Pb < 2 + > adsorbing material as well as preparation method and application thereof

Abstract

The invention discloses a Pb < 2 + > adsorption material and a preparation method and application thereof, and belongs to the technical field of adsorption materials.The preparation method comprises the steps that tetrapropylammonium hydroxide and deionized water are mixed, tetraethyl orthosilicate is added, and violent magnetic stirring is conducted; adding tetrabutyl titanate and continuously stirring to prepare a mixed solution; adding caprolactam into the mixed solution, and stirring to remove alcohol to obtain transparent glue solution; transferring the obtained transparent glue solution into a reaction kettle with a polytetrafluoroethylene lining, putting the reaction kettle into a drying oven, firstly heating to 80 DEG C, preserving heat for 12 hours, then heating to 120 DEG C, preserving heat for 24 hours, naturally cooling to room temperature, centrifuging the obtained white emulsion, washing with deionized water until the white emulsion is neutral, and drying and grinding the obtained material; the ground material is placed in a tubular furnace to be subjected to heat preservation treatment to remove the template agent, and the Pb < 2 + > adsorption material is obtained and has efficient adsorption performance on Pb < 2 + > at low concentration.

Description

Technical Field

[0001] This invention belongs to the field of adsorption materials technology, specifically relating to a Pb 2+ Adsorption materials, their preparation methods, and applications. Background Technology

[0002] Lead is a common heavy metal that poses a serious threat to human health. It is used in many industries, such as electronics, batteries, plastic container coatings, and mining. Lead-containing wastewater is toxic and difficult to degrade, posing a significant threat to plants and animals. Once it enters the environment, even at very low levels, it can circulate indefinitely, inevitably eventually entering the human food chain. It has adverse effects on many parts of the human body, particularly the central nervous system, and can also affect children's growth and development, even leading to death.

[0003] Therefore, a method for treating low concentrations of Pb at room temperature was designed. 2+ Materials exhibiting excellent capture capabilities have significant practical implications.

[0004] Currently, the main technologies for treating lead-containing wastewater include chemical precipitation, adsorption, ion exchange, membrane separation, and electrolysis. Chemical precipitation is widely used and offers a variety of precipitants, but it requires subsequent treatment of the sludge and is prone to secondary pollution. Ion exchange is simple to operate and effective, but the ion exchange resin is easily oxidized and decomposed, causing pollution. Membrane separation is widely used for liquid purification due to its low maintenance and low energy consumption, but it is itself susceptible to contamination. Electrolysis is simple to manage and easy to operate, but it is costly. These methods suffer from secondary pollution and high cost, limiting their widespread application. In practical applications, adsorption using porous materials is commonly used. This method does not require additional equipment, making adsorption easy. To date, various materials have been used to remove and retain heavy metal pollutants, including zeolites, metal-organic frameworks, porous alumina, resins, and activated carbon. Among these, activated carbon remains the primary adsorbent in the purification field due to its excellent specific surface area, low price, wide pore size range, and tunable chemical properties.

[0005] Although activated carbon has a large specific surface area, its selective adsorption capacity is poor, and its adsorption efficiency for trace (ppb level) lead ions is very low. Traditional modification methods involve impregnation modification of activated carbon, introducing active sites through modifiers to enhance the chemisorption of lead ions. However, the introduction of modifiers reduces the specific surface area of ​​activated carbon, limiting the effective contact between the adsorbent and the adsorbate. Furthermore, the introduction of modifiers through impregnation can block the channels within the activated carbon, thereby altering the material's pore structure and hindering the contact between lead ions and the active sites, thus failing to meet the requirements of practical applications.

[0006] Therefore, a new method for treating Pb at low concentrations is provided. 2+ Adsorption materials with high adsorption performance have important practical significance. Summary of the Invention

[0007] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0008] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0009] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a Pb 2+ Preparation method of adsorption material.

[0010] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a Pb 2+ Methods for preparing adsorbent materials include, Mix tetrapropylammonium hydroxide with deionized water, add tetraethyl orthosilicate, and stir vigorously with a magnetic force. Add tetrabutyl titanate and continue stirring to obtain a mixed solution; Add caprolactam to the mixed solution, stir to remove alcohol, and obtain a transparent adhesive solution; The obtained transparent adhesive liquid was transferred into a polytetrafluoroethylene-lined reactor. The reactor was placed in an oven, heated to 80°C and kept at that temperature for 12 hours, then heated to 120°C and kept at that temperature for 24 hours. The mixture was then allowed to cool naturally to room temperature. The obtained white emulsion was centrifuged and washed with deionized water until neutral. The resulting material was dried and ground. The ground material was placed in a tube furnace for heat treatment to remove the template agent, and the resulting white powder sample was Pb. 2+ Adsorbent materials.

[0011] In a preferred embodiment of the preparation method described in this invention, the mass concentration of the tetrapropylammonium hydroxide is 20-40%.

[0012] In a preferred embodiment of the preparation method described in this invention, the ratio of tetrapropylammonium hydroxide, deionized water, tetraethyl orthosilicate, and tetrabutyl titanate is 12.71g:90ml:22.4ml:0.681g.

[0013] In a preferred embodiment of the preparation method described in this invention, the ratio of caprolactam to tetrabutyl titanate is 3.395g:0.681g.

[0014] In a preferred embodiment of the preparation method described in this invention, the vigorous magnetic stirring is performed at a temperature of 30°C, a stirring speed of 1200 rpm, and a stirring time of 115 min.

[0015] In a preferred embodiment of the preparation method described in this invention, the addition of tetrabutyl titanate and continued stirring takes 5 minutes and the stirring speed is 1200 rpm.

[0016] In a preferred embodiment of the preparation method described in this invention, the stirring to remove alcohol is carried out at a temperature of 80°C, a stirring speed of 1200 rpm, and a stirring time of 3 hours.

[0017] As a preferred embodiment of the preparation method of the present invention, the heat preservation treatment removes the template agent, wherein the temperature is increased to 550°C at 5°C / min and kept at 5°C for 6 hours.

[0018] Another objective of this invention is to overcome the shortcomings of the prior art and provide an adsorption material.

[0019] Another objective of this invention is to overcome the shortcomings of the prior art and provide an adsorbent material for the preparation of low concentrations of Pb. 2+ Applications in materials with high adsorption capacity.

[0020] Beneficial effects of this invention: (1) This invention provides a Pb 2+ Adsorbent material for Pb at low concentrations 2+ It exhibits highly efficient adsorption properties. During the preparation process, a small amount of caprolactam (CPL) is added as a promoter. Caprolactam can act as an auxiliary guide, attracting titanium and silicon atoms in the synthesis solution, accelerating their entry into the framework to form crystal nuclei more quickly, inhibiting the formation of non-framework titanium, shortening the crystallization time, and providing more surface active sites. This solves the problems of long hydrothermal synthesis time, high energy consumption, and high time cost of existing materials, and improves the Pb of the material. 2+ Adsorption effect.

[0021] (2) The present invention employs a two-step crystallization method to construct a rich mesoporous structure. The first step is carried out at a low temperature of 80°C, which is conducive to the formation of a large number of crystal nuclei; the second step is carried out at 120°C to promote the crystallization process and form a stacked molecular sieve structure with mesopores in both the intergranular and intragranular regions. Compared with the adsorbent material prepared by the classical hydrothermal method, the adsorbent material forms new mesoporous channels inside, which is conducive to the rapid diffusion of the substrate into the interior of the grains. This solves the problem of narrow material channels and restricted substrate diffusion, and improves the grain utilization rate.

[0022] (3) This invention changes the grain size of the material by changing the ratio of silicon source to water and by vigorous stirring during the preparation of the adhesive solution. Tetraethyl orthosilicate (TEOS) is used as the silicon source and deionized water is used as the solvent. Adjusting the ratio of the two can control the grain size of the material. Vigorous stirring during hydrolysis results in a more uniformly dispersed adhesive solution, a smaller average particle size of the material, and nanoscale adsorption material particles ranging from 100 to 250 nm. This increases the specific surface area and provides more surface active sites.

[0023] (4) This invention adjusts the mixing time of the titanium and silicon sources to match their hydrolysis. Tetraethyl orthosilicate (TEOS) is used as the silicon source, with an optimal hydrolysis time of 2 hours, while tetrabutyl titanate (TBOT) is used as the titanium source, with an optimal hydrolysis time of 5 minutes. The silicon source is first hydrolyzed for 115 minutes, then the titanium source is added, and hydrolysis continues for another 5 minutes. The hydrolyzed Ti is rapidly surrounded and combined with a large amount of Si to form Ti-O-Si bonds, rather than agglomerating to form anatase impurities. Conventional methods require the addition of inhibitors to suppress titanium source hydrolysis; this method does not require inhibitors, and the adsorbent material does not contain anatase impurities. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a low concentration of Pb in an embodiment of the present invention. 2+ A flowchart of the preparation method of adsorption materials.

[0025] Figure 2 The image shows the XRD pattern of the adsorbent material prepared in the embodiments of the present invention.

[0026] Figure 3 The image shows the FTIR spectrum of the adsorption material in an embodiment of the present invention.

[0027] Figure 4 This is the UV-Vis spectrum of the adsorption material in an embodiment of the present invention. Figure 5 This is a SEM image of the adsorbent material in an embodiment of the present invention.

[0028] Figure 6 The nitrogen isothermal adsorption-desorption curves are shown in the embodiments of the present invention.

[0029] Figure 7 This is a graph showing the distribution of mesopores in an embodiment of the present invention.

[0030] Figure 8 Pb is the adsorbent material in the embodiments of the present invention.2+ Adsorption results diagram.

[0031] Figure 9 The graph shows the adsorption test results of TS-1-12 / 24, TS-1-A, and TS-1-B of this invention. Detailed Implementation

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0033] All raw materials used in this invention are commercially available products.

[0034] Example 1

[0035] (1) First, add 12.71g of tetrapropylammonium hydroxide (TPAOH) with a mass fraction of 40% to 90ml of deionized water, then add 22.4ml of tetraethyl orthosilicate (TEOS), and stir vigorously with a magnetic force at 30℃ and 1200rpm for 115min; (2) Then add 0.681g of tetrabutyl titanate (TBOT) and continue stirring for 5 minutes; Add 3.395 g of caprolactam (CPL) to the above solution and remove alcohol by magnetic stirring at 80 °C and 1200 rpm for 3 h.

[0036] (3) The obtained transparent adhesive liquid was then transferred into a polytetrafluoroethylene-lined reactor. The reactor was placed in an oven and heated to 80°C for 12 hours. Then it was heated to 120°C for 24 hours. After the heating was completed, it was naturally cooled to room temperature and then removed from the oven.

[0037] (4) Centrifuge the obtained white emulsion and wash it with deionized water until neutral. Dry and grind the obtained material at 100°C.

[0038] (5) The ground material was placed in a tube furnace and heated to 550°C at 5°C / min. The temperature was maintained for 6 hours to remove the template agent. The resulting white powder sample was named TS-1-12 / 24.

[0039] Example 2

[0040] Under the conditions of Example 1, the hydrothermal time in step (3) was changed to 6h / 12h, that is: the obtained transparent adhesive liquid was transferred into a reaction vessel with a polytetrafluoroethylene liner, the reaction vessel was placed in an oven, the temperature was first raised to 80°C and kept for 6h, then the temperature was raised to 120°C and kept for 12h, and after the heat preservation was completed, it was naturally cooled to room temperature and then taken out of the oven.

[0041] All other conditions were the same as in Example 1, and the resulting sample was named TS-1-6 / 12.

[0042] Example 3

[0043] Under the conditions of Example 1, the hydrothermal time in step (3) was changed to 18h / 36h, that is: the obtained transparent adhesive liquid was transferred into a reaction vessel with a polytetrafluoroethylene liner, the reaction vessel was placed in an oven, the temperature was first raised to 80°C and kept for 18h, then the temperature was raised to 120°C and kept for 36h, and after the heat preservation was completed, it was naturally cooled to room temperature and then taken out of the oven.

[0044] All other conditions were the same as in Example 1, and the resulting sample was named TS-1-18 / 36.

[0045] Example 4

[0046] Under the conditions of Example 1, the hydrothermal time in step (3) was changed to 24h / 48h, that is: the obtained transparent adhesive liquid was transferred into a reaction vessel with a polytetrafluoroethylene liner, the reaction vessel was placed in an oven, the temperature was first raised to 80°C and kept for 24h, then the temperature was raised to 120°C and kept for 48h, and after the heat preservation was completed, it was naturally cooled to room temperature and then taken out of the oven.

[0047] All other conditions were the same as in Example 1, and the resulting sample was named TS-1-24 / 48.

[0048] low concentration Pb 2+ See the flowchart for the preparation method of the adsorption material. Figure 1 ; See the XRD pattern of the adsorbent material. Figure 2 Observation of the spectra shows that the materials with different crystallization times all exhibited characteristic diffraction peaks of the MFI topology at 2θ=7.8°, 8.8°, 23.2°, 23.8°, and 24.3°. At 24.4° and 29.3°, the double diffraction peaks changed to single peaks, indicating that titanium has entered the framework. It can be concluded that titanium silicon molecular sieve TS-1 was successfully synthesized under different crystallization times.

[0049] When the two-step crystallization time was extended from 6h / 12h to 12h / 24h, the relative crystallinity of the sample significantly increased. Further extending the hydrothermal time did not change the relative crystallinity. This is because CPL (Crystal Plasma Phosphate) acts as an auxiliary guide during molecular sieve synthesis. In the synthesis solution, CPL attracts titanium and silicon atoms, accelerating their entry into the framework and faster crystal nucleation, thus shortening the crystallization time.

[0050] See the FTIR spectrum of the adsorbent material. Figure 3 It can be seen that 1225 cm -1 The nearby absorption peaks are characteristic peaks of the MFI topology and are attributed to the stretching vibrations of the Si-O bond.

[0051] 960 cm -1The nearby absorption peaks are considered to be stretching vibrations of adjacent Si-O bonds after the introduction of titanium atoms, and are therefore regarded as indirect evidence of titanium introduction into the framework. The characterization results readily show that all four samples at different crystallization times possess the MFI topology, and that titanium atoms have been introduced into the molecular sieve framework. Furthermore, the absorption peak at 1100 cm⁻¹... -1 and 800cm -1 The nearby absorption peaks are attributed to the symmetric and antisymmetric stretching vibrations of Si-O or Ti-O bonds in the tetrahedral structure.

[0052] See the UV-Vis spectrum of the adsorbent material. Figure 4 As can be seen, the absorption peak at 210 nm is the signal of four-coordinated titanium in the framework, which appears in all four samples and is strong evidence of titanium entering the framework. The intensity of the signal peak can characterize the content of titanium in the framework. At the same time, no obvious absorption peaks were found in the 260-280 nm and 310-330 nm ranges in any of the samples, indicating that the content of six-coordinated non-framework titanium and anatase TiO2 was very low in all samples. This suggests that the use of CPL promoter can accelerate the entry of titanium species into the framework, and a complete crystal structure can be formed in 12-24 hours of crystallization.

[0053] See SEM images of the adsorbent material Figure 5 The microstructure and grain size of the obtained TS-1 samples were clearly observed. All samples were formed by the stacking of layered or granular structures, resulting in abundant intracrystalline and intercrystalline mesopores. The samples formed a complete crystal structure with ellipsoidal grains of uniform size. Specifically, TS-1-6 / 12, TS-1-18 / 36, and TS-1-24 / 48 had grain sizes of 100-150 nm, while TS-1-12 / 24 had a grain size of 200-250 nm. No amorphous substances were observed in the SEM images, indicating good crystallinity of the samples.

[0054] See the nitrogen isothermal adsorption-desorption curve of the material. Figure 6 See the mesopore distribution curve. Figure 7 As can be seen, all materials exhibit a distinct H4-type hysteresis loop when P / P0 > 0.4, indicating a mixed structure of micropores and mesopores. Within the 2-50 nm range, all samples show a significant peak, indicating the presence of abundant mesoporous structures. Furthermore, the mesopore distribution decreases with increasing hydrothermal time, due to more fully developed grains and a more compact stacked structure.

[0055] Example 5

[0056] TS-1-12 / 24 exhibits good crystallinity and abundant mesoporous structure, and its Pb content was analyzed. 2+ Adsorption test.

[0057] The lead ion adsorption rate η is obtained by measuring the mass conservation before and after adsorption. The specific calculation method is as follows: η = (C0 - C) e ) / C0 Wherein, η, C0, C e These represent the adsorption rate, the lead ion concentration in the solution before adsorption, and the lead ion concentration in the solution after adsorption, respectively.

[0058] At pH=7, Pb 2+ 10 mg of TS-1-12 / 24 adsorbent was added to 20 ml of a solution with a concentration of 108.55 ppb. After adsorption equilibrium was reached, the Pb concentration in the solution was... 2+ When the concentration was reduced to 0.36 ppb, the adsorption rate reached 99.67%, demonstrating excellent removal efficiency for trace lead ions. (See results below.) Figure 8 .

[0059] Comparative sample TS-1-A was prepared by one-step crystallization. The preparation conditions were the same as those for TS-1-12 / 24, except that the hydrothermal conditions were adjusted to 170℃ for 24 hours, while other conditions remained unchanged.

[0060] Based on TS-1-A, without adding caprolactam and keeping other conditions unchanged, a comparative sample TS-1-B was prepared.

[0061] Under the same pH, solution, and adsorbent dosage, Pb 2+ Adsorption tests were conducted on TS-1-12 / 24, TS-1-A, and TS-1-B at a concentration of 237.37 ppb, and their adsorption effects were compared and analyzed. The results are shown in [link to results]. Figure 9 .

[0062] After adsorption by samples TS-1-A and TS-1-B, Pb 2+ The concentrations decreased from 237.37 ppb to 5.13 ppb and 15.14 ppb, respectively, with adsorption efficiencies of 97.84% and 93.62%. This demonstrates that the addition of caprolactam not only shortened the hydrothermal time but also significantly improved the adsorption effect. This is because, under the guiding effect of caprolactam, titanium atoms and silicon atoms better combine to form framework titanium species, inhibiting the formation of non-framework titanium species and providing more surface active sites.

[0063] After adsorption by samples TS-1-12 / 24 and TS-1-A, Pb 2+The concentrations decreased from 237.37 ppb to 4.86 ppb and 5.13 ppb, respectively, with adsorption efficiencies of 98.00% and 97.84%. Compared to TS-1-A, TS-1-12 / 24 obtained through the two-step crystallization method showed slightly better adsorption performance. This is because the two-step crystallization method constructs intracrystalline mesoporous channels, allowing the substrate to more easily reach the interior of the grains and improving grain utilization. In this example, the improvement was not significant because, through optimized preparation conditions, the obtained adsorbent material had reached the nanoscale, with extremely short substrate diffusion paths and already very high, near-saturation, grain utilization. In micron-scale adsorbent materials, the adsorption performance improvement brought by the two-step crystallization method will be further amplified.

[0064] Low temperatures favor nucleation, while high temperatures favor growth. In the two-step crystallization process, the first stage is the nucleation stage. A low temperature of 80℃ can inhibit crystal growth and form a large number of crystal nuclei. Further increases in temperature (such as 90℃) are not conducive to nucleation, while further decreases in temperature (such as 70℃) will lead to an excessively slow reaction. The second stage is the growth stage. 120℃ is conducive to grain growth and the formation of a stacked structure, resulting in abundant intracrystalline and intercrystalline mesopores. Further decreases in temperature (such as 100℃) are not conducive to growth, while further increases in temperature (such as 140℃) will lead to an overly dense stacked structure, reducing intracrystalline and intercrystalline mesopores.

[0065] The water-to-silicon ratio is significantly positively correlated with the particle size of TS-1. A higher water-to-silicon ratio indicates a greater water content in the synthesis system, typically resulting in larger TS-1 crystals. Under low water-to-silicon ratio conditions (10–40), the concentrations of silicon source, titanium source, and template agent in the reaction mixture are relatively high, leading to the formation of numerous nuclei. Due to the fixed total amount of precursors, each nucleus has limited growth material, restricting crystal growth and resulting in smaller particle sizes (typically nanometers) and ellipsoidal crystal morphology. Conversely, under high water-to-silicon ratio conditions (>50), the nucleation process becomes slower and more uniform, resulting in sufficient crystal growth, larger particle sizes (reaching several micrometers or even tens of micrometers), and a tendency towards cubic crystal morphology. Smaller particle sizes of adsorbent materials have higher specific surface areas, providing more surface active sites.

[0066] In summary, this invention uses caprolactam as a promoter to accelerate crystal nucleation, shorten hydrothermal crystallization time, and improve adsorption efficiency. The two-step crystallization method controls grain growth behavior, constructs a rich mesoporous structure, and improves grain utilization. Vigorous stirring makes the solution more homogeneous and breaks up agglomerates, thereby altering grain size. The delayed addition of the titanium source ensures a Si-rich environment and prevents Ti aggregation, which could lead to anatase impurities.

[0067] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A type of Pb 2+ The method for preparing adsorbent materials is characterized by: include, Mix tetrapropylammonium hydroxide with deionized water, add tetraethyl orthosilicate, and stir vigorously with a magnetic force. Add tetrabutyl titanate and continue stirring to obtain a mixed solution; Add caprolactam to the mixed solution, stir to remove alcohol, and obtain a transparent adhesive solution; The obtained transparent adhesive liquid was transferred into a polytetrafluoroethylene-lined reactor. The reactor was placed in an oven, heated to 80°C and kept at that temperature for 12 hours, then heated to 120°C and kept at that temperature for 24 hours. The mixture was then allowed to cool naturally to room temperature. The obtained white emulsion was centrifuged and washed with deionized water until neutral. The resulting material was dried and ground. The ground material was placed in a tube furnace for heat treatment to remove the template agent, and the resulting white powder sample was Pb. 2+ Adsorbent materials.

2. The preparation method according to claim 1, characterized in that: The mass concentration of the tetrapropylammonium hydroxide is 20-40%.

3. The preparation method according to claim 1 or 2, characterized in that: The ratio of tetrapropylammonium hydroxide, deionized water, tetraethyl orthosilicate, and tetrabutyl titanate is 12.71g:90ml:22.4ml:0.681g.

4. The preparation method according to claim 3, characterized in that: The ratio of caprolactam to tetrabutyl titanate is 3.395g:0.681g.

5. The preparation method according to claim 1, characterized in that: The intense magnetic stirring is carried out at a temperature of 30°C, a stirring speed of 1200 rpm, and a stirring time of 115 min.

6. The preparation method according to claim 1 or 5, characterized in that: The addition of tetrabutyl titanate and continued stirring, wherein the stirring time is 5 minutes and the stirring speed is 1200 rpm.

7. The preparation method according to claim 1, characterized in that: The alcohol removal process involves stirring at a temperature of 80°C, a stirring speed of 1200 rpm, and a stirring time of 3 hours.

8. The preparation method according to claim 1, characterized in that: The heat preservation treatment removes the template agent, wherein the temperature is increased to 550°C at a rate of 5°C / min and kept at that temperature for 6 hours.

9. The adsorbent material prepared by any one of the preparation methods according to claims 1 to 8.

10. The adsorbent material according to claim 9, when prepared at low concentrations, is effective for adsorbing Pb. 2+ Applications in materials with high adsorption capacity.

Images