Preparation Method of Zirconium Phosphate Confined Carbon Nanotube Material and Its Application as Adsorbent in Adsorbing In(Ⅲ) Ions

Abstract

The present invention relates to a preparation method of a zirconium phosphate-confined carbon nanotube material and its application as an adsorbent in the adsorption of In(III) ions. The technical solution adopted is as follows: First, an appropriate amount of carbon nanotubes is dissolved in a mixed acid of sulfuric acid and nitric acid, refluxed in a water bath, filtered until neutral, and the material is dried to obtain acidified carbon nanotubes (CNT). A certain amount of ZrOCl2·8H2O is weighed into a sample tube, an appropriate amount of absolute ethanol is added, and it is ultrasonically dissolved. A certain amount of CNT is weighed into a petri dish, and the ethanol solution of ZrOCl2·8H2O is added dropwise to the above petri dish using a dropper, and ultrasonically mixed evenly; then it reacts at room temperature for a period of time, the ethanol is evaporated, and then 5M phosphoric acid solution is added. After soaking for a certain time, it is washed until neutral and dried to obtain the product, namely zirconium phosphate-confined carbon nanotubes n-ZrP@CNT (where n is the mass ratio of ZrP to CNT). The composite material prepared by the present invention can be used as an adsorbent for the recovery of trivalent indium in electronic waste or minerals, and has the characteristics of high adsorption efficiency and good selectivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of composite materials and adsorption of In(III), and specifically relates to a preparation method of zirconium phosphate confined carbon nanotube material and application of the material as an adsorbent in adsorbing In(III) ions. Background Art

[0002] Indium is a rare metal widely used in high-tech applications such as electronic displays due to its excellent electrical conductivity. Its irreplaceable nature has led to its designation as a critical raw material and strategic reserve by the European Union. However, existing proven indium resources are extremely limited, with no independent deposits. Indium is often found in association with other minerals. The recycling value of indium is typically determined by whether the raw material contains greater than 0.002%. Research has found that the indium content in electronic displays is approximately 0.03%, making it extremely valuable for recycling. Therefore, developing a method for efficiently recovering indium from electronic displays and minerals is crucial.

[0003] Adsorption methods are simple to operate and suitable for recovering low-trace components in multi-component solutions. Based on the functional groups that act as adsorbents, indium adsorbents can be divided into four categories: hydroxyl, carboxyl, amino, and phosphate. The hydrogen ions on the phosphate group (P-OH) readily ionize, giving the material a negative charge. This allows for ion exchange with metal cations through electrostatic attraction, making it the most common adsorbent functional group on indium.

[0004] There are many types of adsorbents. Carbon materials are commonly used as adsorbent matrices due to their stable chemical properties and ease of modification. Carbon materials are generally divided into one-dimensional carbon materials, two-dimensional carbon materials, and three-dimensional carbon materials.

[0005] Nanoconfinement can improve the adsorption selectivity of the material by limiting the guest material in a certain space, and then limiting the growth of the guest material, and the P-OH of the phosphate group on the zirconium phosphate can selectively adsorb metal ions. Carbon nanotubes have good internal cavity structure and unique electronic tuning characteristics, which provide an ideal microenvironment for the nanoconfinement environment, and carbon nanotubes are typical one-dimensional carbon materials. Compared with two-dimensional and three-dimensional carbon materials, the stability of one-dimensional materials is higher, which is conducive to improving the recycling performance of the adsorption material. Therefore, the present invention adopts one-dimensional carbon nanotube materials as the matrix material of confinement, selects a top-down synthesis method, and prepares a nanoconfinement material of zirconium phosphate confined carbon nanotubes to improve the adsorption capacity, adsorption selectivity, adsorption recycling performance, and dynamic adsorption performance of indium. Summary of the Invention

[0006] The present invention mainly focuses on the modification research of carbon-based materials. Using carbon nanotubes as a carbon source, a nano-confined material of zirconium phosphate @ carbon nanotubes is prepared by a top-down synthesis method. The present invention has excellent adsorption performance, is easy to operate, and has extremely high practical value.

[0007] The present invention is realized through the following technical solutions:

[0008] For the zirconium phosphate-confined carbon nanotube material, ZrP grows in-situ on the matrix material CNT to obtain the composite material n-ZrP@CNT.

[0009] The preparation method of the above-mentioned zirconium phosphate-confined carbon nanotube material includes the following steps:

[0010] 1) Dissolve carbon nanotubes in a mixed acid of sulfuric acid and nitric acid, carry out water bath reflux, filter until neutral, and dry to obtain acidified carbon nanotubes CNT.

[0011] 2) Place ZrOCl2·8H2O in a sample tube, add absolute ethanol, and ultrasonically dissolve to obtain an ethanol solution of ZrOCl2·8H2O.

[0012] 3) Place the CNT obtained in step 1) in a petri dish, use a dropper to add the ethanol solution of ZrOCl2·8H2O to the above petri dish, and ultrasonically mix it evenly; then react at room temperature. Wait until the ethanol evaporates completely, and then add an excess of 5M phosphoric acid solution to soak. At this time, ZrP gradually grows in-situ on the surface or inside the tube of CNT; wash the obtained material until neutral, and dry to obtain the target product n-ZrP@CNT.

[0013] Further, in the preparation method of the above-mentioned zirconium phosphate-confined carbon nanotube material, in step 1), the mass of the carbon nanotubes is 380 - 430 mg, and by volume ratio, sulfuric acid: nitric acid = 3:1.

[0014] Further, in the preparation method of the above-mentioned zirconium phosphate-confined carbon nanotube material, in step 1), the temperature of the water bath reflux is 30 - 50 °C, and the reaction time is 1 - 3 h.

[0015] Further, in the preparation method of the above-mentioned zirconium phosphate-confined carbon nanotube material, in steps 1) and 3), the drying temperature is 35 - 55 °C, and the drying time is 20 - 24 h.

[0016] Further, in the preparation method of the above-mentioned zirconium phosphate-confined carbon nanotube material, in step 2), the mass of ZrOCl2·8H2O is 40 - 90 mg, and the amount of absolute ethanol used is 4 - 8 mL.

[0017] Further, in the preparation method of the above-mentioned zirconium phosphate-confined carbon nanotube material, in step 3), the mass of CNT is 10 - 250 mg.

[0018] Further, in the preparation method of the above-mentioned zirconium phosphate-confined carbon nanotube material, in step 3), the reaction time at room temperature is 22 - 40 h, and the soaking time is 24 - 48 h.

[0019] Application of the above-mentioned zirconium phosphate-confined carbon nanotube material as an adsorbent in the adsorption of indium(III).

[0020] Further, for the above-mentioned application, the method is as follows: in a solution containing indium(III), adjust the pH to 1 - 3.5, add the zirconium phosphate-confined carbon nanotube material, and shake at 303 K for 24 h.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. In the adsorbent n-ZrP@CNT, the hydrogen ions on the phosphate group P-OH of zirconium phosphate ionize, making the material negatively charged. Through electrostatic attraction, the positively charged In 3+ ions in the solution are successfully adsorbed, and a cation exchange reaction occurs.

[0023] 2. The synthesis of the present invention is simple. First, the carbon nanotubes are acidified with a mixed acid, and then zirconium phosphate is confined in the carbon nanotubes by a top-down synthesis method to obtain the adsorbent n-ZrP@CNT.

[0024] 3. The adsorbent n-ZrP@CNT prepared by the present invention has excellent adsorption performance, and the adsorption effect on In(III) is the best when pH = 2.5.

[0025] 4. In the present invention, when pH = 2.5, the saturated adsorption capacity of the adsorbent 2.5-ZrP@CNT for In(III) can reach 173.19 mg·g -1 , and the dynamic saturated adsorption capacity is 58.26 mg·g -1 , and it can be eluted seven times in cycles, with particularly prominent adsorption ability.

[0026] 5. The adsorbent 2.5-ZrP@CNT prepared by the present invention can effectively adsorb In(III), and can successfully separate indium and iron in waste electronic displays, with good selectivity and strong practical application ability. Description of the Drawings

[0027] Figure 1 (a) is the transmission electron microscope image of non-in-situ grown ZrP in Example 1; Figure 1 (b) is the transmission electron microscope image of CNT prepared in Example 1; Figure 1 (c - d) are the transmission electron microscope images of 2.5-ZrP@CNT prepared in Example 1.

[0028] Figure 2X-ray diffraction patterns of CNT prepared in Example 1, in-situ grown ZrP, and 2.5-ZrP@CNT.

[0029] Figure 3 (a) N2 adsorption-desorption isotherm and pore size distribution diagram of CNT prepared in Example 1; Figure 3 (b) N2 adsorption-desorption isotherm and pore size distribution diagram of 2.5-ZrP@CNT prepared in Example 1.

[0030] Figure 4 (a) Saturated adsorption isotherm of In(Ⅲ) by CNT prepared in Example 1; Figure 4 (b) Saturated adsorption isotherm of In(Ⅲ) by in-situ grown ZrP in Example 1; Figure 4 (c) Saturated adsorption isotherm of 0.2-ZrP@CNT prepared in Example 1; Figure 4 (d) Saturated adsorption isotherm of In(Ⅲ) by 0.3-ZrP@CNT prepared in Example 1; Figure 4 (e) Saturated adsorption isotherm of In(Ⅲ) by 1-ZrP@CNT prepared in Example 1; Figure 4 (f) Saturated adsorption isotherm of In(Ⅲ) by 2-ZrP@CNT prepared in Example 1; Figure 4 (g) Saturated adsorption isotherm of In(Ⅲ) by 2.5-ZrP@CNT prepared in Example 1; Figure 4 (h) Saturated adsorption isotherm of In(Ⅲ) by 3.3-ZrP@CNT prepared in Example 1; Figure 4 (i) Saturated adsorption isotherm of In(Ⅲ) by 5-ZrP@CNT prepared in Example 1.

[0031] Figure 5 Variation diagrams of the adsorption capacities of 0.2-ZrP@CNT, 0.3-ZrP@CNT, 1-ZrP@CNT, 2-ZrP@CNT, 2.5-ZrP@CNT, 3.3-ZrP@CNT, and 5-ZrP@CNT prepared in Example 1 for In(Ⅲ) at different acidities.

[0032] Figure 6 (a) Elution rate of In(Ⅲ) by 2.5-ZrP@CNT prepared in Example 1 under different concentrations of eluent; Figure 6 (b) Recycling performance of 2.5-ZrP@CNT prepared in Example 1 for adsorbing In(Ⅲ).

[0033] Figure 7 Dynamic adsorption breakthrough curve of 2.5-ZrP@CNT prepared in Example 1 for In(Ⅲ).

[0034] Figure 8 (a) XPS survey spectra of 2.5-ZrP@CNT prepared in Example 1 before and after adsorbing In(III). Figure 8 (b) In 3d characteristic peak spectra of 2.5-ZrP@CNT prepared in Example 1 after adsorbing In(III). Figure 8 (c) O1s characteristic peak spectra of 2.5-ZrP@CNT prepared in Example 1 before adsorbing In(III). Figure 8 (d) O1s characteristic peak spectra of 2.5-ZrP@CNT prepared in Example 1 after adsorbing In(III).

[0035] Figure 9 Mechanism diagram of 2.5-ZrP@CNT as an adsorbent for adsorbing In(III).

[0036] Figure 10 Synthesis route diagram of zirconium phosphate-confined carbon nanotube material n-ZrP@CNT. Detailed implementation mode

[0037] Example 1 Zirconium phosphate-confined carbon nanotube material n-ZrP@CNT

[0038] The synthesis route of zirconium phosphate-confined carbon nanotube material n-ZrP@CNT is as Figure 10 shown.

[0039] (I) Preparation method

[0040] 1) Accurately weigh 0.4 g of carbon nanotubes with a diameter of 4 - 6 nm into a 250 mL single-neck flask, measure 75 mL of commercially available sulfuric acid and 25 mL of concentrated nitric acid, pour them into the flask, sonicate for half an hour, mix evenly, then place it in a heating mantle and reflux at 40 °C for 2 h; filter and wash until neutral, and dry at 50 °C for 24 h to obtain acidified carbon nanotubes CNT.

[0041] 2) Accurately weigh 50 mg of ZrOCl2·8H2O into a 5 mL sample tube, then add 5 mL of absolute ethanol to this sample tube and sonicate until the solution is clear to obtain an ethanol solution of ZrOCl2·8H2O.

[0042] 3) Weigh 10 mg, 15 mg, 20 mg, 25 mg, 50 mg, 150 mg, and 250 mg of the CNT obtained in step 1) on an analytical balance into a petri dish (with a diameter of 35 mm). Then, use a dropper to add an ethanol solution of ZrOCl₂·8H₂O to the above petri dish, ultrasonically mix evenly, and then react at room temperature for 24 h. Wait until the absolute ethanol has completely evaporated, and then add an excessive amount of 5 M phosphoric acid solution and soak for 24 h. ZrP grows in-situ on the surface or inside the CNT. Wash until neutral and dry at 50 °C for 24 h to obtain the target products, which are denoted as 0.2-ZrP@CNT, 0.3-ZrP@CNT, 1-ZrP@CNT, 2-ZrP@CNT, 2.5-ZrP@CNT, 3.3-ZrP@CNT, and 5-ZrP@CNT respectively.

[0043] 4) Preparation method of non-in-situ grown zirconium phosphate (ZrP):

[0044] ① Prepare 5 M phosphoric acid solution: Measure 33 mL of commercially available phosphoric acid, dilute it in a beaker, and then transfer it to a 100 mL volumetric flask with a glass rod. Make up the volume with deionized water to prepare a 5 M phosphoric acid solution.

[0045] ② Prepare 2 M hydrochloric acid solution: Measure 16.7 mL of concentrated hydrochloric acid and prepare a 100 mL hydrochloric acid solution with a concentration of 2 M.

[0046] ③ Weighing: Accurately weigh 3.0000 g of ZrOCl₂·8H₂O on a balance and place it in a 250 mL single-neck flask.

[0047] ④ Ultrasonic treatment: Place the prepared 2 M hydrochloric acid solution in the above single-neck flask and ultrasonicate until ZrOCl₂·8H₂O is completely dissolved.

[0048] ⑤ Water bath: Place the above single-neck flask in a water bath, and then slowly add the 5 M phosphoric acid solution prepared in step ① to this single-neck flask by controlling the dropping rate with a dropper. During the experiment, add ice packs to ensure that the water bath temperature is 0 °C, and at the same time, keep this reaction at this temperature for 48 h.

[0049] ⑥ Centrifugation: Centrifuge the material after the water bath with deionized water and absolute ethanol repeatedly until the acidity is neutral. Vacuum dry at 60 °C for a certain period of time to obtain the final product ZrP.

[0050] Tables 2, 3, Figure 1 and Figure 2 and Figure 4 In the above, ZrP all refers to the non-in-situ grown zirconium phosphate synthesized in the above steps.

[0051] (II) Detection

[0052] 1. The products prepared in Example 1 were characterized by transmission electron microscopy, X-ray diffraction, and N2 adsorption, as Figure 1 , Figure 2 and Figure 3 shown. From the Figure 1 transmission electron micrograph, we can see that the grain size of zirconium phosphate alone is approximately 64 nm. Then, a nitrogen adsorption test was carried out, as Figure 3 and Table 1 show. It was found that the pore size of the carbon nanotubes after confinement decreased from 5.04 nm to 3.33 nm, proving that the in-situ growth of zirconium phosphate may block some pores, resulting in a decrease in the average pore size of the composite material. It can also be found from the transmission electron micrograph that the size of zirconium phosphate after confinement decreased to about 3 - 4 nm. Therefore, we believe that there is a possibility of confining zirconium phosphate into the carbon nanotubes. Figure 2 The XRD pattern of

[0053] shows that it is α-type zirconium phosphate. -1 2. Method for adsorbing In(III): Prepare indium(III) solutions with concentrations of 20, 50, 100, 150, 200, 300, 400, and 500 mg·L Figure 4 . Adjust the pH of the solution to 2.5, add 2.5-ZrP@CNT at a solid-liquid ratio of 1 mg:1 mL, and shake and adsorb at 303 K for 24 h. Then filter, and determine the concentration of In(III) in the filtrate by atomic absorption spectrometer. Fit the data through three adsorption isotherm models, namely Langmuir, Freundlich, and Temkin, calculate the adsorption capacity, and draw the adsorption isotherm curve, as 2 shown. By comparing the correlation coefficient R -1 , it can be known that the adsorption process of 2.5-ZrP@CNT for In(III) conforms to the Langmuir model, which is a single-molecule adsorption process. The maximum saturated adsorption capacity of 2.5-ZrP@CNT for In(III) can reach 173.19 mg·g

[0054] 3. Method for recycling-eluting In(III): Accurately weigh 5 mg of the adsorbent on an analytical balance into a shaking vial, add the In(III) solution at a solid-liquid ratio of 1:1, mix well, and place the vial in a constant-temperature shaking incubator and shake until adsorption saturation. Then filter and retain the filtrate for further testing; then dry the filtered adsorbent material, add different eluents at a solid-liquid ratio of 1:1 for elution, shake and filter again under the same conditions, collect the filtrate, and determine the concentration of In(III) by atomic absorption spectrometer. As can be seen from Figure 6 (a), nitric acid, sulfuric acid, and hydrochloric acid were used for elution experiments in this experiment. Among them, nitric acid has the best elution efficiency. When the concentration of nitric acid is 1 M, the elution efficiency can reach more than 90%; Figure 6 As can be seen from

[0055] (b), this material can be recycled-eluted 7 times, and the adsorption efficiency is above 92% each time.4. Method for dynamic adsorption of In(III): First, add an appropriate amount of quartz sand into the adsorption column, and the height of the added quartz sand is close to half of the height of the adsorption column; then add a little cotton (note that it should not be compacted and only needs to be in contact with the quartz sand); then add 50 mg of adsorbent into the column; continue to add cotton and quartz sand in sequence, and finally the height of the filled quartz sand is slightly lower than the height of the water outlet of the adsorption column, and the column loading process is completed. Adsorption process: First, pass in a certain amount of water to ensure the normal flow of the adsorption column, and then pass in the In(III) solution, and adjust the flow rate to 11.32 mL·h -1 , collect the effluent with a receiver, and measure the indium ion concentration in the effluent. It can be calculated that the maximum dynamic saturation adsorption capacity of 2.5-ZrP@CNT for In(III) can reach 58.26 mg·g -1 .

[0056] 5. Selective adsorption method of In(III): Weigh the nitrates corresponding to each metal and dissolve them in water to make a certain concentration. Then adjust the acidity of the mixed solution with a certain concentration of HNO3 and NaOH, and prepare and store it for later use. Weigh the adsorbent and the mixed solution according to the solid-liquid ratio of 1:1 in a small bottle, shake well, filter, and then use an inductively coupled plasma emission spectrometer to measure the concentration of each metal ion. The results are shown in Tables 2 and 3. Whether in the LCD simulated feed liquid or in the sphalerite simulated feed liquid, the selective adsorption performance of the composite material 2.5-ZrP@CNT is significantly better than that of ZrP itself, and in the LCD simulated feed liquid, 2.5-ZrP@CNT can successfully separate In(III) from Fe(III).

[0057] 6. It can be seen from Figure 8 (a - d) that the O1s before the adsorption of 2.5-ZrP@CNT can be fitted into four peaks of C=O(531.57 eV), C - O(533.46 eV), P=O(530.99 eV), and P - O(532.50 eV). After adsorption, an O - In peak appears at 530.88 eV; and the binding energy of P=O shifts to 531.34 eV respectively; the binding energy of P - O shifts to 532.15 eV respectively. The appearance of the In 3d characteristic peak in the XPS spectrum and the changes in the positions of the P - O and P=O peaks in the O 1s characteristic peak both indicate that the phosphate group has interacted with In(III), that is, the hydrogen ions on P - OH in 2.5-ZrP@CNT are ionized, making 2.5-ZrP@CNT negatively charged, and the positively charged In in the solution is successfully adsorbed through positive and negative electrostatic attraction 3+ ions, and cation exchange occurs.

[0058] Table 1 Summary of pore structure parameters of CNT and 2.5-ZrP@CNT prepared in Example 1

[0059]

[0060] Table 2 Selectivity factors of 2.5-ZrP@CNT and ZrP prepared in Example 1 in the simulated LCD feed solution for the mixed metal ion solution

[0061]

[0062] Table 3 Selectivity factors of 2.5-ZrP@CNT and ZrP prepared in Example 1 in the sphalerite simulated feed solution for the mixed metal ion solution

[0063]

[0064] Example 2 Adsorption of In(Ⅲ) by the zirconium phosphate-confined carbon nanotube material 2.5-ZrP@CNT

[0065] Method: Take a trivalent indium solution containing 20 mg·L -1 , adjust the pH to 1 - 3.5, and add the zirconium phosphate-confined carbon nanotube material 2.5-ZrP@CNT prepared in Example 1 according to the solid-liquid ratio of 1 mg:1 mL, and shake and adsorb at 303 K for 24 h.

[0066] Adsorption method: Take a trivalent indium solution containing 20 mg·L -1 , adjust the pH to 1, 1.5, 2, 2.5, 3, 3.5 respectively, and add a series of adsorbents n-ZrP@CNT prepared in Example 1 according to the solid-liquid ratio of 1 mg:1 mL, and shake and adsorb at 303 K for 24 h. Measure the adsorption efficiency, and the results are as Figure 5 shown. The adsorption trends of a series of zirconium phosphate-confined carbon nanotube materials are the same, that is, as the pH increases, the adsorption efficiency first increases and then levels off. Because the actual indium feed solution is acidic, the optimal adsorption acidity is selected as pH = 2.5.

Claims

1. Application of zirconium phosphate-confined carbon nanotube material as an adsorbent in adsorbing indium(III), characterized in that, The method is as follows: In a solution containing trivalent indium, adjust the pH to 1 - 3.5, add the zirconium phosphate-confined carbon nanotube material, and shake at 303 K for 24 h; The zirconium phosphate-confined carbon nanotube material is ZrP in-situ grown on the matrix material CNT to obtain the composite material n-ZrP@CNT.

2. The application according to claim 1, characterized in that, The preparation method of the zirconium phosphate-confined carbon nanotube material includes the following steps: 1) Dissolve carbon nanotubes in a mixed acid of sulfuric acid and nitric acid, carry out water bath reflux, filter until neutral, and dry to obtain acidified carbon nanotubes CNT; 2) Place ZrOCl2·8H2O in a sample tube, add absolute ethanol, and dissolve it by ultrasonic treatment to obtain an ethanol solution of ZrOCl2·8H2O; 3) Place the CNT obtained in step 1) in a petri dish, use a dropper to add the ethanol solution of ZrOCl2·8H2O to the above petri dish, and mix them evenly by ultrasonic treatment; then react at room temperature until the ethanol has completely evaporated, and then add an excessive amount of 5 M phosphoric acid solution to soak, at this time ZrP gradually grows in-situ on the surface or inside the tube of CNT; wash the obtained material until neutral, and dry to obtain the target product n-ZrP@CNT.

3. The application according to claim 2, wherein In step 1), the mass of the carbon nanotubes is 380 - 430 mg, and by volume ratio, sulfuric acid:nitric acid = 3:

1.

4. The application according to claim 2, characterized in that, In step 1), the temperature of the water bath reflux is 30 - 50 °C, and the reaction time is 1 - 3 h.

5. The application according to claim 2, characterized in that, In steps 1) and 3), the drying temperature is 35 - 55 °C, and the drying time is 20 - 24 h.

6. The application according to claim 2, wherein In step 2), the mass of ZrOCl2·8H2O is 40 - 90 mg, and the amount of absolute ethanol used is 4 - 8 mL.

7. The application according to claim 2, characterized in that, In step 3), the mass of CNT is 10 - 250 mg.

8. The application according to claim 2, characterized in that, In step 3), the reaction time at room temperature is 22 - 40 h, and the soaking time is 24 - 48 h.

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