A photocatalyst magnetized by magnetic separation concentrate and a preparation method and application thereof

Abstract

The present application relates to the technical field of ore-dressing wastewater treatment, and particularly relates to a magnetized photocatalyst through magnetic separation concentrate, and a preparation method and application thereof. The present application disperses the magnetic separation concentrate after ball milling into a mixed solution of anhydrous ethanol, water and ammonia water to obtain a suspension 1; a mixed solution of tetraethyl orthosilicate and anhydrous ethanol is added into the suspension 1 to perform coating to obtain gamma-Fe2O3@SiO2; the photocatalyst, a solvent and gamma-Fe2O3@SiO2 are mixed to obtain the magnetized photocatalyst; the photocatalyst is bismuth tungstate or bismuth oxyiodide. Under the optimal conditions, the degradation efficiency of the photocatalyst on xanthate can reach 100%, and the photocatalyst can be recycled through magnetism, so that the operation cost is greatly reduced, and the photocatalyst has a good application prospect. The present application utilizes the natural magnetic hematite gamma-Fe2O3, avoids the problems of numerous artificial synthesis steps and high cost, and has a wide application prospect in the field of magnetic photocatalysts.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ore dressing wastewater treatment, and particularly relates to a photocatalyst endowed with magnetism by magnetic separation of concentrate, and a preparation method and application thereof. BACKGROUND

[0002] A large amount of collecting agents, foaming agents, depressants and other ore dressing reagents are used in the mineral flotation process, among which the collecting agent has the highest dosage of xanthate. Most of the xanthate will enter the flotation froth product, but part of it will still remain in the ore dressing wastewater. The xanthate itself is toxic and has a pungent odor, and will pollute water resources if discharged without treatment; on the other hand, the xanthate will naturally degrade into CS2 and other organic substances in the wastewater, and CS2 is easy to volatilize and will pollute the air environment by changing into SO2 in the air. Therefore, it is of great significance to the environment to fully degrade the xanthate in the ore dressing wastewater.

[0003] At present, the degradation technology of residual xanthate in ore dressing wastewater can be roughly divided into six categories: coagulation sedimentation method, biological method, hydrogen peroxide method, Fenton method, ozone method and photocatalytic method. In recent years, photocatalytic oxidation technology is favored in the treatment of organic waste in wastewater because of its economy, high efficiency, easy operation, high mineralization degree and no secondary pollution, and is a "green" wastewater treatment technology with strong operability. The catalysts used for photocatalytic degradation of xanthate include bismuth tungstate (Bi2WO6), bismuth iodine oxide (BiOI), bismuth ferrite / zinc indium sulfide (Bi2Fe4O9 / ZnIn2S4), etc., which have good degradation effect on xanthate. However, since the photocatalyst needs to be dispersed in the wastewater to degrade the xanthate, the catalyst needs to be recovered when the xanthate molecules in the wastewater are completely degraded or the catalyst is deactivated, and then the regenerated catalyst is used again. Fine particle photocatalysts are difficult to recover by effective filtration or centrifugation, so a large amount of catalyst remains in the water, causing serious secondary pollution to the water body. Due to the loss of catalyst, the running cost of wastewater treatment is greatly increased by reusing fresh catalyst. Therefore, the catalyst is compounded with magnetic material to improve its recyclability, so as to facilitate the recycling of photocatalyst.

[0004] The magnetic carriers of existing magnetic photocatalysts are mostly artificial synthetic ferrite. Although these materials have high purity, the synthesis steps are long and the cost is high, which is not suitable for industrialization. Therefore, how to simplify the preparation steps of the magnetic carrier has become a technical problem to be solved by those skilled in the art. SUMMARY

[0005] The application aims to provide a photocatalyst magnetized by magnetic separation concentrate and a preparation method and application thereof, which uses magnetic separation concentrate (γ-Fe2O3) as a magnetic material loaded on bismuth tungstate (Bi2WO6) and bismuth oxyiodide (BiOI) to endow the photocatalyst with magnetism for easy recovery. To ensure the degradation efficiency of the photocatalyst, γ-Fe2O3 is also coated with SiO2, i.e. two kinds of photocatalysts based on γ-Fe2O3@SiO2 as a magnetic material, i.e. γ-Fe2O3@SiO2 / Bi2WO6 and γ-Fe2O3@SiO2 / BiOI, are prepared to degrade residual xanthate in ore dressing wastewater.

[0006] To achieve the above-mentioned application purposes, the application provides the following technical solutions.

[0007] The application provides a preparation method of a photocatalyst magnetized by magnetic separation concentrate, which comprises the following steps:

[0008] 1) After the magnetic separation concentrate is ball milled, it is dispersed into a mixed solution of anhydrous ethanol, water and ammonia water to obtain a suspension 1;

[0009] 2) A mixed solution of tetraethyl orthosilicate and anhydrous ethanol is added into the suspension 1 for coating to obtain γ-Fe2O3@SiO2;

[0010] 3) The photocatalyst, solvent and γ-Fe2O3@SiO2 are mixed to obtain the magnetized photocatalyst;

[0011] The photocatalyst is bismuth tungstate or bismuth oxyiodide;

[0012] When the photocatalyst is bismuth tungstate, the γ-Fe2O3@SiO2 accounts for 3-7% of the dosage of bismuth tungstate;

[0013] When the photocatalyst is bismuth oxyiodide, the γ-Fe2O3@SiO2 accounts for 5-20% of the dosage of bismuth oxyiodide.

[0014] Optionally, the content of γ-Fe2O3 in the magnetic separation concentrate is ≥90%;

[0015] The speed of the ball milling is 500-1000 r / min, and the time is 60-120 min;

[0016] The particle size of the magnetic separation concentrate after the ball milling is 0.5-1 μm.

[0017] Optionally, the volume ratio of the anhydrous ethanol, water and ammonia water is 50-100:10-30:1;

[0018] The dosage ratio of the magnetic separation concentrate to the mixed solution of anhydrous ethanol, water and ammonia water is 0.4-0.6 g:400-500 mL.

[0019] Optionally, the volume ratio of the tetraethyl orthosilicate and the absolute ethanol is 1:20-30.

[0020] Optionally, the dosage ratio of the magnetic separation concentrate and the tetraethyl orthosilicate is 0.4-0.6 g:0.5-1 mL;

[0021] The coating time is 10-15 h.

[0022] Optionally, the solvent comprises methanol or ethanol;

[0023] The dosage ratio of the photocatalyst and the solvent is 0.1-0.5 g:100 mL.

[0024] Optionally, the mixing temperature is 30-40 DEG C, and the mixing time is 12-48 h.

[0025] The application further provides the magnetic separation concentrate magnetized photocatalyst prepared by the preparation method.

[0026] The application further provides application of the magnetic separation concentrate magnetized photocatalyst in degradation of residual xanthate in beneficiation wastewater.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] The application coats a layer of silicon dioxide (SiO2) on the surface of the magnetic separation concentrate gamma-Fe2O3 by a simple mechanical stirring method, obtains gamma-Fe2O3@SiO2, synthesizes bismuth tungstate and bismuth oxyiodide by a hydrothermal method, and then loads the gamma-Fe2O3@SiO2 on the bismuth tungstate or bismuth oxyiodide by a mechanical stirring method, to obtain the composite catalyst gamma-Fe2O3@SiO2 / Bi2WO6 or gamma-Fe2O3@SiO2 / BiOI, which has a good degradation effect on xanthate. Under the optimal conditions, the degradation efficiency of xanthate by the gamma-Fe2O3@SiO2 / Bi2WO6 and the gamma-Fe2O3@SiO2 / BiOI can both reach 100%. Compared with the existing photocatalyst, the two magnetic photocatalysts involved in the application have high degradation efficiency, can be recycled by magnetism, greatly reduce the operation cost, and have a good application prospect.

[0029] The application utilizes the natural magnetic hematite gamma-Fe2O3, avoids the problems of many artificial synthesis steps and high cost, and has a wide application prospect in the field of magnetic photocatalysts. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The XRD pattern of the magnetic separation concentrate gamma-Fe2O3 of the application;

[0031] Figure 2 XRD pattern of γ-Fe2O3@SiO2, Bi2WO6, 5% γ-Fe2O3@SiO2 / Bi2WO6 prepared for example 1 of the present invention;

[0032] Figure 3 FTIR pattern of γ-Fe2O3@SiO2, Bi2WO6, 5% γ-Fe2O3@SiO2 / Bi2WO6 prepared for example 1 of the present invention;

[0033] Figure 4 Graph showing the effect of different loading ratios of γ-Fe2O3@SiO2 Bi2WO6 based catalyst on degradation efficiency of xanthate;

[0034] Figure 5 Magnetic hysteresis loop graph of γ-Fe2O3@SiO2, Bi2WO6, 5% γ-Fe2O3@SiO2 / Bi2WO6;

[0035] Figure 6 Cycle experiment graph of 5% γ-Fe2O3@SiO2 / Bi2WO6;

[0036] Figure 7 XRD pattern of γ-Fe2O3@SiO2, BiOI, 5% γ-Fe2O3@SiO2 / BiOI;

[0037] Figure 8 FTIR pattern of γ-Fe2O3@SiO2, BiOI, 5% γ-Fe2O3@SiO2 / BiOI;

[0038] Figure 9 Graph showing the effect of different loading ratios of γ-Fe2O3@SiO2 BiOI based catalyst on degradation efficiency of xanthate;

[0039] Figure 10 Magnetic hysteresis loop graph of γ-Fe2O3@SiO2, BiOI, 5% γ-Fe2O3@SiO2 / BiOI;

[0040] Figure 11 Cycle experiment graph of 5% γ-Fe2O3@SiO2 / BiOI. DETAILED DESCRIPTION

[0041] Various illustrative embodiments of the present application are now described in detail below. The following description includes specific details for the purpose of providing a thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without these specific details. In other instances, well-known structures and functions have not been described in detail in order to avoid obscuring the understanding of the present application.

[0042] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. In addition, where a range of values is provided, it is understood that each intervening value, to the upper and lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and are also encompassed by the application, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of the limits are also included.

[0043] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in detail the methods and / or materials which are described in them. In the case of conflict between the present specification and any document incorporated herein by reference, the present specification will control.

[0044] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application. The specification and examples are illustrative only.

[0045] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended and to mean including, but not limited to.

[0046] As used herein, the terms "room temperature", "ambient temperature" are intended to mean 25±2°C, unless otherwise specified.

[0047] The raw materials used in the following examples of the present application are commercially available.

[0048] The present application provides a preparation method of a magnetized photocatalyst by magnetically separating a concentrate, comprising the following steps:

[0049] 1) After ball milling, the concentrate is dispersed into a mixed solution of anhydrous ethanol, water and ammonia water to obtain a suspension 1;

[0050] 2) A mixed solution of tetraethyl orthosilicate and anhydrous ethanol is added to the suspension 1 to perform coating to obtain γ-Fe2O3@SiO2;

[0051] 3) The magnetized photocatalyst is obtained by mixing the photocatalyst, solvent and γ-Fe2O3@SiO2.

[0052] In the present application, the photocatalyst is bismuth tungstate or bismuth oxyiodide;

[0053] When the photocatalyst is bismuth tungstate, the γ-Fe2O3@SiO2 accounts for 3-7% of the amount of bismuth tungstate, preferably 4-6%, and most preferably 5%.

[0054] When the photocatalyst is bismuth oxyiodide, the γ-Fe2O3@SiO2 accounts for 5-20% of the amount of bismuth oxyiodide, preferably 10-15%, and most preferably 5%.

[0055] In the present application, γ-Fe2O3 has no effect on photocatalytic degradation of xanthate, and direct compounding of γ-Fe2O3 with Bi2WO6 or BiOI will inhibit the catalytic degradation performance of Bi2WO6 or BiOI on xanthate. In order to prevent the inhibitory effect of γ-Fe2O3, a SiO2 layer is introduced to wrap γ-Fe2O3, so as to separate γ-Fe2O3 and Bi2WO6 or BiOI, and avoid direct contact between them to reduce the photocatalytic activity of Bi2WO6 or BiOI.

[0056] In the present application, the preparation method of bismuth tungstate comprises the following steps: dispersing bismuth nitrate pentahydrate into a nitric acid solution, dispersing by a magnetic stirrer, and recording as suspension 1; dissolving sodium tungstate dihydrate in ultrapure water and performing magnetic stirring, recording as solution 2; slowly adding solution 2 into suspension 1, and adjusting the pH by sodium hydroxide solution and nitric acid solution, recording as precursor solution 3; pouring precursor solution 3 into a polytetrafluoroethylene-lined reaction kettle for hydrothermal reaction, after the reaction is completed and naturally cooled to room temperature, washing with ultrapure water and anhydrous ethanol for multiple times, finally putting the product into a constant temperature drying box for drying, and then grinding to obtain Bi2WO6 powder.

[0057] In the present application, the preparation method of bismuth tungstate comprises the following steps: dispersing bismuth nitrate pentahydrate into a nitric acid solution, dispersing by a magnetic stirrer, and recording as suspension 1; dissolving sodium tungstate dihydrate in ultrapure water and performing magnetic stirring, recording as solution 2; slowly adding solution 2 into suspension 1, and adjusting the pH by sodium hydroxide solution and nitric acid solution, recording as precursor solution 3; pouring precursor solution 3 into a polytetrafluoroethylene-lined reaction kettle for hydrothermal reaction, after the reaction is completed and naturally cooled to room temperature, washing with ultrapure water and anhydrous ethanol for multiple times, finally putting the product into a constant temperature drying box for drying, and then grinding to obtain Bi2WO6 powder.

[0058] In the present application, the magnetic separation concentrate is mainly γ-Fe2O3, and the specific oxide composition of the magnetic separation concentrate is: Na2O, MgO, Al2O3, SiO2, P2O5, SO3, Cl, K2O, CaO, TiO2, V2O5, MnO, Fe2O3, CuO, ZnO.

[0059] The content of Na2O is 0.1-0.2%; the content of MgO is 1-2%; the content of Al2O3 is 1-2%; the content of SiO2 is 3-4%; the content of P2O5 is 0.01-0.1%; the content of SO3 is 0.1-1%; the content of Cl is 0.01-0.1%; the content of K2O is 0.1-0.3%; the content of CaO is 0.1-1%; the content of TiO2 is 0.1-0.2%; the content of V2O5 is 0.05-0.1%; the content of MnO is 0.1-0.2%; the content of Fe2O3 is 88-95%; the content of CuO is 0.01-0.06%; the content of ZnO is 0.01-0.05%;

[0060] The sum of the contents of the oxides is 100%.

[0061] In the present application, the content of γ-Fe2O3 in the magnetic separation concentrate is preferably about 91%;

[0062] The speed of the ball milling is 500-1000 r / min, preferably 600-900 r / min, and further preferably 700-800 r / min; and the time is 60-120 min, preferably 70-100 min, and further preferably 80-90 min.

[0063] The particle size of the magnetic separation concentrate after the ball milling is 0.5-1 μm, preferably 0.6-0.9 μm, further preferably 0.7-0.8 μm, and most preferably about 0.724 μm.

[0064] In the present application, the volume ratio of the absolute ethanol, water and ammonia water is 50-100:10-30:1, preferably 60-90:15-25:1, and further preferably 70-80:18-20:1.

[0065] The usage ratio of the mixture of the magnetic separation concentrate, absolute ethanol, water and ammonia water is 0.4-0.6 g:400-500 mL, preferably 0.42-0.58 g:450-490 mL, and further preferably 0.5 g:480 mL.

[0066] In the present application, the volume concentration of the ammonia water is 20-40%, preferably 25-35%, and further preferably 28-30%.

[0067] In the present application, the magnetic separation concentrate after the ball milling is dispersed into the mixture of the absolute ethanol, water and ammonia water, and is ultrasonically treated for 10-20 min, preferably 12-18 min, further preferably 14-16 min, and more further preferably 15 min, to obtain a suspension 1.

[0068] In the present application, the volume ratio of the tetraethyl orthosilicate and anhydrous ethanol is 1:20-30, preferably 1:22-28, further preferably 1:24-27, and more preferably 1:25-26.

[0069] In the present application, the dosage ratio of the magnetic separation concentrate and the tetraethyl orthosilicate is 0.4-0.6 g:0.5-1 mL, preferably 0.42-0.58 g:0.6-0.9 mL, and further preferably 0.5 g:0.9 mL.

[0070] The coating time is 10-15 h, preferably 11-14 h, and more preferably 12-13 h, and the temperature is room temperature.

[0071] In the present application, step 2) is to add the mixture of the tetraethyl orthosilicate and anhydrous ethanol dropwise into the suspension A, and mechanically stir at room temperature. After the stirring is completed, the product is collected by centrifugation, and washed with ultrapure water and anhydrous ethanol for three times each. The product is dried in a vacuum oven to obtain the γ-Fe2O3@SiO2 particles.

[0072] In the present application, the solvent comprises methanol or ethanol, and preferably methanol.

[0073] The dosage ratio of the photocatalyst and the solvent is 0.1-0.5 g:100 mL, preferably 0.2-0.4 g:100 mL, and further preferably 0.3 g:100 mL.

[0074] In the present application, the mixing temperature is 30-40℃, preferably 35℃, and the mixing time is 12-48 h, preferably 16-40 h, further preferably 20-36 h, and more preferably 24-30 h.

[0075] In the present application, the photocatalyst is dispersed into the solvent and subjected to ultrasonic treatment to form a uniform suspension; the γ-Fe2O3@SiO2 is added into the suspension and subjected to ultrasonic treatment, and then mechanical stirring is performed; after the stirring is completed, the solid is separated by centrifugation, and the product is dried in a vacuum oven to obtain the magnetized photocatalyst.

[0076] The present application also provides the magnetized photocatalyst of the magnetic separation concentrate prepared by the preparation method.

[0077] The present application also provides the application of the magnetized photocatalyst of the magnetic separation concentrate in degrading the residual xanthate in the beneficiation wastewater.

[0078] The technical solutions provided by the present application will be described in detail below in combination with the embodiments, but they should not be understood as limiting the scope of protection of the present application.

[0079] In the embodiment of the application, the oxide compositions of the magnetic separation concentrate are as follows: Na2O, MgO, Al2O3, SiO2, P2O5, SO3, Cl, K2O, CaO, TiO2, V2O5, MnO, Fe2O3, CuO, ZnO;

[0080] The content of Na2O is 0.15%; the content of MgO is 1.7%; the content of Al2O3 is 1.32%; the content of SiO2 is 3.47%; the content of P2O5 is 0.05%; the content of SO3 is 0.57%; the content of Cl is 0.05%; the content of K2O is 0.2%; the content of CaO is 0.84%; the content of TiO2 is 0.17%; the content of V2O5 is 0.06%; the content of MnO is 0.16%; the content of Fe2O3 is 91.19%; the content of CuO is 0.04%; and the content of ZnO is 0.03%.

[0081] Example 1

[0082] Preparation of γ-Fe2O3@SiO2 / Bi2WO6, the specific steps are as follows:

[0083] Preparation of Bi2WO6: 3 mmol of Bi(NO3)3·5H2O was dispersed into 25 mL of 0.3 mol / L HNO3 solution and magnetically stirred at room temperature for 30 min, denoted as suspension A. 1.5 mmol of Na2WO4·2H2O was dissolved in 55 mL of ultrapure water and magnetically stirred for 30 min, denoted as solution B. Solution B was slowly poured into suspension A, and magnetically stirred for 20 min, denoted as suspension C. Then, 4.5 mol / L NaOH solution was added dropwise to suspension C, and the pH of C was adjusted to 2, denoted as precursor solution D. Precursor solution D was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reaction kettle, which was placed in a constant-temperature drying box and heated to 180℃, and reacted for 24 h. After the reaction was completed, the high-pressure reaction kettle was naturally cooled to room temperature, the product was collected by a high-speed centrifuge, and washed with ultrapure water and anhydrous ethanol three times each. The product was placed in a constant-temperature drying box at 60℃ and dried for 12 h, and then ground to obtain Bi2WO6 powder.

[0084] Preparation of γ-Fe2O3@SiO2: The magnetic concentrate was first pretreated by ball milling (ball milling for 90 min, rotation speed of 700 r / min, particle size of about 0.724 μm). 0.5 g of the pretreated magnetic concentrate γ-Fe2O3 was uniformly dispersed into a mixture of 375 mL of anhydrous ethanol, 100 mL of ultrapure water and 5.0 mL of ammonia water (28%), and ultrasonic treatment was performed for 15 min, and the mixture was recorded as suspension A. A mixture of 0.9 mL of tetraethyl orthosilicate (TEOS) and 25 mL of anhydrous ethanol was added dropwise into suspension A, and mechanical stirring was performed at room temperature for 12 h. After the stirring was completed, the product was collected by centrifugation, and washed with ultrapure water and anhydrous ethanol three times each. The product was placed in a vacuum oven and dried at 80 °C for 3 h to obtain γ-Fe2O3@SiO2 particles.

[0085] Preparation of γ-Fe2O3@SiO2 / Bi2WO6: 0.2 g of Bi2WO6 was dispersed into 100 mL of methanol and ultrasonic treatment was performed for 15 min, and the mixture was recorded as suspension A. 0.01 g of γ-Fe2O3@SiO2 was added into suspension A and ultrasonic treatment was performed for 15 min, and the mixture was recorded as suspension B. Suspension B was transferred into a constant-temperature water bath and mechanical stirring was performed at 35 °C for 24 h. After the stirring was completed, the product was collected by centrifugation. The product was dried in a vacuum oven at 60 °C for 12 h, and after grinding, 5% γ-Fe2O3@SiO2 / Bi2WO6 was obtained.

[0086] Figure 2 and Figure 3 are the XRD and FTIR patterns of Bi2WO6, γ-Fe2O3@SiO2 and 5% γ-Fe2O3@SiO2 / Bi2WO6, respectively. From the XRD spectrum of 5% γ-Fe2O3@SiO2 / Bi2WO6, it can be seen that there are obvious Bi2WO6 diffraction peaks and some weak γ-Fe2O3@SiO2 diffraction peaks, and the existence of γ-Fe2O3 and SiO2 can also be proved in the FTIR spectrum of 5% γ-Fe2O3@SiO2 / Bi2WO6, which indicates that 5% γ-Fe2O3@SiO2 / Bi2WO6 is successfully compounded.

[0087] Example 2

[0088] The difference from Example 1 is that 0.006 g of γ-Fe2O3@SiO2 was added into suspension A, and recorded as 3% γ-Fe2O3@SiO2 / Bi2WO6.

[0089] Example 3

[0090] The difference from Example 1 is that 0.014 g of γ-Fe2O3@SiO2 was added into suspension A, and recorded as 7% γ-Fe2O3@SiO2 / Bi2WO6.

[0091] Comparative Example 1

[0092] The difference from Example 1 is that 0.01 g of γ-Fe2O3 is directly added to the suspension A without coating, which is denoted as 5% γ-Fe2O3 / Bi2WO6.

[0093] Application Example 1

[0094] The specific implementation process of the experiment of degrading xanthate by γ-Fe2O3@SiO2 / Bi2WO6 is as follows:

[0095] Purified xanthate: a certain amount of xanthate is dissolved in acetone, and the supernatant is obtained after filtration. Anhydrous ether is added to the supernatant until no precipitate is precipitated. Then, the precipitate is separated and dried in a vacuum oven to obtain the purified xanthate solid.

[0096] 15 mg of xanthate is weighed, and a 60 mg / L xanthate solution of 250 mL is prepared. 25 mg of γ-Fe2O3@SiO2 / Bi2WO6 prepared in Examples 1-3, Bi2WO6 prepared in Example 1, γ-Fe2O3@SiO2, and 5% γ-Fe2O3 / Bi2WO6 prepared in Comparative Example 1 are weighed in a quartz test tube. 50 mL of the xanthate solution is added to the test tube, and the catalyst is dispersed uniformly by ultrasonic for 2 min. Then, the test tube is placed in a light reaction instrument. After 30 min of dark reaction, the catalyst reaches adsorption-desorption equilibrium, and then the xenon lamp is turned on for 30 min of light reaction. Every 10 min, a sample is taken into a 10 mL centrifuge tube, centrifuged to obtain the supernatant, and then the absorbance is measured at a wavelength of 301 nm by a UV spectrophotometer.

[0097] The degradation efficiency of the catalyst on xanthate within 60 min is shown in Table 1. Figure 4 The degradation efficiency of Bi2WO6 and 5% γ-Fe2O3@SiO2 / Bi2WO6 on xanthate is 100%, and γ-Fe2O3@SiO2 has little degradation effect on xanthate. When the loading ratio of γ-Fe2O3@SiO2 increases from 3% to 5%, the degradation rate of the catalyst on xanthate increases, and when the loading ratio increases to 7%, the degradation effect of the catalyst on xanthate becomes poor (the degradation efficiency on xanthate within 60 min is about 85%), so the optimal loading ratio of γ-Fe2O3@SiO2 is 5%. It can also be seen from Table 1 that the degradation rate of Bi2WO6 loaded with γ-Fe2O3@SiO2 on xanthate is higher than that of directly loaded γ-Fe2O3, so covering SiO2 on the surface of γ-Fe2O3 is beneficial to the degradation of the catalyst on xanthate. The degradation rate of γ-Fe2O3@SiO2 / Bi2WO6 on xanthate is not as high as that of Bi2WO6, but it does not affect the degradation efficiency, and the catalyst has good magnetism (the saturation magnetization is 2.48 emug-1). Figure 4 The degradation rate of Bi2WO6 loaded with γ-Fe2O3@SiO2 on xanthate is higher than that of directly loaded γ-Fe2O3, so covering SiO2 on the surface of γ-Fe2O3 is beneficial to the degradation of the catalyst on xanthate. The degradation rate of γ-Fe2O3@SiO2 / Bi2WO6 on xanthate is not as high as that of Bi2WO6, but it does not affect the degradation efficiency, and the catalyst has good magnetism (the saturation magnetization is 2.48 emug-1).-1 , coercivity is 371.60 Oe, as shown in Figure 5 , has good recyclability. As can be seen from Figure 6 , the catalytic activity of 5% γ-Fe2O3@SiO2 / Bi2WO6 remains about 100% after five cycles, indicating that the catalyst has excellent chemical stability and can realize efficient regeneration of the catalyst, and has broad industrial application prospects.

[0098] Example 4

[0099] Preparation of 5% γ-Fe2O3@SiO2 / BiOI, the specific steps are as follows:

[0100] Preparation of BiOI: 4 mmol of bismuth nitrate pentahydrate and 4 mmol of potassium iodide were dissolved in 35 mL of ethylene glycol solution, respectively, and stirred at room temperature for 30 min, denoted as solution A and solution B. Slowly add B to A to form a suspension, and stir at room temperature for 30 min to form a precursor solution C. Pour C into a 100 mL polytetrafluoroethylene-lined stainless steel autoclave, and place it in a constant temperature drying box at 140°C for 12h. After the reaction is completed, the high-pressure reactor is naturally cooled to room temperature, and the product is collected by a high-speed centrifuge and washed with ultrapure water and anhydrous ethanol three times each. The obtained solid is placed in a constant temperature drying box at 80°C for 12h, and then ground to obtain BiOI powder.

[0101] The preparation method of γ-Fe2O3@SiO2 is the same as that of Example 1;

[0102] Preparation of 5% γ-Fe2O3@SiO2 / BiOI: 0.2g of BiOI was dispersed in 100mL of methanol and ultrasonicated for 15min, denoted as suspension A. 0.01g of γ-Fe2O3@SiO2 was added to suspension A and ultrasonicated for 15min, denoted as suspension B. Suspension B was transferred to a constant temperature water bath, and mechanically stirred at 35°C for 24h. After stirring, the product was collected by centrifugation. The product was dried in a vacuum oven at 60°C for 12h, and then ground to obtain 5% γ-Fe2O3@SiO2 / BiOI.

[0103] Figure 7 and Figure 8 are the XRD and FTIR patterns of BiOI, γ-Fe2O3@SiO2, and γ-Fe2O3@SiO2 / BiOI. From the XRD pattern of γ-Fe2O3@SiO2 / BiOI, it can be seen that there are strong BiOI diffraction peaks and some weak γ-Fe2O3 and SiO2 diffraction peaks, and in the FTIR spectrum of γ-Fe2O3@SiO2 / BiOI, the existence of γ-Fe2O3 and SiO2 can also be seen, which proves that γ-Fe2O3@SiO2 / BiOI is successfully compounded.

[0104] Example 5

[0105] The difference from Example 4 is only that 0.02 g γ-Fe2O3@SiO2 is added to suspension A, denoted as 10% γ-Fe2O3@SiO2 / BiOI.

[0106] Example 6

[0107] The difference from Example 4 is only that 0.03 g γ-Fe2O3@SiO2 is added to suspension A, 15% γ-Fe2O3@SiO2 / BiOI.

[0108] Example 7

[0109] The difference from Example 4 is only that 0.04 g γ-Fe2O3@SiO2 is added to suspension A, 20% γ-Fe2O3@SiO2 / BiOI.

[0110] Application Example 2

[0111] The specific implementation process of the experiment of degradation of xanthate by γ-Fe2O3@SiO2 / BiOI is as follows:

[0112] 25 mg of xanthate is weighed and 250 mL of a xanthate solution of 100 mg / L is prepared; 25 mg of γ-Fe2O3@SiO2 / BiOI of different proportions prepared in Examples 4-7 and BiOI prepared in Example 1 are weighed in a quartz test tube; 50 mL of the xanthate solution is added to the test tube, and the catalyst is dispersed uniformly by ultrasonic for 2 min, and then the test tube is placed in a light reaction instrument; the catalyst is allowed to reach adsorption-desorption equilibrium by dark reaction for 30 min, and then the xenon lamp is turned on for light reaction for 60 min; samples are taken every 10 min into 10 mL centrifuge tubes, the supernatant is taken by centrifugation, and then the absorbance is measured at a wavelength of 301 nm by a UV spectrophotometer.

[0113] The degradation efficiency of the catalyst on xanthate within 90 min is shown in Table 1. Figure 9 The degradation efficiency of BiOI and 5% γ-Fe2O3@SiO2 / BiOI on xanthate is 100%. When the loading ratio of γ-Fe2O3@SiO2 is increased from 5% to 20%, the degradation rate of the catalyst on xanthate gradually slows down, and when the loading ratio is increased to 20%, the effect of the catalyst on degradation of xanthate becomes poor (the degradation efficiency on xanthate within 90 min is about 83%), so the optimal loading ratio of γ-Fe2O3@SiO2 is 5%. Figure 9 It can also be seen that the degradation rate of γ-Fe2O3@SiO2 / BiOI on xanthate is not as good as that of BiOI, but it does not affect the degradation efficiency, and the catalyst has good magnetism (the saturation magnetization is 3.35 emug -1, coercivity is 409.70 Oe, as shown in Figure 10 Fig. 4, and has good recyclability. Figure 11 It can be seen that 5% γ-Fe2O3@SiO2 / BiOI can still degrade 92.34% of xanthate after five cycles, indicating that the catalyst has good chemical stability and can be reused, and has broad industrial application prospects.

[0114] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. The application of a photocatalyst magnetized by magnetic separation concentrate in degrading residual xanthate in beneficiation wastewater, characterized in that, The preparation method of the photocatalyst comprises the following steps: 1) After the magnetic separation concentrate is ball milled, it is dispersed into a mixed solution of anhydrous ethanol, water and ammonia water to obtain a suspension 1; 2) A mixed solution of tetraethyl orthosilicate and anhydrous ethanol is added into the suspension 1 to perform coating to obtain γ-Fe2O3@SiO2; 3) Bismuth tungstate or bismuth oxyiodide is mixed with a solvent and γ-Fe2O3@SiO2 to obtain a magnetized photocatalyst; When the bismuth tungstate is added, the γ-Fe2O3@SiO2 accounts for 3-7% of the amount of bismuth tungstate; When the bismuth oxyiodide is added, the γ-Fe2O3@SiO2 accounts for 5-20% of the amount of bismuth oxyiodide; The photocatalyst is γ-Fe2O3@SiO2 / Bi2WO6 or γ-Fe2O3@SiO2 / BiOI.

2. Use according to claim 1, characterized in that, The content of γ-Fe2O3 in the magnetic separation concentrate is ≥90%; The speed of the ball milling is 500-1000 r / min, and the time is 60-120 min; The particle size of the magnetic separation concentrate after the ball milling is 0.5-1 μm.

3. Use according to claim 2, characterized in that, The volume ratio of the anhydrous ethanol, water and ammonia water is 50-100:10-30:1; The use amount ratio of the magnetic separation concentrate to the mixed solution of anhydrous ethanol, water and ammonia water is 0.4-0.6 g:400-500 mL.

4. Use according to claim 1, characterized in that, The volume ratio of the tetraethyl orthosilicate to anhydrous ethanol is 1:20-30.

5. Use according to claim 2 or 4, characterized in that, The use amount ratio of the magnetic separation concentrate to the tetraethyl orthosilicate is 0.4-0.6 g:0.5-1 mL; The coating time is 10-15 h.

6. Use according to claim 1, characterized in that, The solvent comprises methanol or ethanol; The use amount ratio of the bismuth tungstate or bismuth oxyiodide to the solvent is 0.1-0.5 g:100 mL.

7. The use according to claim 1, characterized in that, The mixing temperature is 30-40℃, and the time is 12-48 h.

Images