A calcium silicate hydrate-based nano-adsorbent and its preparation method and application

Abstract

The present invention discloses a calcium silicate hydrate-based nano-adsorbent and a preparation method and application thereof. The nano-adsorbent is a composite of modified calcium silicate hydrate nano-particles and a dispersant. The modified calcium silicate hydrate nano-particles include calcium silicate hydrate nano-particles and iron ions, magnesium ions and aluminum ions doped in the calcium silicate hydrate nano-particles. After structural modification, the particle size of the calcium silicate hydrate-based nano-adsorbent is reduced, the specific surface area is greatly increased, and the number of adsorption sites on its surface that can adsorb heavy metals is significantly increased, thereby improving its adsorption efficiency and adsorption capacity for heavy metal ions.

Description

Technical Field

[0001] The present invention relates to the technical field, and in particular to a calcium silicate hydrate-based nano-adsorbent and a preparation method and application thereof. Background Art

[0002] Heavy metal pollution is characterized by high toxicity, accumulation, and non-degradability. With the development of industries such as mining, electroplating, batteries, fuels, and chemicals, more and more heavy metal-contaminated wastewater is being discharged into the environment, seriously affecting human survival and development. Cadmium, cobalt, copper, and chromium are common heavy metal ions found in heavy metal pollution. When cadmium concentrations exceed the safe range, they can cause significant damage to organisms that ingest the contaminated water, leading to osteoporosis, kidney damage, and an increased risk of cancer. Excessive intake of cobalt ions can cause tinnitus and sensorineural hearing loss, as well as radiation esophagitis and radiation pneumonitis. In severe cases, hypoxia, coma, and even death can occur. Excessive intake of copper ions can easily lead to copper poisoning, resulting in complications such as hepatitis and acute renal failure. Excessive chromium intake can also damage various human systems, making it prone to chronic oxidative diseases and a greater risk of developing abnormal growths such as tumors.

[0003] Methods for treating heavy metal ions include chemical precipitation, redox, solvent extraction, and heavy metal adsorption. Among them, the traditional heavy metal adsorption method is widely used due to its advantages of convenient operation, low cost, and efficient treatment. Its principle is to bind heavy metal ions in wastewater to the adsorption sites of the adsorbent through physical or chemical effects, thereby reducing the heavy metal ion content in the wastewater and achieving the purpose of water purification. Common heavy metal adsorbents have high production costs and low adsorption capacity. Nanoadsorbents have attracted widespread attention due to their large specific surface area and good adsorption effect. However, nanoadsorbents are expensive to prepare and are prone to aggregation and instability, which greatly reduces their adsorption effect after long-term storage.

[0004] Therefore, it is necessary to provide a nano-adsorbent with good stability and strong adsorption capacity for removing heavy metals from water. Summary of the Invention

[0005] In view of this, the present application provides a calcium silicate hydrate-based nano-adsorbent and its preparation method and application, to solve the problem of how to improve the stability and adsorption capacity of the nano-adsorbent.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a calcium silicate hydrate-based nano-adsorbent, which is a composite of modified calcium silicate hydrate nanoparticles and a dispersant, wherein the modified calcium silicate hydrate nanoparticles include calcium silicate hydrate nanoparticles and iron ions, magnesium ions, and aluminum ions doped in the calcium silicate hydrate nanoparticles.

[0008] In a second aspect, the present application provides a method for preparing a calcium silicate hydrate-based nano-adsorbent, comprising the following steps:

[0009] S1. The iron salt solution, magnesium salt solution, aluminum salt solution and water are mixed to obtain a mixed solution; the dispersant and water are mixed to obtain a bottom liquid;

[0010] S2. Add the mixed solution, calcium salt solution and silicate solution to the base liquid at the same time, stir and react, and obtain the hydrated calcium silicate-based nano-adsorbent.

[0011] Preferably, the iron salt includes one or more of ferric chloride, ferric nitrate, and ferric sulfate, the magnesium salt includes one or more of magnesium chloride, magnesium nitrate, and magnesium sulfate, and the aluminum salt includes one or more of aluminum chloride, aluminum nitrate, and aluminum sulfate.

[0012] Preferably, the calcium salt includes one or more of calcium chloride and calcium nitrate.

[0013] Preferably, the silicate is sodium metasilicate.

[0014] Preferably, the dispersant comprises a polycarboxylate water-reducing agent having a molecular weight of 5,000-100,000 g / mol, and the molar ratio of the dispersant to the silicate is 0.001-0.1:1.

[0015] Preferably, the molar ratio of the calcium salt to the silicate is (0.5-3):1.

[0016] Preferably, the ratio of the molar amount of the iron salt, magnesium salt, aluminum salt to the molar amount of the silicate is (0.01-0.5):(0.01-0.5):(0.01-0.5):1.

[0017] Preferably, in step S2, the reaction pH is 10-13.

[0018] In a third aspect, the present application provides an application of a calcium silicate hydrate-based nano-adsorbent in removing heavy metals from water bodies.

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

[0020] The present invention incorporates iron ions, magnesium ions, and aluminum ions into the calcium silicate hydrate structure. The iron ions are arranged in the silicon chain of the calcium silicate hydrate in the form of iron oxygen octahedron coordination, which can reduce the structural defects of the calcium silicate hydrate; the magnesium ions enter the calcium silicate hydrate structure and can fill the calcium ion defects in the structure; and the aluminum ions can fill the silicon oxygen tetrahedron vacancies in the silicon chain in the form of aluminum oxygen tetrahedrons. Therefore, these three ions can synergistically optimize the nanostructure of the calcium silicate hydrate, thereby improving the structural stability of the calcium silicate hydrate.

[0021] This application utilizes the comb-shaped structure of polycarboxylate water-reducing agent (PCE), the carboxyl groups on its main chain are used to complex cations, and the long side chains are used to exert steric hindrance, which has a good dispersing and stabilizing effect; and the incorporation of iron ions, magnesium ions and aluminum ions into the calcium silicate hydrate structure can complex more PCE, thereby promoting the adsorption of PCE by calcium silicate hydrate, strengthening the dispersing and stabilizing effect of the dispersant, and suppressing the particle agglomeration phenomenon of the calcium silicate hydrate-based nanoadsorbent, avoiding the precipitation of the suspension during long-term storage, and thus affecting the use effect of the calcium silicate hydrate-based nanoadsorbent.

[0022] The particle size of the calcium silicate-based nano-adsorbent after structural modification in the present application is reduced, the specific surface area is greatly increased, and the number of adsorption sites on its surface that can adsorb heavy metals is also significantly increased, which significantly improves its adsorption efficiency and adsorption capacity for heavy metal ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The XRD patterns of the calcium silicate hydrate-based nano-adsorbents of Example 1 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] The present application provides a calcium silicate hydrate-based nano-adsorbent, comprising calcium silicate hydrate nanoparticles and iron ions, magnesium ions, and aluminum ions doped in the calcium silicate hydrate nanoparticles.

[0026] In the calcium silicate hydrate nanoparticles of the present application, iron, magnesium, and aluminum optimize the structure of calcium silicate on the one hand, and improve the adsorption of calcium silicate to dispersants on the other hand. Both aspects are conducive to the stability of calcium silicate particles and prevent agglomeration. These three ions can synergistically optimize the nanostructure of calcium silicate hydrate, thereby improving the structural stability of calcium silicate hydrate. At the same time, the introduction of these three ions can complex more dispersants, thereby promoting the adsorption of calcium silicate hydrate to dispersants, strengthening the dispersion and stabilization effect of dispersants, and suppressing the particle agglomeration phenomenon of calcium silicate hydrate-based nano-adsorbents, thereby avoiding precipitation of the suspension during long-term storage, thereby affecting the use effect of calcium silicate hydrate-based nano-adsorbents.

[0027] The present application provides a method for preparing a calcium silicate hydrate-based nano-adsorbent, comprising the following steps:

[0028] S1. The iron salt solution, magnesium salt solution, aluminum salt solution and water are mixed to obtain a mixed solution; the dispersant and water are mixed to obtain a bottom liquid;

[0029] S2. Add the mixed solution, calcium salt solution and silicate solution to the base liquid at the same time, stir and react, and obtain the hydrated calcium silicate-based nano-adsorbent.

[0030] In this scheme, the calcium salt solution and the silicate solution must be added dropwise together, otherwise the calcium-silicon ratio in the synthesized calcium silicate will fluctuate greatly, and iron, magnesium, aluminum and calcium will react with silicate together.

[0031] In some embodiments, the iron salt includes one or more of ferric chloride, ferric nitrate, and ferric sulfate; the magnesium salt includes one or more of magnesium chloride, magnesium nitrate, and magnesium sulfate; and the aluminum salt includes one or more of aluminum chloride, aluminum nitrate, and aluminum sulfate.

[0032] In some embodiments, the calcium salt includes one or more of calcium chloride and calcium nitrate.

[0033] In some embodiments, the silicon salt is sodium metasilicate.

[0034] In some embodiments, the dispersant comprises a polycarboxylate water-reducing agent having a molecular weight of 5,000-100,000 g / mol, and the molar ratio of the dispersant to the silicate is 0.001-0.1:1.

[0035] In some embodiments, the molar ratio of the calcium salt to the silicate is (0.5-3):1.

[0036] In some embodiments, the ratio of the sum of the molar amounts of the iron salt, magnesium salt, and aluminum salt to the molar amount of the silicate is (0.01-0.5):(0.01-0.5):(0.01-0.5):1; more preferably, the ratio of the sum of the molar amounts of the iron salt, magnesium salt, and aluminum salt to the molar amount of the silicate is 0.2-0.3:0.05-0.08:0.1-0.2:1.

[0037] In some embodiments, in step S2, the reaction pH is 10-13, the dropwise addition time is 0.1-5 h, the reaction time after the dropwise addition is completed is 1-72 h, and the stirring rate is 100-800 rpm.

[0038] The present application provides an application of a calcium silicate hydrate-based nano-adsorbent in removing heavy metals from water bodies.

[0039] The present application is further described below through specific examples.

[0040] The dispersant selected is WQ-I type polycarboxylate water reducer produced by Guizhou Wanqian Building Materials Co., Ltd., with a molecular weight of 12850 g / mol.

[0041] Example 1

[0042] A method for preparing a calcium silicate hydrate-based nano-adsorbent comprises the following steps:

[0043] Weigh 1.5 mol of calcium chloride and 625.0 g of water and mix them to obtain a calcium chloride solution, then weigh 1.0 mol of sodium silicate and 550.0 g of water and mix them to obtain a sodium silicate solution; weigh 0.20 mol of ferric chloride, 0.05 mol of magnesium chloride, 0.10 mol of aluminum chloride and 700.0 g of water and mix them to obtain a mixed solution; add 0.01 mol / g of dispersant and 2500.0 g of water as a base liquid into the reaction vessel, set the stirring speed to 400 rpm and start stirring; add the calcium chloride solution, the mixed solution and the sodium silicate solution dropwise into the reaction vessel at the same time, control the dropping time to 0.5 h and the reaction pH to 11.0; after the dropping is completed, continue stirring for 18 h to obtain a hydrated calcium silicate-based nano-adsorbent. XRD spectrum is as follows Figure 1 shown.

[0044] Example 2

[0045] A method for preparing a calcium silicate hydrate-based nano-adsorbent comprises the following steps:

[0046] 0.8 mol of calcium chloride and 625.0 g of water are weighed and mixed to obtain a calcium chloride solution, and then 1.0 mol of sodium silicate and 550.0 g of water are weighed and mixed to obtain a sodium silicate solution; 0.20 mol of ferric chloride, 0.05 mol of magnesium chloride, 0.10 mol of aluminum chloride and 700.0 g of water are weighed and mixed to obtain a mixed solution; 0.01 mol / g of a dispersant and 2500.0 g of water are added to a reaction vessel as a base liquid, and the stirring speed is set to 400 rpm and stirring is started; the calcium chloride solution, the mixed solution and the sodium silicate solution are simultaneously added dropwise to the reaction vessel, and the dropping time is controlled to be 0.5 h and the reaction pH is controlled to be 11.0; after the dropwise addition is completed, stirring is continued for 18 h to obtain a hydrated calcium silicate-based nanoadsorbent.

[0047] Example 3

[0048] A method for preparing a calcium silicate hydrate-based nano-adsorbent comprises the following steps:

[0049] 1.5 mol of calcium chloride and 625.0 g of water are weighed and mixed to obtain a calcium chloride solution, and then 1.0 mol of sodium silicate and 550.0 g of water are weighed and mixed to obtain a sodium silicate solution; 0.20 mol of ferric chloride, 0.05 mol of magnesium chloride, 0.10 mol of aluminum chloride and 700.0 g of water are weighed and mixed to obtain a mixed solution; 0.03 mol / g of a dispersant and 2500.0 g of water are added to a reaction vessel as a base liquid, and the stirring speed is set to 400 rpm and stirring is started; the calcium chloride solution, the mixed solution and the sodium silicate solution are simultaneously added dropwise to the reaction vessel, and the dropping time is controlled to be 0.5 h and the reaction pH is controlled to be 11.0; after the dropwise addition is completed, stirring is continued for 18 h to obtain a hydrated calcium silicate-based nanoadsorbent.

[0050] Example 4

[0051] A method for preparing a calcium silicate hydrate-based nano-adsorbent comprises the following steps:

[0052] 1.5 mol of calcium chloride and 625.0 g of water are weighed and mixed to obtain a calcium chloride solution, and then 1.0 mol of sodium silicate and 550.0 g of water are weighed and mixed to obtain a sodium silicate solution; 0.20 mol of ferric chloride, 0.05 mol of magnesium chloride, 0.10 mol of aluminum chloride and 700.0 g of water are weighed and mixed to obtain a mixed solution; 0.01 mol / g of a dispersant and 2500.0 g of water are added to a reaction vessel as a base liquid, and the stirring speed is set to 400 rpm and stirring is started; the calcium chloride solution, the mixed solution and the sodium silicate solution are simultaneously added dropwise to the reaction vessel, and the dropping time is controlled to be 0.5 h and the reaction pH is controlled to be 12.5; after the dropwise addition is completed, stirring is continued for 18 h to obtain a hydrated calcium silicate-based nanoadsorbent.

[0053] Comparative Example 1

[0054] A method for preparing a hydrated calcium silicate-based nano-adsorbent, the other contents are the same as those in Example 1, except that ferric chloride, magnesium chloride and aluminum chloride are not added. Figure 1 shown.

[0055] Comparative Example 2

[0056] A method for preparing a hydrated calcium silicate-based nano-adsorbent is the same as Example 1 in other aspects, except that raw material powders are prepared in proportion, water is directly added, and the mixture is stirred for reaction.

[0057] Comparative Example 3

[0058] A method for preparing a hydrated calcium silicate-based nano-adsorbent is the same as Example 1 except that the mixture of ferric chloride, magnesium chloride, and aluminum chloride is replaced by an equal molar amount of ferric chloride (0.35 mol).

[0059] Comparative Example 4

[0060] A method for preparing a hydrated calcium silicate-based nano-adsorbent is the same as Example 1 except that the mixture of ferric chloride, magnesium chloride, and aluminum chloride is replaced by an equimolar amount of magnesium chloride (0.35 mol).

[0061] Comparative Example 5

[0062] A method for preparing a hydrated calcium silicate-based nano-adsorbent is the same as Example 1 except that the mixture of ferric chloride, magnesium chloride, and aluminum chloride is replaced by an equimolar amount of aluminum chloride (0.35 mol).

[0063] Comparative Example 6

[0064] A method for preparing a hydrated calcium silicate-based nano-adsorbent is the same as Example 1 except that the mixture of ferric chloride, magnesium chloride, and aluminum chloride is replaced by an equimolar amount of sodium chloride (0.35 mol).

[0065] Evaluation Test

[0066] Weigh 0.5g of hydrated calcium silicate-based nano-adsorbent into a wide-mouth bottle with an effective volume of 1000ml, and add 60mg / L of Co 2+ solution, 60 mg / L Cu 2+ solution, 60 mg / L Cr 3+ solution and 60 mg / L Cd 2+ The solution was prepared and the pH value of the solution was adjusted between 10 and 14 by adding acid and alkali. The jar was placed on a thermostatic magnetic stirrer (200 rpm). After 3 hours, the solution was centrifuged to obtain a supernatant. The concentration of heavy metals remaining in the supernatant was measured, and the adsorption capacity of the adsorbent for each heavy metal ion was finally calculated. The results are shown in Table 1.

[0067] Table 1 Adsorption capacity of various metal ions (mg / g -1 )surface

[0068] Ion type <![CDATA[Cu 2+ ]]> <![CDATA[Cd 2+ ]]> <![CDATA[Co 2+ ]]> <![CDATA[Cr 2+ ]]> Experimental Example 1 465.21 253.42 388.16 280.55 Experimental Example 2 415.65 257.18 315.39 252.64 Experimental Example 3 344.62 226.53 252.41 203.28 Experimental Example 4 483.26 277.53 396.18 304.76 Comparative Example 1 245.42 165.73 212.34 179.86 Comparative Example 2 50.64 23.85 64.73 43.51 Comparative Example 3 328.12 202.78 276.38 222.95 Comparative Example 4 312.75 188.62 224.73 198.24 Comparative Example 5 334.78 211.84 282.31 237.06 Comparative Example 6 221.56 152.83 184.64 152.35

[0069] It can be seen that the adsorption capacity of the calcium silicate hydrate-based nano-adsorbent of the present application is significantly greater than that of the comparative example.

[0070] To further characterize the stability of the calcium silicate hydrate-based nanoadsorbents proposed herein, the particle size of samples from Example 1 and Comparative Examples 1-6 was measured using dynamic light scattering. The test results are shown in Table 2. As can be seen from Table 2, the particle size of the calcium silicate hydrate-based nanoadsorbents remained stable over time only in the presence of iron, magnesium, and aluminum ions, demonstrating excellent stability.

[0071] Table 2 Particle size (nm) under the same indoor conditions for different time periods

[0072] 1d 30d 180d 360d Example 1 85 86 88 88 Comparative Example 1 172 253 324 407 Comparative Example 2 326 452 517 583 Comparative Example 3 116 142 171 183 Comparative Example 4 141 187 203 242 Comparative Example 5 107 132 145 169 Comparative Example 6 196 281 357 429

[0073] Figure 1 The XRD patterns of the calcium silicate hydrate-based nano-adsorbents prepared in Example 1 and Comparative Example 1 show that the structure of the calcium silicate hydrate-based nano-adsorbents after the simultaneous addition of iron ions, magnesium ions and aluminum ions is obviously amorphous, proving that the iron ions, magnesium ions and aluminum ions have modified their structure.

[0074] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A calcium silicate hydrate-based nano-adsorbent, characterized in that: The invention relates to a composite of modified calcium silicate hydrate nanoparticles and a dispersant. The modified calcium silicate hydrate nanoparticles include calcium silicate hydrate nanoparticles and iron ions, magnesium ions and aluminum ions doped in the calcium silicate hydrate nanoparticles. The preparation method of the calcium silicate hydrate-based nanoadsorbent comprises the following steps: S1. The iron salt solution, magnesium salt solution, aluminum salt solution and water are mixed to obtain a mixed solution; the dispersant and water are mixed to obtain a bottom liquid; S2. The mixed solution, calcium salt solution and silicate solution are simultaneously added dropwise to the base liquid, and the reaction is stirred to obtain the hydrated calcium silicate-based nano-adsorbent; the dispersant comprises a polycarboxylate water-reducing agent having a molecular weight of 5000-100000 g / mol; in step S2, the reaction pH is 10-13.

2. The calcium silicate hydrate-based nano-adsorbent according to claim 1, characterized in that: The iron salt includes one or more of ferric chloride, ferric nitrate, and ferric sulfate; the magnesium salt includes one or more of magnesium chloride, magnesium nitrate, and magnesium sulfate; and the aluminum salt includes one or more of aluminum chloride, aluminum nitrate, and aluminum sulfate.

3. The calcium silicate hydrate-based nano-adsorbent according to claim 1, characterized in that: The calcium salt includes one or more of calcium chloride and calcium nitrate.

4. The calcium silicate hydrate-based nano-adsorbent according to claim 1, characterized in that: The silicate is sodium metasilicate.

5. The calcium silicate hydrate-based nano-adsorbent according to claim 1, characterized in that: The molar ratio of the calcium salt to the silicate is (0.5-3):

1.

6. The calcium silicate hydrate-based nano-adsorbent according to claim 1, characterized in that: The ratio of the molar amount of the iron salt, magnesium salt, and aluminum salt to the molar amount of the silicate is (0.01-0.5):(0.01-0.5):(0.01-0.5):

1.

7. Use of the calcium silicate hydrate-based nano-adsorbent according to claim 1 in removing heavy metals from water.

Images