Preparation method and application of algal-based red mud catalyst

Abstract

The application discloses a preparation method and application of an algae-based red mud catalyst and belongs to the technical field of catalysts. The algae-based red mud catalyst is prepared by using industrial waste residue red mud and blue algae in Dianchi Lake as raw materials through a hydrothermal-pyrolysis method, that is, magnetite in the red mud is reduced into magnetite by using blue algae biomass, and nitric acid is added in the preparation process to adjust pH, so that the problem of low reaction activity of the current pure red mud catalyst caused by high alkalinity, small specific surface area and high iron valence state can be effectively solved, water pollution treatment and solid waste resource utilization are simultaneously realized, and the algae-based red mud catalyst can be applied to 17alpha-ethynyl estradiol (EE2) adsorption and degradation. After 17alpha-ethynyl estradiol (EE2) with an initial concentration of 2 mg / L is adsorbed for 50 min, the removal rate of 17alpha-ethynyl estradiol (EE2) can reach 42.67%, and then 0.08 mM persulfate (PDS) is added to remove 99.99% of 17alpha-ethynyl estradiol (EE2) in 30 min.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and relates to a preparation method and application of an algal-based red mud catalyst, and further relates to a preparation method and application of an algal-based red mud catalyst for efficiently removing 17alpha-ethinyl estradiol (EE2). BACKGROUND

[0002] In recent years, new pollutants have attracted widespread attention in the society and the environmental protection field. Among them, environmental endocrine disruptors (Endocrine Disrupting Compounds, EDCs), also known as environmental estrogens (Environmentalestrogens, EEs), are a new and persistent endocrine disruptor widely existing in water bodies and drinking water, and have attracted much attention in recent years. 17alpha-ethinyl estradiol (EE2) is a typical and harmful environmental endocrine disruptor, which can cause serious growth, development and reproduction interference problems to organisms even at an environmental concentration below 1 ng / L. At present, there are studies on the removal of EE2 in water bodies by adsorption, microbial degradation, advanced oxidation and other technical means, which have achieved good results, but there are still problems such as slow adsorption speed and incomplete degradation.

[0003] The advanced oxidation process (AOPs) based on persulfate is an effective method for degrading organic pollutants. The main feature of this process is to activate persulfate (PS) to produce reactive oxidative species (ROS), and the degradation mechanism includes two types of free radicals and non-free radicals. There are many ways to activate persulfate, including transition metals (such as Fe, Co, Cu, Mn, Zn, Ag and Ni), carbon materials, alkali and external energy (such as heat, ultraviolet, microwave, electricity and ultrasonic wave) and the like. Among them, Fe-based catalysts are favored due to their high activation efficiency, abundant geological reserves, low energy consumption and low biological toxicity.

[0004] Red mud (RM) often used as a raw material for synthesizing Fe-based catalysts due to its high content of Fe in recent years. However, the red mud has high alkalinity, small specific surface area, and the iron phase is mainly low-activity hematite (Fe2O3), which leads to low actual catalytic activity.

[0005] Due to the influence of human and natural factors such as large pollution load, serious eutrophication, large water body dynamic change, water resource shortage, frequent water replacement, water level rise, vegetation coverage rate decrease, biological diversity decrease, temperature, sunshine, climate and lake morphology, the Dianchi water body has had an outbreak of blue algae every year since the 1980s, and has become one of the three large lakes with serious blue algae outbreak in China every year.

[0006] In view of the above, the problems of removing EE2 from water bodies and reducing the hazards of red mud and blue-green algae pollution are urgent to be solved. SUMMARY

[0007] In view of the above, the problems of removing EE2 from water bodies and reducing the hazards of red mud and blue-green algae pollution are urgent to be solved.

[0008] To achieve the above object, the present application adopts the following technical solution: the preparation method of the algal-based red mud biochar comprises the following steps:

[0009] (1) dispersing the red mud into a nitric acid solution, and stirring magnetically for 30 min to obtain a suspension;

[0010] (2) adding blue-green algae biomass powder into the suspension, and stirring magnetically for 30 min to obtain a mixed solution A;

[0011] (3) placing the mixed solution A in a temperature of 180-220 DEG C for hydrothermal reaction for 6-10 h, and then performing solid-liquid separation, drying the solid, and then placing it in a temperature of 700-900 DEG C under a nitrogen atmosphere for pyrolysis reaction for 1-3 h, and then washing, drying and obtaining the algal-based red mud catalyst.

[0012] Preferably, the concentration of the nitric acid in the step S1 is 0.7 mol / L, and the solid-liquid ratio of the red mud and the nitric acid solution is 1g / 50mL.

[0013] Preferably, the particle size of the red mud and the blue-green algae biomass powder is 100 mesh.

[0014] Preferably, the mass ratio of the red mud and the blue-green algae biomass powder in the step S2 is 1:4.

[0015] Preferably, the hydrothermal reaction is a hydrothermal reaction at a temperature of 200 DEG C for 8 h.

[0016] Preferably, the pyrolysis reaction is a pyrolysis reaction at a temperature of 800 DEG C under a nitrogen atmosphere for 2 h.

[0017] Further, the added amount of the nitric acid solution is 60 mL.

[0018] Application of the algal-based red mud catalyst in removing 17alpha-ethinyl estradiol (EE2).

[0019] Further, application of the algal-based red mud catalyst as an adsorbent in adsorbing 17alpha-ethinyl estradiol (EE2) in water, and adsorption kinetics and adsorption isotherm fitting.

[0020] Further, the concentration of 17alpha-ethinyl estradiol (EE2) is 0.5-5 mg / L, the dosage of the algal-based red mud catalyst is 0.2-0.6 g / L, the oscillation speed is 180 rpm, and the adsorption reaction time is 60 min.

[0021] Further, application of the algal-based red mud catalyst as a catalyst in degrading 17alpha-ethinyl estradiol (EE2) in water.

[0022] Further, application of the algal-based red mud catalyst as an activator of persulfate in degrading 17alpha-ethinyl estradiol (EE2) in water.

[0023] Further, the concentration of 17alpha-ethinyl estradiol (EE2) is 1.5-2.5 mg / L, the dosage of the algal-based red mud catalyst is 0.2-0.6 g / L, the concentration of persulfate is 0.00-0.08 mM, the oscillation speed is 180 rpm, and the adsorption reaction time is 60 min.

[0024] The present application has the advantages that: the preparation method is simple and easy to operate, and has few process steps; the material source is wide, the cost is low, the product yield is high, the 17alpha-ethinyl estradiol (EE2) adsorption performance is good, the catalyst has magnetism, is easy to recycle and reuse, and does not cause secondary pollution; solid waste (red mud waste residue and blue-green algae waste residue) is used as raw material to prepare a high-efficiency catalyst, and water pollution treatment and solid waste resource utilization can be realized at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The figure is the adsorption capacity of the algal-based red mud catalyst RM-BC for EE2 and the fitting curves of the pseudo-first-order kinetic model and the pseudo-second-order kinetic model under different adsorption times according to example 1.

[0026] Figure 2 The figure is the fitting curves of the Langmuir isotherm model and the Freundlich isotherm model of the algal-based red mud catalyst RM-BC adsorbing EE2 according to example 1.

[0027] Figure 3 The figure is the adsorption effect of the algal-based red mud catalyst RM-BC as an adsorbent on different concentrations of 17alpha-ethinyl estradiol (EE2) according to example 1.

[0028] Figure 4The adsorption effect of different dosages of the algal-based red mud catalyst RM-BC of Example 1 on 17α-ethinyl estradiol (EE2);

[0029] Figure 5 The degradation effect of the algal-based red mud catalyst RM-BC of Example 3 on 17α-ethinyl estradiol (EE2);

[0030] Figure 6 The degradation effect of the algal-based red mud catalyst RM-BC of Example 3 in combination with different concentrations of persulfate (PDS) on 17α-ethinyl estradiol (EE2);

[0031] Figure 7 The degradation effect of different dosages of the algal-based red mud catalyst RM-BC of Example 3 in combination with persulfate (PDS) on 17α-ethinyl estradiol (EE2);

[0032] Figure 8 The degradation effect of the algal-based red mud catalyst RM-BC of Example 3 in combination with persulfate (PDS) on different concentrations of 17α-ethinyl estradiol (EE2). DETAILED DESCRIPTION

[0033] The application will be further described in conjunction with the examples below, but in no way limits the application, any transformation or replacement based on the teaching of the application shall fall within the protection scope of the application.

[0034] Example 1

[0035] The red mud from a local alumina refinery in Yunnan Province of China and the blue-green algae biomass powder obtained from the algae in Dianchi Lake are used as raw materials, and the preparation method of the algal-based red mud biochar is as follows:

[0036] S1: The red mud is dispersed into a nitric acid solution, and a suspension is obtained by magnetic stirring for 30 min; the concentration of the nitric acid is 0.7 mol / L, and the solid-liquid ratio of the red mud to the nitric acid solution is 1 g / 50 mL.

[0037] S2: The blue-green algae biomass powder is added into the suspension to obtain a mixture A; the mass ratio of the red mud to the blue-green algae biomass powder is 1:4.

[0038] S3: The mixture A is subjected to hydrothermal reaction at a temperature of 200℃ for 8 h, and then solid-liquid separation is performed; the dried solid is subjected to pyrolysis reaction at a temperature of 800℃ under a nitrogen atmosphere for 2 h, and then washed and dried to obtain the algal-based red mud catalyst, which is marked as RM-BC.

[0039] Example 2

[0040] To explore the adsorption effect of the algal-based red mud catalyst on 17α-ethinyl estradiol (EE2), the RM-BC obtained in Example 1 was applied to adsorb 17α-ethinyl estradiol (EE2) in water, specifically including the following steps:

[0041] The algal-based red mud catalyst RM-BC was added to the organic pollutant 17α-ethinyl estradiol (EE2) sewage and mixed uniformly, wherein the concentration of the organic pollutant 17α-ethinyl estradiol (EE2) was 0.5-5.0 mg / L, the sewage was 50 mL, the catalyst dosage was 0.2-0.6 g / L, and the oscillation reaction was carried out at 25°C, wherein the oscillation speed was 180 rpm, the oscillation reaction time was 60 min, samples were taken at 0, 2, 4, 6, 10, 20, 40, and 60 min, and the remaining 17α-ethinyl estradiol (EE2) concentration in the reaction system was determined immediately after centrifugation using an Agilent 1260 series high-performance liquid chromatograph; the analysis column was Silicagel C18 (Waters, 5 μm, 250 mm x 4.6 mm), the retention time of EE2 was 5.6 min, the instrument operating temperature was 25°C, the quantitative detector used was a fluorescence detector, the excitation wavelength was set to 236 nm, and the emission wavelength was 310 nm. The mobile phase was 60 / 40 volume ratio of acetonitrile (CH3CN) containing 0.1% trifluoroacetic acid and ultrapure water containing 0.1% trifluoroacetic acid, the flow rate was 1 mL / min, and the sample injection amount was 20 μL. Then, according to the change in the concentration of the solution before and after adsorption, the adsorption amount of the algal-based red mud catalyst for EE2 at different adsorption times was calculated using formula (1).

[0042] (1)

[0043] In formula (1), Q t is the adsorption amount of the adsorbent, with units of mg / g; C0 and C t are the initial concentration and the concentration at time t of EE2 in the solution, respectively, with units of mg / L; v is the solution volume, with units of L; and m is the EE2 dosage, with units of g.

[0044] According to formulas (2-3), the experimental data were fitted using pseudo-first-order and pseudo-second-order kinetic equations.

[0045] Pseudo-first-order kinetic model:

[0046] (2)

[0047] Pseudo-second-order kinetic model:

[0048] (3)

[0049] In formulas (2) and (3), t is the adsorption time; Q eQe is the adsorption amount of unit mass of adsorbent at adsorption equilibrium, unit: mg / g; Q t Q is the adsorption amount in t time, unit: mg / L; k1 and k2 are adsorption rate constants of pseudo-first-order kinetic equation and pseudo-second-order kinetic equation respectively, k1 unit is min -1 , k2 unit is g / (mg·min).

[0050] The pseudo-first-order and pseudo-second-order equation nonlinear fitting curves are shown in Figure 1 and Table 1, and it can be calculated that the correlation coefficients (R 2 ) of the pseudo-second-order adsorption kinetic equation of the algal-based red mud catalyst to EE2 are all greater than those of the pseudo-first-order kinetics, so it is reliable to use the pseudo-second-order adsorption kinetic equation to simulate and analyze the removal rate of EE2 by the algal-based red mud catalyst.

[0051] Table 1 Pseudo-first-order and pseudo-second-order equation nonlinear fitting curve data of algal-based red mud catalyst adsorbing EE2 in Example 1

[0052]

[0053] The isotherm data was nonlinearly fitted by Langmuir isotherm model and Freundlich isotherm model. The equations of each model are as follows:

[0054] Langmuir isotherm model:

[0055] (4)

[0056] Freundlich isotherm model:

[0057] (5)

[0058] In formula (4) and (5), Q e is the equilibrium adsorption amount of EE2, unit: mg / g; C e is the solution concentration at adsorption equilibrium, unit: mg / L; K L is the Langmuir isothermal adsorption constant, unit: L / mg; K F and n are Freundlich equation constant and dimensionless constant respectively, K F unit is (mg / g)(L / mg) 1 / n ; Q m is the theoretical maximum adsorption amount, unit: mg / g.

[0059] Table 2 Langmuir isothermal adsorption model and Freundlich isothermal adsorption model fitting curve data of algal-based red mud catalyst adsorbing EE2 in Example 1

[0060]

[0061] Langmuir isotherm adsorption model and Freundlich isotherm adsorption model fitting curve as shown in Figure 2 and Table 2. The correlation coefficient (R 2 ) of Freundlich model is less than the correlation coefficient of Langmuir model, which shows that the Langmuir model is better than the Freundlich model in fitting the results of EE2 adsorption process of algal-based red mud catalyst. Through Langmuir fitting, the maximum adsorption capacity Q m of EE2 of algal-based red mud catalyst is 8.00 mg / g; which shows that the algal-based red mud catalyst can be well applied to the removal of EE2.

[0062] Example 3

[0063] In order to explore the adsorption effect of algal-based red mud catalyst on 17α-ethinyl estradiol (EE2), the RM-BC obtained in Example 1 was applied to adsorb 17α-ethinyl estradiol (EE2) in water, which specifically included the following steps:

[0064] The algal-based red mud catalyst RM-BC was added to the organic pollutant 17α-ethinyl estradiol (EE2) sewage and mixed uniformly, wherein the concentration of the organic pollutant 17α-ethinyl estradiol (EE2) was 0.5-5.0 mg / L, the sewage was 50 mL, the catalyst dosage was 0.2-0.6 g / L, the oscillation reaction was carried out at 25°C, wherein the oscillation speed was 180 rpm, the oscillation reaction time was 60 min, and the samples were taken at 0, 2, 4, 6, 10, 20, 40, and 60 min, and the remaining 17α-ethinyl estradiol (EE2) concentration in the reaction system was determined by Agilent 1260 series high performance liquid chromatograph immediately after centrifugation; wherein the analysis column was Silicagel C18 (Waters, 5 μm, 250 mm x 4.6 mm), the retention time of EE2 was 5.6 min, the instrument operating temperature was 25°C, the quantitative detector used was a fluorescence detector, and the excitation wavelength was set to 236 nm and the emission wavelength was 310 nm. The mobile phase was 60 / 40 volume ratio of acetonitrile (CH3CN) containing 0.1% trifluoroacetic acid and ultrapure water containing 0.1% trifluoroacetic acid, the flow rate was 1 mL / min, and the sample injection amount was 20 μL. The adsorption effect of algal-based red mud catalyst RM-BC on different concentrations of 17α-ethinyl estradiol (EE2) was plotted (see Figure 3 ), from Figure 3It can be seen that when the initial concentration of 17α-ethinyl estradiol (EE2) is 0.5, 1.0, 2.0 and 5.0 mg / L respectively, the dosage of algal-based red mud catalyst is 0.2 g / L, and after 60 min of reaction, the adsorption removal rates of 17α-ethinyl estradiol (EE2) are 56.29%, 50.39%, 35.07% and 23.38% respectively. It shows that the removal rate of algal-based red mud catalyst RM-BC for EE2 is negatively correlated with the initial EE2 concentration. The adsorption effect of algal-based red mud catalyst RM-BC on 17α-ethinyl estradiol (EE2) at different concentrations is plotted (see Figure 4 ), from Figure 4 which can be seen that when the initial dosage of algal-based red mud catalyst RM-BC is 0.2, 0.4 and 0.6 g / L respectively, the initial concentration of 17α-ethinyl estradiol (EE2) is 1.0 mg / L, and after 60 min of reaction, the adsorption removal rates of 17α-ethinyl estradiol (EE2) are 50.39%, 77.38% and 85.94% respectively. The removal rate of algal-based red mud catalyst RM-BC for EE2 is positively correlated with the initial catalyst dosage.

[0065] Example 4

[0066] To explore the degradation effect of algal-based red mud catalyst in cooperation with persulfate (PDS) on 17α-ethinyl estradiol (EE2), the RM-BC obtained in Example 1 was applied to remove 17α-ethinyl estradiol (EE2) in water, which specifically included the following steps: the algal-based red mud catalyst RM-BC was added to the organic pollutant 17α-ethinyl estradiol (EE2) wastewater and mixed uniformly, after 50 min of oscillation, persulfate (PDS) was added to the solution, and the oscillation was continued for 30 min, samples were taken at 0, 50, 50.5, 52, 54, 56, 60, 70 and 80 min, and immediately after centrifugation, the remaining 17α-ethinyl estradiol (EE2) concentration in the reaction system was determined by Agilent 1260 series high performance liquid chromatograph; the analysis column was Silicagel C18 (Waters, 5 μm, 250 mm x 4.6 mm), the retention time of EE2 was 5.6 min, the instrument operating temperature was 25°C, the quantitative detector used was a fluorescence detector, and the excitation wavelength was set to 236 nm and the emission wavelength was set to 310 nm. The mobile phase was 60 / 40 volume ratio of acetonitrile (CH3CN) containing 0.1% trifluoroacetic acid and ultrapure water containing 0.1% trifluoroacetic acid, the flow rate was 1 mL / min, and the sample injection amount was 20 μL. The degradation effect of algal-based red mud catalyst RM-BC on 17α-ethinyl estradiol (EE2) is plotted (see Figure 5 ), from Figure 5It can be seen that when the initial concentration of 17α-ethinyl estradiol (EE2) is 2.0 mg / L, the dosage of red mud carbon-based catalyst is 0.2 g / L, and the concentration of persulfate (PDS) is 0.08 mM, the degradation rate of 17α-ethinyl estradiol (EE2) can reach 100.00% after 30 min of reaction. In the system with only PDS, the degradation efficiency of 17α-ethinyl estradiol (EE2) is only 4.11%. In the system with only RM-BC, the degradation efficiency of 17α-ethinyl estradiol (EE2) is 42.67%. This shows that the red mud carbon-based catalyst RM-BC in combination with PDS is very effective in removing 17α-ethinyl estradiol (EE2) from water. Figure 6 When the initial concentration of 17α-ethinyl estradiol (EE2) is 2.0 mg / L, the dosage of red mud carbon-based catalyst is 0.2 g / L, and the concentration of persulfate (PDS) is 0.00, 0.02, 0.04, 0.06, and 0.08 mM, respectively, the removal rates of 17α-ethinyl estradiol (EE2) are 42.67%, 70.71%, 87.23%, 95.28%, and 100.00%, respectively, after 80 min of reaction. The increase of PDS concentration has a positive effect on the removal of EE2 by RM-BC in combination with PDS. Figure 7 When the initial concentration of 17α-ethinyl estradiol (EE2) is 2.0 mg / L, the concentration of persulfate (PDS) is 0.08 mM, and the dosage of red mud carbon-based catalyst is 0.0 g / L, 0.2 g / L, 0.4 g / L, and 0.6 g / L, respectively, the degradation rates of 17α-ethinyl estradiol (EE2) are 4.46%, 92.33%, 99.68%, and 99.99%, respectively, after 20 min of reaction. This shows that the removal rate of EE2 by RM-BC in combination with PDS is positively correlated with the initial catalyst dosage. Figure 8 When the concentration of persulfate (PDS) is 0.08 mM, the dosage of red mud carbon-based catalyst is 0.2 g / L, and the initial concentration of 17α-ethinyl estradiol (EE2) is 1.0, 2.0, and 3.0 mg / L, respectively, the degradation rates of 17α-ethinyl estradiol (EE2) are 100.00%, 99.68%, and 89.45%, respectively, after 20 min of reaction. This shows that the removal rate of EE2 by RM-BC in combination with PDS is negatively correlated with the initial pollutant concentration.

[0067] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present application.

Claims

1. Use of an algal-based red mud catalyst as activator of persulfate for the degradation of 17α-ethinyl estradiol in water, characterized in that The preparation method of the algal-based red mud catalyst comprises the following steps: (1) dispersing the red mud into a nitric acid solution, and stirring to obtain a suspension; (2) adding blue-green algae biomass powder into the suspension, and stirring to obtain a mixed solution A; (3) placing the mixed solution A in a hydrothermal reaction at a temperature of 180-220 DEG C for 6-10 h, performing solid-liquid separation, drying the solid, and then placing the solid in a pyrolysis reaction at a temperature of 700-900 DEG C in a nitrogen atmosphere for 1-3 h, and then washing, drying and obtaining the algal-based red mud catalyst; The obtained algal-based red mud catalyst is used as an activator of persulfate to degrade 17 alpha-ethynyl estradiol in water.

2. Use according to claim 1, characterized in that In step (1), the concentration of the nitric acid is 0.7 mol / L, and the stirring is magnetic stirring for 30 min.

3. Use according to claim 1, characterized in that In step (1), the solid-liquid ratio of the red mud and the nitric acid solution is 1 g / 50 mL.

4. Use according to claim 1, characterized in that In step (2), the mass ratio of the red mud and the blue-green algae biomass powder is 1:4, and the stirring is magnetic stirring for 30 min.

5. The use according to claim 1, characterized in that In step (3), the hydrothermal reaction is a hydrothermal reaction at a temperature of 200 DEG C for 8 h.

6. Use according to claim 1, characterized in that In step (3), the pyrolysis reaction is a pyrolysis reaction at a temperature of 800 DEG C in a nitrogen atmosphere for 2 h.

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