Controllable preparation method of nanometer cage type thiourea-resorcinol-formaldehyde resin adsorbent and application thereof

Abstract

The application belongs to the technical field of preparation of adsorption separation functional materials, and discloses a controllable preparation method of nano-cage type thiourea-resorcinol-formaldehyde resin adsorbent and application thereof. The method uses silica nanospheres as a hard template, synchronously dopes thiourea and silica during growth of a phenolic resin layer, and finally etches and removes the silica template to controllably prepare cross-wrinkled resin nanocage microspheres. The method not only realizes controllable morphology, but also greatly improves adsorption performance. The application has important economic value in the field of precious metal recovery, can effectively deal with the problems of waste of precious metal resources and environmental pollution in electronic waste, and provides a new idea for designing low-cost high-performance adsorbents.

Description

Technical Field

[0001] This invention belongs to the field of adsorption and separation functional material preparation technology, and relates to the controllable preparation of a nanocage-type thiourea-resorcinol-formaldehyde resin adsorbent and its application in the selective separation of gold. Background Technology

[0002] Gold, as a global strategic resource, is not only of great importance in national defense and economic security, but its superior physical and chemical properties also make it widely used in jewelry, currency, electronic devices, and chemical catalysis. However, high industrial and societal demand for gold has created immense pressure on its mining and recycling. Especially against the backdrop of rapid technological advancements in electronic products, a large amount of electronic waste is generated, with gold content in leachates reaching 1-2000 ppm, far exceeding the 1-30 ppm found in natural ores. This presents significant environmental implications and considerable economic potential for gold extraction from electronic waste. Nevertheless, the gold recycling process is exceptionally complex due to competition with multiple metals such as palladium, copper, silver, chromium, aluminum, and cobalt. This situation underscores the necessity of developing highly selective and efficient gold recycling technologies.

[0003] Adsorption is considered a key method for recovering trace amounts of gold due to its low cost, high safety, and environmental friendliness. Furthermore, its simple operation and suitability for continuous processing further enhance its practicality. The core of adsorption technology lies in the performance of the adsorbent material, which directly determines the recovery efficiency. However, commonly used adsorbents generally suffer from low adsorption efficiency and poor regeneration performance, limiting their practical application. Therefore, developing novel adsorbent materials with high adsorption capacity is particularly important.

[0004] Among numerous materials, phenolic resins are considered a highly promising adsorbent material due to their controllable synthesis conditions, environmental friendliness, strong chemical stability, low cost, and ease of industrial production. Although phenolic resins theoretically possess excellent adsorption capacity, traditional synthesis methods, such as the classic solvothermal method, typically require stringent reaction conditions, and the resulting materials exhibit significant limitations in morphological and size control. To overcome these issues, we based our research on extended... Based on phenol-formaldehyde resin, this study combined hard template method and heteroatom doping technology to conduct in-depth research on the morphology and adsorption properties of the material. This improved strategy helps to enhance the adsorption capacity and selectivity of phenol-formaldehyde resin, enabling it to demonstrate greater potential in the adsorption and separation of gold. Summary of the Invention

[0005] To address the problems of low adsorption capacity, slow adsorption rate, and low site discrimination in existing gold adsorbent technologies, this invention provides a controllable preparation of a nanocage-type thiourea-resorcinol-formaldehyde resin adsorbent and its application in the selective separation of gold. Using silica nanospheres as a hard template, thiourea and silica are simultaneously doped during the growth of the phenolic resin layer. Finally, the silica template is etched away to controllably prepare cross-wrinkled resin nanocage microspheres, which are then applied to efficiently capture gold in electronic waste dissolving solutions.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0007] A controllable preparation method for a nanocage-type thiourea-resorcinol-formaldehyde resin adsorbent includes the following steps:

[0008] (1) Preparation of SiO2 microspheres

[0009] First, a measured amount of ethanol, deionized water, and ammonia were mixed in a flask. Then, a measured amount of (V1) TEOS was added while stirring at a certain speed r, and the mixture was reacted at T1 for a period of time t1. Next, a measured amount of (V2) TEOS was added, and the mixture was reacted at T1 for a period of time t2. The precipitate was collected by centrifugation and washed several times with distilled water and ethanol, respectively. Finally, the powder was vacuum dried.

[0010] (2) Preparation of SiO2@TRF nanospheres

[0011] Take the silica nanospheres from step (1) and place them in a round-bottom flask. Add an appropriate amount of distilled water and sonicate to disperse them completely. Add a measured amount of ammonia, resorcinol, and thiourea while stirring. After stirring for a period of time t3, add a measured amount of formaldehyde and silane coupling agent. Stir and react for a period of time t4 at T2. Collect the product by centrifugation and wash it several times with distilled water and ethanol respectively. Finally, vacuum dry the powder to obtain SiO2@TRF.

[0012] (3) Preparation of TRF nanospheres

[0013] Take the SiO2@TRF obtained in step (2) and place it in a centrifuge tube. Add a certain amount of hydrofluoric acid aqueous solution and etch it for a period of time t5 under shaking. Centrifuge to collect the product and wash it several times with distilled water and ethanol respectively. Finally, vacuum dry the powder.

[0014] Preferably, in step (1), the ratio of the amount of ethanol, water, ammonia and silane coupling agent is 30mL:5mL:2mL:5.2mL, the volume ratio of V1 to V2 is 0.2:5, T1 is 25-30℃, the reaction time t1 is 20-30min, and the reaction time t2 is 12h.

[0015] Preferably, in step (2), the ratio of silica nanospheres, resorcinol, formaldehyde, thiourea, ammonia, silane coupling agent and deionized water is 200mg:0.00182mol:0.00373mol:0.00342mol:150μl:100μl:25-30mL; T2 is 30℃, reaction time t3 is 20min, and reaction time t4 is 24h.

[0016] In step (2), the silane coupling agent is tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), or tetrapropoxysilane (TPOS). Depending on the type of silane coupling agent used, the material is named TRF- (silane coupling agent).

[0017] Preferably, in step (3), the ratio of SiO2@TRF to hydrofluoric acid aqueous solution is 50mg:5mL, wherein the concentration of hydrofluoric acid is 1%wt, and the reaction time t5 is 0.5-3h.

[0018] The nanocage-type thiourea-resorcinol-formaldehyde resin adsorbent prepared in this invention can be controllably used for the selective adsorption and separation of gold ions in solution.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention utilizes the strong affinity between nitrogen, sulfur, and noble metal ions, employs relatively mild synthesis conditions, and modulates the microstructure of the material through a template method to prepare nitrogen and sulfur co-doped phenolic resin nanomaterials, achieving high-capacity and excellent selective adsorption of gold ions. Attached Figure Description

[0021] Figure 1 Scanning electron microscope (SEM) images of TRF materials prepared using different silane coupling agents.

[0022] Figure 2 The effects of different silane coupling agents and etching on the adsorption capacity of gold ions by TRF.

[0023] Figure 3 The infrared spectra of the SiO2@TRF and TRF-TEOS materials prepared in Example 1 are shown.

[0024] Figure 4 The effect of pH value on the adsorption capacity of gold ions by the TRF-TEOS adsorbent prepared in Example 1.

[0025] Figure 5 The adsorption kinetics of gold ions by the TRF-TEOS adsorbent prepared in Example 1 and its model fitting curve are shown.

[0026] Figure 6The effect of temperature on the adsorption equilibrium of gold ions by the TRF-TEOS adsorbent prepared in Example 1 and its model fitting curve are shown.

[0027] Figure 7 The adsorption selectivity of the TRF-TEOS adsorbent prepared in Example 1 is shown.

[0028] Figure 8 The adsorption and regeneration performance of the TRF-TEOS adsorbent prepared in Example 1 is shown. Detailed Implementation

[0029] In a specific embodiment of this invention, the performance evaluation was conducted as follows: Static adsorption experiments were performed. The adsorption capacity of 1.0 mg of TRF-TEOS for gold ions was tested within a pH range of 1.0-8.0. The gold ion content after adsorption was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the optimal adsorption pH was determined based on the results. Next, the effect of adsorption time on the adsorption capacity of TRF-TEOS was studied. Pseudo first-order and Pseudo second-order models were used to fit and analyze the data. To study the maximum adsorption capacity of TRF-TEOS, adsorption equilibrium experiments were conducted within a gold ion concentration range of 500-1000 ppm. Langmuir and Freundlich models were used to fit the adsorption data, and the adsorption capacity was calculated based on the results. A printed circuit board was selected as the actual sample to study the selective adsorption performance of TRF-TEOS. Finally, its adsorption-regeneration performance was tested.

[0030] The invention will be further explained below with reference to specific implementation examples.

[0031] Example 1:

[0032] Preparation of TRF-TEOS:

[0033] (1) Preparation of 400nm SiO2 microspheres

[0034] First, 30 mL of ethanol, 5 mL of deionized water, and 2 mL of ammonia were mixed in a 100 mL flask. Then, 0.2 mL of TEOS was added while stirring (600 rpm), and the mixture was reacted at 30 °C for 30 min. Next, 5 mL of TEOS was added, and the reaction was continued at 30 °C for 12 h. The precipitate was collected by centrifugation and washed twice with distilled water and ethanol, respectively. Finally, the powder was vacuum dried at 60 °C for 24 h.

[0035] (2) Preparation of SiO2@TRF nanospheres

[0036] Take 200 mg of the product from step (1) and place it in a 100 ml round-bottom flask. Add 25 ml of distilled water and sonicate to disperse it completely. Then, while stirring (600 rpm), add 150 μl of ammonia, 200 mg of resorcinol, and 260 mg of thiourea. After stirring for 20 min, add 280 μl of formaldehyde and 100 μl of TEOS, and stir the reaction at 30 °C for 24 h. Collect the product by centrifugation, wash it twice with distilled water and ethanol, respectively, and finally, dry the powder under vacuum at 60 °C for 24 h.

[0037] (3) Preparation of TRF-TEOS nanospheres

[0038] Take 50 mg of SiO2@TRF obtained in step (2) and place it in a centrifuge tube. Add 5 ml of 1% hydrofluoric acid aqueous solution and place it on a shaker for 1 h to etch. Collect the product by centrifugation and wash it twice with distilled water and ethanol, respectively. Finally, dry the powder under vacuum at 60 °C for 24 h.

[0039] Figure 1 This indicates that the microstructure of the material can be controlled by using different silane coupling agents;

[0040] Figure 2 This indicates that among TRF-TMOS, TRF-TEOS, and TRF-TPOS, TRF-TEOS exhibits the best adsorption performance.

[0041] Figure 3 The presence of the characteristic peak of the NC=S bond indicates successful doping of thiourea.

[0042] Example 2:

[0043] Preparation of TRF-TPOS:

[0044] (1) Preparation of 400nm SiO2 microspheres

[0045] First, mix 30 ml of ethanol, 5 ml of deionized water, and 2 ml of ammonia in a 100 ml flask. Then, while stirring (600 rpm), add 0.2 ml of TEOS and react at 30 °C for 30 min. Next, add 5 ml of TEOS and continue reacting at 25 °C for 12 h. Centrifuge to collect the precipitate, and wash twice with distilled water and ethanol, respectively. Finally, vacuum dry the powder at 60 °C for 24 h.

[0046] (2) Preparation of SiO2@TRF nanospheres

[0047] Take 200 mg of the product from step (1) and place it in a 100 ml round-bottom flask. Add 25 ml of distilled water and sonicate to disperse it completely. Then, while stirring (600 rpm), add 150 μl of ammonia, 200 mg (0.00182 mol) of resorcinol, and 260 mg (0.00342 mol) of thiourea. After stirring for 20 min, add 280 μl (0.00373 mol) of formaldehyde and 100 μl of TPOS, and stir the reaction at 30 °C for 24 h. Collect the product by centrifugation, wash it twice with distilled water and ethanol, respectively, and finally, dry the powder under vacuum at 60 °C for 24 h.

[0048] (3) Preparation of TRF-TPOS nanospheres

[0049] Take 50 mg of SiO2@TRF obtained in step (2) and place it in a centrifuge tube. Add 5 ml of 1% hydrofluoric acid aqueous solution and place it on a shaker for 1 h to etch. Collect the product by centrifugation and wash it twice with distilled water and ethanol, respectively. Finally, dry the powder under vacuum at 60 °C for 24 h.

[0050] Example 3

[0051] Fabrication of TRF-TMOS:

[0052] (1) Preparation of 400nm SiO2 microspheres

[0053] First, mix 30 ml of ethanol, 5 ml of deionized water, and 2 ml of ammonia in a 100 ml flask. Then, while stirring (600 rpm), add 0.2 ml of TEOS and react at 30 °C for 30 min. Next, add 5 ml of TEOS and continue reacting at 25 °C for 12 h. Centrifuge to collect the precipitate, and wash twice with distilled water and ethanol, respectively. Finally, vacuum dry the powder at 60 °C for 24 h.

[0054] (2) Preparation of SiO2@TRF nanospheres

[0055] Take 200 mg of the product from step (1) and place it in a 100 ml round-bottom flask. Add 25 ml of distilled water and sonicate to disperse it completely. Then, while stirring (600 rpm), add 150 μl of ammonia, 200 mg (0.00182 mol) of resorcinol, and 260 mg (0.00342 mol) of thiourea. After stirring for 20 min, add 280 μl (0.00373 mol) of formaldehyde and 100 μl of TMOS, and stir the reaction at 30 °C for 24 h. Collect the product by centrifugation, wash it twice with distilled water and ethanol, respectively, and finally, dry the powder under vacuum at 60 °C for 24 h.

[0056] (3) Preparation of TRF-TPOS nanospheres

[0057] Take 50 mg of SiO2@TRF obtained in step (2) and place it in a centrifuge tube. Add 5 ml of 1% hydrofluoric acid aqueous solution and place it on a shaker for 1 h to etch. Collect the product by centrifugation and wash it twice with distilled water and ethanol, respectively. Finally, dry the powder under vacuum at 60 °C for 24 h.

[0058] Experimental Example 1:

[0059] Eight 1 mg portions of TRF-TEOS prepared under the conditions described in Example 1 were accurately weighed and added to 3 mL of gold ion solutions with pH values ​​of 1, 2, 3, 4, 5, and 6, respectively, at a concentration of 1000 mg / L. The solutions were placed on a shaker at 25°C for 12 h for adsorption, and the supernatant was collected. The concentration of remaining gold ions in the solution was detected by inductively coupled plasma atomic emission spectrometry (ICP). Three parallel experiments were performed.

[0060] Figure 4 This indicates that TRF-TEOS achieves optimal adsorption performance at a pH of 5.

[0061] Experimental Example 2:

[0062] Accurately weigh 10 portions of 1 mg TRF-TEOS and add them to 3 mL of a 1000 mg / L gold ion solution with a pH of 6. Incubate the solution at 25°C on a shaker for adsorption at 5, 10, 15, 30, 60, 90, 120, 240, 480, and 720 min, collecting the supernatant each time. The concentration of remaining gold ions in the solution is detected by inductively coupled plasma atomic emission spectrometry (ICP). Perform three parallel experiments.

[0063] Figure 5 This indicates that the adsorption of gold by TRF-TEOS conforms to a pseudo-first-order kinetic model, suggesting that the adsorption process is mainly controlled by chemisorption.

[0064] Experimental Example 3:

[0065] Accurately weigh six 1 mg TRF-TEOS aliquots and add them to 5 mL of gold ion solutions (pH 5) with concentrations of 400, 500, 600, 700, 800, and 900 mg / L, respectively. Incubate the solutions at 25°C for 12 h on a shaker and collect the supernatant. Incubate the solutions at 35°C for 12 h on a shaker and collect the supernatant. Incubate the solutions at 45°C for 12 h on a shaker and collect the supernatant. The remaining gold ion concentration in the solutions is detected by inductively coupled plasma atomic emission spectrometry (ICP). Perform three parallel experiments.

[0066] Figure 6 The results show that the adsorption capacity of TRF-TEOS increases significantly with increasing temperature, indicating that the adsorption process has endothermic characteristics.

[0067] Experimental Example 4:

[0068] Accurately weigh 3 mg of TRF-TEOS prepared under the conditions described in Example 1, add 5 mL of actual test sample (pH=3) containing Au(III), Pd(II), Al(III), Co(II), Cr(III), Cu(II), Na(I), Ni(II), Zn(II) and other elements, which was leached from 10 g of waste circuit board using aqua regia. Place the sample on a shaker at 25 °C for 12 h for adsorption, collect the supernatant, and use inductively coupled plasma atomic emission spectrometry (ICP) to detect the remaining concentration of various ions in the solution. Perform two parallel experiments.

[0069] Figure 7 This indicates that TRF-TEOS achieved a gold recovery rate of 83.8%, which significantly exceeded the adsorption performance for other ions in the solution, demonstrating excellent selectivity for gold ions.

[0070] Experimental Example 5:

[0071] Accurately weigh 10 mg of TRF-TEOS and add 10 mL of a 300 mg / L gold ion solution with a pH of 5. Place the solution on a shaker at 25 °C for 12 h for adsorption. After collecting the supernatant, remove the solution and wash with deionized water. Add 10 mL of an eluent prepared from 1 mol / L thiourea and 0.1 mol / L hydrochloric acid and continue desorption on a shaker for 1.5 h. Centrifuge to collect the adsorbent, remove the solution, wash with deionized water and dry. This is one cycle, and a total of six cycles are performed. The concentration of the remaining gold ions in the solution is detected by inductively coupled plasma atomic emission spectrometry (ICP). Three sets of parallel experiments are performed.

[0072] Figure 8 The absorption efficiency remained at 93.8% after five absorption-desorption cycles, demonstrating the excellent durability and reusability of TRF-TEOS.

[0073] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A controllable preparation method for a nanocage-type thiourea-resorcinol-formaldehyde resin adsorbent, characterized in that, Includes the following steps: (1) Preparation of SiO2 microspheres First, a measured amount of ethanol, deionized water, and ammonia are mixed in a flask. Then, under a certain stirring speed r, a volume of V1 TEOS is added, and the reaction is carried out at a reaction temperature T1 for a period of time t1. Next, a volume of V2 TEOS is added, and the reaction is carried out at T1 for a period of time t2. The precipitate is collected by centrifugation and washed several times with distilled water and ethanol respectively. Finally, the powder is dried under vacuum. (2) Preparation of SiO2@TRF nanospheres Take the silica microspheres from step (1) and place them in a round-bottom flask. Add an appropriate amount of distilled water and sonicate them to disperse them completely. Add a quantitative amount of ammonia, resorcinol and thiourea while stirring. After stirring for a period of time t3, add a quantitative amount of formaldehyde and silane coupling agent. Stir and react for a period of time t4 at T2. Collect the product by centrifugation and wash it several times with distilled water and ethanol respectively. Finally, dry the powder under vacuum to obtain SiO2@TRF. The ratio of silica microspheres, resorcinol, formaldehyde, thiourea, ammonia, silane coupling agent, and deionized water is 200 mg: 0.00182 mol: 0.00373 mol: 0.00342 mol: 150 µl: 100 µl: 25-30 mL; T2 is 30 °C, reaction time t3 is 20 min, and reaction time t4 is 24 h; (3) Preparation of TRF nanospheres Take the SiO2@TRF obtained in step (2) and place it in a centrifuge tube. Add a certain amount of hydrofluoric acid aqueous solution and etch it for a period of time t5 under shaking. Centrifuge to collect the product and wash it several times with distilled water and ethanol respectively. Finally, vacuum dry the powder.

2. The controllable preparation method of the nanocage-type thiourea-resorcinol-formaldehyde resin adsorbent as described in claim 1, characterized in that, In step (1), the ratio of the amount of ethanol, water, ammonia and silane coupling agent is 30mL:5mL:2mL:5.2mL, and the volume ratio of V1 to V2 is 0.2:

5.

3. The controllable preparation method of the nanocage-type thiourea-resorcinol-formaldehyde resin adsorbent as described in claim 1, characterized in that, In step (1), T1 is 25-30℃, reaction time t1 is 20-30 min, and reaction time t2 is 12 h.

4. The controllable preparation method of the nanocage-type thiourea-resorcinol-formaldehyde resin adsorbent as described in claim 1, characterized in that, In step (2), the type of silane coupling agent is tetramethoxysilane TMOS, tetraethoxysilane TEOS, or tetrapropoxysilane TPOS.

5. The controllable preparation method of the nanocage-type thiourea-resorcinol-formaldehyde resin adsorbent as described in claim 1, characterized in that, In step (3), the ratio of SiO2@TRF to hydrofluoric acid aqueous solution is 50 mg: 5 mL, wherein the concentration of hydrofluoric acid is 1%wt, and the reaction time t5 is 0.5-3 h.

6. The use of the nanocage-type thiourea-resorcinol-formaldehyde resin adsorbent prepared by the preparation method according to any one of claims 1 to 5 for the selective adsorption and separation of gold ions in solution.

Images