阅读说明：本技术 一种用于非均相电芬顿体系的Fe-Ce-LDH/13X颗粒型催化剂的制备及应用 (Preparation and application of Fe-Ce-LDH/13X granular catalyst for heterogeneous electro-Fenton system ) 是由 孙治荣 轩芳芳 于 2021-11-01 设计创作，主要内容包括：一种用于非均相电芬顿体系的Fe-Ce-LDH/13X颗粒型催化剂的制备及应用,涉及电化学水处理技术领域。本发明以13X型分子筛为载体,通过浸渍吸附法使金属离子与分子筛充分接触,后再向混合溶液中加入尿素与NH-(4)F,在高压反应釜中进行水热反应,制备得到Fe-Ce-LDH/13X颗粒型催化剂。本发明方法制作简易,方便可控,反应体系稳定,催化剂易回收,无后续污染问题,能够高效的降解有机污染物废水,具有良好的应用前景。(Preparation and application of a Fe-Ce-LDH/13X granular catalyst for a heterogeneous electro-Fenton system relate to the technical field of electrochemical water treatment. The invention takes 13X type molecular sieve as carrier, metal ions are fully contacted with the molecular sieve by an impregnation adsorption method, and then urea and NH are added into the mixed solution 4 And F, carrying out hydrothermal reaction in a high-pressure reaction kettle to prepare the Fe-Ce-LDH/13X granular catalyst. The method of the invention is simpleThe method has the advantages of easiness, convenience, controllability, stable reaction system, easiness in catalyst recovery, no subsequent pollution problem, capability of efficiently degrading organic pollutant wastewater and good application prospect.)

1. A preparation method of a Fe-Ce-LDH/13X particle type catalyst for a heterogeneous electro-Fenton system is characterized by comprising the following specific steps:

(1) soaking the sieved 13X-type molecular sieve in water and hydrochloric acid in sequence for ultrasonic cleaning to remove oil stains and impurities on the surface of the molecular sieve, finally cleaning the molecular sieve to be neutral by using deionized water, and drying for later use;

(2) FeSO (ferric oxide) is added₄·7H₂O and Ce (NO)₃)₃·6H₂Dissolving O in water to prepare a metal ion water solution with a certain molar ratio of ferrum and cerium and a concentration of 2-8 mM; adding 5g of step (1)) Soaking the obtained molecular sieve in the metal ion solution for at least 4h to ensure that the molecular sieve is fully contacted with metal ions; the molar ratio of iron to cerium is 3:7-7: 3; every 10ml of metal ion solution corresponds to 0.5-lg of molecular sieve;

(3) adding 10-20mM of urea and NH into the mixed solution of the molecular sieve and the metal ions obtained in the step (2)₄F, stirring for 5min to enable urea and NH₄F is fully dissolved and the solution is uniformly mixed;

(4) transferring the mixed solution obtained in the step (4) and the molecular sieve into a high-pressure reaction kettle, and keeping the temperature constant for 24 hours at 90-180 ℃;

(5) and washing the molecular sieve with deionized water for several times to remove residual salt solution on the surface of the molecular sieve, and drying for later use.

The granular catalyst obtained by the invention has a structure of Fe-Ce-LDH (hydrotalcite structure of Fe-Ce), and is loaded on a 13X carrier.

The Fe-Ce-LDH/13X particles obtained by the preparation method are used as a catalyst in a heterogeneous electro-Fenton system and used for efficiently degrading refractory organic wastewater, the adding amount of the catalyst is preferably 2.1g, and the pH value of a degradation liquid is preferably 3.

2. The method for preparing a Fe-Ce-LDH/13X particle-type catalyst for a heterogeneous electro-Fenton system according to claim 1, wherein the metal ratio of the iron-cerium metal solution prepared in the step (2) is 1:1 to 7: 3.

3. The method for preparing a Fe-Ce-LDH/13X particle-type catalyst for a heterogeneous electro-fenton system according to claim 1, wherein the hydrothermal temperature in step (5) is preferably 120 ℃.

4. The process for the preparation of a Fe-Ce-LDH/13X particle catalyst for use in heterogeneous electro-Fenton's system as claimed in claim 1, wherein Fe is derived from FeSO₄·7H₂O, Ce is derived from Ce (NO)₃)₃·6H₂O。

5. A Fe-Ce-LDH/13X particle-type catalyst prepared according to the process of any one of claims 1 to 4.

6. The application of the Fe-Ce-LDH/13X granular catalyst prepared by the method of any one of claims 1 to 4 as an addition catalyst in a heterogeneous electro-Fenton system for removing organic pollutants in water and facilitating subsequent recycling.

Technical Field

The invention relates to the technical field of electrochemical water treatment, in particular to a preparation method of a novel Fe-Ce-LDH/13X bimetallic particle type catalyst and application of the catalyst in a heterogeneous electro-Fenton system.

Background art:

one of the electro-Fenton technology advanced oxidation methods is a combination of the traditional Fenton method and an electrochemical system, can efficiently degrade organic pollutants in water, reduces dissolved oxygen in water body by a cathode to generate hydrogen peroxide in situ, and is opposite to the traditional Fenton methodCompared with the method without adding hydrogen peroxide externally, the hydrogen peroxide generated in situ and the Fe in the solution²⁺The reaction generates hydroxyl free radical (. OH), and the hydroxyl free radical can efficiently and non-selectively degrade organic pollutants which are difficult to degrade in water. The electro-Fenton technology is used as a green and environment-friendly sewage treatment technology, and particularly has good prospect in the removal direction of water pollutants in the field of water treatment.

The electro-Fenton technique is classified into a homogeneous electro-Fenton method and a heterogeneous electro-Fenton method. Homogeneous phase electro-Fenton reaction is carried out by adding exogenous iron ions to react with hydrogen peroxide generated by a cathode, in order to avoid iron ion precipitation, the pH value of the system needs to be ensured to be about 3, and the iron ions in water need to be removed by a precipitation mode after the reaction, so that secondary pollution is easily caused and the subsequent treatment is complicated. Heterogeneous electro-fenton oxidation technology has emerged due to limitations of homogeneous electro-fenton. The heterogeneous electro-Fenton oxidation technology can effectively overcome the defects that the catalyst is easy to lose and difficult to recover, needs strict pH adjustment, is easy to generate sludge and the like in the homogeneous electro-Fenton oxidation technology, and gradually becomes a research hotspot in the advanced water treatment oxidation technology.

In the heterogeneous electro-fenton oxidation technology, a particulate type supported catalyst is widely studied. Compared with the powder catalyst, the granular catalyst has the advantages of stability, convenient recovery, difficult loss and the like. In the preparation of supported catalysts of the particulate type, the nature of the support is of critical importance. A good support material should have several characteristics: (1) the electrolyte has chemical inertia and is not easy to generate chemical reaction in an electrolytic solution; (2) can be firmly combined with the metal and the oxide thereof which are required to be loaded; (3) the specific surface area is high, and the adsorption capacity to active metals and target pollutants is good; (4) facilitating the separation of solid and liquid phases. Currently commonly used carriers can be classified into organic carriers, inorganic carriers and ion exchange resins. The molecular sieve as an inorganic carrier has unique performances of selective adsorption, efficient adsorption, ion exchange and the like, and is worthy of being noticed that compared with the dispersion force action of activated carbon adsorption, the molecular sieve also has certain electrostatic adsorption capacity, so that the molecular sieve has stronger adsorption capacity, and is widely applied to the field of carrier materials. Therefore, the invention uses the molecular sieve as a carrier to load metal ions, and prepares a granular catalyst for degrading organic pollutants in an electro-Fenton system.

Disclosure of Invention

The invention aims to provide a preparation method and application of a Fe-Ce-LDH/13X granular catalyst for a heterogeneous electro-Fenton system. The synthesis process is simple, convenient and controllable, and the prepared granular catalyst is applied to a heterogeneous electro-Fenton system, has a good catalytic effect, and overcomes the defects that the traditional electro-Fenton method is easy to generate iron sludge and the catalyst is difficult to recover.

A preparation method of a Fe-Ce-LDH/13X particle type catalyst for a heterogeneous electro-Fenton system is characterized by comprising the following specific steps:

(1) soaking the sieved molecular sieve (model 13X) in water and hydrochloric acid in sequence, ultrasonically cleaning to remove oil stains and impurities on the surface of the molecular sieve, finally cleaning to neutrality with pure water, and drying in a 60 ℃ forced air drying oven for 24h for later use;

(2) FeSO (ferric oxide) is added₄·7H₂O and Ce (NO)₃)₃·6H₂Dissolving O in water, and preparing a metal ion solution with a certain molar ratio of iron to cerium and a concentration of 2-8 mM; soaking 5g of the molecular sieve obtained in the step (1) in the metal ion solution for 4 hours to ensure that the molecular sieve is fully contacted with metal ions; the molar ratio of iron to cerium is 3:7-7:3, preferably 1:1-7: 3; every 10ml of metal ion solution corresponds to 0.5-lg of molecular sieve;

(3) adding 10-20mM of urea and 10-20mM of NH into the mixed solution of the molecular sieve and the metal ions obtained in the step (2)₄F, stirring for 5min to uniformly mix;

(4) transferring the mixed solution obtained in the step (3) and the molecular sieve into a high-pressure reaction kettle, and keeping the temperature of the mixed solution at 90-180 ℃ for 24 hours;

(5) and (4) washing the molecular sieve with deionized water to remove residual salt solution on the surface of the molecular sieve, drying in a drying box for 24h, and taking out for later use.

The granular catalyst obtained by the invention has a structure of Fe-Ce-LDH (hydrotalcite structure of Fe-Ce), and is loaded on a 13X carrier.

The Fe-Ce-LDH/13X particles obtained by the preparation method are used as a catalyst in a heterogeneous electro-Fenton system and used for efficiently degrading refractory organic wastewater, the adding amount of the catalyst is preferably 2.1g, and the pH value of the degradation liquid is preferably 3.

Compared with the prior art, the invention has the following excellent effects:

1. the invention takes the molecular sieve as the catalyst carrier, and solves the problem of catalyst deactivation due to agglomeration by utilizing the advantages of loose and porous structure, easy material loading and stable structure of the molecular sieve.

2. The method loads iron and cerium metal ions in a hydrothermal mode, is simple to manufacture, convenient and controllable, and solves the problem that oxides are dispersed unevenly in the traditional coating, dipping and other modes.

3. The granular catalyst prepared by the method is more convenient to recycle, and the defect that the catalyst is difficult to recycle is overcome.

Drawings

FIG. 1 is a XRD result diagram of the Fe-Ce-LDH/13X particle type catalyst prepared in example 1.

FIG. 2 is a graph showing the effect of adding catalysts prepared from different carriers on diuron wastewater degradation in example 2 as compared to comparative example 2. Wherein the ordinate corresponds to the diuron removal efficiency during degradation.

FIG. 3 shows the effect of catalysts prepared by adding different iron-cerium ratios in example 3 on diuron wastewater degradation. Wherein the ordinate corresponds to the ratio of the concentration of the diuron wastewater relative to the concentration of the original diuron wastewater in the degradation process.

FIG. 4 is a graph showing the effect of adding catalysts prepared at different hydrothermal temperatures on diuron wastewater degradation in example 4. Wherein the ordinate corresponds to the ratio of the diuron concentration to the original diuron concentration during degradation.

Curve a in fig. 5 is the degradation of diuron wastewater by adding the molecular sieve in comparative example 1; curve b is the degradation condition of diuron wastewater by adding Fe-Ce-LDH/13X particle-type catalyst in example 1, wherein the ordinate corresponds to the ratio of diuron concentration to the original diuron concentration in the degradation process.

Detailed Description

The following description is given in conjunction with the accompanying drawings and specific embodiments, but the present invention is not limited to the following embodiments.

Example 1

(1) Soaking the sieved molecular sieve (model 13X) in water and hydrochloric acid sequentially, ultrasonically cleaning to remove oil stains and impurities on the surface of the molecular sieve, cleaning with pure water to neutrality, and drying for later use;

(2) a certain amount of FeSO₄·7H₂O and Ce (NO)₃)₃·6H₂Dissolving O in 70mL of solution (the amount of the substance is 5mM), adding a certain proportion of iron cerium metal salt into pure water (the metal ratio of Fe and Ce is 7:3) to prepare a metal ion solution; then soaking 5g of the molecular sieve obtained in the step (1) in the metal ion solution for 4 hours to ensure that the molecular sieve is fully contacted with metal ions;

(3) adding 20mM of urea and 16mM of NH into the mixed solution of the molecular sieve and the metal ions obtained in the step (2)₄F, stirring for 5min to uniformly mix the solution;

(4) transferring the mixed solution obtained in the step (3) and the molecular sieve into a high-pressure reaction kettle, and keeping the constant temperature for 24 hours when the temperature is raised to 120 ℃;

(5) and (4) washing the molecular sieve with deionized water to remove residual salt solution on the surface of the molecular sieve, and drying for later use.

The Fe-Ce-LDH/13X particles obtained by the preparation method are used as a catalyst to be applied to a heterogeneous electro-Fenton system and used for efficiently degrading refractory organic wastewater. The catalyst (fixed addition of 2.1g) was added to the reaction solution, graphite felt as the cathode, platinum sheet as the anode, a 3cm distance between the anode and cathode, 0.05M sodium sulfate solution as the electrolyte, and a current density of 5mA/cm²When the pH is 3.0, the aeration amount is 0.6L/min, 300mL of diuron wastewater with the concentration of 10mg/L is degraded, and the removal rate of diuron reaches 100% in 60min as shown by a curve b in figure 5.

Example 2

(1) Soaking the sieved molecular sieve (model 13X) in water and hydrochloric acid sequentially, ultrasonically cleaning to remove oil stains and impurities on the surface of the molecular sieve, cleaning with pure water to neutrality, and drying for later use;

(2) a certain amount of FeSO₄·7H₂O and Ce (NO)₃)₃·6H₂Dissolving O in 70mL of solution (the amount of the substance is 5mM), adding a certain proportion of iron cerium metal salt into pure water (the metal ratio of Fe and Ce is 1:1) to prepare a metal ion solution; then soaking 5g of the molecular sieve obtained in the step (1) in the metal ion solution for 4 hours to ensure that the molecular sieve is fully contacted with metal ions;

(3) adding 20mM of urea and 16mM of NH into the mixed solution of the molecular sieve and the metal ions obtained in the step (2)₄F, stirring for 5min to uniformly mix the solution;

(4) transferring the mixed solution obtained in the step (3) and the molecular sieve into a high-pressure reaction kettle, and keeping the temperature at 120 ℃ for 24 hours;

(5) and (4) washing the molecular sieve with deionized water to remove residual salt solution on the surface of the molecular sieve, and drying for later use.

The Fe-Ce-LDH/13X particles obtained by the preparation method are used as a catalyst to be applied to a heterogeneous electro-Fenton system and used for efficiently degrading refractory organic wastewater. The catalyst (fixed addition of 2.1g) was added to the reaction solution, graphite felt as the cathode, platinum sheet as the anode, a 3cm distance between the anode and cathode, 0.05M sodium sulfate solution as the electrolyte, and a current density of 5mA/cm²The pH value is 3.0, the aeration amount is 0.6L/min, 300mL of diuron wastewater with the concentration of 10mg/L is degraded, and as shown in figure 2, the removal rate of diuron reaches 100% in 120 min.

Example 3

The specific preparation process is the same as that of example 1, but in the step (2), the ratio of Fe to Ce metal is changed to 10:0, 7: 3. 1:1, 3:7 and 0: 10. The above catalyst (fixed amount of 2.1g) was added to the reaction solution, and a platinum plate as an anode and a 0.05M sodium sulfate solution as an electrolyte were used to give a current density of 5mA/cm²And degrading 300mL of diuron wastewater with the concentration of 10mg/L with the pH value of 3 and the aeration amount of 0.6L/min, wherein the diuron removal rate is optimal when the metal ratio is 7:3 and reaches 100% at 60min as shown by a curve in figure 3.

Example 4

The preparation process is the same as that of example 1, except that the hydrothermal temperature in step (4) is changed to 90 ℃, 120 ℃, 150 ℃ and 180 ℃ in sequence. The catalyst (fixed addition of 2.1g) was added to the reaction solution, graphite felt as the cathode, platinum sheet as the anode, 0.05M sodium sulfate as the electrolyte, and the current density was 5mA/cm²And the pH value is 3, the aeration amount is 0.6L/min, 300mL of diuron wastewater with the concentration of 10mg/L is degraded, as shown by a curve in figure 4, when the hydrothermal temperature is 180 ℃, the diuron removal rate is optimal and reaches 100% in 50min, and the hydrothermal time is fixed to be 120 ℃ in consideration of safety problems caused by overhigh temperature.

Comparative example 1

The specific preparation process is the same as that of example 1, except that the steps (2), (3), (4) and (5) are omitted in order to not load metal ions, but pretreat the molecular sieve only. Adding the above treated molecular sieve (fixed addition amount is 2.1g) into the solution, graphite felt as cathode, platinum sheet as anode, sodium sulfate solution with a distance of 3cm between anode and cathode and 0.05M as electrolyte, and current density of 5mA/cm²The pH value is 3, the aeration amount is 0.6L/min, and 300mL of diuron wastewater with the concentration of 10mg/L is degraded.

The results of the example 1 and the comparative example 1 show that the catalytic performance of the Fe-Ce-LDH/13X particle type catalyst is greatly improved compared with that of the original molecular sieve, when the original molecular sieve is used as the catalyst, the removal rate of diuron is 44% in 60min, and the removal rate of diuron reaches 100% in 60min by using the Fe-Ce-LDH/13X particle type catalyst. It can be seen that the pollutant-degrading ability of the Fe-Ce-LDH/13X particle-type catalyst is significantly enhanced compared to the original molecular sieve. The invention is applied to an electro-Fenton system and can efficiently degrade high-concentration diuron.

Comparative example 2

(1) Soaking activated carbon (biochar, BC) in water and hydrochloric acid in sequence, ultrasonically cleaning to remove oil stains and impurities on the surface of the activated carbon, cleaning with pure water to be neutral, and drying for later use;

(2) a certain amount of FeSO₄·7H₂O and Ce (NO)₃)₃·6H₂Dissolving O in 70mL of aqueous solution (the amount of the substance is 5mM), adding a certain proportion of iron cerium metal salt into pure water (the metal ratio of Fe and Ce is 1:1) to prepare a metal ion solution; then soaking 5g of the activated carbon obtained in the step (1) in the metal ion solution for 4 hours to ensure that the activated carbon is fully contacted with metal ions;

(3) adding 20mM of urea and 16mM of NH into the mixed solution of the activated carbon and the metal ions obtained in the step (2)₄F, stirring for 5min to uniformly mix the solution;

(4) transferring the mixed solution obtained in the step (3) and activated carbon into a high-pressure reaction kettle, and keeping the temperature at 120 ℃ for 24 hours;

(5) and (4) washing the activated carbon by using deionized water to remove residual salt solution on the surface of the molecular sieve, and drying for 24 hours for later use.

The Fe-Ce-LDH/BC particles obtained by the preparation method are applied to a heterogeneous electro-Fenton system as a catalyst, and are used for efficiently degrading refractory organic wastewater. The catalyst (fixed addition of 2.1g) was added to the reaction solution, graphite felt as the cathode, platinum sheet as the anode, a 3cm distance between the anode and cathode, 0.05M sodium sulfate solution as the electrolyte, and a current density of 5mA/cm²The pH value is 3.0, the aeration amount is 0.6L/min, and 300mL of diuron wastewater with the concentration of 10mg/L is degraded. The results of comparing example 2 with comparative example 2 show that the molecular sieve as a carrier has better effect on degrading diuron than the catalyst prepared by using active carbon as a carrier.