Application of iron-silicon composite adsorbent in removal of arsenic in water body

Abstract

The invention provides application of an iron-silicon composite adsorbent to removal of arsenic in a water body, and belongs to the technical field of adsorbents. According to the method, the iron-silicon composite adsorbent is added into the arsenic-containing wastewater at room temperature and stirred, so that arsenic can be removed; the iron-silicon composite adsorbent is formed by compounding iron salt particles and silicon dioxide aerogel prepared from tetraethoxysilane; the molar ratio of the Si element in the tetraethoxysilane to the iron element in the ferric salt is (0.05-0.5): (0.01-0.2). The adsorbent provided by the invention has the advantages of high removal rate and high adsorption speed on arsenic in the water body, high removal efficiency can be obtained at the same time of low adsorbent dosage, and the adsorption efficiency on arsenic in the water body reaches up to 99%.

Description

Technical Field

[0001] This invention relates to the field of adsorbent technology, and in particular to the application of an iron-silicon composite adsorbent in the removal of arsenic from water. Background Technology

[0002] Arsenic is a metalloid element widely found in nature and commonly used in the production of herbicides and pesticides. Its widespread use leads to its accumulation in the environment. Arsenic enters the human body through various routes, such as skin contact, inhalation, and digestion, causing arsenic poisoning. Arsenic compounds are stable and not easily broken down in the human body or other organisms, ultimately leading to arsenic accumulation in the human body due to the food chain effect, seriously endangering human health. The toxicity of arsenic is related to its chemical form and solubility. Inorganic arsenic is more toxic than organic arsenic; inorganic arsenic includes trivalent and pentavalent arsenic. Trivalent arsenic is more toxic than pentavalent arsenic, mainly because trivalent arsenic compounds are easily absorbed and accumulated by cells, binding to sulfhydryl groups, hindering cell respiration, division, and proliferation, causing abnormal cell metabolism; it also inhibits the respiration, division, and proliferation of various enzymes, causing abnormal cell metabolism, and inhibits various enzymes, leading to cell damage.

[0003] Extensive research has been conducted on arsenic removal technologies, with current remediation methods including adsorption, ion exchange, phytoremediation, chemical precipitation, coagulation, and membrane separation. Adsorption is widely adopted due to its simplicity, high efficiency, low cost, and adaptability to varying water volumes. The preparation of adsorbents with excellent adsorption properties is crucial for achieving low arsenic levels in water. Commonly used adsorbents include inorganic, organic, and composite adsorbents. However, some inorganic adsorbents have low adsorption efficiency, organic adsorbents may cause secondary pollution, and the preparation process of composite adsorbents is complex. Among the many developed adsorbents, iron and its oxides have a stronger affinity for arsenic ions, are simple to prepare, and have widely available raw materials, leading to their large-scale application in treating high-arsenic water. However, in practical applications, iron salt particles inevitably suffer from aggregation, leaching, and separation difficulties. Therefore, it is necessary to find porous carriers to load Fe to effectively solve these problems.

[0004] SiO2 aerogels have been extensively studied in the field of environmental adsorption. Existing technologies include loading Fe onto SiO2 aerogels for arsenic removal. However, the Fe element merely adheres to the surface of the SiO2 aerogel, resulting in poor adsorption of arsenic in water, low adsorption dosage, and a long time to reach adsorption equilibrium. This fails to effectively remove arsenic from water, and the preparation process of the adsorbent is complex and time-consuming. Therefore, exploring SiO2 aerogels as an adsorbent carrier material for the removal of arsenate and arsenite has significant practical value. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide an application of an iron-silicon composite adsorbent in the removal of arsenic from water.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an application of an iron-silicon composite adsorbent in the removal of arsenic from water, wherein the iron-silicon composite adsorbent is added to arsenic-containing wastewater and stirred at room temperature to remove arsenic;

[0007] The iron-silicon composite adsorbent is composed of iron salt particles and silica aerogel made of tetraethyl orthosilicate; the molar ratio of Si in tetraethyl orthosilicate to iron in iron salt is (0.05-0.5):(0.01-0.2).

[0008] Preferably, the pH of the arsenic-containing wastewater is 2-7.

[0009] Preferably, the dosage of the iron-silicon composite adsorbent is 0.2-1.4 g / L.

[0010] Preferably, the iron-silicon composite adsorbent is prepared by: using tetraethyl orthosilicate as the silicon source, adding iron salt during the preparation of silica wet gel by sol-gel method, and then aging, drying, grinding, and sieving the obtained wet gel to obtain the iron-silicon composite adsorbent.

[0011] Preferably, the iron salt is ferric chloride hexahydrate.

[0012] More preferably, the step of incorporating iron salt in the process of preparing silica wet gel by sol-gel method is as follows: mix tetraethyl orthosilicate, anhydrous ethanol and iron salt and stir in a water bath, then adjust the pH while stirring until gel is formed.

[0013] More preferably, the water bath stirring temperature is 30-50℃, the time is 1 hour, and the stirring speed is 200-600 r / min.

[0014] More preferably, the pH value is 5-8.5.

[0015] More preferably, the aging method is to immerse the wet gel in anhydrous ethanol for aging; the aging temperature is 40-60℃ and the time is 10-15h.

[0016] More preferably, the drying temperature is 85-100℃.

[0017] Beneficial technical effects:

[0018] 1. The arsenic adsorbent prepared by this invention uses tetraethyl orthosilicate, anhydrous ethanol and ferric chloride hexahydrate as raw materials. It has low preparation cost and wide availability, simple preparation process and good product stability.

[0019] 2. The adsorbent provided by this invention has a high removal rate and fast adsorption speed for arsenic in water, and can achieve high removal efficiency with low adsorbent dosage, with an adsorption efficiency of up to 99% for arsenic in water.

[0020] 3. This invention is the first to incorporate iron salts into the preparation process of silica aerogel to form a novel composite adsorbent for arsenic removal, providing a new approach for arsenic removal from water. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in 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.

[0022] Figure 1 The image shows the microstructure of the adsorbent in Example 1.

[0023] Figure 2 The graph shows the effect of different dosages of adsorbent on the arsenic adsorption capacity in Example 1.

[0024] Figure 3 This is a graph showing the effect of the adsorbent on the arsenic adsorption capacity at different initial pH levels in Example 1.

[0025] Figure 4 The graph shows the effect of the adsorbent on the arsenic adsorption capacity at different adsorption times in Example 1. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] This invention provides an application of an iron-silicon composite adsorbent in the removal of arsenic from water. Arsenic can be removed by adding the iron-silicon composite adsorbent to arsenic-containing wastewater and stirring at room temperature.

[0032] The iron-silicon composite adsorbent is composed of iron salt particles and silica aerogel made of tetraethyl orthosilicate; the molar ratio of Si element in tetraethyl orthosilicate to iron element in iron salt is preferably (0.05-0.5):(0.01-0.2), more preferably (0.05-0.25):(0.01-0.2).

[0033] Iron and arsenic have a special affinity, so iron salts are often introduced when preparing arsenic removal adsorbents. When the iron content is low, the adsorbent has a small arsenic adsorption capacity; when the iron content is too high, the pore structure on the surface of the composite adsorbent is reduced and it exhibits a blocky structure. This change in pore structure will inevitably reduce the adsorption performance of the material.

[0034] The adsorbent prepared by this invention has excellent adsorption performance for arsenic. The main mechanism of the adsorption process is as follows: As in the solution diffuses to the surface of the composite material through the liquid film; the porous structure of the composite material promotes its diffusion into the interior; chemical adsorption of As with O-containing functional groups occurs, and a stable complex is formed with arsenic.

[0035] In some embodiments, the pH of the arsenic-containing wastewater is 2-7.

[0036] In some embodiments, the dosage of the iron-silicon composite adsorbent is 0.2-1.4 g / L.

[0037] This invention achieves high removal efficiency with low adsorbent dosage by adjusting the pH value of arsenic-containing wastewater, with an arsenic removal rate of up to 99%.

[0038] In some embodiments, the iron-silicon composite adsorbent is prepared by: using tetraethyl orthosilicate as the silicon source, adding iron salt during the preparation of silica wet gel by sol-gel method, and then aging, drying, grinding, and sieving the obtained wet gel to obtain the iron-silicon composite adsorbent.

[0039] This invention incorporates iron salts during the preparation of silica aerogel, solving the problem of iron salt particles easily agglomerating and leaching. At the same time, combined with the advantages of silica aerogel such as high porosity, high specific surface area, and low cost and availability, the iron-based salt particles are utilized efficiently.

[0040] In some embodiments, the iron salt is ferric chloride hexahydrate. When such adsorbents are synthesized using iron salts such as ferric sulfate and ferric nitrate, the adsorption effect on arsenic in solution decreases significantly. This is because such iron salts contain anions such as SO42-. 2- NO3 - Similar in structure to the existing forms of arsenic (arsenate and arsenite), it readily generates competitive adsorption, inhibiting the adsorption of arsenic by the composite adsorbent.

[0041] In a preferred embodiment, the step of incorporating iron salts during the preparation of silica wet gel using the sol-gel method is as follows: tetraethyl orthosilicate, anhydrous ethanol, and iron salts are mixed and stirred in a water bath, while the pH is adjusted continuously until gel formation occurs; the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, and iron salts is (0.05-0.5):(1-7):(0.01-0.2), preferably (0.05-0.25):1:(0.01-0.2).

[0042] In a preferred embodiment, the water bath stirring temperature is 30-50°C, the time is 1 hour, and the stirring speed is 200-600 r / min. Excessively high stirring temperature will accelerate the evaporation rate of anhydrous ethanol, while excessively low temperature will result in incomplete mixing of various reactants, affecting the synthesis of the adsorbent. Therefore, the above parameter range is preferred in this invention.

[0043] In a preferred embodiment, the pH value is 5-8.5. Preferably, the pH is adjusted by slowly adding NaOH or HCl solution dropwise during water bath stirring.

[0044] In a preferred embodiment, the aging method involves immersing the wet gel in anhydrous ethanol for aging; the aging temperature is 40-60°C, and the time is 10-15 hours. The gel aging process aims to enhance the network structure of the silica aerogel. Too short an aging time will result in incomplete formation of the silica aerogel structure, while too long an aging time increases time costs. Too high an aging temperature will cause the sol-gel aerogel to melt, while too low an aging temperature will slow down the rate of network structure enhancement. Therefore, the above parameter ranges are preferred in this invention.

[0045] In a preferred embodiment, the drying temperature is 85-100℃. The present invention does not impose any particular limitation on the drying method; any method well-known to those skilled in the art can be used.

[0046] In a preferred embodiment, the preparation method of the iron-silicon composite adsorbent specifically includes the following steps:

[0047] (1) Mix tetraethyl orthosilicate, anhydrous ethanol and ferric chloride hexahydrate in a molar ratio of (0.05-0.5):(1-7):(0.01-0.2), stir in a water bath, and then slowly add NaOH solution or HCl solution dropwise while stirring to adjust the pH until a wet gel is formed.

[0048] (2) The formed wet gel was aged by immersing it in anhydrous ethanol;

[0049] (3) After the aged wet gel is dried at normal pressure, it is ground and sieved to obtain iron-silicon composite adsorbent.

[0050] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0051] Unless otherwise specified, all instruments and reagents used in the examples are available through commercial channels.

[0052] Example 1

[0053] Arsenic can be removed by adding the iron-silicon composite adsorbent to arsenic-containing wastewater and stirring at room temperature.

[0054] The preparation of the iron-silicon composite adsorbent is as follows:

[0055] (1) Mix 22.3 ml tetraethyl orthosilicate, 58 ml anhydrous ethanol and 13.5 g ferric chloride hexahydrate in proportion, stir in a water bath at 50°C for 1 h at a stirring rate of 300 r / min, and then slowly add 0.1 M NaOH solution and 0.1 M HCl solution dropwise while stirring to adjust the pH to 7 until gel is formed;

[0056] (2) The formed wet gel was soaked in anhydrous ethanol at 40°C for 10 hours to age;

[0057] (3) The aged wet gel was dried at 95℃ and normal pressure for 12 hours, then ground and sieved to obtain the iron-silicon composite adsorbent. The microstructure of the obtained iron-silicon composite adsorbent was observed. Figure 1 It can be seen that the composite adsorbent exhibits an uneven porous structure on its surface, and has a rough surface and a large specific surface area, thus possessing a good adsorption structure.

[0058] 1. Determine the dosage of the iron-silicon composite adsorbent.

[0059] The adsorbent used was the iron-silicon composite adsorbent prepared in Example 1, and the target material was laboratory-simulated arsenic-contaminated water. The initial concentration of As(V) was 100 mg / L. Seven 100 mL portions of laboratory-simulated arsenic-contaminated wastewater were poured into 100 mL capped glass bottles, and 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, and 0.14 g of the composite adsorbent from Example 1 were added, corresponding to dosages of 0.2, 0.4, 0.6, 0.8, 1, 1.2, and 1.4 g / L, respectively. The bottles were placed in a constant temperature water bath shaking chamber, and the relevant parameters were set. The rotation speed was 350 r / min, and the reaction temperature was 25 °C. After the reaction, the bottles were removed and filtered, and the remaining arsenic content in the arsenic-contaminated water was detected by ICP. The adsorption capacity Q was calculated. e (mg·g -1 The adsorption capacity of arsenic varies with the adsorbent dosage as follows: (The text abruptly ends here, so the translation stops as well.) Figure 2 .Depend on Figure 2 It can be seen that the amount of arsenic adsorbed increases with the increase of the dosage, and the optimal dosage is 0.6 g / L.

[0060] 2. Determine the pH of arsenic wastewater when using silicon-iron composite adsorbent for arsenic removal.

[0061] The adsorbent used was the iron-silicon composite adsorbent prepared in Example 1, and the target material was laboratory-simulated arsenic-contaminated water. The initial concentration of As(V) was 100 mg / L. Nine 100 mL portions of laboratory-simulated arsenic wastewater were poured into 100 mL capped glass bottles. The pH values ​​of the nine arsenic wastewater portions were adjusted sequentially to 2, 3, 4, 5, 6, 7, 8, 9, and 10 using 0.1 M NaOH and 0.1 M HCl, respectively. 0.06 g of [agent name missing] was added to each glass bottle.

[0062] Example 1: Composite Adsorbent. The adsorbent was placed in a constant temperature water bath shaking chamber, and the relevant parameters were set. The rotation speed was 350 r / min, and the reaction temperature was 25℃. After the reaction, the adsorbent was removed and filtered. The remaining arsenic content in the arsenic-contaminated water was detected by ICP. The adsorption capacity Q was calculated. e (mg·g -1 The adsorption capacity of arsenic varies with pH as shown in the figure. Figure 3 .Depend on Figure 3It can be seen that the adsorption capacity of arsenic gradually decreases with the increase of pH. In order to ensure the adsorption capacity of arsenic, the optimal adsorption pH of arsenic wastewater is determined to be 2.

[0063] 3. Determine the adsorption equilibrium time.

[0064] The adsorbent used was the iron-silicon composite adsorbent prepared in Example 1, and the treatment target was laboratory-simulated arsenic-contaminated water. The initial concentration of As(V) was 100 mg / L. 100 mL of the laboratory-simulated arsenic-contaminated wastewater was poured into a 100 mL capped glass bottle, and the pH of the arsenic-containing wastewater was adjusted to 2 using 0.1 M NaOH and 0.1 M HCl. 0.06 g of the composite adsorbent from Example 1 was added. The bottle was placed in a constant temperature water bath shaker, and the relevant parameters were set. The rotation speed was 350 r / min, and the reaction temperature was 25 °C. Samples were taken and filtered sequentially at 5 min, 15 min, 30 min, 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, 24 h, 48 h, 72 h, and 96 h. The remaining arsenic content in the arsenic-contaminated water was detected by ICP, and the adsorption capacity Q was calculated. e (mg·g -1 ).Depend on Figure 4 It can be seen that adsorption equilibrium is reached at an adsorption time of 12 hours.

[0065] Example 2

[0066] Arsenic can be removed by adding the iron-silicon composite adsorbent to arsenic-containing wastewater and stirring at room temperature.

[0067] The preparation of the iron-silicon composite adsorbent is as follows:

[0068] (1) Mix 22.3 ml of tetraethyl orthosilicate, 58 ml of anhydrous ethanol and 27 g of ferric chloride hexahydrate in proportion, stir in a water bath at 50°C for 1 h at a stirring rate of 300 r / min, and then slowly add 0.1 M NaOH solution and 0.1 M HCl solution dropwise while stirring to adjust the pH to 7 until gel is formed;

[0069] (2) The formed wet gel was soaked in anhydrous ethanol at 50°C for 15 hours to age;

[0070] (3) After drying the aged wet gel at 85°C and normal pressure for 12 hours, it was ground and sieved to obtain the iron-silicon composite adsorbent.

[0071] The experiments in this embodiment, which determined the dosage of the iron-silicon composite adsorbent, the pH of the arsenic wastewater, and the adsorption equilibrium time, were the same as in Example 1. The experimental results were similar to those in Example 1. When the pH of the thallium-containing wastewater was 2-7, the dosage of the iron-silicon composite adsorbent was 0.2-1.4 g / L, with the optimal dosage being 0.6 g / L. Adsorption equilibrium was reached after 12 hours of adsorption.

[0072] Example 3

[0073] Arsenic can be removed by adding the iron-silicon composite adsorbent to arsenic-containing wastewater and stirring at room temperature.

[0074] The preparation of the iron-silicon composite adsorbent is as follows:

[0075] (1) Mix 11.2 ml tetraethyl orthosilicate, 58 ml anhydrous ethanol and 27 g ferric chloride hexahydrate in proportion, stir in a water bath at 50°C for 1 h at a stirring rate of 300 r / min, and then slowly add 0.1 M NaOH solution and 0.1 M HCl solution dropwise while stirring to adjust the pH to 7 until gel is formed;

[0076] (2) The formed wet gel was soaked in anhydrous ethanol at 40°C for 12 hours to age;

[0077] (3) After drying the aged wet gel at 85°C and normal pressure for 12 hours, it was ground and sieved to obtain the iron-silicon composite adsorbent.

[0078] The experiments in this embodiment, which determined the dosage of the iron-silicon composite adsorbent, the pH of the arsenic wastewater, and the adsorption equilibrium time, were the same as in Example 1. The experimental results were similar to those in Example 1. When the pH of the thallium-containing wastewater was 2-7, the dosage of the iron-silicon composite adsorbent was 0.2-1.4 g / L, with the optimal dosage being 0.4-0.8 g / L. Adsorption equilibrium was reached after 12 hours of adsorption.

[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An application of an iron-silicon composite adsorbent in the removal of arsenic from water, characterized in that, Arsenic can be removed by adding the iron-silicon composite adsorbent to arsenic-containing wastewater and stirring at room temperature. The iron-silicon composite adsorbent is composed of iron salt particles and silica aerogel made of tetraethyl orthosilicate; the molar ratio of Si in tetraethyl orthosilicate to iron in iron salt is (0.05-0.5):(0.01-0.2).

2. The application according to claim 1, characterized in that, The pH of the arsenic-containing wastewater is 2-7.

3. The application according to claim 1, characterized in that, The dosage of the iron-silicon composite adsorbent is 0.2-1.4 g / L.

4. The application according to claim 1, characterized in that, The preparation method of the iron-silicon composite adsorbent is as follows: using tetraethyl orthosilicate as the silicon source, iron salt is added during the preparation of silica wet gel by sol-gel method, and then the obtained wet gel is aged, dried, ground, and sieved to obtain the iron-silicon composite adsorbent.

5. The application according to claim 1 or 4, characterized in that, The iron salt is ferric chloride hexahydrate.

6. The application according to claim 4, characterized in that, The step of incorporating iron salts in the preparation of silica wet gel using the sol-gel method is as follows: Tetraethyl orthosilicate, anhydrous ethanol, and iron salts are mixed and stirred in a water bath, and then the pH is adjusted while stirring until gel is formed.

7. The application according to claim 6, characterized in that, The water bath stirring temperature is 30-50℃, the time is 1 hour, and the stirring speed is 200-600 r / min.

8. The application according to claim 6, characterized in that, The pH value is 5-8.

5.

9. The application according to claim 4, characterized in that, The aging method involves immersing the wet gel in anhydrous ethanol for aging; the aging temperature is 40-60℃ and the time is 10-15h.

10. The application according to claim 4, characterized in that, The drying temperature is 85-100℃.

Images