A waste heating pad-derived oxygen-rich vacancy iron-based catalyst and its preparation method and application

Abstract

The present invention discloses an oxygen-rich vacancy iron-based catalyst derived from a discarded heating pad, which uses the contents of the discarded heating pad as raw materials, obtains an iron-based catalyst uniformly mixed with activated carbon, vermiculite and Fe3O4 after anaerobic calcination, and then introduces abundant oxygen vacancies into the Fe3O4 structure through potassium borohydride reduction treatment to obtain an oxygen-rich vacancy iron-based catalyst. The present invention also discloses the use of the oxygen-rich vacancy iron-based catalyst in the degradation of organic pollutants in water bodies by Fenton-like oxidation technology. The method for preparing the oxygen-rich vacancy iron-based catalyst of the present invention is simple and mild, and the obtained catalyst has high yield, good effect, easy magnetic separation and recovery, reusability, regeneration, and a wide range of applications. The present invention uses discarded heating pads commonly seen in daily life as raw materials, which not only solves the resource utilization of waste, but also obtains a catalyst with application value, realizes the application in the remediation of organic pollutant wastewater, and meets the environmental goal of "treating waste with waste".

Description

Technical Field

[0001] The present invention belongs to the field of solid waste recycling and relates to an oxygen-rich vacancy iron-based catalyst and a preparation method and application thereof, and specifically relates to an oxygen-rich vacancy iron-based catalyst derived from a waste heating pad and a preparation method thereof, as well as application of the oxygen-rich vacancy iron-based catalyst in heterogeneous Fenton-type catalytic degradation of organic pollutants in water. Background Art

[0002] In recent years, the research on degradation of organic pollutants in water by Fenton-like advanced oxidation technology based on persulfate activation has attracted more and more attention. 2+ Activate H2O2 to generate hydroxyl radicals ( · OH), while the Fenton-like oxidation technology is to 2+ Activated peroxydisulfate (PDS, S2O8 2- ) produces sulfate radicals (SO4 ·- Compared with the traditional Fenton oxidation technology, PDS has good chemical stability, is easy to store and transport, and SO4 ·- The Fenton oxidation technology has a stronger oxidation ability, longer existence life, stronger selectivity, and a wider working pH range, so it has better application value. 2+ The activated PDS system for degrading organic pollutants still has many defects, such as Fe 2+ Or the PDS dosage is too high, the pH of the reaction solution needs to be acidic, Fe 2+ Too fast conversion to inactive Fe 3+ , Fe 3+ / Fe 2+ Low circulation efficiency, easy to produce a lot of iron-containing sludge, Fe 2+ Difficult to recycle, etc. In order to solve these problems, iron-based catalysts based on heterogeneous Fenton-like reactions have been widely studied.

[0003] At present, iron-based catalysts derived from iron-containing solid waste have achieved good application results in the degradation of organic pollutants by heterogeneous Fenton-like reactions. However, as a common iron-containing waste in daily life, there are few reports on the preparation of iron-based catalysts for PDS activation using discarded heating pads. Discarded heating pads are rich in iron oxides, activated carbon and vermiculite components, with a wide source and low cost. After recycling, they can be derived into catalysts rich in the active component Fe3O4; in addition, the magnetic separation properties of Fe3O4 are also beneficial to the separation of the catalyst from the aqueous phase. However, during the Fe3O4 activation process for PDS, Fe 3+ Reduction to Fe 2+The low efficiency still limits its subsequent reactivity. To overcome this difficulty, defect engineering, especially the construction of oxygen vacancies (OVs) in metal oxide structures, seems to be a promising strategy. OVs are inherent basic defects in solid catalysts. They do not require the introduction of any foreign elements and can maintain the original crystal structure and catalytic persistence. In addition, OVs can significantly promote the Fenton-like catalytic activity of metal oxides by generating two localized electrons and unsaturated metal sites, leading to electrostatic enrichment on the catalyst surface. At the same time, OVs can extend the OO bond of PDS, reduce its adsorption energy on iron oxides, and facilitate interfacial electron transfer. Summary of the invention

[0004] The purpose of the present invention is to provide a simple method for recycling discarded heating pads, recycling the discarded heating pads to prepare Fe3O4 iron-based catalysts rich in oxygen vacancies. The catalyst is easy to separate magnetically, has good stability, can be recycled, and has great application potential. The oxygen-vacancy-rich iron-based catalyst is used to activate PDS to degrade organic pollutants in water bodies, providing an application technology for reference for the reuse of solid waste and the remediation of organic wastewater.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] An oxygen-rich vacancy iron-based catalyst is prepared from the contents of a discarded heating pad as a raw material, and an iron-based catalyst uniformly combining activated carbon, vermiculite and Fe3O4 is obtained after anaerobic calcination, and then abundant oxygen vacancies are introduced into the Fe3O4 structure through potassium borohydride reduction to obtain an oxygen-rich vacancy iron-based catalyst.

[0007] Specifically, the oxygen-rich vacancy iron-based catalyst is prepared by the following method: using the contents of discarded heating pads as raw materials, crushing, screening, washing, drying, and anaerobically calcining to obtain an iron-based catalyst with a uniform combination of activated carbon, vermiculite and Fe3O4, and then introducing abundant oxygen vacancies in the Fe3O4 structure through potassium borohydride reduction to obtain an oxygen-rich vacancy iron-based catalyst.

[0008] The oxygen-vacancy-rich iron-based catalyst is composed of the following substances: activated carbon, vermiculite and Fe3O4 rich in oxygen vacancies.

[0009] Another object of the present invention is to provide a method for preparing the oxygen-rich vacancy iron-based catalyst, comprising the following steps:

[0010] Step (1), the waste heating pad contents are naturally dried and then ground, and passed through a 200-mesh sieve to obtain a solid powder, the solid powder is washed with deionized water, and dried in an air atmosphere to obtain a catalyst raw material;

[0011] Step (2), placing the catalyst raw material in a tubular furnace, under N2 protection, raising the temperature from room temperature to 400-600°C at a heating rate of 5-10°C / min, and keeping it at 400-600°C for 1-2h, naturally cooling it to room temperature, and collecting the powder material; this step is to remove insoluble organic impurities that may exist in the raw material and obtain a Fe3O4 composite material with uniformly loaded and dispersed activated carbon and vermiculite;

[0012] Step (3), adding the powder material obtained in step (2) to a potassium borohydride solution, performing a reduction treatment under ultrasonic conditions for 1 to 2 hours, and preventing the material from sinking to the bottom by ultrasonic dispersion; then, magnetically separating the material in the suspension, washing the material obtained by magnetic separation with deionized water until the supernatant is neutral, and then washing the material with anhydrous ethanol to remove excess water, and naturally drying at room temperature to obtain an oxygen-rich vacancy iron-based catalyst.

[0013] In step (1), the solid powder is washed three times with deionized water to remove soluble salt impurities; each time the solid powder is washed with 100 mL of deionized water per gram of the solid powder.

[0014] The solid powder washed with deionized water is dried in an air atmosphere at 60-90° C. for 6-12 hours.

[0015] In step (2), preferably, the temperature is increased from room temperature to 500°C at a heating rate of 5°C / min, and maintained at 500°C for 2h.

[0016] In step (3), the concentration of the potassium borohydride solution is 0.5 to 2.0 mol / L, preferably 1.0 mol / L.

[0017] The temperature of the reduction treatment is room temperature to 40°C.

[0018] The powder material and the potassium borohydride solution were mixed at a mass volume ratio of 0.2:40 g / mL.

[0019] Another object of the present invention is to provide the use of the oxygen-vacancy-rich iron-based catalyst in the degradation of organic pollutants in water using a Fenton-like oxidation technology.

[0020] Another object of the present invention is to provide a method for degrading organic pollutants in water using a Fenton-like oxidation technology, comprising: adding sodium persulfate to organic pollutant wastewater in an amount of 0.2 to 1.0 mmol / L; adjusting the pH of the wastewater to 3 to 10; adding the oxygen-rich vacancy iron-based catalyst according to claim 1 to the organic pollutant wastewater in an amount of 0.05 to 0.2 g / L; and fully mixing the reaction at room temperature (25°C) to degrade the organic pollutants.

[0021] The wastewater containing organic pollutants contains at least one of the following organic pollutants: carbaryl, chloramphenicol, phenacetin, and paracetamol; the concentration of organic pollutants is 0.5-2.0 mg / L.

[0022] Sodium hydroxide and / or sulfuric acid are used to adjust the pH of organic micropollutant wastewater.

[0023] Preferably, the dosage of sodium persulfate is 0.5 mmol / L.

[0024] Preferably, the oxygen-vacancy-rich iron-based catalyst is used in an amount of 0.1 g / L.

[0025] As a preferred technical solution of the method for degrading organic pollutants in water using the Fenton-like oxidation technology described in the present invention, it also includes: after the reaction is completed, using a magnet to separate the oxygen-rich vacancy iron-based catalyst.

[0026] As a preferred technical scheme of the method for degrading organic pollutants in water by using the Fenton-like oxidation technology described in the present invention, the method also includes: when the oxygen-rich vacancy iron-based catalyst degrades an equal amount of organic pollutants, the time for degrading the organic pollutants is extended by 4 times compared with the first use, indicating that the performance of the oxygen-rich vacancy iron-based catalyst has obviously declined. At this time, the oxygen-rich vacancy iron-based catalyst is regenerated: the oxygen-rich vacancy iron-based catalyst with declined performance is treated by potassium borohydride solution reduction method and ultrasonically dispersed for 1 to 2 hours; the material in the suspension is magnetically separated, the material obtained by magnetic separation is washed with deionized water until the supernatant is neutral, and then the material is washed with anhydrous ethanol to remove excess water, and naturally dried at room temperature to obtain the oxygen-rich vacancy iron-based catalyst.

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

[0028] 1. Abandoned heating pads are common iron-containing solid waste in daily life, with low cost, high output and wide sources. Abandoned heating pads are used as raw materials, and oxygen vacancies are introduced through potassium borohydride reduction to prepare oxygen-rich vacancy iron-based catalysts. This can not only solve the resource utilization of waste, but also obtain catalysts with application value, realize the remediation of wastewater containing organic pollutants, kill two birds with one stone, and achieve the environmental goal of "treating waste with waste".

[0029] 2. The preparation method of the oxygen-vacancy-rich iron-based catalyst of the present invention is simple and mild. Activated carbon and vermiculite are inherent components of discarded heating pads. When preparing the catalyst, they can effectively disperse Fe3O4 and prevent its agglomeration. The obtained catalyst has high yield and good effect. By successfully constructing rich oxygen vacancies in the active structure of the iron-based catalyst Fe3O4, the performance of activated PDS in degrading organic pollutants is significantly improved.

[0030] 3. The oxygen-rich vacancy iron-based catalyst activated PDS of the present invention can achieve the degradation of organic pollutants in wastewater in a wide pH range, and is effective against a variety of organic pollutants, has a certain broad spectrum, and the catalyst is easy to magnetically separate and recover, can be reused, and can be regenerated, and has a wide range of adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the X-ray diffraction (XRD) spectrum of the oxygen vacancy-rich iron-based catalyst.

[0032] Figure 2 This is the X-ray diffraction photoelectron spectroscopy (XPS) of the oxygen vacancy-rich iron-based catalyst.

[0033] Figure 3 Scanning electron microscope (SEM) image and element distribution map of oxygen vacancy-rich iron-based catalyst.

[0034] Figure 4 This is a diagram showing the effect of oxygen-vacancies-rich iron-based catalyst activating PDS to degrade carbaryl (pH = 3.6).

[0035] Figure 5 This is a diagram showing the degradation effect of PDS activated by oxygen-rich vacancy iron-based catalyst on carbaryl at different pH values.

[0036] Figure 6 It is the magnetic separation and recovery of oxygen vacancy-rich iron-based catalyst after reaction.

[0037] Figure 7 This is a diagram showing the cyclic regeneration effect of oxygen-vacancy-rich iron-based catalyst.

[0038] Figure 8 This is a diagram showing the effect of oxygen-vacancies-rich iron-based catalyst activating PDS to degrade phenacetin, chloramphenicol or paracetamol. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is described below by means of specific embodiments, but is not intended to limit the protection scope of the present invention.

[0040] Example 1

[0041] The oxygen-vacancy-rich iron-based catalyst is prepared by the following preparation method, and the specific process is as follows:

[0042] Step (1), collecting the contents of the discarded heating pad, which are mainly composed of iron oxide, vermiculite and activated carbon, with the mass percentages of 58.0%, 21.3% and 20.7%, respectively, and drying them naturally at room temperature, weighing 20g of the contents of the discarded heating pad in a mortar, grinding and crushing, passing through a 200-mesh sieve, collecting solid powder with a particle size less than 200 mesh, washing the solid powder three times with deionized water, and placing it in a blast drying oven at 60°C for 12 hours to obtain a catalyst raw material;

[0043] Step (2), weigh 4 g of the catalyst raw material obtained in step (1) into a porcelain boat, place it in a tube furnace, and under N2 protection, increase the temperature from room temperature to 500°C at a heating rate of 5°C / min, and keep it at 500°C for 2h, cool it naturally to room temperature, and collect the resulting powder material;

[0044] Step (3), preparing 40mL 1 mol / L potassium borohydride solution, adding 0.2g of the powder material obtained in step (2) to the potassium borohydride solution, and ultrasonically dispersing at room temperature for 1h; magnetically separating the material in the suspension, washing the material obtained by magnetic separation with deionized water until the supernatant is neutral, then washing the material with anhydrous ethanol to remove excess water in the material, and naturally drying at room temperature to obtain an oxygen-rich vacancy iron-based catalyst.

[0045] The oxygen vacancy-rich iron-based catalyst of this example was characterized accordingly. Figure 1 , Figure 2 The X-ray diffraction spectra (XRD) and X-ray diffraction photoelectron spectroscopy (XPS) of the oxygen vacancy-rich iron-based catalyst are shown, respectively, and the powder material (i.e. Figure 1 , Figure 2 Compared with before reduction in the medium, the structural composition of the oxygen-rich vacancy iron-based catalyst obtained by potassium borohydride reduction method has not changed. The oxygen-rich vacancy iron-based catalyst is mainly composed of Fe3O4 and SiO2, among which SiO2 comes from activated carbon and vermiculite. At the same time, after reduction with potassium borohydride, the adsorbed oxygen content in the XPS graph of the O element of the oxygen-rich vacancy iron-based catalyst increased significantly while the lattice oxygen content decreased significantly, indicating that abundant oxygen vacancies were successfully constructed in the Fe3O4 structure. Figure 3 The scanning electron microscope (SEM) image and element distribution map of the oxygen-rich vacancy iron-based catalyst are shown. The surface of the oxygen-rich vacancy iron-based catalyst is loose and porous, and the elements are evenly distributed. It can be seen that the catalyst is uniformly assembled from activated carbon, vermiculite and oxygen-rich Fe3O4.

[0046] Comparative Example 1

[0047] The powder material (i.e., oxygen-free iron-based catalyst) obtained in step (2) of Example 1 was used to replace the oxygen-rich iron-based catalyst, and the pollutants in the organic micro-pollutant wastewater were degraded by Fenton-like catalysis. The specific method is as follows: 50 mL of organic wastewater containing carbaryl (1.0 mg / L) was prepared, and sodium persulfate (PDS) was added to make its concentration 0.5 mmol / L; the pH of the wastewater was adjusted to 3.6 with 0.1 mol / L NaOH and 0.1 mol / L H2SO4; 5 mg of oxygen-free iron-based catalyst was quickly added to the wastewater with the above pH to start the reaction, and the reaction was started in a water bath shaker, and the reaction was continuously shaken at a temperature of 25°C and a speed of 180 rpm. Within a set time interval, 1 mL of the reaction solution was taken out with a 5 mL syringe, and the reaction was quickly mixed with 1 mL of methanol to quench the reaction, and filtered through a 0.22 μm organic (nylon) filter membrane. The residual carbaryl concentration was analyzed on a high performance liquid chromatograph (HPLC). The degradation effect of carbaryl is as follows: Figure 4 shown.

[0048] Example 2

[0049] The oxygen-rich vacancy iron-based catalyst of Example 1 was used to degrade pollutants in organic pollutant wastewater by Fenton-like catalysis. The specific method is as follows: 50 mL of organic wastewater containing carbaryl (1.0 mg / L) was prepared, and sodium persulfate (PDS) was added to make its concentration 0.5 mmol / L; the pH of the wastewater was adjusted to 3, 3.6, 5, 7, 9, and 10 with 0.1 mol / L NaOH and 0.1 mol / L H2SO4; 5 mg of oxygen-rich vacancy iron-based catalyst was quickly added to the wastewater with different pH values ​​to start the reaction, and the mixture was placed in a water bath shaker and continuously shaken at a temperature of 25° C. and a speed of 180 rpm. Within the set time interval, 1 mL of the reaction solution was taken out with a 5 mL syringe, and the reaction was quickly mixed with 1 mL of methanol to quench the reaction, and filtered through a 0.22 μm organic (nylon) filter membrane, and the residual carbaryl concentration was analyzed on a high performance liquid chromatograph (HPLC).

[0050] The degradation effect of carbaryl (pH 3.6) is as follows Figure 4 As shown in Figure 1, the catalytic performance of the oxygen-rich iron-based catalyst for PDS is significantly better than that of the oxygen-free iron-based catalyst (Comparative Example 1), and effective degradation of carbaryl can be achieved within 30 minutes; at the same time, the system can achieve efficient degradation of carbaryl in a wide pH range of pH 3 to 10 (such as Figure 5 ).

[0051] Example 3

[0052] After the reaction in Example 2 is completed, the oxygen-rich vacancy iron-based catalyst is separated and collected by magnetic attraction.

[0053] Second use: Take 50 mL of organic wastewater containing carbaryl (1.0 mg / L), add sodium persulfate (PDS) to make its concentration 0.5 mmol / L; adjust the pH of the wastewater to 3.6 with 0.1 mol / L NaOH and 0.1 mol / L H2SO4; add the oxygen-rich vacancy iron-based catalyst recovered in Example 2 (pH 3.6) to the above organic wastewater, place it in a water bath shaker, and oscillate continuously at a temperature of 25°C and a speed of 180 rpm, start the cycle reaction, and sample and analyze the residual carbaryl concentration according to Example 2 until the carbaryl is completely degraded.

[0054] The oxygen-rich vacancy iron-based catalyst was separated and collected by magnetic attraction, and the "third use" was performed according to the "second use". The performance of the oxygen-rich vacancy iron-based catalyst was significantly reduced, and it took 120 minutes to achieve complete degradation of carbaryl. After the oxygen-rich vacancy iron-based catalyst was recovered after the third use, it was regenerated according to step (3) in Example 1, and the regenerated oxygen-rich vacancy iron-based catalyst was used again to degrade carbaryl according to the "second use" (i.e., the fourth use).

[0055] The magnetic separation and recycling effects of oxygen vacancy-rich iron-based catalysts are shown in Figure 6 , Figure 7 The catalyst can be quickly separated from the water body by magnetic attraction, and the repeated circulation and regeneration process of the catalyst are controllable.

[0056] Example 3

[0057] Referring to Example 2, carbaryl was replaced by phenacetin, chloramphenicol and paracetamol, respectively, and the pollutants were degraded by Fenton-like catalysis at pH 3.6.

[0058] The degradation effects of different pollutants are shown in Figure 8 , indicating that PDS activated by oxygen-vacancies-rich iron-based catalysts can achieve effective degradation of the above three organic pollutants.

[0059] The above embodiments are only some preferred examples of the present invention, but the specific implementation of the present invention is not limited to the contents of the above embodiments. For those skilled in the art of the present invention, any changes, modifications, simplifications or modifications made within the scope of implementation of the concept and principle of the present invention are within the protection scope of the present invention.

Claims

1. A method for degrading organic pollutants in water using a Fenton-like oxidation technique, characterized in that: include: Adding sodium persulfate to the organic pollutant wastewater in an amount of 0.2-1.0 mmol / L; adjusting the pH of the wastewater to 3-10; adding an oxygen-rich vacancy iron-based catalyst to the organic pollutant wastewater in an amount of 0.05-0.2 g / L, and degrading the organic pollutants at room temperature; Organic pollutants: Wastewater contains at least one of the following organic pollutants: carbaryl, chloramphenicol, phenacetin, paracetamol; the concentration of organic pollutants is 0.5-2.0 mg / L; The oxygen-rich vacancy iron-based catalyst is made from the contents of discarded heating pads as raw materials. After anaerobic calcination, an iron-based catalyst uniformly mixed with activated carbon, vermiculite and Fe3O4 is obtained. Then, potassium borohydride reduction treatment is performed to introduce abundant oxygen vacancies into the Fe3O4 structure to obtain an oxygen-rich vacancy iron-based catalyst.

2. The method for degrading organic pollutants in water using Fenton-like oxidation technology according to claim 1, characterized in that: Sodium hydroxide and / or sulfuric acid are used to adjust the pH of wastewater containing organic pollutants.

3. The method for degrading organic pollutants in water using Fenton-like oxidation technology according to claim 1, characterized in that: Also includes: After the degradation reaction is completed, the oxygen-vacancy-rich iron-based catalyst is separated using a magnet.

4. The method for degrading organic pollutants in water using Fenton-like oxidation technology according to claim 1, characterized in that: The oxygen-rich vacancy iron-based catalyst is prepared by the following method, comprising the following steps: Step (1), the waste heating pad contents are naturally dried and then ground, and passed through a 200-mesh sieve to obtain a solid powder, the solid powder is washed with deionized water, and dried in an air atmosphere to obtain a catalyst raw material; Step (2), placing the catalyst raw material in a tubular furnace, under N2 protection, heating from room temperature to 400-600°C at a heating rate of 5-10°C / min, and keeping the temperature for 1-2 h, cooling naturally to room temperature, and collecting the powder material; Step (3), adding the powder material obtained in step (2) to a potassium borohydride solution, and performing a reduction treatment under ultrasonic conditions for 1 to 2 hours; performing magnetic separation on the material in the suspension, washing the material obtained by magnetic separation with deionized water until the supernatant is neutral, and then washing the material with anhydrous ethanol to remove moisture, and drying naturally at room temperature to obtain an oxygen-rich vacancy iron-based catalyst.

5. The method for degrading organic pollutants in water using Fenton-like oxidation technology according to claim 4, characterized in that: In step (3), the concentration of the potassium borohydride solution is 0.5 to 2 mol / L.

6. The method for degrading organic pollutants in water using Fenton-like oxidation technology according to claim 4, characterized in that: In step (3), the powder material and the potassium borohydride solution are mixed according to a mass volume ratio of the powder material to the potassium borohydride solution of 0.2:40 g / mL.

7. The method for degrading organic pollutants in water using Fenton-like oxidation technology according to claim 1, characterized in that: According to step (3) of claim 4, the used oxygen vacancy-rich iron-based catalyst is regenerated.

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