FIG. 15 shows four mixed ions (Cd)²⁺、Pd²⁺、Cu²⁺And Hg²⁺) The result of the detected data of (1).

Detailed Description

The features and advantages of the present invention will become more apparent and appreciated from the following detailed description of the invention.

The present invention is described in detail below.

According to th aspect of the invention, three-dimensional layered CoAl double metal hydroxide nano-materials are provided, which are prepared from raw materials comprising cobalt salt, aluminum salt and surfactant.

The cobalt salt is kinds or two kinds selected from cobalt nitrate, cobalt chloride, cobalt sulfate and cobalt carbonate, and preferably, the cobalt salt is cobalt nitrate.

The aluminum salt is or two selected from aluminum nitrate, aluminum chloride, aluminum sulfate and aluminum carbonate, and preferably, the aluminum salt is aluminum nitrate.

The molar ratio of the cobalt salt to the aluminum salt is (0.5-8): 1, preferably (1-4): 1, more preferably (2-3:): 1, such as 2: 1.

The surfactant is selected from anionic surfactants and nonionic surfactants, and the nonionic surfactants are at least selected from alkylphenol ethoxylates, high-carbon fatty alcohol polyoxyethylene ether and sucrose ester;

the anionic surfactant is selected from sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, α -sodium alkenyl sulfonate, sodium lignin sulfonate and sodium secondary alkyl sulfonate, and is preferably Sodium Dodecyl Sulfate (SDS) in step ;

preferably, the surfactant is an anionic surfactant, more preferably, the surfactant is Sodium Dodecyl Sulfate (SDS).

Preferably, the molar ratio of the aluminum salt to the sodium lauryl sulfate is 1: (0.5 to 30), preferably 1: (1-15), preferably 1: 1.

the raw material also comprises a precipitator which is selected from sodium hydroxide solution, potassium hydroxide solution and ammonia water, and is preferably sodium hydroxide solution.

Preferably, the concentration of the sodium hydroxide solution is (1-3) mol/L, such as 2 mol/L.

Preferably, the dosage of the sodium hydroxide solution is that the molar ratio of the volume of the sodium hydroxide solution to the aluminum salt is (5-15) mL: 0.0004 mol.

In the invention, the SEM image of the three-dimensional layered CoAl double-metal hydroxide nano material has rich layer structures, the layers form a flower-shaped structure, the specific surface area of the flower-shaped layered double-metal hydroxide is larger, and pores are formed between the flower-shaped layered double-metal hydroxide layers.

In an XRD pattern, diffraction peaks are obvious at 11.528 degrees, 23.205 degrees, 34.604 degrees, 38.783 degrees and 60.024 degrees.

According to a second aspect of the present invention, there is provided a method for preparing three-dimensional layered CoAl double metal hydroxide nanomaterials, preferably for preparing the material of aspect , the method comprising the steps of:

step 1, adding cobalt salt, aluminum salt and a precipitator into a solvent, and uniformly mixing;

step 2, reacting at room temperature;

and 3, filtering, washing and drying to obtain the composite material.

In the step 1, the method comprises the following steps of,

the cobalt salt is or two selected from cobalt nitrate, cobalt chloride, cobalt sulfate and cobalt carbonate, preferably, the cobalt salt is cobalt nitrate.

The aluminum salt is or two selected from aluminum nitrate, aluminum chloride, aluminum sulfate and aluminum carbonate, preferably, the aluminum salt is aluminum nitrate.

In the invention, the cobalt salt adopts cobalt nitrate hexahydrate; the aluminum salt is aluminum nitrate nonahydrate.

In embodiments, the molar ratio of cobalt salt to aluminum salt is (0.5-8): 1, preferably (1-4): 1, preferably (2-3): 1, e.g., 2: 1.

The precipitant is selected from sodium hydroxide solution, potassium hydroxide solution and ammonia water, preferably sodium hydroxide solution.

Preferably, the concentration of the sodium hydroxide solution is (1-3) mol/L, such as 2 mol/L.

Preferably, the dosage of the sodium hydroxide solution is that the molar ratio of the volume of the sodium hydroxide solution to the aluminum salt is (5-15) mL: 0.0004 mol.

The inventors have found that the co-precipitation process can be better achieved with sodium hydroxide solution.

Preferably, a surfactant is further added in the step 1, the surfactant is selected from at least of anionic surfactants and nonionic surfactants, the nonionic surfactants are selected from alkylphenol ethoxylates, higher fatty alcohol ethoxylates and sucrose esters, the anionic surfactants are selected from sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, α -sodium alkenyl sulfonate, sodium lignin sulfonate and secondary sodium alkyl sulfonate, and the step is preferably Sodium Dodecyl Sulfate (SDS).

Preferably, the surfactant is an anionic surfactant, and further steps are preferably sodium lauryl sulfate.

Preferably, the molar ratio of the aluminum salt to the sodium lauryl sulfate is 1: (0.5 to 30), preferably 1: (1-15), such as 1: 1.

The inventor finds that when the surfactant sodium dodecyl sulfate is used for preparing the material, the obtained material has better performance, and can better trap heavy metal ions in water, so that the detection limit is lower, and the detection time is shorter.

Compared with CN 201810575816.5' the three-dimensional layered CoAl bimetal hydroxide composite material prepared by cobalt nitrate, aluminum nitrate, ammonium fluoride and urea in the prior art, the three-dimensional layered CoAl bimetal hydroxide nano material prepared by cobalt nitrate, aluminum nitrate, SDS and sodium hydroxide solution has more excellent effect in detecting heavy metal ions in water body, probably because, in the preparation method, the invention adopts a coprecipitation synthesis mode, is simpler and easier to operate than a step synthesis hydrothermal method, and saves energy consumption, in addition, in , hydroxide is more suitable to form in alkaline environment, which creates a better environment for synthesis.

In cases, the solvent is selected from ethanol, methanol, isopropanol, and water, preferably, the solvent is deionized water, distilled water, purified water, preferably deionized water.

Preferably, the mass ratio of the total mass (the sum of the mass of the cobalt salt, the aluminum salt, the surfactant and the precipitator) of the raw materials to the deionized water is (2.0-2.5): 40.

preferably, the four raw materials are mixed with solvent water and then subjected to ultrasonic treatment, wherein the ultrasonic power is 90-150W, and preferably 100-140W.

The ultrasonic treatment time is 5-20 min, preferably 5-10 min, until the solid is completely dissolved. So that the hydrated nitrate substance and SDS are better dispersed in the aqueous solution.

Preferably, after the ultrasonic treatment, the mixed solution is continuously stirred for 20-30 min at the stirring speed of 400-800 rpm/min, preferably 500 rpm/min.

In the step 2, the step of the method is carried out,

and (3) reacting the mixed solution obtained in the step (1) at 15-40 ℃, preferably 20-35 ℃ (room temperature reaction), and stirring for reaction for 12-36 h, such as 24 h.

The inventor finds that the material obtained by the room-temperature reaction has better performance and higher detection sensitivity on heavy metals in water.

The reaction principle of the present invention is presumed as follows:

during co-precipitation, cobalt and aluminum salts form Co (OH) (H) in aqueous solution₃O)⁺ _n-1And Al (OH) (H)₃O)²⁺ _n-1As the reaction proceeds, the sodium hydroxide decomposes to provide hydroxide ions, rendering the solution alkaline, and finally Co (OH) (H)₃O)⁺ _n-1、Al(OH)(H₃O)²⁺ _n-1、OH^-And CO₃ ^2-The reaction forms a double metal hydroxide.

In the step 3, the step of the method is that,

and the post-treatment comprises the steps of filtering the reaction liquid obtained in the step 2 to obtain a precipitate, washing the precipitate obtained by filtering with deionized water until the pH of the washing liquid is neutral, then washing with absolute ethyl alcohol for 2-3 times, and finally drying the precipitate in a drying box to obtain the three-dimensional layered CoAl bimetal hydroxide nano material.

The drying method comprises the following steps: drying for 10-24 h at 50-90 ℃.

The preparation method is simple, the SEM image of the three-dimensional layered CoAl double-metal hydroxide nano material prepared by the method has rich layer structures, the layers form a flower-shaped structure, the specific surface area of the flower-shaped layered double-metal hydroxide is larger, and pores are formed between the flower-shaped layered double-metal hydroxide layers.

In an XRD pattern, diffraction peaks are obvious at 11.528 degrees, 23.205 degrees, 34.604 degrees, 38.783 degrees and 60.024 degrees.

According to a third aspect of the present invention, there is provided a use of the three-dimensional layered CoAl double hydroxide nanomaterial of or the three-dimensional layered CoAl double hydroxide nanomaterial prepared by the preparation method of the second aspect, for detecting heavy metals in a water body.

Preferably, the application relates to detection methods for detecting heavy metal ions in water bodies, and the method preferably comprises the following steps of preparing a membrane substance solution by using a set amount of three-dimensional layered CoAl bimetallic hydroxide nano material and a 0.1% chitosan ethanol solution, dripping the membrane substance solution onto a glassy carbon electrode, and detecting the solution containing the heavy metal ions by using an electrochemical workstation.

, preparing a mixed solution of Co-Al LDHs dispersed in chitosan ethanol solution (for preventing the composite material for detection from falling off, adding adhesive chitosan), performing ultrasonic treatment on the obtained mixed solution to obtain a mixed solution with uniform dispersion, adding 5 mu L of the mixed solution dropwise onto the glassy carbon electrode by using a liquid transfer gun, and obtaining the glassy carbon electrode dropwise added with the membrane substance after ethanol is completely volatilized at room temperature.

The kit can detect single heavy metal ions and can also detect mixed solution of multiple heavy metal ions at the same time, wherein the heavy metal ions include but are not limited to Cd (II), Pb (II), Cu (II) and Hg (II).

In the invention, the method for detecting the heavy metal comprises the following steps:

the three-dimensional layered CoAl bimetal hydroxide nano material is used as a sensing material, and a film forming substance solution prepared from the sensing material and a 0.1% chitosan ethanol solution is dripped onto a glassy carbon electrode, and a solution containing heavy metal ions is detected by an electrochemical workstation at room temperature.

The method of making a membrane material includes the steps of:

dissolving the three-dimensional layered CoAl bimetal hydroxide nano material in a proper amount of ethanol to obtain an ethanol solution of the nano material;

dissolving chitosan in ethanol to prepare 0.1% chitosan ethanol solution;

mixing a proper amount of ethanol solution of chitosan with the ethanol solution of the obtained material, and performing ultrasonic treatment to obtain a membrane substance solution;

and (3) uniformly dripping quantitative membrane substance solution on the glassy carbon electrode, and naturally airing (ethanol is volatilized at room temperature) to obtain the glassy carbon electrode with the membrane substance.

The method can be used for directly detecting a water body sample (the water body sample refers to a solution containing heavy metal ions) at room temperature by adding electrolytes KCl, NaAc and HAc buffer solution and utilizing an electrochemical workstation.

In embodiments, HAc-NaAc as the buffer solution system is used, and 0.1 mol.L of acetic acid and sodium acetate solution are prepared^-1Preparing buffer solution with pH of 5 by the same volume, and selecting electrolyte solution of 0.1 mol.L^-1KCl。

When an electrochemical workstation is used for detecting a solution to be detected of heavy metal ions, a reference electrode, a carbon breaking electrode and a fragment electrode are sequentially inserted into the prepared solution to be detected, then the electrochemical workstation is started, and electrochemical workstation software is started on a computer for detection.

In the present invention, for single ion detection:

in the detection process, detection is carried out according to the deposition time of 300s ( longer time can enable adsorption to reach relative saturation), the detection of the deposition potential is carried out by taking the deposition time as reference, approximate parabolas can be formed by taking a determined deposition potential range, and the corresponding deposition potential with the highest stripping peak (namely the highest current intensity) is the optimal deposition potential.

The peak value of the stripping peak is increased along with the increase of time, namely the longer the detection time is, the larger the peak value of the stripping peak is, however, the amount of heavy metal ions in the solution to be detected is less and less, so that the amount of ions which can be trapped is less and less, and the relatively optimal deposition time can be obtained by considering that the peak value of the stripping peak is changed less in relative times.

In the present invention, the peeling peak represents a chemical change process of electron transfer on the electrode surface, which is represented by the magnitude of current intensity. The higher the current intensity is, the higher the response degree of the material prepared by the invention to heavy metal ions is, and the stronger the trapping capacity is.

After the deposition potential and the relative optimal deposition time are determined, the detected change concentration of the heavy metal ions is detected under the deposition potential and the deposition time.

Note: the response degree of each metal ion to different LDHs materials is different, so that in the detection process, the ions are different, and the corresponding deposition potential and time are also different.

In the present invention, single ions are detected first, and then mixed ions are detected.

In the invention, the three-dimensional layered CoAl double-metal hydroxide nano material provided by the invention has the lowest detection concentration of 0.3 mu mol.L of Cd (II) when the deposition potential is-1.8V and the deposition time is 300s^-1(ii) a The minimum concentration of Pb (II) detected at a deposition potential of-1.7V for a deposition time of 360s was 0.5. mu. mol. L^-1(ii) a The lowest concentration of Cu (II) detected at-1.4V deposition potential for 180s deposition time is 0.5 mu mol.L^-1(ii) a The minimum Hg (II) concentration was 0.3. mu. mol. L at a deposition potential of-1.6V and a deposition time of 240s^-1(ii) a When the deposition potential is-1.7V and the deposition time is 360s, the four types of mixed ions are separatedThe lowest concentration of the probe was 1. mu. mol. L^-1。

The inventor believes that in the preparation process of the three-dimensional layered CoAl bimetal hydroxide nano material, carbonate ions are inserted into the laminate as laminate anions, and the insertion of the carbonate ions is equivalent to the propping of a metal cation layer, so that the interlayer spacing is changed, the trapping of heavy metal ions is facilitated, and the detection sensitivity is improved.

The inventor finds that the three-dimensional layered CoAl bimetal hydroxide nano material has a rich layer structure, the layers form a flower-shaped structure, the specific surface area of the flower-shaped layered bimetal hydroxide is larger, more active sites can be provided for trapping heavy metal ions, and pores are formed between the flower-shaped layered bimetal hydroxide layers, so that the trapping of the heavy metal ions is facilitated, an electron transmission channel is increased, therefore, the flower-shaped layered bimetal hydroxide has a good heavy metal detection effect, the detection sensitivity can be improved, the detection limit can be reduced, and the detection time is short.