A method for synthesizing in-situ silver modified trithiocyanate polymer and application thereof as a photocatalyst

Abstract

The application discloses a method for synthesizing in-situ silver modified trithiocyanate polymer and application of the in-situ silver modified trithiocyanate polymer as a photocatalyst. The material is based on soft / hard acid-base theory, and is obtained by using the strong affinity between trithiocyanate and silver ions and combining with a photocatalytic reduction technology. The preparation of the catalysts with different proportions in the experiment is controlled by the mass ratio x of two precursors, silver nitrate and trithiocyanate, wherein the range of x is controlled to be 0.01-0.4. In the synthesis process of the composite photocatalytic material, the silver ions can be used as the center point of the trithiocyanate polymerization, finally forming dispersed nanoparticles, improving the number of reactive sites, and greatly improving the visible light absorption capacity by the local surface plasmon resonance of silver. The application provides a novel in-situ silver modified trithiocyanate polymer photocatalyst method, raw materials are simple, synthesis is simple, and the in-situ silver modified trithiocyanate polymer has good visible light catalytic degradation performance of organic pollutants.

Description

Technical Field

[0001] This invention relates to an in-situ silver-modified trithiocyanate polymer (Ag-TTCA) catalyst and its preparation method, as well as its use in the visible light catalytic degradation of bisphenol A. Background Technology

[0002] Photocatalysis, as an advanced oxidation technology, utilizes the active substances generated on the surface of a catalyst by a light source to degrade pollutants. Photocatalysis has been widely applied in environmental remediation, fuel production, and photocatalytic sterilization. The photocatalyst is key to photocatalysis technology. Among numerous semiconductor photocatalysts, trithiocyanate (TTCA) is a particularly interesting one. Initially used as a precursor for the preparation of graphitic carbon nitride, researchers were surprised to discover that it is itself a photocatalyst. The triazine ring structure of TTCA can effectively utilize sunlight to generate photogenerated carriers.

[0003] Currently, trithiocyanate has been widely used in photocatalysis, but its inherent photocatalytic ability has certain limitations, requiring modification to improve its performance. Literature reports that the self-polymerization of trithiocyanate can effectively enhance photocatalytic activity. In trithiocyanate polymers, the trithiol form of trithiocyanate polymers polymerizes via SS bonds, exhibiting optical properties and band structure similar to graphitic carbon nitride. SS bonds possess good electron transfer capabilities, facilitating the separation of photogenerated electron-hole pairs, significantly enhancing the photocatalytic activity of polymerized trithiocyanate. For example, the hydrogen-bonded trithiocyanate aggregates synthesized by Yang et al. demonstrate that the conjugation between the electrons of the sulfur atoms and the triazine ring structure enhances photocatalytic activity (Hydrogen-Bonded Aggregates Featuring n→π). * Electronic Transition for Efficient Visible-Light-Responsive Photocatalysis. ACS Catalysis, 2022, 12(11):6276-6284).

[0004] Besides the modification methods mentioned above, noble metal deposition is also a common modification method in the field of photocatalysis. Noble metals deposited on the catalyst surface can capture photogenerated electrons and generate a plasma resonance (SPR) effect when irradiated by sunlight. For example, Li et al. prepared a novel silver-modified graphitic carbon nitride / carbon composite material. Silver nanoparticles can effectively capture photogenerated electrons in graphitic carbon nitride, thereby promoting the separation of photogenerated electrons and improving the material's electrical conductivity and electron transfer capability. 2. (Journal of Colloid and Interface Science, 2022, 606: 1311-1321). Although metal deposition-modified catalysts can now be successfully synthesized, most metals are deposited randomly on the material surface, and the binding force between the metal and the parent material is not strong. According to the soft / hard acid-base theory, trithiocyanic acid, as a soft base containing nitrogen and sulfur groups, has a strong affinity for silver ions, which are soft acids. Therefore, based on the affinity between silver and trithiocyanic acid and the polymerization reaction of trithiocyanic acid, the synthesis of in-situ silver-modified trithiocyanic acid polymer photocatalysts through the self-assembly process of trithiocyanic acid and silver nitrate and photocatalytic reduction technology shows great promise. Summary of the Invention

[0005] This invention aims to provide a method for preparing and using an in-situ silver-modified trithiocyanate polymer (Ag-TTCA) catalyst for the visible light-catalyzed degradation of bisphenol A. The catalyst synthesized using this invention has advantages such as simple and mild conditions, low energy consumption, easy management and operation during the experiment, and the catalytic reaction occurring under ambient temperature and pressure conditions, thus showing promising application prospects.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] The Ag-TTCA catalyst of this invention utilizes the strong affinity between trithiocyanate and silver ions, combined with photocatalytic reduction technology to obtain dispersed in-situ noble metal modified nanomaterials.

[0008] Firstly, this invention provides a method for preparing Ag-TTCA materials, the specific preparation steps of which are as follows:

[0009] Step 1: Take trithiocyanate and stir it evenly in methanol to obtain a trithiocyanate solution;

[0010] Step 2: Take silver nitrate of different contents and sonicate it in methanol to obtain silver nitrate solution; wherein the mass ratio of silver nitrate to trithiocyanate is 0.01 to 0.4:1.

[0011] Step 3: Add the silver nitrate solution obtained in Step 2 dropwise to the trithiocyanate solution in Step 1, stir for 22 hours, wash three times by centrifugation with methanol, and dry at 60°C.

[0012] Step 4: Take the sample obtained from step 3 and disperse it in a deionized aqueous solution. Perform a photochemical reaction under a 500W xenon lamp for 240 minutes. Then wash and dry the mixed solution after the reaction with deionized water to finally obtain the composite material Ag-TTCA.

[0013] This invention is based on the soft / hard acid-base theory. It utilizes trithiocyanate, a soft base containing nitrogen and sulfur groups, which has a strong affinity for silver ions, a soft acid. Trithiocyanate can form coordination with metal ions (based on the -SH group). Silver ions and trithiocyanate monomers are coordinated and then promoted to polymerize trithiocyanate, resulting in an in-situ silver-modified trithiocyanate polymer (Ag-TTCA).

[0014] This invention further investigates the photocatalytic performance of in-situ silver-modified trithiocyanate polymer (Ag-TTCA). It was found that silver, as a modifying metal for trithiocyanate polymers, can effectively capture photogenerated electrons generated on the polymer surface and effectively promote the separation of photogenerated electron-hole pairs, thereby improving photocatalytic performance.

[0015] Ag-TTCA exhibits excellent photocatalytic activity and can be used to degrade organic pollutants. Specific application methods are as follows:

[0016] Photocatalytic reaction process: The prepared Ag-TTCA photocatalyst was added to a 20 mg / L solution containing organic pollutants. The solution was stirred in the dark for 1 h to reach adsorption-desorption equilibrium. After turning on the lamp (500W xenon lamp, visible light), 1 mL of the suspension was taken out at regular intervals. The sample was filtered through a 0.22 μm high-efficiency membrane filter. The concentration of organic pollutants was determined by high-performance liquid chromatography (HPLC).

[0017] Furthermore, the organic pollutant is one of bisphenol A, phenol, 4-chlorophenol, or sulfamethazine. Furthermore, the Ag-TTCA photocatalyst exhibits high degradation activity for bisphenol A.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] Due to the strong affinity between silver ions and trithiocyanate (TTCA), silver ions, acting as the central site for TTCA polymerization, can achieve in-situ metal reduction under photocatalytic reduction technology, ultimately forming dispersed nanoparticles and thus increasing the reactive sites. Through polymerization and metal modification, the original electronic structure of TTCA is altered, significantly enhancing its visible light absorption capacity. Simultaneously, silver can capture photogenerated electrons, leaving holes for pollutant degradation reactions and inhibiting electron-hole pair recombination in the catalyst, thereby improving catalytic activity. Attached Figure Description

[0020] Figure 1 XRD patterns of 0.08Ag-TTCA and TTCA catalysts obtained in Example 1 and Comparative Example 1 of this invention.

[0021] Figure 2 TEM images of the 0.08Ag-TTCA and TTCA catalysts obtained in Example 1 and Comparative Example 1 of this invention.

[0022] Figure 3 Photocurrent diagrams of 0.08Ag-TTCA and TTCA catalysts obtained in Example 1 and Comparative Example 1 of this invention.

[0023] Figure 4 Photocatalytic effects of 0.08Ag-TTCA, 0.01Ag-TTCA, 0.04Ag-TTCA, 0.2Ag-TTCA, 0.4Ag-TTCA and TTCA catalysts obtained in Examples 1, 2, 3, 4, 5 and Comparative Example 1 on bisphenol A.

[0024] Figure 5 Visible light photocatalytic effects of 0.08Ag-TTCA on phenol, 4-chlorophenol, and sulfamethazine obtained in Example 1 of this invention.

[0025] Figure 6 Diagram illustrating the formation mechanism of Ag-TTCA in this invention. Figure 6 Based on the soft / hard acid-base theory, trithiocyanate, as a soft base, has a strong affinity for silver ions, which are soft acids, and can coordinate with metal ions. During preparation, the -SH groups in trithiocyanate form coordination polymers with silver ions. Through photocatalytic reduction, the trithiocyanate polymer centered on silver ions is reduced to form dispersed nanoparticles. Detailed Implementation

[0026] To better illustrate the present invention and facilitate understanding of its technical solutions, the following are typical non-limiting examples of the present invention:

[0027] Example 1: Preparation and application of 0.08Ag-TTCA

[0028] (1) Take 1.2g of trithiocyanate and stir in 50mL of methanol for 30min;

[0029] (2) Take 0.1g of silver nitrate and sonicate it in 10mL of methanol for 30min;

[0030] (3) Add the solution obtained in (2) dropwise to the solution in (1) above, control the mass ratio of silver nitrate and trithiocyanate to be 0.08:1, stir for 22 h, centrifuge and wash 3 times with methanol, and dry at 60 °C.

[0031] (4) Then, the sample obtained in (3) was dispersed in 50 mL of deionized water and subjected to photochemical reaction for 240 min under visible light (500 W xenon lamp). The mixed solution after the reaction was washed with deionized water and dried to finally obtain the composite material Ag-TTCA.

[0032] from Figure 1 The characterization results show that bulk TTCA has a distinct diffraction peak at 26.4°, corresponding to its (002) crystal plane. Compared to bulk TTCA, Ag-TTCA exhibits lower crystallinity, indicating that Ag-TTCA is an amorphous material. The formation of silver-modified trithiocyanate polymers reduces the crystallinity of TTCA, resulting in an amorphous catalyst. Figure 2 The Ag-TTCA clearly exhibits a loose granular distribution, with TTCA forming multiple uniformly dispersed nanoparticles surrounding silver ions. The nanoparticles are approximately 50 nm in size, and their smaller size provides more specific surface area and reaction sites, which is beneficial for improving photocatalytic activity. Figure 3 This indicates that Ag-TTCA has a good photocurrent response under illumination conditions.

[0033] Applications of 0.08Ag-TTCA:

[0034] Photocatalytic reaction process: 0.03 g of the prepared 0.08Ag-TTCA photocatalyst was added to 50 mL of 20 mg / L bisphenol A solution. The mixture was stirred in the dark for 1 h to reach adsorption-desorption equilibrium. After turning on the lamp (500W xenon lamp, visible light), 1 mL of the suspension was taken out at regular intervals. The sample was filtered through a 0.22 μm high-efficiency membrane filter. The BPA concentration was determined by high-performance liquid chromatography (HPLC).

[0035] The study investigated the use of 0.08Ag-TTCA catalyst for the visible light-catalyzed degradation of bisphenol A. From... Figure 4 It can be seen that 0.08Ag-TTCA has a degradation rate of up to 96.4% for bisphenol A within 4 hours.

[0036] Comparative Example 1: Preparation and Application of TTCA

[0037] Comparative Example 1 used trithiocyanate solid powder directly without further processing.

[0038] Bisphenol A was photocatalytically degraded using TTCA as a catalyst. Under the same reaction conditions as in Example 1, TTCA showed almost no degradation effect on bisphenol A within 4 hours (see Example 1). Figure 4 It is evident that under the same conditions, 0.08Ag-TTCA exhibits higher catalytic activity than TTCA.

[0039] Example 2: Preparation and application of 0.01Ag-TTCA

[0040] Trithiocyanate and silver nitrate were used as raw materials, and the mass ratio of silver nitrate to trithiocyanate in step (2) was changed to 0.01:1. Other operating steps were carried out in accordance with Example 1.

[0041] Bisphenol A was photocatalytically degraded using 0.01 Ag-TTCA as a catalyst. Under the same reaction conditions as in Example 1, 0.01 Ag-TTCA achieved a degradation rate of 35.2% for bisphenol A within 4 hours (see Example 1). Figure 4 It can be seen that under the same conditions, the catalytic activity of 0.01Ag-TTCA is higher than that of TTCA, but lower than that of 0.08Ag-TTCA.

[0042] Example 3: Preparation and application of 0.04Ag-TTCA

[0043] Trithiocyanate and silver nitrate were used as raw materials, and the mass ratio of silver nitrate to trithiocyanate in step (2) was changed to 0.04:1. Other operating steps were carried out in accordance with Example 1.

[0044] Bisphenol A was photocatalytically degraded using 0.04Ag-TTCA as a catalyst. Under the same reaction conditions as in Example 1, 0.04Ag-TTCA achieved a degradation rate of 90.8% for bisphenol A within 4 hours (see Example 1). Figure 4 It can be seen that under the same conditions, the catalytic activity of 0.04Ag-TTCA is higher than that of 0.01Ag-TTCA and TTCA, but lower than that of 0.08Ag-TTCA.

[0045] Example 4: Preparation and application of 0.2Ag-TTCA

[0046] Trithiocyanate and silver nitrate were used as raw materials, and the mass ratio of silver nitrate to trithiocyanate in step (2) was changed to 0.2:1. Other operating steps were carried out in accordance with Example 1.

[0047] Bisphenol A was photocatalytically degraded using 0.2Ag-TTCA as a catalyst. Under the same reaction conditions as in Example 1, 0.2Ag-TTCA achieved a degradation rate of 76.0% for bisphenol A within 4 hours (see Example 1). Figure 4 It can be seen that under the same conditions, the catalytic activity of 0.2Ag-TTCA is higher than that of 0.01Ag-TTCA and TTCA, but lower than that of 0.08Ag-TTCA and 0.04Ag-TTCA.

[0048] Example 5: Preparation and application of 0.4Ag-TTCA

[0049] Trithiocyanate and silver nitrate were used as raw materials, and the mass ratio of silver nitrate to trithiocyanate in step (2) was changed to 0.4:1. Other operating steps were carried out in accordance with Example 1.

[0050] Bisphenol A was photocatalytically degraded using 0.4Ag-TTCA as a catalyst. Under the same reaction conditions as in Example 1, 0.4Ag-TTCA achieved a degradation rate of 71.0% for bisphenol A within 4 hours (see Example 1). Figure 4 It can be seen that under the same conditions, the catalytic activity of 0.4Ag-TTCA is higher than that of 0.01Ag-TTCA and TTCA, but lower than that of 0.08Ag-TTCA, 0.04Ag-TTCA and 0.2Ag-TTCA.

[0051] Example 6: Study on the photocatalytic degradation of phenol, 4-chlorophenol, or sulfamethazine using 0.08Ag-TTCA.

[0052] Photocatalytic reaction process: 0.03 g of the prepared 0.08Ag-TTCA photocatalyst was added to 50 mL of 20 mg / L phenol, 4-chlorophenol, or sulfamethazine solution, respectively. The mixture was stirred in the dark for 1 h to reach adsorption-desorption equilibrium. After the light was turned on, 1 mL of the suspension was taken out at regular intervals. The sample was filtered through a 0.22 μm high-efficiency membrane filter. The concentrations of phenol, 4-chlorophenol, or sulfamethazine were determined by high-performance liquid chromatography (HPLC).

[0053] from Figure 5 It can be seen that 0.08Ag-TTCA has a degradation rate of 22% for phenol, 33% for 4-chlorophenol, and 49% for sulfamethazine within 4 hours.

Claims

1. A method for synthesizing in-situ silver-modified trithiocyanate polymer, characterized in that: (1) Add trithiocyanate to methanol and stir until homogeneous to obtain trithiocyanate solution; (2) Take silver nitrate and sonicate it in methanol to obtain silver nitrate solution; (3) Add the silver nitrate solution obtained in step (2) dropwise to the trithiocyanate solution in step (1), stir for a period of time, centrifuge with methanol, and dry; the mass ratio of silver nitrate to trithiocyanate is 0.01~0.4:1; (4) Take the solid dried in step (3) and disperse it in a deionized aqueous solution. Then carry out a photochemical reaction under visible light. The photochemical reaction conditions are 240 min under a 500W xenon lamp. After the reaction, wash and dry the mixed solution with deionized water to finally obtain the in-situ silver-modified trithiocyanate polymer Ag-TTCA.

2. The method for synthesizing in-situ silver-modified trithiocyanate polymer according to claim 1, characterized in that: The mass ratio of silver nitrate to trithiocyanate is 0.08:

1.

3. The application of the in-situ silver-modified trithiocyanate polymer synthesized according to the method of claim 1 or 2 as a photocatalyst in the photocatalytic degradation of bisphenol A.

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