An activated carbon loaded zinc manganate photocatalytic renewable adsorbent, and a preparation method and application thereof

Abstract

The application discloses a preparation method of an activated carbon loaded zinc manganate (AC / ZnMn2O4) photocatalytic renewable adsorbent and application thereof. The AC / ZnMn2O4 photocatalytic renewable adsorbent is composed of activated carbon AC and zinc manganate ZnMn2O4, wherein the mass ratio of the AC and the ZnMn2O4 is 0.1-3:10. The AC / ZnMn2O4 photocatalytic renewable adsorbent is prepared through three steps, first, a strip-shaped ZnMn2O4 is prepared by using a coprecipitation-calcination method, then the AC is activated by using an acid or alkali solution for impregnation, finally, the AC treated by the acid or alkali is compounded with the ZnMn2O4 through a mechanical grinding method to obtain the AC / ZnMn2O4 photocatalytic renewable adsorbent. The photocatalytic renewable adsorbent has a large specific surface area and porous structure, good adsorption photocatalytic regeneration capacity and recycling property, and excellent adsorption performance for tannic acid.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of photocatalysis, and particularly relates to an activated carbon loaded zinc manganate (AC / ZnMn2O4) photocatalytic renewable adsorbent as well as a preparation method and application thereof. BACKGROUND

[0002] In the zinc hydrometallurgy process, germanium is a rare associated metal with high recovery value and is enriched in zinc oxide fume. At present, the main method for recovering germanium in the zinc smelting process is to add excess tannic acid to the acid leaching solution of zinc oxide fume to precipitate germanium. However, a large amount of excess tannic acid returns to the leaching solution after liquid-solid separation, which increases the viscosity of the electrolyte and reduces the electric efficiency. In severe cases, it may cause the cathode zinc to be dissolved in reverse and even cause the plate to be burned. The main method for removing tannic acid in the zinc leaching solution in industry is the activated carbon adsorption method. This method can only adsorb a certain amount of tannic acid and cannot achieve the effect of degrading tannic acid and recycling. Even after use, it is easy to form secondary pollution. As an ideal green technology for solving energy and environmental problems, the photocatalytic method has broad application prospects in the efficient degradation of organic matter.

[0003] ZnMn2O4 is a new type of spinel photocatalyst, which has the advantages of visible light response, good photochemical stability and excellent catalytic activity. At the same time, ZnMn2O4 has low solubility in an acidic environment, and the dissolved zinc and manganese ions will not cause secondary pollution to the zinc leaching solution. However, the adsorption performance and recycling of ZnMn2O4 still need to be improved. SUMMARY

[0004] In order to solve the technical problems and deficiencies in the prior art, the purpose of the present application is to provide an activated carbon loaded zinc manganate (AC / ZnMn2O4) photocatalytic renewable adsorbent, a preparation method thereof and application thereof.

[0005] In order to achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0006] In the first aspect, the present application provides a preparation method of an activated carbon loaded zinc manganate (AC / ZnMn2O4) photocatalytic renewable adsorbent, comprising the following steps:

[0007] (1) preparing ZnMn2O4:

[0008] Zinc acetate (CH3COO)2Zn·2H2O and manganese acetate (CH3COO)2Mn·4H2O are added to an ethanol-water solution, and after stirring until completely dissolved, a solution A is obtained;

[0009] Oxalic acid H2C2O4·2H2O is added to an ethanol-water solution, and after stirring until completely dissolved, a solution B is obtained;

[0010] The solution A is quickly poured into the solution B under heating and stirring to obtain a mixture, and the mixture is filtered, washed and dried after cooling to room temperature to obtain a precursor;

[0011] The precursor is calcined to obtain ZnMn2O4 with a long strip shape;

[0012] (2) Activating the activated carbon AC by using an acid solution or an alkali solution; preferably, the activated carbon AC is activated by using an alkali solution;

[0013] (3) Preparing the AC / ZnMn2O4 photocatalytic renewable adsorbent:

[0014] The ZnMn2O4 obtained in step (1) and the activated carbon AC obtained in step (2) are thoroughly ground in anhydrous ethanol until the ZnMn2O4 and the AC are uniformly mixed, a sticky paste appears, and a brownish gray color is presented, and the AC / ZnMn2O4 photocatalytic renewable adsorbent is obtained after drying.

[0015] As a preferred, in step (1), the total metal ion concentration of zinc and manganese in the solution A is 0.02-0.16 mol / L.

[0016] As a preferred, in step (1), the molar amount ratio of zinc acetate to manganese acetate is 1:2, and the molar amount ratio of oxalic acid to zinc acetate is 3-3.6:1.

[0017] As a preferred, in step (1), the heating and stirring is performed at a heating temperature of 50-60℃ and a stirring rate of 500-1000 r / min for 2-2.5 h.

[0018] As a preferred, in step (1), the volume ratio of ethanol to water in the ethanol-water solution is 9:1.

[0019] As a preferred, in step (1), the precursor is calcined at a temperature rising rate of 2-10℃ / min to 450-550℃, and the calcination holding time is 2-2.5 h.

[0020] The volume ratio of ethanol to water in the precipitation medium plays a key role in the change of the aspect ratio of the ZnMn2O4 particles. By using the preferred scheme of step (1) described above, long strip-shaped porous ZnMn2O4 with a larger specific surface area and pore volume can be prepared, which is conducive to the full contact of the photocatalyst with the degradation target, and provides more mass transfer channels and reaction active sites, reduces the recombination rate of photo-generated electrons and holes, and improves the photocatalytic degradation efficiency.

[0021] As preferred, in step (2), the mass-volume ratio of activated carbon and acid / alkali solution is 1:5-1:4 (g / mL); as preferred, the alkali solution is 1%-5% (w / w) KOH solution, and the acid solution is 4-5 mol / L nitric acid solution.

[0022] The specific operation is as follows:

[0023] The activated carbon is added into the KOH solution, and after fully stirring and mixing at room temperature for a period of time, the activated carbon is filtered, and the activated carbon filtrate is continuously washed with dilute hydrochloric acid and distilled water until the pH of the activated carbon filtrate is neutral, and then the activated carbon is dried overnight to obtain the alkali-activated AC;

[0024] Or, the activated carbon is added into the nitric acid solution, and after heating and continuous stirring for a period of time, the activated carbon is filtered, and the activated carbon filtrate is continuously washed with distilled water until the pH of the activated carbon filtrate is neutral, and then the activated carbon is dried overnight to obtain the acid-activated AC.

[0025] The stirring rate is 500-700 r / min, the stirring time is 22-24 h, and the heating temperature during heating and stirring is 70-80℃.

[0026] As preferred, in step (3), the mass ratio of the activated activated carbon AC and ZnMn2O4 is 1:10-3:10.

[0027] In a second aspect, the present application provides an activated carbon loaded zinc manganate (AC / ZnMn2O4) photocatalytic renewable adsorbent, which is composed of activated carbon AC and zinc manganate ZnMn2O4 and is prepared by the aforementioned preparation method, wherein the mass ratio of AC and ZnMn2O4 is 1:10-3:10.

[0028] In a third aspect, the present application provides the use of the aforementioned activated carbon loaded zinc manganate (AC / ZnMn2O4) photocatalytic renewable adsorbent in the cyclic adsorption of tannic acid.

[0029] Compared with the prior art, the present application has the following characteristics:

[0030] (1) The AC / ZnMn2O4 photocatalytic renewable adsorbent prepared by the simple co-precipitation-calcination and mechanical grinding method of the present application has small zinc leaching liquid pollution, strong operability, and will not generate secondary pollution, and has excellent adsorption performance for tannic acid.

[0031] (2) The AC / ZnMn2O4 photocatalytic renewable adsorbent prepared by the present application has a porous structure and a large specific surface area.

[0032] (3) The AC / ZnMn2O4 photocatalytic renewable adsorbent prepared by the present application has good adsorption photocatalytic regeneration ability and cyclic utilization, and has good practical value and potential application prospect in removing tannic acid in zinc leaching liquid. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 (a) SEM, (b-e) C, O, Zn, Mn element distribution map of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1.

[0034] Figure 2 N2 adsorption-desorption curve of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1.

[0035] Figure 3 Pore size distribution map of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1.

[0036] Figure 4 Adsorption effect diagram of tannic acid of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1, Example 2, Comparative Example 1 and the alkali-activated AC prepared in Example 1.

[0037] Figure 5 Cycle stability column chart of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1. Figure 5 1 is the adsorption rate of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1 when degrading tannic acid for 120 minutes in the first cycle; 2 is the adsorption rate of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1 when degrading tannic acid for 120 minutes in the second cycle; 3 is the adsorption rate of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1 when degrading tannic acid for 120 minutes in the third cycle; 4 is the adsorption rate of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1 when degrading tannic acid for 120 minutes in the fourth cycle. DETAILED DESCRIPTION

[0038] The purposes, technical solutions and advantages of the present application are described in detail below, but the present application is not limited to the following description.

[0039] The present application composites AC and ZnMn2O4 to construct an AC / ZnMn2O4 photocatalytic renewable adsorbent, which has great significance in enhancing the adsorption performance of AC on tannic acid in zinc leaching solution, realizing the recycling of the adsorbent and avoiding secondary pollution.

[0040] The technical solutions of the present application are described below in combination with specific examples:

[0041] Example 1:

[0042] (1) Preparation of ZnMn2O4:

[0043] In an ethanol-water solution (90 mL + 10 mL), 0.220 g of zinc acetate (CH3COO)2Zn·2H2O and 0.490 g of manganese acetate (CH3COO)2Mn·4H2O were added, and after stirring until complete dissolution, a solution A with a total concentration of 0.02 mol / L of zinc and manganese metal ions was obtained; similarly, 0.378 g of oxalic acid H2C2O4·2H2O was added to an ethanol-water solution (45 mL + 5 mL), and after stirring until complete dissolution, a solution B was obtained; solution A was quickly poured into solution B, and the mixture was stirred at 60°C and 1000 r / min for 2 h; after the mixture was cooled to room temperature, it was suction filtered, washed, and dried to obtain a precursor sample; finally, the dried precursor was calcined in an air atmosphere, with a heating rate of 2°C / min, at 450°C for 2 h, and a long strip-shaped porous ZnMn2O4 was finally obtained.

[0044] (2) Preparation of acid- or base-activated activated carbon:

[0045] 25 g of AC was added to 100 mL of a 1% (w / w) KOH solution, and after continuous stirring at room temperature for 24 h, it was filtered, washed with dilute hydrochloric acid and distilled water until the pH of the AC filtrate was neutral, and then dried overnight to obtain base-activated AC; 20 g of AC was added to 100 mL of a 5 mol / L nitric acid solution, and after continuous stirring at an 80°C water bath temperature for 24 h, it was filtered, washed with distilled water until the pH of the activated carbon filtrate was neutral, and then dried overnight to obtain acid-activated AC.

[0046] (3) Preparation of AC / ZnMn2O4 photocatalytic regenerable adsorbent:

[0047] 0.10 g of ZnMn2O4 obtained in step (1) and 0.01 g of base-activated activated carbon obtained in step (2) were placed in an agate mortar, 1-2 mL of anhydrous ethanol was added, and the agate mortar rod was used to grind thoroughly for 30 min until the ZnMn2O4 and AC were uniformly mixed and a brownish gray sticky paste appeared; after drying, the AC / ZnMn2O4 photocatalytic regenerable adsorbent was obtained.

[0048] The field scanning electron microscope photos of the AC / ZnMn2O4 photocatalytic regenerable adsorbent prepared in this example are shown in detail in Figure 1 , and Figure 1 It can be seen that the ZnMn2O4 is in the form of fine strips covering the smooth surface of the AC, indicating that the ZnMn2O4 and the AC are closely compounded together.

[0049] The nitrogen adsorption-desorption curve and pore size distribution graph of the AC / ZnMn2O4 photocatalytic regenerable adsorbent prepared in this example are shown in detail in Figure 2 and Figure 3As can be seen from the figure, the AC / ZnMn204 photocatalytic renewable adsorbent has a large specific surface area and pore volume, which are 90.885 m 2 ·g -1 and 0.210 cm 3 ·g -1 , the pore size mainly distributes in 5-120 nm, the average pore size is 46 nm, and it belongs to a porous structure.

[0050] Example 2:

[0051] The difference between this example and Example 1 is that the activated carbon in step (3) is acid-activated AC. The other steps are the same as those in Example 1.

[0052] Example 3:

[0053] The difference between this example and Example 1 is that the total concentration of zinc and manganese metal ions in step (1) is 0.16 mol / L. The other steps are the same as those in Example 1.

[0054] Example 4:

[0055] The difference between this example and Example 1 is that the heating temperature in step (1) is 50℃. The other steps are the same as those in Example 1.

[0056] Example 5:

[0057] The difference between this example and Example 1 is that the stirring rate in step (1) is 500 r / min.

[0058] Example 6:

[0059] The difference between this example and Example 1 is that the calcination temperature in step (1) is 400℃.

[0060] Example 7:

[0061] The difference between this example and Example 1 is that the temperature rising rate in step (1) is 10℃ / min.

[0062] Example 8:

[0063] The difference between this example and Example 1 is that the alkali-activated activated carbon in step (3) is 0.02 g.

[0064] Example 9:

[0065] The difference between this example and Example 1 is that the alkali-activated activated carbon in step (3) is 0.03 g. Comparative Example 1:

[0066] The difference between this example and Example 1 is that the activated carbon in step (3) is a commercial activated carbon without treatment.

[0067] Application Example:

[0068] 1. Adsorption performance experiment

[0069] 20 mg of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1, Example 2, Example 8, Example 9, Comparative Example 1 and the alkali-activated AC prepared in Example 1 were respectively taken and added into 50 mL of a tannin solution with an initial concentration of 200 mg·L -1 -1, and stirred at a constant stirring rate for 10, 20, 35, 60, 90 and 120 minutes at room temperature in the dark. 2 mL of supernatant was taken and filtered with a 0.22 μm filter membrane. The absorbance was measured by colorimetry to obtain the residual concentration of tannin, and the adsorption rate was calculated.

[0070] The adsorption effect of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1, Example 2, Example 8, Example 9 and Comparative Example 1 and the alkali-activated AC on tannin is shown in Figure 4 , wherein the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1 has the fastest adsorption rate (the adsorption rate on tannin is 71.4% within 20 minutes), and the highest adsorption rate on tannin is 98.3% within 120 minutes. The adsorption rates of the remaining samples are shown in Table 1. This shows that the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1 has excellent adsorption performance on tannin.

[0071] Table 1: Adsorption rate of each experimental group on tannin

[0072]

[0073]

[0074] 2. Circulation performance experiment

[0075] The photocatalytic reaction was carried out under the simulation of sunlight by a 500w xenon lamp. The tannin solution containing the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1 after the first adsorption was placed under xenon light for photocatalytic regeneration experiment at room temperature. After 150 minutes of light irradiation, all the first adsorbed AC / ZnMn2O4 photocatalytic renewable adsorbent was centrifuged and dried to obtain the first circulated AC / ZnMn2O4 photocatalytic renewable adsorbent.

[0076] The first circulated AC / ZnMn2O4 photocatalytic renewable adsorbent obtained in the photocatalytic regeneration experiment was added into 50 mL of a tannin solution with an initial concentration of 200 mg·L -1The AC / ZnMn2O4 photocatalytic renewable adsorbent is dark adsorbed for 120 minutes in the tannin solution to obtain a tannin solution containing the AC / ZnMn2O4 photocatalytic renewable adsorbent after the second adsorption, and the removal rate is as follows Figure 5 The tannin removal rate of each cycle is obtained by repeating the above process four times.

[0077] The cycle stability histogram of the AC / ZnMn2O4 photocatalytic renewable adsorbent prepared in Example 1 is shown in Figure 2. Figure 5 The tannin removal rate of each cycle is obtained by repeating the above process four times.

[0078] The above examples only express several preferred embodiments of the present application, and detailed description cannot be understood as the limitation of the scope of the present application. Any modification and equivalent modification made according to the present application without departing from the technical concept and characteristics of the present application belongs to the protection scope of the present application.

Claims

1. The application of an AC / ZnMn2O4 photocatalytic regenerable adsorbent in the cyclic adsorption of tannic acid, characterized in that, The preparation method of the AC / ZnMn2O4 photocatalytic regenerable adsorbent includes the following steps: (1) Preparation of ZnMn2O4: Zinc acetate (CH3COO)2Zn·2H2O and manganese acetate (CH3COO)2Mn·4H2O were added to an ethanol-water solution and stirred until completely dissolved to obtain solution A. Oxalic acid (H₂C₂O₄·2H₂O) was added to an ethanol-water solution and stirred until completely dissolved to obtain solution B. Solution A was quickly poured into solution B and heated and stirred to obtain a mixture. After the mixture was cooled to room temperature, it was filtered, washed and dried to obtain the precursor. The precursor was calcined to obtain ZnMn2O4 with an elongated morphology. (2) Activate activated carbon AC using acid or alkaline solutions; (3) Preparation of AC / ZnMn2O4 photocatalytic regenerable adsorbent: The ZnMn2O4 obtained in step (1) and the activated carbon AC obtained in step (2) are thoroughly ground in anhydrous ethanol until ZnMn2O4 and AC are mixed evenly and a distinct viscous paste appears, which is brownish-gray. After drying, AC / ZnMn2O4 photocatalytic regenerable adsorbent is obtained. The AC / ZnMn2O4 photocatalytic regenerable adsorbent has a stable cyclic removal effect on tannic acid.

2. The application according to claim 1, characterized in that, In step (1), the total metal ion concentration in solution A is 0.02 to 0.16 mol / L.

3. The application according to claim 1, characterized in that, In step (1), the molar ratio of zinc acetate to manganese acetate is 1:2, and the molar ratio of oxalic acid to zinc acetate is 3 to 3.6:

1.

4. The application according to claim 1, characterized in that, In step (1), the heating and stirring are carried out at a temperature of 50-60°C, a stirring rate of 500-1000 r / min, and a stirring time of 2-2.5 h.

5. The application according to claim 1, characterized in that, In step (1), the volume ratio of ethanol to water in the ethanol-water solution is 9:

1.

6. The application according to claim 1, characterized in that, In step (1), the precursor is heated to 450-550°C at a heating rate of 2-10°C / min and calcined for 2-2.5 hours.

7. The application according to any one of claims 1 to 6, characterized in that, In step (2), the mass-to-liquid ratio of activated carbon and acid / alkali solution is 1:5 to 1:4 g / mL; the alkali solution is 1% to 5% w / w KOH solution, and the acid solution is 4 to 5 mol / L nitric acid solution.

8. The application according to claim 1, characterized in that, In step (3), the mass ratio of AC to ZnMn2O4 is 1:10 to 3:10.

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