A nanocatalyst for sewage treatment and preparation method thereof

Abstract

The invention provides a nanocatalyst for sewage treatment and a preparation method thereof, comprising the following steps: step one, mixing zinc salt, titanium salt and deionized water, adjusting pH to obtain a metal salt solution; step two, mixing chitosan powder with an organic acid solution to obtain a chitosan solution; step three, mixing sodium hydroxide, organic sodium acid and deionized water to obtain a precipitant solution; step four, mixing the metal salt solution and the chitosan solution to obtain a mixed solution; heating the precipitant solution in a water bath, adding the mixed solution dropwise into the precipitant solution, cooling to room temperature after the reaction is completed to obtain a precursor; calcining the precursor to obtain a nanocatalyst; the invention realizes complementary advantages by compounding TiO2 and ZnO to further improve catalytic performance, and the synthesized TiO2-ZnO nanoparticle composite nanoparticles have the advantages of larger specific surface area and faster surface reaction rate, and increase the reaction active sites of photogenerated holes and solutions.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a nanocatalyst for sewage treatment and a preparation method thereof. Background Art

[0002] Water is one of the most common substances on earth and an important resource for all life. At present, most river basins in the world are under tremendous pressure from human activities. With the continuous development of global industry, a large amount of industrial wastewater and domestic sewage are discharged into natural water bodies, and water pollution is becoming increasingly serious. The treatment of water pollutants has become a research hotspot in the field of environment.

[0003] In order to ensure that recycled water is free of persistent organic pollutants, advanced water treatment technology is needed. In the past few decades, people have developed a variety of methods for purifying water resources, including adsorption, membrane separation, coagulation, etc. Among them, due to the development of the field of nanomaterials, new nano-adsorbent materials have emerged, so the adsorption method is considered to be the most effective of many water treatment methods, with the advantages of simple operation, strong versatility and low cost.

[0004] However, the traditional adsorption method only enriches or converts it into a solid phase. For industrial wastewater with complex pollutant components, it can no longer be completely removed by traditional physical adsorption. Currently, semiconductor photocatalytic materials and photocatalytic degradation of pollutants are considered to be an effective water treatment technology. Therefore, seeking composite photodegradation catalysts with high degradation efficiency, wide response range and strong stability is of great significance to materials science and water pollution control.

[0005] Among the research on various photocatalysts, nano-TiO2 and ZnO have received the most attention due to their excellent photocatalytic performance. However, the unstable crystal form of TiO2, the difficulty in controlling it, the high price, and the high recombination rate of photogenerated carriers restrict the application of TiO2; nano-ZnO has a higher solar light absorption rate than TiO2, and its cost is lower than TiO2, but pure nano-ZnO has the disadvantages of low visible light catalytic efficiency, fast recombination of photogenerated electron-hole pairs, and photocorrosion.

[0006] Therefore, providing an efficient nanocatalyst with stable crystal form, high catalytic efficiency and low cost has become an urgent problem to be solved. Summary of the invention

[0007] In view of the above problems, the present invention provides a nanocatalyst for sewage treatment and a preparation method thereof, which specifically comprises the following steps:

[0008] Step 1: Mix zinc salt, titanium salt, and deionized water, adjust the pH to 3-4 with sulfuric acid, heat and stir until all solids are dissolved, and obtain a metal salt solution;

[0009] Preferably, the mixing ratio of the zinc salt, titanium salt and deionized water is (50-60) g: (2-3) g: 100 ml.

[0010] Preferably, the zinc salt is one of ZnCl2 and its hydrate, Zn(NO3)2 and its hydrate, and ZnSO4 and its hydrate, the titanium salt is TiOSO4, and the concentration of sulfuric acid is 5×10 -4 -5×10 -5 mol / L.

[0011] Step 2, mixing chitosan powder with an organic acid solution, heating and stirring to obtain a chitosan solution;

[0012] Preferably, the mixing mass ratio of chitosan to organic acid solution is 1:60;

[0013] Preferably, the organic acid solution is one of a 10-90% by mass acetic acid solution and a 20-30% by mass citric acid solution;

[0014] Step 3, mixing sodium hydroxide solid powder, organic acid sodium solid powder and deionized water, heating and stirring until all the solids are dissolved, to obtain a precipitant solution;

[0015] Preferably, the mixing ratio of the sodium hydroxide solid powder, the organic acid sodium solid powder and the deionized water is 2g:5g:10ml;

[0016] Preferably, the organic acid sodium is the sodium salt corresponding to the organic acid in step 2, specifically sodium acetate and sodium citrate;

[0017] Step 4, mixing the metal salt solution and the chitosan solution, eliminating bubbles by ultrasound, and obtaining a mixed solution; heating the precipitant solution in a water bath, adding the mixed solution dropwise to the precipitant solution, and cooling to room temperature after the reaction is completed to obtain a precursor;

[0018] Preferably, the mixed volume ratio of the metal salt solution to the chitosan solution is 1:1, and the mixed volume ratio of the mixed solution to the precipitant solution is 1:40;

[0019] Step 5, after filtering the filtrate, washing the precursor with deionized water until the washing solution is neutral, and then vacuum drying;

[0020] Step six, calcining the dried precursor to obtain a nanocatalyst.

[0021] Preferably, in step 1, the temperature is 70-80° C., the rotation speed is 100-120 r / min, and the stirring time is 10-15 min;

[0022] In step 2, the temperature is 35-45°C, the speed is 100-120r / min, and the stirring time is 5-10min;

[0023] In step 3, the temperature is 35-45°C, the speed is 100-120r / min, and the stirring time is 3-5min;

[0024] In step 4, 20-25 kHz ultrasound is applied for 15-25 min, the water bath temperature is 80-90°C, and the reaction is performed for 2-3 h;

[0025] In step 5, drying at 40-50° C. for 30-60 min;

[0026] In step six, calcination is performed at 400-500° C. for 2-3 hours.

[0027] The present invention has the following advantages:

[0028] (1) The TiO2-ZnO composite nanocatalyst prepared by the present invention has a large specific surface area, abundant active sites, excellent catalytic activity and good stability.

[0029] (2) The nanocatalyst prepared by the present invention exhibits a wide pH applicability range (pH = 3-11), strong anti-interference ability, strong selectivity and strong repeatability in the process of degrading pollutants.

[0030] (3) The preparation method of the TiO2-ZnO composite nanocatalyst provided by the present invention comprises the following steps: using a coprecipitation method to uniformly disperse titanium ions and zinc ions into a chitosan solution, and then adding an alkaline precipitant to the titanium ions, zinc ions and OH - The chitosan shell gradually decomposes at high temperature to release the coated precursors, which are then gradually converted into TiO2-ZnO nanoparticles under high temperature calcination.

[0031] (4) The present invention achieves complementary advantages through the composite of TiO2 and ZnO, thereby further improving the catalytic performance and significantly improving the number of cycles of the material. The synthesized TiO2-ZnO nanoparticle composite nanoparticles have the advantages of larger specific surface area and faster surface reaction rate, as well as high conductivity and low photogenerated carrier recombination rate. The reactive active sites of photogenerated holes and solutions are increased, thereby improving the photocatalytic performance of the material.

[0032] (5) The nanocatalyst prepared by the present invention has low requirements for sewage treatment equipment and mild sewage treatment process conditions, can achieve effective sewage treatment, can be adapted to conventional water treatment processes and equipment, has a wide range of applications, and does not require modification of existing sewage treatment equipment.

[0033] (6) The TiO2-ZnO composite nanocatalyst prepared by the present invention is not prone to agglomeration and has strong antioxidant capacity. At the same time, it also retains the environmental friendliness of TiO2 and ZnO. The preparation method is easy to operate, the process is simple, and the conditions are controllable. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the invention, not all of the embodiments. Based on the embodiments of the invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the invention.

[0035] Example 1

[0036] Step 1: Mix ZnCl2, TiOSO4, and deionized water at a ratio of 55 g:2.5 g:100 ml and add 5×10 -4 mol / L sulfuric acid to adjust pH to 3, 75°C, rotation speed 120r / min, stirring time 15min until all solids are dissolved to obtain a metal salt solution;

[0037] Step 2, mixing chitosan powder with 50% acetic acid solution in a mass ratio of 1:60, stirring at 40° C., rotating speed 120 r / min, and stirring time 10 min to obtain a chitosan solution;

[0038] Step 3, mixing sodium hydroxide solid powder, sodium acetate solid powder and deionized water in a ratio of 2g:5g:10ml, stirring at 40°C, rotating speed 120r / min, stirring time 5min, to obtain a precipitant solution;

[0039] Step 4: Mix the metal salt solution and the chitosan solution in a volume ratio of 1:1, and perform ultrasound at 25 kHz for 15 minutes to obtain a mixed solution; heat the precipitant solution in a water bath at 85° C., add the mixed solution dropwise to the precipitant solution, and mix the mixed solution with the precipitant solution in a volume ratio of 1:40. After the reaction is completed, cool to room temperature to obtain a precursor;

[0040] Step 5, after filtering the filtrate, washing the precursor with deionized water until the washing solution is neutral, and then vacuum drying at 45°C for 40 minutes;

[0041] Step six, calcining the dried precursor in a muffle furnace at 450° C. for 2.5 h to obtain a nanocatalyst.

[0042] Example 2

[0043] Different from Example 1, this example uses citric acid solution and sodium citrate solid with a mass fraction of 20%.

[0044] Test Example 1

[0045] Purchase nano-TiO2 particles (Ningbo Jiwei Nano New Material Technology Co., Ltd., particle size 30-50nm) and nano-ZnO particles (Bohuasi Nano Technology (Ningbo), 20nm) on the market.

[0046] 10 g / L NaClO standard solution, 300 mg / L phenol standard solution, 30 mg / L methylene blue standard solution, 4 g / L rhodamine (RhB) standard solution and 4 g / L toluene (MB) standard solution were prepared respectively to simulate pollutants in sewage.

[0047] Take 1L of the above standard solution and mix it with 50mg of the nanocatalyst prepared in Example 1-2 and nano TiO2 particles and nano ZnO particles purchased on the market, degrade it for 2h under the same ultraviolet lamp, and measure the solution concentration. Repeat 3 times for each group and take the average value. The results are shown in Table 1.

[0048] Table 1

[0049]

[0050]

[0051] As can be seen from Table 1, the nanocatalyst prepared by the present invention has good catalytic degradation ability for pollutants in sewage, the concentration of pollutants after treatment is greatly reduced, and the catalytic performance is significantly better than the existing pure TiO2 particles and pure nano ZnO particles.

[0052] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a nanocatalyst for sewage treatment, characterized in that: The following steps are involved: Step 1: Mix zinc salt, titanium salt, and deionized water, adjust the pH to 3-4 with sulfuric acid, heat and stir until all solids are dissolved, and obtain a metal salt solution; Step 2, mixing chitosan powder with an organic acid solution, heating and stirring to obtain a chitosan solution; Step 3, mixing sodium hydroxide solid powder, organic acid sodium solid powder and deionized water, heating and stirring until all the solids are dissolved, to obtain a precipitant solution; Step 4, mixing the metal salt solution and the chitosan solution, and eliminating bubbles by ultrasound to obtain a mixed solution; Heat the precipitant solution in a water bath, add the mixed solution dropwise into the precipitant solution, and cool to room temperature after the reaction is completed to obtain a precursor; Step 5, after filtering the filtrate, washing the precursor with deionized water until the washing solution is neutral, and then vacuum drying; Step six, calcining the dried precursor to obtain a nanocatalyst.

2. The method for preparing a nanocatalyst for sewage treatment according to claim 1, characterized in that: In step 1, the zinc salt is one of ZnCl2, Zn(NO3)2 and ZnSO4, the titanium salt is TiOSO4, and the concentration of sulfuric acid is 5×10 -4 -5×10 -5 mol / L.

3. The method for preparing a nanocatalyst for sewage treatment according to claim 1, characterized in that: The organic acid solution in step 2 is one of an acetic acid solution with a mass fraction of 10-90% and a citric acid solution with a mass fraction of 20-30%.

4. The method for preparing a nanocatalyst for sewage treatment according to claim 1, characterized in that: The organic acid sodium in step three is the sodium salt corresponding to the organic acid in step two.

5. The method for preparing a nanocatalyst for sewage treatment according to claim 1, characterized in that: The mixing ratio of the zinc salt, titanium salt and deionized water in step 1 is (50-60) g: (2-3) g: 100 ml.

6. The method for preparing a nanocatalyst for sewage treatment according to claim 1, characterized in that: The mixing mass ratio of chitosan to organic acid solution in step 2 is 1:

60.

7. The method for preparing a nanocatalyst for sewage treatment according to claim 1, characterized in that: The mixing ratio of the sodium hydroxide solid powder, the organic acid sodium solid powder and the deionized water in step 3 is 2g:5g:10ml.

8. The method for preparing a nanocatalyst for sewage treatment according to claim 1, characterized in that: In step 4, the mixing volume ratio of the metal salt solution and the chitosan solution is 1:1, and the mixing volume ratio of the mixed solution and the precipitant solution is 1:

40.

9. The method for preparing a nanocatalyst for sewage treatment according to claim 1, characterized in that: In step 1, the temperature is 70-80°C, the speed is 100-120r / min, and the stirring time is 10-15min; In step 2, the temperature is 35-45°C, the speed is 100-120r / min, and the stirring time is 5-10min; In step 3, the temperature is 35-45°C, the speed is 100-120r / min, and the stirring time is 3-5min; In step 4, 20-25 kHz ultrasound is applied for 15-25 min, the water bath temperature is 80-90°C, and the reaction is performed for 2-3 h; In step 5, drying at 40-50° C. for 30-60 min; In step six, calcination is performed at 400-500° C. for 2-3 hours.

10. The nanocatalyst prepared by the method according to any one of claims 1 to 9.

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