Photocatalytic reduction material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electronic waste recovery treatment, in particular to a photocatalytic reduction material and a preparation method and application thereof. According to the preparation method of the photocatalytic reduction material, a rigid framework is constructed by crosslinking low-cost 2, 4, 6-triphenyltriazine and thiophene, rich thiophene groups on the rigid framework show high selectivity on gold ions, Au (III) can be reduced into elemental gold in situ, and therefore the gold recovery efficiency is remarkably improved. Meanwhile, thiophene serves as a donor, 2, 4, 6-triphenyltriazine serves as an acceptor, the photocatalytic activity of the photocatalytic reduction material is remarkably improved through the synergistic effect of the thiophene and the 2, 4, 6-triphenyltriazine in a rigid framework, an additional Au (III) photocatalytic reduction mechanism can be generated under visible light irradiation, and therefore the recovery capacity is further remarkably improved, adsorption kinetics is accelerated, and the recovery efficiency is improved. Therefore, the technical problem of low recovery efficiency of the existing adsorbent is solved.

Description

Technical Field

[0001] The invention relates to the technical field of electronic waste recycling and treatment, and in particular to a photocatalytic reduction material and a preparation method and application thereof. Background Art

[0002] Gold plays a vital role in electrical and electronic equipment due to its unique physical and chemical properties, including good electrical and thermal conductivity, corrosion resistance, ductility and plasticity. The rapid development of electronic technology has led to the generation of a large amount of electronic waste. The recycling of the resulting electronic waste has become a thorny issue, causing serious environmental pollution and public health problems.

[0003] The gold concentration in electronic waste is more than 40 times higher than that in natural gold ore. This discovery reveals the huge economic value of electronic waste and also points out the importance and urgency of electronic waste recycling and treatment. It can be foreseen that extracting gold from electronic waste can not only reduce environmental pollution, but also turn waste into treasure.

[0004] In the past few decades, many classical absorbents based on polymer solids have been developed for gold recovery, such as thiourea grafted polyacrylonitrile fiber, guanidinothiourea functionalized resin, and polythiourea membrane. The soft skeleton of the polymer usually leads to its dense structure, and only the sites exposed on the solid surface can bind gold, which greatly limits the gold recovery performance. Therefore, in order to improve the utilization of binding sites, some rigid fragments are introduced into the skeleton to obtain an open framework, such as 4-AP / PCMS and Imi-PPOPs-Br. Among them, the gold recovery capacity of 4-AP / PCMS is 437.68 mg g -1 The gold recovery capacity of Imi-PPOPs-Br is 710.0 mg g -1 However, the high production costs and limited recycling efficiency of these polymers make them unsuitable for large-scale industrial applications. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art, provide a photocatalytic reduction material and a preparation method and application thereof, and solve the technical problem of low recovery efficiency of the prior adsorbent.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a photocatalytic reduction material, comprising the following steps:

[0008] 2,4,6-triphenyltriazine and thiophene are mixed in a solvent system, and a photocatalytic reduction material is prepared by Scholl reaction under the action of a catalyst; the photocatalytic reduction material forms a structure in which a plurality of 2,4,6-triphenyltriazines constitute a rigid skeleton, and at least one thiophene group is grafted on the connected phenyl groups; the molar ratio of the 2,4,6-triphenyltriazine to the thiophene is 0.625:1-3.

[0009] By cross-linking low-cost 2,4,6-triphenyltriazine and thiophene to construct a rigid framework, the abundant thiophene groups on the rigid framework show high selectivity for gold ions, and can reduce Au(III) to elemental gold in situ, thereby significantly improving the gold recovery efficiency. At the same time, thiophene acts as a donor and 2,4,6-triphenyltriazine acts as an acceptor. The synergistic effect of the two in the rigid framework significantly improves the photocatalytic activity of the photocatalytic reduction material. Additional Au(III) photocatalytic reduction mechanisms can occur under visible light irradiation, thereby further significantly improving the recovery capacity and accelerating the adsorption kinetics, thereby solving the technical problem of low recovery efficiency of existing adsorbents.

[0010] Optionally, the reaction temperature of the Scholl reaction is 55° C. to 60° C., and the reaction time of the Scholl reaction is 36 h to 72 h.

[0011] Optionally, the mass volume ratio of the 2,4,6-triphenyltriazine to the solvent is 12 kg·m -3 ~13kg·m -3 , the solvent is CHCl3, and the catalyst for the Scholl reaction is AlCl3.

[0012] Optionally, the Scholl reaction needs to be carried out under a protective atmosphere.

[0013] The invention provides a photocatalytic reduction material, which is prepared by adopting the preparation method of the photocatalytic reduction material.

[0014] Optionally, the pore size of the photocatalytic reduction material is 0.4 nm to 4 nm, and the specific surface area of ​​the photocatalytic reduction material is 1014.55 m 2 ·g -1 ~1034.24m 2 ·g -1 .

[0015] The present invention provides an application of the above-mentioned photocatalytic reduction material as an adsorption material in recovering Au from electronic waste leachate.

[0016] Optionally, the gold ion concentration in the electronic waste leachate is greater than 0 ppm and less than or equal to 1400 ppm, and the pH is 1-7.

[0017] Optionally, the mass volume ratio of the photocatalytic reduction material to the electronic waste leachate is 0.01 kg·m -3 ~0.05kg·m -3 .

[0018] Optionally, the photocatalytic reduction material is applied under illumination conditions, and the wavelength of the illumination is ≥420nm.

[0019] The beneficial effect of the present invention is that, compared with the prior art, a rigid skeleton is constructed by cross-linking low-cost 2,4,6-triphenyltriazine and thiophene. The abundant thiophene groups on the rigid skeleton show high selectivity for gold ions, and Au(III) can be reduced to elemental gold in situ, thereby significantly improving the gold recovery efficiency. At the same time, thiophene acts as a donor and 2,4,6-triphenyltriazine acts as an acceptor. The synergistic effect of the two in the rigid skeleton significantly improves the photocatalytic activity of the photocatalytic reduction material. Additional Au(III) photocatalytic reduction mechanisms can occur under visible light irradiation, thereby further significantly improving the recovery capacity and accelerating the adsorption kinetics, thereby solving the technical problem of low recovery efficiency of existing adsorbents. According to subsequent experimental results, the gold recovery capacity of the photocatalytic reduction material under visible light irradiation reached 3227.3 mg·g -1 , which is 2.5 times that in dark conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 An X-ray powder diffraction detection spectrum of a photocatalytic reduction material provided by the present invention.

[0021] Figure 2 This is an infrared spectrum of a photocatalytic reduction material provided by the present invention.

[0022] Figure 3 The present invention provides a N2 adsorption-desorption isotherm of a photocatalytic reduction material.

[0023] Figure 4 This is a BET surface area diagram of a photocatalytic reduction material provided by the present invention.

[0024] Figure 5 This is a pore size distribution diagram of a photocatalytic reduction material provided by the present invention.

[0025] Figure 6 The infrared spectra of a photocatalytic reduction material provided by the present invention before and after being treated under different severe conditions.

[0026] Figure 7 The UV-visible absorption spectrum and Mott-Schottky diagram of the photocatalytic reduction material prepared in Example 1, wherein a is the UV-visible absorption spectrum diagram and b is the transient photocurrent response diagram.

[0027] Figure 8 The present invention provides a photocatalytic reduction material for the adsorption isotherm diagram of gold ions.

[0028] Fig. 9 The present invention provides a photocatalytic reduction material for adsorption kinetics of gold ions. DETAILED DESCRIPTION

[0029] In order to solve the above technical problems, the present invention provides a photocatalytic reduction material and a preparation method and application thereof. The technical scheme and embodiments of the present invention are now described in detail in conjunction with the accompanying drawings.

[0030] The photocatalytic reduction material provided by the present invention may have the following structural formula:

[0031]

[0032] In the present invention, the photocatalytic reduction material is a light brown powder. The pore size of the photocatalytic reduction material is preferably 0.4 nm to 4 nm, and the specific surface area is preferably 1034.24 m 2 g -1 .

[0033] In the present invention, the photocatalytic reduction material has a large number of accessible high-affinity binding sites and thus has a higher adsorption capacity; at the same time, the photocatalytic reduction material provided by the present invention has high stability and selectivity as well as excellent optical activity, and can photocatalytically reduce the efficiently adsorbed gold ions into insoluble elemental gold under light irradiation, thereby achieving gold fixation.

[0034] The present invention also provides a method for preparing the photocatalytic reduction material of the above technical solution, comprising the following steps:

[0035] The mixture of 2,4,6-triphenyltriazine, thiophene, solvent and catalyst is cross-linked by Scholl reaction to obtain a photocatalytic reduction material.

[0036] In the present invention, unless otherwise specified, all raw materials are conventional commercially available products in the art.

[0037] In the present invention, the solvent is preferably CHCl3. In the present invention, the catalyst is preferably AlCl3.

[0038] In the present invention, the molar ratio of 2,4,6-triphenyltriazine to thiophene is preferably 0.625:1 to 3, and more preferably 0.625:1.

[0039] In the present invention, the mass ratio of 2,4,6-triphenyltriazine to AlCl3 is preferably 0.19 g:2 g.

[0040] In the present invention, the molar ratio of thiophene to AlCl 3 is preferably 1 to 3:15, more preferably 1:15.

[0041] In the present invention, mixing preferably comprises the following steps:

[0042] 2,4,6-triphenyltriazine and thiophene are first mixed to obtain a first mixed solution.

[0043] AlCl3 and a solvent are added to the first mixed solution.

[0044] The invention is conducive to uniform mixing of materials through step-by-step mixing.

[0045] In the present invention, after mixing, the step of reacting under a N2 atmosphere is preferably further included.

[0046] In the present invention, the temperature of the Scholl reaction crosslinking is preferably 58°C; the time of the Scholl reaction is preferably 48 hours. In the present invention, the Scholl reaction is preferably accompanied by stirring. The present invention has no special requirements for stirring, as long as the reaction can be fully achieved.

[0047] In the present invention, after the Scholl reaction, it is preferred that the process further comprises: cooling the system after the Scholl reaction, sequentially performing solid-liquid separation, washing and vacuum drying to obtain a photocatalytic reduction material. In the present invention, the temperature after cooling is preferably room temperature, and the room temperature is preferably 20°C to 35°C, more preferably 25°C to 30°C. The present invention has no special requirements for the method of solid-liquid separation, and a conventional method in the art can be used.

[0048] The present invention preferably washes the solid separated from the solid-liquid separation. In the present invention, the washing is preferably carried out in sequence with ethanol, a HCl-H2O mixture with a volume ratio of 2:1, and ethanol as a detergent. In the present invention, washing is performed once with ethanol, twice with a HCl-H2O mixture with a volume ratio of 2:1, three times with ethanol, and finally washing with ethanol in a Soxhlet solution for 24 hours.

[0049] In the present invention, the vacuum drying temperature is preferably 70° C. to 80° C., more preferably 75° C.; the vacuum drying time is preferably 22 h to 26 h, more preferably 24 h.

[0050] The present invention also provides the use of the photocatalytic reduction material of the above technical solution or the photocatalytic reduction material prepared by the preparation method of the above technical solution as an adsorbent and a reducing agent in gold recovery.

[0051] The present invention also provides a method for recovering gold by using photocatalytic reduction materials, comprising the following steps:

[0052] The photocatalytic reduction material and the gold ion-containing solution are mixed and the pH value is adjusted to 5, and adsorption and reduction are performed to obtain a photocatalytic reduction material adsorbed with gold; the photocatalytic reduction material is the photocatalytic reduction material of the above technical solution or the photocatalytic reduction material prepared by the preparation method of the above technical solution.

[0053] In the present invention, the concentration of gold ions in the gold ion-containing solution is greater than 0 and less than or equal to 1400 ppm, preferably 600 ppm; the mass ratio of the photocatalytic reduction material to the volume ratio of the gold ion-containing solution is 0.1 mg to 0.5 mg:10 ml, preferably 0.3 mg:10 ml.

[0054] In the present invention, the photocatalytic reduction material and the gold ion-containing solution are mixed and the pH value is adjusted to 1-7, preferably 5. The present invention has no special restrictions on the type and amount of the pH adjuster used to adjust the pH value, as long as the required pH value can be achieved.

[0055] In the present invention, adsorption and reduction are carried out in darkness or under illumination, preferably under illumination. In the present invention, when adsorption and reduction are carried out under illumination, the mixed system obtained by mixing needs to be irradiated with a xenon lamp. The light source for irradiation is preferably a 500W xenon lamp equipped with an ultraviolet cutoff filter, that is, the wavelength of the light source is ≥420nm.

[0056] In the present invention, the time for adsorption and reduction is preferably 24 hours to 72 hours, more preferably 48 hours. In the present invention, the gold ions are preferably adsorbed into the pores of the photocatalytic reduction material before reduction.

[0057] When the adsorption and reduction are carried out under dark conditions, the photocatalytic reduction material is used as a reducing agent to chemically reduce the gold ions; when the adsorption and reduction are carried out under light conditions, the photocatalytic reduction material is used as a photocatalyst to photocatalytically reduce the gold ions.

[0058] In the present invention, after the adsorption and reduction, the following step is preferably further included: filtering the system after the adsorption and reduction to obtain the photocatalytic reduction material adsorbed with gold.

[0059] In the present invention, the pore size of the filtration membrane is preferably 0.22 μm.

[0060] The present invention is described in detail below through specific examples. The examples are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0061] Example 1

[0062] This embodiment provides a method for preparing a photocatalytic reduction material, and the specific method is as follows:

[0063] Under nitrogen atmosphere, 15mmol, 2g of AlCl3 was added to 0.625mmol, 0.19g of 4,6-triphenyltriazine and 1mmol, 0.08g of thiophene in 15mL CHCl3 under magnetic stirring at 58°C, and the reaction was carried out at the same temperature in N2 atmosphere for 48 hours. The obtained precipitate was washed once with ethanol, twice with a 2:1 volume ratio of HCl-H2O, three times with ethanol, and finally washed with ethanol in Soxhlet solution for 24 hours, and then dried in a vacuum oven at 75°C for 24 hours to obtain a light brown powder with a yield of 99%.

[0064] Example 2

[0065] This embodiment provides a method for preparing a photocatalytic reduction material, and the specific method is as follows:

[0066] Under nitrogen atmosphere, 15mmol, 2g of AlCl3 was added to 0.625mmol, 0.19g of 4,6-triphenyltriazine and 2mmol, 0.16g of thiophene in 15mL CHCl3 under magnetic stirring at 58°C, and the reaction was carried out at the same temperature in N2 atmosphere for 48 hours. The obtained precipitate was washed once with ethanol, twice with a 2:1 volume ratio of HCl-H2O, three times with ethanol, and finally washed with ethanol in Soxhlet solution for 24 hours, and then dried in a vacuum oven at 75°C for 24 hours to obtain a light brown powder with a yield of 99%.

[0067] Example 3

[0068] This embodiment provides a method for preparing a photocatalytic reduction material, and the specific method is as follows:

[0069] Under nitrogen atmosphere, 15mmol, 2g of AlCl3 was added to 0.625mmol, 0.19g of 4,6-triphenyltriazine and 3mmol, 0.24g of thiophene in 15mL CHCl3 under magnetic stirring at 58°C, and the reaction was carried out at the same temperature in N2 atmosphere for 48 hours. The obtained precipitate was washed once with ethanol, twice with a 2:1 volume ratio of HCl-H2O, three times with ethanol, and finally washed with ethanol in Soxhlet solution for 24 hours, and then dried in a vacuum oven at 75°C for 24 hours to obtain a light brown powder with a yield of 99%.

[0070] The photocatalytic reduction material prepared in Example 1 was characterized and its performance tested according to the following methods.

[0071] Test Example 1: X-ray powder diffraction test.

[0072] The photocatalytic reduction material in Example 1 was subjected to X-ray powder diffraction detection to obtain an X-ray powder diffraction detection spectrum as shown in Figure 1 As shown. Figure 1 It can be seen that the X-ray powder diffraction detection spectrum of the photocatalytic reduction material shows a diffraction peak at 24°, which corresponds to the characteristic peak of the photocatalytic reduction material, indicating that the photocatalytic reduction material has been successfully synthesized using the method of the present invention.

[0073] Test Example 2: Infrared spectrum analysis test.

[0074] The photocatalytic reduction material in Example 1 was subjected to infrared detection to obtain an infrared spectrum as shown in FIG. Figure 2 As shown. Figure 2 It can be seen that the photocatalytic reduction material is at 803 cm -1 The characteristic vibration peak of thiophene is shown at , proving the successful introduction of the thiophene group.

[0075] Test Example 3: BET specific surface area test.

[0076] The BET specific surface area test method was used to characterize the porous structure of the photocatalytic reduction material prepared in Example 1. Figure 3 This is the N2 adsorption-desorption isotherm of the photocatalytic reduction material, which is a type IV isotherm. Figure 4 It is the specific surface area of ​​photocatalytic reduction material calculated by nitrogen adsorption-desorption isotherm. Figure 5 This is the pore size distribution diagram of the photocatalytic reduction material calculated by non-local density functional theory. The pore size of the photocatalytic reduction material is mainly concentrated in 0.4nm~4nm. The above results show that the photocatalytic reduction material has a loose porous structure and a large specific surface area.

[0077] Test Example 4: Chemical stability test.

[0078] The same mass of the photocatalytic reduction material prepared in Example 1 was used to set up a control experiment, and was divided into a blank control group, an illumination group, an N,N-dimethylformamide group, a hydrochloric acid group, and a sodium hydroxide group according to the test conditions. Among them, the photocatalytic reduction material in the blank control group was not treated and directly subjected to infrared spectrum test, the photocatalytic reduction material in the illumination group was subjected to 600W illumination treatment, the photocatalytic reduction material in the ethanol group was soaked in ethanol, the photocatalytic reduction material in the hydrochloric acid group was soaked in a HCl solution with a concentration of 6.0 mol / L, and the photocatalytic reduction material in the sodium hydroxide group was soaked in a NaOH solution with a concentration of 6.0 mol / L, and the above treatment time was 24 h.

[0079] The photocatalytic reduction material after the soaking treatment is filtered together with the soaking liquid to obtain the filtered solid mixture. The solid mixture is washed with ultrapure water until the supernatant becomes neutral, and then vacuum dried at 80°C, and infrared spectrum test is performed to obtain an infrared spectrum diagram, such as Figure 6 shown.

[0080] Depend on Figure 6 It can be seen that the infrared spectrum of the photocatalytic reduction material did not change significantly before and after the treatment, indicating that the photocatalytic reduction material has excellent stability.

[0081] Test Example 5: Photoelectric performance test.

[0082] The photoelectric properties of the photocatalytic reduction material prepared in Example 1 were detected by UV-visible absorption spectroscopy and transient photocurrent response spectrum. Figure 7 As shown, a is the UV-visible absorption spectrum, and b is the transient photocurrent response spectrum. Figure 7 It can be seen that the photocatalytic reduction material has good photoelectric properties.

[0083] Test Example 6: Testing of the gold ion adsorption performance of photocatalytic reduction materials at different gold ion concentrations.

[0084] 3 mg of photocatalytic reduction material was added to 10 mL of chloroauric acid solution at pH = 5 at room temperature, and the Au(III) concentration of the solution was 20 ppm to 1400 ppm. The solution was stirred at 200 rpm for 6 hours under visible light irradiation or in the dark. The mixed solution was separated and the Au(III) content was analyzed by ICP-OES.

[0085] Table 1 Adsorption capacity of photocatalytic reduction materials for solutions with different gold ion concentrations at different gold ion concentrations

[0086] <![CDATA[Au 3+ Initial concentration / ppm]]> Residual gold ion concentration / ppm <![CDATA[Adsorption capacity / mg·g -1 > 20 0.025 66.58333 50 0.056 166.48 100 1.542 328.19333 200 5.277 649.07667 400 9.623 1301.25667 600 28.6 1904.66667 800 58.2 2472.66667 1000 131.32 2895.6 1200 242.442 3191.86 1400 431.8 3227.33333

[0087] Combining Table 1 and Figure 8 It can be seen that the adsorption capacity of photocatalytic reduction materials for gold increases with the 3+ The adsorption of Au by photocatalytic reduction materials increases with the increase of concentration and reaches the adsorption equilibrium state. 3+ The maximum adsorption capacity is 3227.3 mg g -1 .

[0088] Test Example 7: Testing the adsorption kinetics of gold ions by photocatalytic reduction materials.

[0089] Adsorption kinetics. For adsorption kinetics measurements, 12 mg of photocatalytic reduction material was added to 40 mL of chloroauric acid solution at pH = 5 and Au (III) concentration of 1400 ppm at room temperature. The mixtures were stirred at 200 rpm under visible light and dark conditions. At the specified time intervals of 3 minutes, 6 minutes, 12 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes, 120 minutes, and 180 minutes, a total of 18 mL of the mixture was taken out and filtered to remove the photocatalytic reduction material. The gold content in the solution was measured by ICP-OES.

[0090] Table 2 Adsorption kinetics of photocatalytic reduction materials to 1400ppm gold ion concentration solution

[0091]

[0092]

[0093] According to Table 2, a columnar comparison chart of the adsorption performance of photocatalytic reduction materials for different ions is drawn, such as Fig. 9 Combining Table 2 and Fig. 9 It can be seen that the photocatalytic reduction material provided by the present invention has ultrafast adsorption kinetics, reaching 3170.87 mg·g in 60 min. -1 , which can be used as an efficient photocatalyst for gold.

[0094] The above description is only a preferred embodiment of the present invention, and the above specific embodiment is not intended to limit the present invention. Various deformations and modifications may occur within the scope of the technical concept of the present invention, and any modification, modification or equivalent replacement made by a person of ordinary skill in the art based on the above description shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a photocatalytic reduction material, characterized in that: The following steps are involved: 2,4,6-triphenyltriazine and thiophene are mixed in a solvent system, and a photocatalytic reduction material is prepared by Scholl reaction under the action of a catalyst. The photocatalytic reduction material forms a structure in which a plurality of 2,4,6-triphenyltriazines constitute a rigid skeleton, and at least one thiophene group is grafted onto the connected phenyl groups; The molar ratio of the 2,4,6-triphenyltriazine to the thiophene is 0.625:1-3.

2. The method for preparing the photocatalytic reduction material according to claim 1, characterized in that: The reaction temperature of the Scholl reaction is 55° C. to 60° C., and the reaction time of the Scholl reaction is 36 h to 72 h.

3. The method for preparing the photocatalytic reduction material according to claim 1, characterized in that: The mass volume ratio of the 2,4,6-triphenyltriazine to the solvent is 12 kg·m -3 ~13kg·m -3 , the solvent is CHCl3, and the catalyst for the Scholl reaction is AlCl3.

4. The method for preparing the photocatalytic reduction material according to claim 1, characterized in that: The Scholl reaction needs to be carried out under a protective atmosphere.

5. A photocatalytic reduction material, characterized in that: The photocatalytic reduction material is prepared by the preparation method of the photocatalytic reduction material according to any one of claims 1 to 4.

6. The photocatalytic reduction material according to claim 5, characterized in that: The pore size of the photocatalytic reduction material is 0.4 nm to 4 nm, and the specific surface area of ​​the photocatalytic reduction material is 1014.55 m 2 ·g -1 ~1034.24m 2 ·g -1 .

7. Use of the photocatalytic reduction material according to claim 5 or 6 as an adsorption material for recovering Au from electronic waste leachate.

8. The use according to claim 7, characterized in that: The gold ion concentration in the electronic waste leachate is greater than 0 ppm and less than or equal to 1400 ppm, and the pH value is 1-7.

9. The use according to claim 8, characterized in that: The mass volume ratio of the photocatalytic reduction material to the electronic waste leachate is 0.01 kg·m -3 ~0.05kg·m -3 .

10. The use according to claim 8, characterized in that: The photocatalytic reduction material is used under illumination conditions, and the wavelength of the illumination is ≥420nm.

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