CN106807376A - A kind of magnetic Nano composite catalyst and preparation method and application - Google Patents

Abstract

The invention discloses a magnetic nanocomposite catalyst, in particular a preparation method of a cobalt iron oxide/graphene magnetic nanocomposite catalyst and its application in degrading organic wastewater. The catalyst acts on hydrogen persulfate to generate strong oxidizing sulfate radicals, thereby efficiently removing organic matter in wastewater. As a solid-phase catalyst, because of its large specific surface area, high catalytic activity and low ion dissolution rate, the catalyst can continuously and efficiently activate persulfate to generate sulfate radicals, effectively reducing cobalt ions Give way. The catalyst preparation method of the present invention is simple, has high catalytic performance, does not cause secondary pollution, and is an environmentally friendly material. Because it has magnetism, it can be recycled and reused after reaction, which reduces the treatment cost of organic wastewater and is difficult to degrade. The treatment of organic wastewater offers broad application prospects.

Description

A kind of magnetic nanocomposite catalyst and its preparation method and application

technical field

The invention belongs to nanocomposite materials, in particular to a preparation method of a cobalt iron oxide/graphene magnetic nanocomposite catalyst and its application in treating organic wastewater.

Background technique

Water pollution has become one of the important factors restricting social and economic development. In particular, organic wastewater with strong toxicity, high concentration, and refractory biodegradation has brought unprecedented challenges to traditional sewage biological treatment processes. In recent years, advanced oxidation water treatment technology based on strong oxidizing free radicals (such as hydroxyl radicals) has attracted much attention. Due to the strong oxidizing properties of free radicals, organic matter in wastewater can usually be decomposed into non-toxic or low-toxic small molecule organic matter, and even completely mineralized and transformed into water and carbon dioxide. Among them, the Fenton method and derived Fenton-like methods such as optical Fenton method, electric Fenton method, ultrasonic Fenton method, and ultrasonic/light combined Fenton method have been widely used due to their ability to effectively generate strong oxidizing hydroxyl radicals. application. However, the large amount of chemical reagents used, the high cost, the low reaction pH (2-4), and the generation of a large amount of chemical sludge obviously restrict the further development of the Fenton method.

Compared with hydroxyl radicals, advanced oxidation technology based on sulfate radicals is a promising water treatment technology, and its advantages are: (1) Sulfate radicals have a higher oxidation potential (2.5-3.1V) (2) Sulfate radical has stronger selectivity; (3) The scope of application based on Sulfate radical reaction is wider (pH 2～9); (4) Sulfate radical is more stable, and half-life is longer ( 30～40μs).

Methods for activating persulfate/bipersulfate to generate sulfate radicals include physical methods such as light, microwave radiation, heat, and ultraviolet rays, and chemical activation of transition metals such as Co ²⁺ , Mn ²⁺ , Ni ²⁺ , Fe ²⁺ , etc. Law. Compared with the physical activation method, the reaction of transition metal ion activated persulfate/bipersulfate can be carried out rapidly at room temperature without external energy, showing great advantages and more development potential. Among all transition metal ions, Co ²⁺ has been proven to efficiently activate persulfate/bipersulfate to generate sulfate radicals, but Co ²⁺ is biologically toxic and will cause secondary pollution if it remains in wastewater. Graphene is composed of monoatomic layer carbon, has high specific surface area, good electrical conductivity, excellent electrochemical and mechanical properties, and is a research hotspot in the field of functional materials. Studies have shown that graphene can activate persulfate/bipersulfate to generate sulfate radicals, and has broad application prospects in advanced oxidation treatment of organic wastewater. However, graphene nanomaterials are difficult to effectively separate from wastewater, which limits its application in the field of sewage treatment. At present, there is no report on the organic combination of graphene and cobalt iron oxide for catalytic treatment of organic wastewater.

Contents of the invention

Object of the invention: The object of the invention is to provide a method for preparing a magnetic nanocomposite catalyst and the application of the prepared magnetic nanocomposite catalyst in catalytic treatment of organic wastewater.

Technical solution: a method for preparing a magnetic nanocomposite catalyst according to the present invention comprises the following steps:

(1) Get graphene oxide and add in dehydrated alcohol, mix well, obtain the first mixed solution;

(2) dissolving the metal salt containing Fe ³⁺ ions and the metal salt containing Co ²⁺ ions in absolute ethanol, stirring to obtain the second mixed solution;

(3) Mix the first mixed solution obtained in step (1) with the second mixed solution obtained in step (2), stir and adjust the pH to 8-10, and continue to stir to obtain a dark green reaction precursor solution;

(4) Transfer the reaction precursor solution obtained in step (3) to a reaction kettle, react at 150-200° C. for 15-24 hours, wash and dry after the reaction to obtain a cobalt-iron oxide/graphene magnetic nanocomposite catalyst.

In step (1), the mixing condition is ultrasonic treatment at a power of 20-100w for 0.5-1.5h. Preferably, ultrasonic treatment is performed for 1 hour at a power of 50w.

In step (1), the mass volume ratio of the graphene oxide to absolute ethanol is 2-5:3 (mg:ml).

In step (2), the volume ratio of the amount of the substance containing Fe ³⁺ ions to absolute ethanol is 1:80-20 (mmol:mL). In step (2), the volume ratio of the amount of the substance containing Co ²⁺ ions to absolute ethanol is 1:40-10 (mmol:mL).

In step (2), the molar ratio of Fe ³⁺ ions to Co ²⁺ ions is 1.9:1˜2.1:1.

The most preferred is 2:1.

In step ( ² ), the metal salt containing Fe ³⁺ ions is ferric chloride or ferric nitrate nonahydrate, and the metal salt containing Co ²⁺ ions is cobalt nitrate hexahydrate, cobalt chloride or cobalt acetate.

In step (2), stir for 20-40 minutes.

In step (3), the stirring time of the initial mixed solution and the alkaline mixed solution is 20-40 minutes.

In step (3), NaOH solution is used to adjust the mixed solution to pH 8-10.

In step (4), the washing is with distilled water, and the drying is air atmosphere drying; preferably, the drying temperature is 60° C., and the drying time is 6 hours.

The magnetic nanocomposite catalyst prepared according to the above method is also within the protection scope of the present invention.

The application of the above-mentioned magnetic nanocomposite catalyst in treating organic wastewater is also within the protection scope of the present invention.

The application of the above-mentioned magnetic nanocomposite catalyst in the treatment of organic wastewater is specifically that the magnetic nanocomposite catalyst activates persulfate to generate strongly oxidizing sulfate radicals, and oxidizes organic matter in wastewater.

When using the catalyst to treat organic wastewater, under normal temperature conditions, add cobalt iron oxide/graphene magnetic composite catalyst to the wastewater containing organic pollutants so that the solid content is 0.1-0.3g/L, and add persulfuric acid The concentration of the hydrogen salt is 0.1-0.4g/L, and the treatment is done for 5-30 minutes under the environment of pH 3-9.

Preferably, the cobalt iron oxide/graphene magnetic composite catalyst is added to make the solid content 0.12g/L, and hydrogen persulfate is added to make the concentration 0.3g/L, and the pH is 6-7.

After being treated by this method, the removal rate of organic waste water can reach more than 80%. When the conditions are suitable, the removal rate of organic wastewater can reach 100%, and the effect is very significant.

Beneficial effects: (1) the cobalt-iron oxide/graphene magnetic nanocomposite catalyst in the present invention is insoluble in water, and it belongs to heterogeneous catalytic oxidation in the process of activating bisulfate to degrade organic wastewater, and the material has magnetism, This makes it easier for the catalytic material to be separated from the water phase for recycling after the catalytic process is over. Compared with the homogeneous catalysis of transition metal ions, the composite catalyst only has a small amount of cobalt ions dissolved during the catalytic process, which will not affect the Significant impact on water quality. (2) cobalt-iron oxide/graphene magnetic nanocomposite catalyst utilizes the synergistic effect of graphene and cobalt-iron oxide to catalyze bisulfate jointly among the present invention, and graphene specific surface area is big, and cobalt-iron oxide is loaded with fine particle On the surface of graphene, more reaction sites are provided, which can effectively inhibit the agglomeration of cobalt-iron oxide nanoparticles, so that it can efficiently generate sulfate radicals, with high utilization efficiency of free radicals, short reaction time, and no pollution to pollutants. Removes well. (3) In the present invention, the amount of catalyst is less, and it can be carried out at normal temperature without external energy, and the operation is simple, economically feasible, recyclable and reusable, and is suitable for the treatment of refractory organic wastewater.

Description of drawings

Fig. 1 is the transmission electron micrograph of the catalyst prepared in embodiment 1;

Fig. 2 is the effect comparison of embodiment 2 processing acetamiprid wastewater;

Fig. 3 is to embodiment 3 processing effect comparison;

Fig. 4 is the comparison of embodiment 4 to acetamiprid wastewater treatment effect;

Fig. 5 is the comparison of embodiment 6 processing effect;

Fig. 6 is a comparison of the treatment effects of Example 7.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments.

Example 1

The method for preparing cobalt iron oxide/graphene magnetic nanocomposite catalyst comprises the following steps:

(1) Get 80mg of graphene oxide powder and add it to 60mL of absolute ethanol, and ultrasonically treat it for 1h at a power of 50W to obtain a uniformly dispersed graphene mixture;

(2) Take 0.146g Co(NO ₃ ) ₂ ·6H ₂ O and 0.403g Fe(NO ₃ ) ₃ ·9H ₂ O (the molar ratio of cobalt and iron is 1:2) and add it to 20ml of absolute ethanol. Stir for 30 minutes to obtain a homogeneous mixture;

(3) mixing and stirring the graphene mixed solution obtained in step (1) with the mixed solution obtained in step (2) for 30 min, then adjusting the pH to 10 with 6M NaOH, and continuing to stir for 30 min to obtain a dark green reaction precursor solution;

(4) Transfer the reaction precursor solution obtained in step (3) to a hydrothermal reaction kettle, conduct hydrothermal reaction at 180°C for 20h, centrifuge and wash the obtained product with distilled water for 5 times, then filter, and dry in an air atmosphere at 60°C for 6h, The cobalt iron oxide/graphene magnetic nanocomposite catalyst is obtained.

The transmission electron microscope photo of the obtained cobalt-iron oxide/graphene magnetic nanocomposite catalyst prepared by embodiment 1 is as shown in Figure 1, as seen from Figure 1, cobalt-iron oxide nanoparticles are evenly distributed on the graphene layer, thus it can be known that this The invented magnetic nanocomposite catalyst was successfully prepared.

Example 2

In order to verify the effect of the cobalt iron oxide/graphene magnetic nanocomposite catalyst prepared in Example 1 on activating potassium hydrogen persulfate to treat acetamiprid wastewater, the following three sets of experiments were done.

Test Ⅰ

A conical flask was used as the reactor, the reaction volume of the acetamiprid wastewater was 50 mL, the initial concentration of acetamiprid was 20 mg/L, and the pH was 7.0. Simultaneously in reactor, add embodiment 1 to prepare gained catalyst, make its solid content be 0.12g/L, add potassium hydrogen persulfate and make its concentration be 0.3g/L, then reactor is placed in shaker, rotating speed is 150rpm , react at room temperature, take samples regularly, and detect the remaining concentration of acetamiprid with a liquid chromatograph.

Test II

Potassium hydrogen persulfate was not added, and the other conditions were the same as experiment Ⅰ.

Test III

No cobalt iron oxide/graphene magnetic nanocomposite catalyst was added, and other conditions were the same as experiment Ⅰ.

The treatment results are shown in Fig. 2. It can be seen from Fig. 2 that the acetamiprid removal rate was only 5% and 8% respectively after 30 minutes in test II and test III, while in test I, the catalyst activated The treatment effect of the potassium hydrogen persulfate system is very significant, and the removal rate of acetamiprid reaches 83% after 30 minutes.

Example 3

Example 1 The prepared cobalt iron oxide/graphene magnetic nanocomposite catalyst was used to activate potassium hydrogen persulfate to treat acetamiprid wastewater with different initial pH.

Using a conical flask as a reactor, the reaction volume of acetamiprid wastewater is 50mL, the initial concentration of acetamiprid is 20mg/L, and the initial pH of acetamiprid wastewater is adjusted to 3 and 5 respectively with 1M NaOH and H ₂ SO ₄ , 7, 9, in the reactor, add the catalyst prepared by embodiment 1 simultaneously so that its solid content is 0.12g/L, add potassium persulfate so that its concentration is 0.3g/L, and place the reactor in a shaker , the rotating speed is 150rpm, and the temperature is room temperature. Samples were taken regularly, and the remaining concentration of acetamiprid was detected with a liquid chromatograph.

See Figure 3 for the specific processing results.

The results in Figure 3 show that the degradation effect of acetamiprid is the best under the neutral condition of pH 7, and the removal rate of acetamiprid reaches 83% after 30 minutes, while the removal rate of acetamiprid under acidic conditions is significantly higher than that under alkaline conditions removal rate. When the initial pH was 3 and 5, the removal rate of acetamiprid was about 40% after 30 min, but when the initial pH was 9, the removal rate of acetamiprid was only 15% after 30 min.

Example 4

Embodiment 1 prepares the obtained cobalt iron oxide/graphene magnetic nanocomposite catalyst, under the condition of different potassium hydrogen persulfate dosage, cobalt iron oxide/graphene magnetic nanocomposite catalyst activates potassium hydrogen persulfate to process acetamiprid waste water.

Adopt Erlenmeyer flask as reactor, acetamiprid waste water reaction reaction volume is 50mL, and the initial concentration of acetamiprid is 20mg/L, and pH is 7.0, adds the obtained catalyst that embodiment 1 prepares in reactor simultaneously and makes its solid content be: 0.12g/L, add potassium hydrogen persulfate to make the concentration respectively 0.1, 0.2, 0.3 and 0.4g/L, and place the reactor in a shaker with a rotating speed of 150rpm and a temperature of room temperature. Samples were taken regularly, and the remaining concentration of acetamiprid was detected by liquid chromatography.

See Figure 4 for the specific processing results.

The results in Fig. 4 show that the potassium hydrogen persulfate concentration is in the range of 0.1 to 0.3 g/L, the greater the dosage of potassium hydrogen persulfate, the better the effect of catalyst activation on potassium hydrogen persulfate to remove acetamiprid. After 30min of reaction, the removal rate of acetamiprid increased from 35% when the concentration of potassium persulfate was 0.1g/L to 83% when the concentration of potassium persulfate was 0.3g/L. But when the concentration of potassium hydrogen persulfate exceeds 0.3g/L, the removal rate of acetamiprid does not increase significantly after 30min.

Example 5

Example 1 Prepared the cobalt iron oxide/graphene magnetic nanocomposite catalyst, and activated potassium hydrogen persulfate to treat acetamiprid wastewater under the conditions of different catalyst dosages.

Adopt Erlenmeyer flask to make reactor, acetamiprid waste water reaction reaction volume is 50mL, and the initial concentration of acetamiprid is 20mg/L, and pH is 7.0, adds the obtained catalyst prepared by embodiment 1 in reactor so that its solid content is respectively 0.05, 0.08, 0.1, 0.2, 0.3, 0.35 and 0.4g/L, add potassium hydrogen persulfate to make the concentration 0.3g/L, and place the reactor in a shaker with a rotation speed of 150rpm and a temperature of room temperature. Samples were taken regularly, and the remaining concentration of acetamiprid was detected by liquid chromatography. The results are shown in Table 1.

Table 1

The results in Table 1 show that the larger the catalyst dosage, the better the removal effect of acetamiprid after 30 min. When the dosage of catalyst reaches 0.3g/L, the removal rate of acetamiprid reaches 100%, and it is meaningless to continue to increase the dosage of catalyst.

Example 6

Example 1 The obtained cobalt iron oxide/graphene magnetic nanocomposite catalyst was activated to treat acetamiprid wastewater by activating potassium hydrogen persulfate, and the catalyst was reused.

Adopt Erlenmeyer flask as reactor, acetamiprid wastewater reaction volume is 50mL, the initial concentration of acetamiprid is 20mg/L, and pH is 7.0, adds the obtained catalyst that embodiment 1 prepares in reactor simultaneously and makes its solid content be 0.12 g/L, potassium persulfate was added to make the concentration 0.3g/L, and the reactor was placed in a shaker with a rotation speed of 150 rpm and a temperature of room temperature for 30 min. After the reaction is over, use a magnet to hold the catalyst on the outer wall of the Erlenmeyer flask for solid-liquid separation. After the separation, the catalyst participates in the above reaction again. Repeat six times. The specific processing results are shown in Figure 5.

The results in Figure 5 show that the catalyst was reused five times, and the removal rate of acetamiprid had no significant change after 30 minutes of treatment. The removal rate of acetamiprid was only significantly decreased when the catalyst was used for the sixth time, indicating that the catalyst has good stability. long life.

Example 7

A pure cobalt-iron oxide catalyst is prepared, and the pure cobalt-iron oxide catalyst activates potassium hydrogen persulfate to treat acetamiprid wastewater.

The concrete preparation steps of pure cobalt-iron oxide catalyst are:

Step 1: Add 0.146g Co(NO ₃ ) ₂ 6H ₂ O and 0.403g Fe(NO ₃ ) ₃ 9H ₂ O (the molar ratio of cobalt to iron is 1:2) into 20ml of absolute ethanol, and stir at room temperature 30min to obtain a homogeneous mixture.

Step 2: Adjust the pH of the mixed solution obtained in Step 1 to 10 with 6M NaOH, and continue stirring for 30 minutes to obtain a reaction precursor solution.

Step 3: transfer the reaction precursor solution to a hydrothermal reaction kettle, and conduct a hydrothermal reaction at 180° C. for 20 hours to obtain a reaction product.

Step 4: The reaction product obtained in Step 3 was centrifuged and washed 5 times with distilled water, filtered, and dried in an air atmosphere at 60° C. for 6 hours to obtain the final material.

In the reaction of utilizing pure cobalt iron oxide catalyst to activate potassium hydrogen persulfate, an Erlenmeyer flask is used as the reactor, the waste water reaction volume is 50mL, the initial concentration of acetamiprid is 20mg/L, and the pH is 7.0. Add pure cobalt-iron oxide catalyst to make its solid content 0.12g/L, add potassium hydrogen persulfate to make its concentration 0.3g/L, and place the reactor in a shaker with a rotating speed of 150rpm and a temperature of room temperature. Samples were taken regularly, and the remaining concentration of acetamiprid was detected with a liquid chromatograph.

The specific processing results are shown in Figure 6.

Figure 6 shows that the cobalt-iron oxide/graphene magnetic nanocomposite catalyst activates potassium hydrogen persulfate to treat acetamiprid wastewater, and the removal rate of acetamiprid reaches 83% after 30 minutes, while pure cobalt-iron oxide is used as a catalyst, and the removal rate of acetamiprid is 30 minutes. The removal rate of acetamiprid in the waste water was only 40%.

It shows that the catalytic performance of the catalyst of the present invention is significantly better than that of the pure cobalt-iron oxide catalyst.

Claims (10)

1. a preparation method of magnetic nanocomposite catalyst, is characterized in that, comprises the following steps: (1) Get graphene oxide and add in dehydrated alcohol, mix well, obtain the first mixed solution; (2) dissolving the metal salt containing Fe ³⁺ ions and the metal salt containing Co ²⁺ ions in absolute ethanol, stirring to obtain the second mixed solution; (3) Mix the first mixed solution obtained in step (1) with the second mixed solution obtained in step (2), stir and adjust the pH to 8-10, and continue to stir to obtain a dark green reaction precursor solution; (4) Transfer the reaction precursor solution obtained in step (3) to a reaction kettle, react at 150-200° C. for 15-24 hours, wash and dry after the reaction to obtain a cobalt-iron oxide/graphene magnetic nanocomposite catalyst. 2. The preparation method of the magnetic nanocomposite catalyst according to claim 1, characterized in that, in step (1), the mixing condition is ultrasonic treatment at a power of 20-100w for 0.5-1.5h. 3 . The preparation method of magnetic nanocomposite catalyst according to claim 1 , characterized in that, in step (2), the molar ratio of Fe ³⁺ ions to Co ²⁺ ions is 1.9:1˜2.1:1. 4. the preparation method of magnetic nanocomposite catalyst according to claim 1, is characterized in that, in step (2), described containing ^Fe The metal salt of ion is iron trichloride or ferric nitrate nonahydrate, and described Metal salts containing Co ²⁺ ions are cobalt nitrate hexahydrate, cobalt chloride or cobalt acetate. 5. the preparation method of magnetic nanocomposite catalyst according to claim 1 is characterized in that, in step (3), the alkali solution that regulates pH is NaOH solution. 6. The magnetic nanocomposite catalyst prepared by any preparation method in claim 1-5. 7. the application of magnetic nanocomposite catalyst described in claim 6 in the treatment of organic waste water. 8. The application according to claim 7, characterized in that, under normal temperature conditions, the cobalt iron oxide/graphene magnetic composite catalyst is added to the wastewater containing organic pollutants to make the solid content 0.1-0.3g/L , add hydrogen persulfate to make the concentration 0.1-0.4g/L, and treat it for 5-30min under the environment of pH 3-9. 9. according to the described application of claim 8, it is characterized in that, dosing cobalt-iron oxide/graphene magnetic composite catalyst makes its solid content be 0.12g/L, and adds perhydrogen sulfate so that its concentration is 0.3g/L . 10. The application according to claim 8, characterized in that the pH is 6-7.