A method for preparing cadmium-removing functionalized oyster shell material and its product

Abstract

This invention provides a method for preparing cadmium-removing functionalized oyster shell material and its product. The method comprises the following steps: (1) Oyster shells are soaked in dilute hydrochloric acid and sodium hydroxide solution, then washed with water, dried in a drying oven, cooled, and ground into 100-120 mesh oyster shell powder (OS) for later use; (2) A certain amount of oyster shell powder is weighed, and 3-mercaptopropyltriethoxysilane (MPTES) is added dropwise at 50-130°C using toluene as the reaction solvent. After the reaction is completed by magnetic stirring and reflux, the powder is thoroughly washed with acetone and ethanol, and dried in a vacuum drying oven to obtain mercapto-functionalized oyster shell material (MPTES-OS). The preparation method of this invention has a short cycle and fewer steps, making it more practical. This invention is the first to use MPTES to modify oyster shells with mercapto groups. The prepared product improves the cadmium removal efficiency of the material, and the material also has good stability and reusability, providing more material options for cadmium removal.

Description

[Technical Field]

[0001] This invention relates to the fields of resource utilization and environmental pollution control, and specifically to a method for preparing cadmium-removing functionalized oyster shell materials. [Background Technology]

[0002] Cadmium, a highly toxic heavy metal, poses a significant potential threat to the health of animals, plants, and humans. Methods for treating cadmium-containing wastewater include chemical precipitation, membrane separation, biological treatment, and adsorption. Among these, adsorption is one of the most commonly used water treatment methods. Commonly used adsorbents in adsorption include zeolite, activated carbon, clay, and modified starch. Oyster shells, which pose a pollution risk, are calcite-type shells and have some effect on cadmium removal, offering advantages such as stable raw material sources, low price, and safety (non-toxicity). However, their cadmium removal efficiency needs improvement. Oyster shells have a unique physical structure containing various organic and inorganic components. Modification can create numerous functional porous structures, giving them strong adsorption, bioloading, and catalytic decomposition properties. Therefore, to improve the adsorption capacity of oyster shells for cadmium ions, modification of oyster shells is necessary.

[0003] Currently, there are two main methods for modifying oyster shells. One method involves physical modifications such as grinding, ultrasonic treatment, and high-temperature calcination to increase the specific surface area and porosity of the oyster shells, thereby improving their adsorption properties. For example, Chinese patent CN201310705734.5 discloses a soil conditioner made from shell powder, composed of the following components by weight: 60-70 parts shell powder, 20-30 parts quicklime, and 2-10 parts wood ash. Further, it also includes 2-7 parts bentonite by weight. This method involves calcining natural oyster shells at 900-1100℃ and then mixing them with pretreated quicklime and wood ash in a certain proportion to prepare the soil conditioner, which improves the soil's structure and physicochemical properties. Another Chinese patent, CN200810012691.1, discloses a water purifier made from seashells and its application method. The method involves crushing the seashells and heating them at 1000–3000℃ to prepare the water purifier, which can increase the pH of the water to prevent the growth of green algae. When used after vacuum oxygenation, it can also enrich the oxygen in freshwater and kill harmful bacteria. Secondly, by adding coupling agents, surfactants, and other modifiers to modify oyster shell powder, grafting functional groups onto the pore surface of the oyster shell enhances its affinity for pollutants. The modified material can improve its adsorption and selectivity, showing broad application prospects. For example, by immobilizing fulvic acid onto oyster shells using a solid-phase grafting method, the resulting modified oyster shell powder can improve the fermentation efficiency of aerobic composting and significantly reduce nitrogen loss (Patent No.: CN201911342688.0); modifying oyster shells with sodium dodecyl sulfonate (SDS) introduces sulfur (S) and establishes S=O bonds, enhancing the oyster shell's adsorption capacity for cadmium. However, existing oyster shell modification processes are complex, involve numerous steps, and have long cycles. Furthermore, there are currently no literature reports on the modification of oyster shells using 3-mercaptopropyltriethoxysilane (MPTES).

[0004] The inventor's prior patent (patent number: CN201910326440.9) discloses a novel oyster shell-based cadmium ion-imprinted material, its preparation method, and its application. The method involves first treating oyster shells with an aluminate coupling agent to improve acid resistance, then coupling and grafting γ-aminopropyltriethoxysilane onto the surface of oyster shell micropowder, and finally performing surface imprinting to further enhance the material's selectivity for cadmium. Through a series of complex processes, an oyster shell-based cadmium ion-imprinted material with good adsorption selectivity for cadmium is obtained. The inventor discovered that the oyster shell modification process was complex, involved many steps, and had a long cycle, leading to the development of this application during later research and development. [Summary of the Invention]

[0005] The technical problem to be solved by the present invention is to provide a method for preparing cadmium-removing functionalized oyster shell material and the product thereof. The preparation method has a short cycle and fewer steps, which can greatly reduce production costs and has greater practicality. The prepared product improves the cadmium removal efficiency of the material, and the material also has good stability and reusability, providing more material options for cadmium removal.

[0006] This invention is implemented as follows:

[0007] A method for preparing cadmium-removing functionalized oyster shell material, the method comprising the following steps:

[0008] (1) Soak oyster shells in dilute hydrochloric acid and sodium hydroxide solution, then wash them with water, dry them in a drying oven, cool them and grind them into 100-120 mesh oyster shell powder for later use.

[0009] (2) Weigh a certain amount of oyster shell powder, use toluene as the reaction solvent, add 3-mercaptopropyltriethoxysilane MPTES dropwise at 50-130℃, after the magnetic stirring and reflux reaction is completed, wash thoroughly with acetone and ethanol, put it in a vacuum drying oven to dry, and obtain mercapto-functionalized oyster shell material MPTES-OS.

[0010] Furthermore, in step (1), the concentration of dilute hydrochloric acid is 5%, the concentration of sodium hydroxide solution is 5%, and the drying temperature is 80°C.

[0011] Further, in step (2), 10g of oyster shell powder is weighed, 100mL of toluene is used, 0.05-0.4mL of MPTES is used, the modification time is 12h, and the drying temperature is 80℃.

[0012] Furthermore, a cadmium-removing functionalized oyster shell material is provided, wherein the cadmium-removing functionalized oyster shell material is prepared by the aforementioned method for preparing cadmium-removing functionalized oyster shell material.

[0013] The present invention has the following advantages:

[0014] This invention involves soaking oyster shells in acidic and alkaline solutions to increase their specific surface area and porosity, exposing more grafting sites. The use of MPTES silane coupling agent introduces -SH functional groups with deprotonating effects, increasing the surface-active binding sites and enhancing the material's affinity for cadmium. Compared to raw oyster shells, the thiol-functionalized oyster shell material of this invention enhances its affinity for cadmium through ion exchange, electrostatic attraction, and surface complexation, thus improving cadmium removal performance. The material also reduces the impact of interfering ions on cadmium removal performance, improving its stability and reusability, and providing more material options for cadmium removal. The preparation method of this invention has a short cycle and fewer steps, significantly reducing production costs and making it more practical. [Attached Image Description]

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] Figure 1 These are SEM images of the OS and MPTES-OS in an embodiment of the present invention.

[0017] Figure 2 These are XRD diagrams of the OS and MPTES-OS in embodiments of the present invention.

[0018] Figure 3 These are FT-IR diagrams of the OS and MPTES-OS in an embodiment of the present invention.

[0019] Figure 4 These are the XPS spectra of MPTES-OS(a), the high-resolution spectra of S2p(b), and the high-resolution spectra of Si2p(c) according to embodiments of the present invention.

[0020] Figure 5 This is a Zeta potential diagram of MPTES-OS at different pH values ​​according to an embodiment of the present invention.

[0021] Figure 6 This is a graph showing the effect of pH value on the adsorption of Cd(II) by OS and MPTES-OS in an embodiment of the present invention.

[0022] Figure 7 This is a graph showing the effect of reaction time on the adsorption of Cd(II) by OS and MPTES-OS in an embodiment of the present invention.

[0023] Figure 8 This is a reusability diagram of the OS and MPTES-OS in an embodiment of the present invention.

[0024] Figure 9 This is a diagram showing the effect of interfering ions on the adsorption of Cd(II) by OS and MPTES-OS according to an embodiment of the present invention.

Detailed Implementation Methods

[0025] The following will be combined with the appendix Figure 1-9 The technical solution of the present invention will be clearly and completely described in detail with specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0026] Example 1

[0027] (1) Soak oyster shells in dilute hydrochloric acid and sodium hydroxide solution, then wash them with clean water, dry them at 80°C, cool them and grind them into 100-120 mesh oyster shell powder (OS) for later use.

[0028] (2) Weigh 10g of oyster shell powder into a three-necked flask, use toluene as the reaction solvent, add 0.1mL of 3-mercaptopropyltriethoxysilane (MPTES) dropwise at 70℃, stir magnetically and reflux, react for 12h, wash thoroughly with acetone and ethanol, and dry in a vacuum drying oven at 80℃ to obtain mercapto-functionalized oyster shell material (MPTES-OS).

[0029] Example 2

[0030] (1) Soak oyster shells in dilute hydrochloric acid and sodium hydroxide solution, then wash them with clean water, dry them at 80°C, cool them and grind them into 100-120 mesh oyster shell powder (OS) for later use.

[0031] (2) Weigh 10g of oyster shell powder into a three-necked flask, use toluene as the reaction solvent, add 0.05mL of 3-mercaptopropyltriethoxysilane (MPTES) dropwise at 70℃, stir magnetically and reflux, react for 12h, wash thoroughly with acetone and ethanol, and dry in a vacuum drying oven at 80℃ to obtain mercapto-functionalized oyster shell material (MPTES-OS).

[0032] Example 3

[0033] (1) Soak oyster shells in dilute hydrochloric acid and sodium hydroxide solution, then wash them with clean water, dry them at 80°C, cool them and grind them into 100-120 mesh oyster shell powder (OS) for later use.

[0034] (2) Weigh 10g of oyster shell powder into a three-necked flask, use toluene as the reaction solvent, add 0.2mL of 3-mercaptopropyltriethoxysilane (MPTES) dropwise at 70℃, stir magnetically and reflux, react for 12h, wash thoroughly with acetone and ethanol, and dry in a vacuum drying oven at 80℃ to obtain mercapto-functionalized oyster shell material (MPTES-OS).

[0035] Example 4

[0036] (1) Soak oyster shells in dilute hydrochloric acid and sodium hydroxide solution, then wash them with clean water, dry them at 80°C, cool them and grind them into 100-120 mesh oyster shell powder (OS) for later use.

[0037] (2) Weigh 10g of oyster shell powder into a three-necked flask, use toluene as the reaction solvent, add 0.3mL of 3-mercaptopropyltriethoxysilane (MPTES) dropwise at 70℃, stir magnetically and reflux, react for 12h, wash thoroughly with acetone and ethanol, and dry in a vacuum drying oven at 80℃ to obtain mercapto-functionalized oyster shell material (MPTES-OS).

[0038] Example 5

[0039] (1) Soak oyster shells in dilute hydrochloric acid and sodium hydroxide solution, then wash them with clean water, dry them at 80°C, cool them and grind them into 100-120 mesh oyster shell powder (OS) for later use.

[0040] (2) Weigh 10g of oyster shell powder (OS) into a three-necked flask, use toluene as the reaction solvent, add 0.4mL of 3-mercaptopropyltriethoxysilane (MPTES) dropwise at 70℃, stir magnetically and reflux, react for 12h, wash thoroughly with acetone and ethanol, and dry in a vacuum drying oven at 80℃ to obtain mercapto-functionalized oyster shell material (MPTES-OS).

[0041] Example 6

[0042] (1) Weigh out multiple portions of 0.2g of the thiol-functionalized oyster shell material (MPTES-OS) and 100-120 mesh oyster shell powder (OS) prepared in Example 1, and add them to 50mL of a solution with an initial Cd(II) concentration of 200mg / L.

[0043] (2) Adjust the pH of the solution to 2, 4, 6, 7, 8, 10, and react in a constant temperature shaking box for 360 min. Set the temperature to 25℃ and the rotation speed to 160 r / min.

[0044] (3) After the reaction is complete, centrifuge for 15 min, filter with a 0.45 μm filter membrane, take the supernatant, and determine the concentration of Cd(II) in the supernatant using an atomic absorption spectrometer (AAS).

[0045] Example 7

[0046] (1) Weigh out multiple portions of 0.2g of MPTES-OS and 100-120 mesh oyster shell powder (OS) prepared in Example 1 and add them to 50mL of a solution with an initial Cd(II) concentration of 200mg / L.

[0047] (2) Adjust the pH of the solution to 6 and react in a constant temperature shaking box for 15, 30, 60, 90, 120, 180, 240, 300, 360, 480 and 720 min, with the temperature set at 25℃ and the rotation speed at 160 r / min.

[0048] (3) After the reaction is complete, centrifuge for 15 min, filter with a 0.45 μm filter membrane, and take the supernatant to determine the concentration of Cd(II) in the supernatant using an atomic absorption spectrometer (AAS).

[0049] Example 8

[0050] (1) Weigh out multiple portions of 0.5g of MPTES-OS and 100-120 mesh oyster shell powder (OS) prepared in Example 1 and add them to 50mL of a solution with an initial Cd(II) concentration of 200mg / L.

[0051] (2) Adjust the pH of the solution to 6, react in a constant temperature shaking box for 360 min, set the temperature to 25℃ and the rotation speed to 160 r / min.

[0052] (3) After the reaction is complete, centrifuge for 15 min, filter with a 0.45 μm filter membrane, and take the supernatant to determine the concentration of Cd(II) in the supernatant using an atomic absorption spectrometer (AAS).

[0053] (4) Repeat steps (1), (2), and (3).

[0054] Example 9

[0055] (1) Weigh out multiple portions of 0.2g of MPTES-OS and 100-120 mesh oyster shell powder (OS) prepared in Example 1, and add them to 50mL of a binary competitive system [Cd(II) / Fe(III), Cd(II) / Ni(II), Cd(II) / Zn(II), Cd(II) / Pb(II)] with an initial concentration of 200mg / L.

[0056] (2) Adjust the pH of the solution to 6, react in a constant temperature shaking box for 360 min, set the temperature to 25℃ and the rotation speed to 160 r / min.

[0057] (3) After the reaction was completed, the mixture was centrifuged for 15 min, filtered through a 0.45 μm filter membrane, and the concentration of Cd(II) in the supernatant was determined by atomic absorption spectrometry (AAS). The adsorption capacity of MPTES-OS for Cd(II) in the binary competitive systems Cd(II) / Fe(III), Cd(II) / Ni(II), Cd(II) / Zn(II), and Cd(II) / Pb(II) was 36 mg / L, 37 mg / L, 17.5 mg / L, and 24.5 mg / L, respectively.

[0058] The results are analyzed as follows:

[0059] SEM image analysis of OS and MPTES-OS: The surface morphology of oyster shell powder and the thiol-functionalized oyster shell material prepared in Example 1 were observed by scanning electron microscopy. The results are as follows: Figure 1 As shown in the figure, the oyster shell powder has an uneven particle size and a large amount of debris adhering to the surface. The surface morphology of the functionalized MPTES-OS material changes to some extent, with more uniform particle size, a denser surface, and fewer fine debris. This indicates that the modification of MPTES affects the surface morphology of the material.

[0060] XRD pattern analysis of OS and MPTES-OS: According to the JCPDS card (No. 05-0586), the characteristic peaks at diffraction angles of 2θ of 23.08°, 29.4°, 36.03°, 39.47°, and 43.23° correspond to the (012), (104), (110), (113), and (202) crystal planes of CaCO3, respectively. Figure 2 It can be seen that the positions of the main diffraction peaks of MPTES-OS prepared in Example 1 are similar to those of OS, and the maximum diffraction peak intensity of MPTES-OS is greater than that of OS, indicating that the crystallinity of the oyster shell material modified by MPTES-OS is better.

[0061] FT-IR plot analysis of OS and MPTES-OS: From Figure 3 As can be seen from this, for the spectrum of OS, at 3436 cm⁻¹ -1 The broadband frequency band centered on this point belongs to the OH stretching vibration, with values ​​of 2985 and 2878 cm⁻¹. -1 This belongs to the CH stretching vibration. CaCO3 exhibits vibrations at 1420, 880, and 713 cm⁻¹. -1 The characteristic absorption peaks at these locations correspond to the antisymmetric expansion of CO and the out-of-plane and in-plane bending vibrations, respectively. In the FT-IR spectrum of the MPTES-OS prepared in Example 1, the SH characteristic peak is relatively weak, particularly in the 2600-2500 cm⁻¹ range. -1 The characteristic peaks overlap at 1082 cm⁻¹. Meanwhile, the -SH peak of OS overlaps at 1082 cm⁻¹. -1 and 880cm -1 The peak value at this point is enhanced, which may be related to the stretching vibration of the Si-O bond. These results indicate that MPTES successfully modifies OS.

[0062] XPS spectra of MPTES-OS(a), high-resolution spectra of S2p(b), and high-resolution spectral analysis of Si2p(c): From Figure 4 As shown in a, the five characteristic peaks of the MPTES-OS prepared in Example 1 are assigned to O1s, Ca2p, C1s, S2p, and Si2p, with binding energies around 531.3, 346.8, 284.8, 167.7, and 101.3 eV, respectively. Figure 4As shown in b, the peaks observed at 162.6 and 163.8 eV likely belong to the S2p1 / 2 and S2p3 / 2 hybrid orbitals of SH, while the other doublet is located at 168.2 and 169.4 eV, which are byproducts of the oxide. Figure 4 As shown in c, the peak at 101.7 eV is likely attributed to Si-OC, which is consistent with the FT-IR results, indicating that no hydrolysis reaction occurred during the modification of oyster shells by MPTES. These results demonstrate that MPTES successfully modified OS, and -SH has been grafted onto the OS surface.

[0063] Zeta potential analysis of MPTES-OS at different pH values: From Figure 5 It is known that the pHpzc of the MPTES-OS prepared in Example 1 is 2.56. With increasing pH, the zeta potential of MPTES-OS decreases; when pH > 2.56, the zeta potential of MPTES-OS is negative. Furthermore, when pH > pHpzc, the surface of MPTES-OS is negatively charged, making it easier for Cd(II) to be electrostatically adsorbed.

[0064] Analysis of the effect of pH on the adsorption of Cd(II) by OS and MPTES-OS: From Figure 6 It was found that the adsorption capacity reached its maximum of 44 mg / g at pH 6. With increasing solution pH, the adsorption capacity of MPTES-OS for Cd(II) first increased and then rapidly decreased. This is mainly because, in the low pH range, the deprotonation effect of surface thiol functional groups increased the number of active binding sites on the MPTES-OS surface; while when the pH was greater than 7, due to the increase of OH-, Cd(II) began or completely formed precipitates.

[0065] Analysis of the effect of reaction time on the adsorption of Cd(II) by OS and MPTES-OS: From Figure 7 As can be seen, with the increase of time, the adsorption capacity of Cd(II) by MPTES-OS prepared in Example 1 first increases and then stabilizes, with an equilibrium time of 360 min. Initially, there are many adsorption sites on the MPTES-OS surface that can bind to Cd(II), so the adsorption capacity increases rapidly; however, as the reaction time continues to increase, when the active sites on the MPTES-OS surface reach saturation and adsorption reaches equilibrium, the adsorption capacity tends to stabilize. The above results indicate that after modification with MPTES, the equilibrium adsorption time of the material for Cd(II) is shortened.

[0066] Reusability analysis of OS and MPTES-OS: The reusability of the functionalized material was investigated by repeating five adsorption-desorption cycles of Cd(II) on the material prepared in Example 1 and 100-120 mesh oyster shell powder. Figure 8 It can be seen that, with the increase of the number of cycles, the functionalized material after grafting thiol functional groups onto the surface of OS improves the reusability of OS compared to oyster shell powder.

[0067] Analysis of the effects of interfering ions on the adsorption of Cd(II) by OS and APTES-OS: The material prepared in Example 1 and 100-120 mesh oyster shell powder were added to a binary competitive system to investigate the effects of interfering ions on the adsorption of Cd(II) by OS and APTES-OS. Figure 9 As can be seen, in the binary system, compared with oyster shell powder, the effect of interfering ions on the adsorption of Cd(II) by OS is reduced after modification by MPTES.

[0068] In summary, this invention uses oyster shell powder as raw material and toluene as the reaction solvent. Under magnetic stirring and reflux, the oyster shell powder is modified with 3-mercaptopropyltriethoxysilane (MPTES) to obtain a mercapto-functionalized oyster shell material that effectively improves the cadmium removal performance of the powder. Simultaneously, the material exhibits good stability and reusability. Compared to existing technologies, the preparation method of this invention has a shorter cycle and fewer steps, significantly reducing production costs and making it more practical.

[0069] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing cadmium-removing functionalized oyster shell material, characterized in that: The method steps are as follows: (1) Soak the oyster shells in dilute hydrochloric acid and sodium hydroxide solution, then wash them with clean water, dry them in a drying oven, cool them and grind them into 100-120 mesh oyster shell powder for later use. (2) Weigh a certain amount of oyster shell powder, use toluene as the reaction solvent, add 3-mercaptopropyltriethoxysilane MPTES dropwise at 50~130 ℃, after the magnetic stirring and reflux reaction is completed, wash thoroughly with acetone and ethanol, put it in a vacuum drying oven to dry, and obtain mercapto-functionalized oyster shell material MPTES-OS.

2. The method for preparing a cadmium-removing functionalized oyster shell material according to claim 1, characterized in that: In step (1), the concentration of dilute hydrochloric acid is 5%, the concentration of sodium hydroxide solution is 5%, and the drying temperature is 80 ℃.

3. The method for preparing a cadmium-removing functionalized oyster shell material according to claim 1, characterized in that: In step (2), 10 g of oyster shell powder was weighed, 100 mL of toluene was used, 0.05-0.4 mL of MPTES was used, the modification time was 12 h, and the drying temperature was 80 ℃.

4. A cadmium-removing functionalized oyster shell material, characterized in that: The cadmium-removing functionalized oyster shell material is prepared by a method for preparing cadmium-removing functionalized oyster shell material according to any one of claims 1-3.

5. The application of the cadmium-removing functionalized oyster shell material according to claim 4 in cadmium removal.

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