Catalyst for activating peroxysulfate to degrade dimethyl sulfoxide wastewater and preparation method thereof

Abstract

The invention discloses a catalyst for activating peroxysulfate to degrade dimethyl sulfoxide wastewater and a preparation method of the catalyst. The method comprises the following steps: placing scrap iron and g-C3N4 powder in a sulfur-containing compound solution, carrying out hydrothermal reaction, drying, and finally carrying out high-temperature carbonization to obtain the iron-sulfur doped g-C3N4 catalyst. When the iron-sulfur-doped g-C3N4 catalyst activates persulfate to degrade dimethyl sulfoxide wastewater, the pH of the wastewater does not need to be adjusted, and the removal rate of dimethyl sulfoxide is high and can reach 99.5% at most.

Description

Technical Field

[0001] The invention belongs to the field of persulfate-advanced oxidation system catalysts and relates to a catalyst for activating peroxysulfate to degrade dimethyl sulfoxide wastewater and a preparation method thereof. Background Art

[0002] Dimethyl sulfoxide (DMSO) has high polarity and boiling point. It is miscible with water and can dissolve most inorganic substances and organic substances such as polymers. It is known as the "universal solvent" and is widely used in the production of carbon fiber materials. Industrial wastewater containing DMSO is generally stable in chemical properties and has poor biodegradability. It is easy to decompose and produce odorous sulfur-containing gases, dimethyl sulfide, formaldehyde, etc., causing secondary pollution. It is one of the difficulties in the field of water treatment. The Fenton method is often used in industry to treat DMSO wastewater, but the traditional Fenton method for treating DMSO wastewater has many disadvantages, such as strong pH dependence, difficulty in regenerating iron ions, easy generation of iron sludge during operation, and high subsequent treatment costs.

[0003] The advanced oxidation process based on peroxymonosulfate (PMS) is currently considered to be a promising method for degrading organic pollutants in water. The persulfate advanced oxidation process refers to the activation of PMS to convert peroxymonosulfate (HSO5 - ) is activated and converted into sulfate radicals, hydroxyl radicals and superoxide radicals, thereby removing organic pollutants through advanced oxidation technology. In persulfate advanced oxidation technology, the main free radical that plays a role in degradation is SO4 - ·, its oxidation potential is 2.5-3.1V, and its half-life is 10 -4 s, which indicates that SO4 - Compared with HO·, PMS has a longer residence time; and PMS has a wider adaptability to the acidity and alkalinity of reaction conditions (3≤pH≤11). Theory shows that the persulfate oxidation method is more conducive to being promoted and applied in actual engineering due to its stronger oxidizing property and wider pH adaptability range.

[0004] Active iron shows excellent activity in activating PMS. Iron-based catalysts can maintain high catalytic activity and stability in a wide pH range. More and more researchers have developed a series of iron-based catalysts for persulfate activation and degradation of organic pollutants in water, with significant results. Scrap iron is an industrial waste from mechanical processing plants. It is easy to obtain, reusable, and low-cost. If these shavings are not properly handled, they will not only pollute the environment, but also waste a potential resource. Scrap iron is an excellent reducing agent material. It has been proven to have long-term stability in actual water pollution engineering applications and is the preferred material for industrial sewage treatment. Summary of the invention

[0005] The object of the present invention is to provide a catalyst for activating peroxysulfate to degrade dimethyl sulfoxide wastewater and a preparation method thereof. The method hydrothermally reacts g-C3N4, scrap iron and a sulfur-containing compound to obtain an iron-sulfur doped g-C3N4 catalyst, which is used to activate peroxysulfate to degrade dimethyl sulfoxide wastewater, exhibits a high dimethyl sulfoxide removal rate, has a short reaction time and can be recycled.

[0006] The technical solution for achieving the purpose of the present invention is as follows:

[0007] The preparation method of a catalyst for activating peroxysulfate to degrade dimethyl sulfoxide wastewater comprises the following steps:

[0008] (1) calcining melamine at 500-600°C for 4±0.5h, cooling to room temperature after calcination, and grinding the product to obtain g-C3N4 powder;

[0009] (2) soaking the shavings in a 30% by mass NaHCO3 solution for 10 to 30 minutes to remove oil and impurities on the surface, and vacuum freeze-drying to obtain clean scrap iron;

[0010] (3) adding g-C3N4 powder and clean scrap iron into the sulfur-containing compound solution, and performing a hydrothermal reaction at 200±10°C for 12 to 24 hours. After the reaction is completed, the mixture is cooled to room temperature, and the product is repeatedly rinsed with ethanol and water, and dried.

[0011] (4) The product after drying in step (3) is naturally cooled to room temperature, and then heated to 400±10° C. in an argon atmosphere and carbonized for 2 to 3 hours to obtain an iron-sulfur doped g-C3N4 catalyst.

[0012] Preferably, in step (1), the heating rate is 3 to 6°C / min.

[0013] Preferably, in step (2), the thickness of the shavings-like scrap iron filings is 30 to 50 μm.

[0014] Preferably, in step (3), the sulfur-containing compound is thiourea, thioacetamide or L-cysteine. In a specific embodiment of the present invention, thiourea is taken as an example.

[0015] Preferably, in step (3), the mass ratio of g-C3N4 powder to scrap iron is 1:5 to 15.

[0016] Preferably, in step (3), the drying temperature is 80° C. and the drying time is 2 h.

[0017] Preferably, in step (4), the heating rate is 8°C / min.

[0018] The present invention also provides an iron-sulfur doped g-C3N4 catalyst prepared by the above preparation method.

[0019] Furthermore, the present invention provides the use of the above-mentioned iron-sulfur doped g-C3N4 catalyst in activating persulfate to degrade dimethyl sulfoxide wastewater.

[0020] Preferably, the specific application method is: firstly add iron-sulfur-doped g-C3N4 catalyst into dimethyl sulfoxide wastewater, and then add peroxymonosulfate solution once or in batches to initiate the catalytic degradation reaction.

[0021] Preferably, the peroxymonosulfate is selected from one or a combination of sodium persulfate, potassium persulfate and ammonium persulfate, and the concentration of the peroxymonosulfate solution is 2 to 5 mmol / L.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The present invention adopts g-C3N4 as a matrix. The g-C3N4 has the characteristics of a two-dimensional layered structure. An iron-sulfur catalyst is loaded on its surface to increase more active sites. When the prepared iron-sulfur-doped g-C3N4 catalyst activates persulfate to degrade dimethyl sulfoxide wastewater, there is no need to adjust the pH of the wastewater, and the dimethyl sulfoxide removal rate is high, which can reach up to 99.5%. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with specific embodiments.

[0025] In the following examples, the thickness of the shavings used is 30 to 50 μm.

[0026] Example 1

[0027] (1) A corundum boat containing 10 g of melamine was placed in a tubular electric furnace and heated to 550°C at a heating rate of 5°C / min, and the temperature was maintained for continuous calcination for 4 h. After the reactant was cooled to room temperature, the obtained light yellow solid was placed in an agate mortar and ground into powder to obtain g-C3N4 powder.

[0028] (2) Soak the shavings in a 30% by mass NaHCO3 solution for 20 minutes to remove oil and impurities on the surface, and then dry them in a vacuum freeze dryer to obtain clean scrap iron.

[0029] (3) Dissolve 0.5 g of thiourea in 50 ml of pure water, add 12.5 mg of g-C3N4 powder and 75 mg of shavings of scrap iron into the thiourea solution, put the mixed solution into a reactor, and perform hydrothermal reaction at 200°C for 24 hours. After the reaction is completed, cool to room temperature, take out the sample, rinse it repeatedly with ethanol and deionized water, and dry it in an oven at 80°C for 2 hours.

[0030] (4) The sample was naturally cooled to room temperature, and then heated to 400 °C at a heating rate of 8 °C / min in an argon atmosphere for carbonization for 2 h to obtain an iron-sulfur doped g-C3N4 catalyst.

[0031] (5) Take 300 ml of DMSO wastewater, the concentration of DMSO is 10 mg / L, put it in a 500 ml beaker on a magnetic stirrer, put 1 g of iron-sulfur-doped g-C3N4 catalyst, add 2 mmol / L of sodium persulfate solution into the beaker under stirring conditions to initiate the catalytic degradation reaction, continue stirring after the sodium persulfate solution is added, and wait for the reaction to proceed for 30 minutes. After the reaction is completed, let it stand and settle, take the supernatant to detect the DMSO content in the supernatant, and the removal rate of dimethyl sulfoxide is measured to be 89%.

[0032] Example 2

[0033] This embodiment is basically the same as embodiment 1, except that in step (5), the concentration of the sodium persulfate solution is 3 mmol / L, and the removal rate of dimethyl sulfoxide is measured to be 95%.

[0034] Example 3

[0035] This embodiment is basically the same as embodiment 1, except that the reaction in step (5) is carried out for 50 minutes, and the removal rate of dimethyl sulfoxide is measured to be 99%.

[0036] Example 4

[0037] This embodiment is basically the same as embodiment 1, except that in step (5), the concentration of the sodium persulfate solution is 3 mmol / L, the reaction time is 50 min, and the removal rate of dimethyl sulfoxide is measured to be 99.5%.

[0038] Comparative Example 1

[0039] Take 300ml DMSO wastewater with a DMSO concentration of 10mg / L, place it in a 500ml beaker on a magnetic stirrer, add 2mmol / L sodium persulfate solution into the beaker under stirring to initiate a catalytic degradation reaction, continue stirring after the sodium persulfate solution is added and wait for the reaction to proceed for 30min, let it stand and settle after the reaction is completed, take the supernatant and detect the DMSO content in the supernatant, and the removal rate of dimethyl sulfoxide is measured to be 56.5%.

[0040] Comparative Example 2

[0041] Take 300ml DMSO wastewater with a DMSO concentration of 10mg / L, place it in a 500ml beaker on a magnetic stirrer, add 1g of shavings-like scrap iron, add 2mmol / L sodium persulfate solution into the beaker to initiate a catalytic degradation reaction, and continue stirring after the sodium persulfate solution is added to wait for the reaction to proceed for 30min. After the reaction is completed, let it stand and settle, take the supernatant to detect the DMSO content in the supernatant, and the removal rate of dimethyl sulfoxide is measured to be 73.5%.

[0042] Comparative Example 3

[0043] (1) Soak the shavings in a 30% by mass NaHCO3 solution for 20 min to remove oil and impurities on the surface, and then dry them in a vacuum freeze dryer to obtain clean scrap iron.

[0044] (2) Dissolve 0.5 g of thiourea in 50 ml of pure water, immerse 1 g of clean scrap iron in the thiourea solution, add the mixed solution into a reactor, and perform a hydrothermal reaction at 200 °C for 24 hours. After the reaction is completed, cool to room temperature, take out the sample, rinse it repeatedly with ethanol and deionized water, and place it in an oven at 80 °C to dry for 2 hours.

[0045] (3) The sample was naturally cooled to room temperature, and then heated to 400° C. at a heating rate of 8° C. / min in an argon atmosphere for carbonization for 2 hours to obtain a sulfur-supported iron shavings composite catalyst.

[0046] (4) Take 300 ml of DMSO wastewater, the concentration of DMSO is 10 mg / L, put it in a 500 ml beaker on a magnetic stirrer, put 1 g of sulfur-loaded iron shavings composite catalyst, add 3 mmol / L of sodium persulfate solution into the beaker under stirring conditions to initiate the catalytic degradation reaction, continue stirring after the sodium persulfate solution is added, wait for the reaction to proceed for 50 min, and after the reaction is completed, let it stand and settle, take the supernatant to detect the DMSO content in the supernatant, and the removal rate of dimethyl sulfoxide is measured to be 91%.

Claims

1. A method for preparing a catalyst for activating persulfate to degrade dimethyl sulfoxide wastewater, characterized in that: The following steps are involved: (1) calcining melamine at 500-600°C for 4±0.5h, cooling to room temperature after calcination, and grinding the product to obtain g-C3N4 powder; (2) Soak the shavings in a 30% by mass NaHCO3 solution for 10 to 30 minutes to remove the oil and impurities on the surface, and then freeze-dry them in vacuum to obtain clean scrap iron; (3) Add g-C3N4 powder and clean scrap iron into the sulfur-containing compound solution, and perform hydrothermal reaction at 200±10℃ for 12~24 hours. After the reaction is completed, cool to room temperature, and rinse the product repeatedly with ethanol and water, and dry it; (4) The product after drying in step (3) is naturally cooled to room temperature, and then heated to 400±10°C in an argon atmosphere for carbonization for 2-3 hours to obtain an iron-sulfur doped g-C3N4 catalyst.

2. The preparation method according to claim 1, characterized in that: In step (1), the heating rate is 3-6°C / min.

3. The preparation method according to claim 1, characterized in that: In step (2), the thickness of the shavings-like scrap iron filings is 30-50 μm.

4. The preparation method according to claim 1, characterized in that: In step (3), the sulfur-containing compound is thiourea, thioacetamide or L-cysteine.

5. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of g-C3N4 powder to scrap iron is 1:5-15; the drying temperature is 80°C and the drying time is 2h.

6. The preparation method according to claim 1, characterized in that In step (4), the heating rate is 8°C / min.

7. An iron-sulfur-doped g-C3N4 catalyst prepared according to the preparation method described in any one of claims 1 to 6.

8. Use of the iron-sulfur doped g-C3N4 catalyst according to claim 7 in activating persulfate to degrade dimethyl sulfoxide wastewater.

9. The use according to claim 8, characterized in that: The specific application method is: firstly add iron-sulfur doped g-C3N4 catalyst into dimethyl sulfoxide wastewater, and then add peroxymonosulfate solution once or in batches to initiate the catalytic degradation reaction.

10. The use according to claim 9, characterized in that The peroxymonosulfate is selected from one or a combination of sodium persulfate, potassium persulfate and ammonium persulfate, and the concentration of the peroxymonosulfate solution is 2-5 mmol / L.