Composite hydrotalcite with corrosion inhibitor growing on surface layer as well as preparation method and application of composite hydrotalcite

Abstract

The invention discloses a preparation method of composite hydrotalcite with a corrosion inhibitor growing on the surface layer. The preparation method comprises the following steps: 1, respectively weighing zinc nitrate hexahydrate, aluminum nitrate nonahydrate and urea, and dissolving the zinc nitrate hexahydrate, the aluminum nitrate nonahydrate and the urea in water to prepare solutions; 2, the solution is heated, stirred, washed and centrifuged, and hydrotalcite is obtained; 3, drying the centrifuged hydrotalcite in vacuum to obtain zinc-aluminum nitrate hydrotalcite; step 4, placing the zinc-aluminum nitrate hydrotalcite in a muffle furnace, calcining, and then cooling to room temperature to obtain roasted zinc-aluminum hydrotalcite powder; step 5, respectively weighing di-methylimidazole and roasted zinc-aluminum hydrotalcite powder, and dissolving the di-methylimidazole and the roasted zinc-aluminum hydrotalcite powder in methanol to prepare a solution; 6, the solution is heated, violently stirred, centrifuged and washed, and ZLO is obtained; and 7, carrying out vacuum drying on the centrifuged ZLO to obtain the composite hydrotalcite ZLO. According to the method, ZIF-8 is synthesized more efficiently through LDHs surface metal point locations, and meanwhile, the use of raw materials is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of corrosion protection of reinforced concrete structures, and particularly relates to a composite hydrotalcite with rust inhibitor grown on the surface, a preparation method and application thereof. BACKGROUND

[0002] In marine environments, the corrosion of steel bars seriously threatens the durability of structures, and poses a major safety hazard and causes economic losses. The complexity of marine environments exposes reinforced concrete structures to high concentrations of chloride ions (Cl-) for a long time. Cl- can penetrate the pores of concrete and reach the surface of steel bars due to its small radius and high diffusivity, which can destroy the passivation film of steel bars and induce corrosion. At the same time, Cl- reacts with cement hydration products (such as Ca(OH)2) to generate expansive crystals (such as Friedel salt), which exacerbates the deterioration of concrete and Cl- penetration.

[0003] Therefore, it is crucial to develop efficient Cl- interception and steel corrosion inhibition products to prolong the service life of reinforced concrete structures in the marine environment.

[0004] Current corrosion protection technologies include high-performance concrete, cathodic protection, and rust inhibitors. Among them, inorganic rust inhibitors (such as nitrite) are limited due to their toxicity, and organic rust inhibitors (such as imidazole derivatives) are environmentally friendly, but they have the defect of insufficient long-term stability. In recent years, intelligent rust inhibition systems based on nano-carriers have attracted much attention. They can load rust inhibition components and achieve controlled release, converting passive protection into active adaptation. Layered double hydroxides (LDHs), hydrotalcite-like compounds, are a kind of inorganic nano-carriers with adjustable interlayer. Its general formula is [M 2+ 1-x M 3+ x (OH)2][A n- ] x / n ·mH2O, where M 2+ and M 3+ are metal ions, A n- is an anion to balance the charge, and x is stable between 0.2 and 0.3. LDHs are a kind of nano-materials with good interlayer anion exchangeability and structural memory effect. At the same time, LDO obtained by calcining LDO has high specific surface area, alkaline surface and ion adsorption capacity, becoming an ideal nano-carrier. However, single LDO has limited adsorption capacity for Cl-, and lacks the function of in-situ release of rust inhibition components.

[0005] As a representative of metal-organic frameworks (MOFs), zeolitic imidazolate framework-8 (ZIF-8) has a microporous structure and pH-responsive characteristics, can selectively adsorb Cl- and release typical organic corrosion inhibitor molecules imidazole molecules in a slightly acidic environment, and has both physical barrier and chemical passivation functions. Its natural fragility and poor separability limit its application, which affects its long-term stability under harsh use conditions. SUMMARY

[0006] In order to overcome the above technical problems, the purpose of the present application is to provide a kind of surface layer growth corrosion inhibitor composite hydrotalcite and its preparation method and application, by LDHs surface metal point more efficient synthesis ZIF-8, while reducing the use of raw materials. In order to delay the destruction of concrete structure caused by steel corrosion in marine concrete, improve the durability of concrete.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0008] A kind of preparation method of surface layer growth corrosion inhibitor composite hydrotalcite, comprising the following steps:

[0009] Step 1: respectively take zinc nitrate hexahydrate, aluminum nitrate nonahydrate and urea dissolved in water to prepare a solution;

[0010] Step 2: the solution is heated and stirred, washed with water, centrifuged, and hydrotalcite is obtained;

[0011] Step 3: vacuum drying the centrifuged hydrotalcite to obtain zinc aluminum nitrate hydrotalcite;

[0012] Step 4: the zinc aluminum nitrate hydrotalcite is placed in a muffle furnace, calcined, and then cooled to room temperature to obtain calcined zinc aluminum hydrotalcite powder;

[0013] Step 5: respectively take dimethyl imidazole and calcined zinc aluminum hydrotalcite powder dissolved in methanol to prepare a solution; the molar ratio of dimethyl imidazole to Zn2+ in calcined zinc aluminum hydrotalcite powder is 1.5:1-2:1;

[0014] Step 6: the solution is heated, stirred vigorously, centrifuged, and washed with water to obtain ZLO;

[0015] Step 7: vacuum drying the centrifuged ZLO to obtain composite hydrotalcite ZLO.

[0016] In the step 1, the molar ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate and urea is 2:0.8-1:8.5-10, the water mass is weighed according to 65%-75% of the preparation container, and the stirring is continued for 20-40 min. The reasonable range of adding aluminum nitrate nonahydrate reduces the occurrence of a large amount of agglomeration. Both water and methanol are 65%-75%. The stirring is for early dispersion, pretreatment of the material.

[0017] In the step 1, the water required for configuring the solution is deionized water after boiling.

[0018] In the step 2, the solution is heated to 90-100℃, and stirred vigorously for 2-3h, and then centrifuged and washed with water for 3-5 times. Under this temperature ratio, the crystallinity, ion activity and reaction rate are increased sharply.

[0019] In the step 3, the zinc-aluminum hydrotalcite after centrifugation is placed in an environment of 65-95℃ for vacuum drying for 12-24h. Under the premise of not damaging the structural stability, the interlayer water and surface moisture are removed as much as possible, and the evaporation efficiency is ensured.

[0020] In the step 4, the heating rate is 6-9℃ / min, the temperature is raised to 580-600℃, and then calcined for 5-6h, and then cooled to room temperature. The heating rate is an optimized parameter that balances the efficiency and material integrity. It ensures the production efficiency and ensures that the zinc-aluminum nitrate hydrotalcite interlayer collapses rather than the material breaks.

[0021] In the step 5, the methanol solution required for configuring the solution is analytical pure and can be used directly without purification; the methanol mass is weighed according to 65%-75% of the preparation container, and the stirring is continued for 20-40 min.

[0022] In the step 6, the solution is heated to 40-50℃, and stirred vigorously for 5-6h, and then centrifuged and washed with water for 3-5 times.

[0023] In the step 7, the ZLO after centrifugation is placed in an environment of 65-95℃ for vacuum drying for 12-24h to obtain the composite hydrotalcite ZLO.

[0024] The composite hydrotalcite of the surface layer growth rust inhibitor prepared by the preparation method has the effects of enhanced adsorption of chloride ions, which is a physical level. Because the rust point generated by the corrosion of the steel bar causes the pH to decrease in the slightly acidic environment, the ZIF-8 in the ZLO adsorbed on the surface of the steel bar produces a protonation reaction to release the rust inhibitor molecule imidazole, which is a chemical level. In the microstructure, it can be seen that the ZIF-8 grown on the surface of ZLO is reduced;

[0025] The rhombic dodecahedron ZIF-8 nanocrystals are uniformly distributed on the particles of the LDO, the particle size is about 70 nm, and part of the ZLO is embedded between the layers of the LDO or attached to the surface, and the edges of part of the ZLO lamella are irregularly wrinkled.

[0026] The application of the surface layer growth of the rust inhibitor composite hydrotalcite in the corrosion prevention of reinforced concrete, by means of an admixture, a certain mass fraction (such as 1%) of cementitious materials is added during the mixing of the concrete.

[0027] The present application has the following beneficial effects:

[0028] The present application is prepared in situ, and the surface zinc in the calcined zinc-aluminum hydrotalcite is used as a binding site, and ZIF-8 is grown on the surface of the calcined zinc-aluminum hydrotalcite by adding di-methyl imidazole and a catalyst sodium formate, and the calcination-reduction is modified to in-situ growth. The control accuracy of the synthesis conditions is relatively low, and the synthesized ZLO has excellent rust resistance, excellent Cl - adsorption effect in the concrete, and forms a ZLO physical barrier on the surface of the steel bar, delays the transmission rate of Cl - and O2, and when the steel bar rusts, a secondary repair coating film is formed on the pitting site, further delaying the rusting process of the steel bar. Therefore, ZLO has greater promotion significance and practical value in the rust resistance of the steel bar. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is an X-ray diffraction pattern of ZLO.

[0030] Figure 2 It is an FTIR spectrum of ZLO.

[0031] Figure 3 It is a BET spectrum of ZLO.

[0032] Figure 4 It is an adsorption isotherm model graph of ZLO for Cl

[0033] Figure 5 It is a Nyquist graph of the steel bar under different Cl - concentration conditions in group A SCPs.

[0034] Figure 6 It is a Nyquist graph of the steel bar under different Cl - concentration conditions in group B SCPs.

[0035] Figure 7 It is a Bode graph of the steel bar under different Cl - concentration conditions in group A SCPs.

[0036] Figure 8For the different Cl values ​​of steel bars in Group B SCPs - Bode plot under concentration conditions.

[0037] Figure 9 The image shows the morphology of composite hydrotalcite ZLO. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the embodiments.

[0039] In this embodiment of the invention, zinc nitrate hexahydrate, aluminum nitrate nonahydrate, and urea are analytical and purified chemical reagents from Aladdin and McLean, respectively. The water required to prepare the solution is boiled deionized water.

[0040] Example 1: A method for preparing a composite hydrotalcite with a surface growth rust inhibitor, comprising the following steps:

[0041] (1) Weigh out 14g of zinc nitrate hexahydrate, 4.4g of aluminum nitrate nonahydrate and 16g of urea respectively, dissolve them in water to prepare a solution, and stir continuously for 40min;

[0042] (2) Heat the solution to 100°C, stir vigorously for 3 hours, then centrifuge and wash with water 3 times;

[0043] (3) The centrifuged hydrotalcite was placed in a vacuum drying environment at 95°C for 15 hours to obtain zinc aluminum nitrate hydrotalcite.

[0044] (4) The zinc-aluminum hydrotalcite powder was placed in a muffle furnace and heated at a rate of 6℃ / min. After heating to 600℃, it was calcined for 6 hours and then cooled to room temperature. The resulting powder was calcined zinc-aluminum hydrotalcite.

[0045] (5) Weigh 8.3g of di-methylimidazole and 5g of calcined zinc aluminum hydrotalcite and dissolve them in methanol to prepare a solution. Stir continuously for 40min.

[0046] (6) Heat the solution to 50°C, stir vigorously for 6 hours, then centrifuge and wash with water 3 times;

[0047] (7) After centrifugation, place the product in a vacuum dryer at 95°C for 15 hours to obtain ZLO.

[0048] Example 2: A method for preparing a composite hydrotalcite with a surface growth rust inhibitor, comprising the following steps:

[0049] (1) Weigh out 14g of zinc nitrate hexahydrate, 5g of aluminum nitrate nonahydrate and 16g of urea respectively, dissolve them in water to prepare a solution, and stir continuously for 40min;

[0050] (2) Heat the solution to 100°C, stir vigorously for 3 hours, then centrifuge and wash with water 3 times;

[0051] (3) The centrifuged hydrotalcite was placed in a vacuum drying environment at 95°C for 15 hours to obtain zinc aluminum nitrate hydrotalcite.

[0052] (4) The zinc-aluminum hydrotalcite powder was placed in a muffle furnace and heated at a rate of 6℃ / min. After heating to 600℃, it was calcined for 6 hours and then cooled to room temperature. The resulting powder was calcined zinc-aluminum hydrotalcite.

[0053] (5) Weigh 8.3g of di-methylimidazole and 5g of calcined zinc aluminum hydrotalcite and dissolve them in methanol to prepare a solution. Stir continuously for 40min.

[0054] (6) Heat the solution to 50°C, stir vigorously for 6 hours, then centrifuge and wash with water 3 times;

[0055] (7) After centrifugation, place the product in a vacuum dryer at 95°C for 15 hours to obtain ZLO.

[0056] Example 3: A method for preparing a composite hydrotalcite with a surface growth rust inhibitor, comprising the following steps:

[0057] (1) Weigh out 14g of zinc nitrate hexahydrate, 5.6g of aluminum nitrate nonahydrate and 16g of urea respectively, dissolve them in water to prepare a solution, and stir continuously for 40min;

[0058] (2) Heat the solution to 100°C, stir vigorously for 3 hours, then centrifuge and wash with water 3 times;

[0059] (3) The centrifuged hydrotalcite was placed in a vacuum drying environment at 95°C for 15 hours to obtain zinc aluminum nitrate hydrotalcite.

[0060] (4) The zinc-aluminum hydrotalcite powder was placed in a muffle furnace and heated at a rate of 6℃ / min. After heating to 600℃, it was calcined for 6 hours and then cooled to room temperature. The resulting powder was calcined zinc-aluminum hydrotalcite.

[0061] (5) Weigh 8.3g of di-methylimidazole and 5g of calcined zinc aluminum hydrotalcite and dissolve them in methanol to prepare a solution. Stir continuously for 40min.

[0062] (6) Heat the solution to 50°C, stir vigorously for 6 hours, then centrifuge and wash with water 3 times;

[0063] (7) After centrifugation, place the product in a vacuum dryer at 95°C for 15 hours to obtain ZLO.

[0064] Comparative Example 1: A method for preparing a composite hydrotalcite with a surface growth rust inhibitor, comprising the following steps:

[0065] (1) Weigh out 14g of zinc nitrate hexahydrate, 3.6g of aluminum nitrate nonahydrate and 16g of urea respectively, dissolve them in water to prepare a solution, and stir continuously for 40min;

[0066] (2) Heat the solution to 100°C, stir vigorously for 3 hours, then centrifuge and wash with water 3 times;

[0067] (3) The centrifuged hydrotalcite was placed in a vacuum drying environment at 95°C for 15 hours to obtain zinc aluminum nitrate hydrotalcite.

[0068] (4) The zinc-aluminum hydrotalcite powder was placed in a muffle furnace and heated at a rate of 6℃ / min. After heating to 600℃, it was calcined for 6 hours and then cooled to room temperature. The resulting powder was calcined zinc-aluminum hydrotalcite.

[0069] (5) Weigh 8.3g of di-methylimidazole and 5g of calcined zinc aluminum hydrotalcite and dissolve them in methanol to prepare a solution. Stir continuously for 40min.

[0070] (6) Heat the solution to 50°C, stir vigorously for 6 hours, then centrifuge and wash with water 3 times;

[0071] (7) After centrifugation, place the product in a vacuum dryer at 95°C for 15 hours to obtain ZLO.

[0072] Comparative Example 2: A method for preparing a composite hydrotalcite with a surface growth rust inhibitor, comprising the following steps:

[0073] (1) Weigh out 14g of zinc nitrate hexahydrate, 10g of aluminum nitrate nonahydrate and 16g of urea respectively, dissolve them in water to prepare a solution, and stir continuously for 40min;

[0074] (2) Heat the solution to 100°C, stir vigorously for 3 hours, then centrifuge and wash with water 3 times;

[0075] (3) The centrifuged hydrotalcite was placed in a vacuum drying environment at 95°C for 15 hours to obtain zinc aluminum nitrate hydrotalcite.

[0076] (4) The zinc-aluminum hydrotalcite powder was placed in a muffle furnace and heated at a rate of 6℃ / min. After heating to 600℃, it was calcined for 6 hours and then cooled to room temperature. The resulting powder was calcined zinc-aluminum hydrotalcite.

[0077] (5) Weigh 8.3g of di-methylimidazole and 5g of calcined zinc aluminum hydrotalcite and dissolve them in methanol to prepare a solution. Stir continuously for 40min.

[0078] (6) Heat the solution to 50°C, stir vigorously for 6 hours, then centrifuge and wash with water 3 times;

[0079] (7) After centrifugation, place the product in a vacuum dryer at 95°C for 15 hours to obtain ZLO.

[0080] Figure 1The XRD patterns of LDHs, LDO, ZIF-8, and ZLO are shown. The LDHs sample exhibits characteristic peaks at 2θ = 11.7°, 23.5°, and 34.7°, corresponding to the (003), (006), and (009) planes, respectively, indicating an ordered layered double hydroxide structure. After calcination at 600°C, these peaks disappear, and broad reflections appear at 2θ = 31.8° and 34.4°, corresponding to the ZnO (100) and Al2O3 (311) planes, respectively, confirming the decomposition of the layered structure and the formation of highly dispersed LDO. In the ZLO sample, the broad peaks of LDO coexist with those of ZIF-8 at 2θ = 7.3°, 10.4°, and 12.7°, corresponding to the (011), (002), and (112) planes of the sodalite-type framework, respectively. The absence of other peaks indicates that the in-situ crystallization of ZIF-8 does not damage the oxide matrix, thus confirming that ZLO has been successfully formed and that both components are intact.

[0081] Figure 2 The displayed spectra are FTIR spectra of LDHs, LDO, ZIF-8, and ZLO. The LDHs sample is at 1380 cm⁻¹. -1 and 830cm -1 A spectral band appears at this point, corresponding to interlayer NO. 3- The ν3 and ν2 vibrations confirmed the presence of the nitrate anion. Due to NO... 3- Thermal decomposition occurs during calcination, and these bands disappear at ZLO. (3130 to 2920 cm⁻¹) -1 The new bands between them correspond to the stretching vibrations of aromatic (sp2) and methyl (sp3) CH, while at 1580 cm⁻¹ -1 and 1450cm -1 The peak at 421 cm⁻¹ is attributed to the C=N and CN stretching vibrations in the imidazole ring. -1 The spectral band at 550 cm⁻¹ confirms Zn-N coordination, while the band at 550 cm⁻¹... -1 and 480cm -1 The vibrations at this location indicate the presence of Zn-O and Al-O bonds. Furthermore, at 3450 cm⁻¹... -1 The broad peak at 1640cm -1 The spectral bands at these locations correspond to the OH stretching vibration and the HOH bending vibration, respectively, reflecting the presence of residual water in the interlayer and confirming structural hydration.

[0082] Figure 3The figures shown are nitrogen adsorption-desorption isotherms for LDHs, LDO, ZIF-8, and ZLO. ZIF-8 exhibits a typical Type I isotherm, with adsorption increasing sharply at low relative pressures (P / P0 < 0.1), indicating abundant micropores (0.3 nm). LDHs and LDO both exhibit Type IV isotherms. Due to structural collapse during calcination, the ZLO composite material exhibits characteristics of both Type I and Type IV isotherms, indicating the coexistence of microporous ZIF-8 and mesoporous LDO structures. The specific surface area of ​​ZLO reaches 458.1 m². 2 / g, significantly higher than LDHs (17.1m 2 / g) and LDO (52.6m 2 ( / g) provides more active sites for adsorption.

[0083] 1. Analysis of ZLO's adsorption capacity for chloride ions

[0084] The chloride ion adsorption capacity was tested using ZLO prepared in Example 1. The specific operating steps are as follows: A certain amount of sodium chloride was dissolved in 100 mL of deionized water to prepare sodium chloride solutions with concentrations of 0.01 mol / L, 0.02 mol / L, 0.04 mol / L, 0.08 mol / L, 0.16 mol / L, and 0.32 mol / L. 0.5 g of ZLO was added to the sodium chloride solutions, and the mixture was shaken at 240 r / min for 5 h, then allowed to stand for 24 h. Subsequently, 5 mL of the supernatant was extracted and mixed with 20 mL of deionized water to prepare a titration solution. The chloride ion concentration in the titration solution was tested using ion chromatography. - The concentration of Cl. - Adsorption capacity (Q) e Calculate according to the equation:

[0085]

[0086] Among them, Q e This represents the adsorption capacity of ZLO under equilibrium conditions, where V is the volume of the solution, and C0 and C2 are also present. e They are Cl - The initial and equilibrium concentrations are given by m, where m is the mass of the adsorbent.

[0087] like Figure 4 As shown, ZLO is related to Cl - The adsorption capacity was 225.5 mg / g, and it conformed to the Langmuir adsorption model as a monolayer adsorption model.

[0088] 2. Electrochemical testing and analysis of ZLO

[0089] Electrochemical tests were performed on the ZLO obtained in Example 1. The specific operating steps are as follows:

[0090] (1) Selection of testing instruments and preparation of test pieces and samples.

[0091] The electrochemical workstation used a PARSTAT 4000A for testing. The electrochemical test used Q235 steel bars with dimensions of Φ10mm×10mm, and the simulated concrete pore solution (SCPs) was a saturated Ca(OH)2 solution.

[0092] (2) Preparation of working electrode.

[0093] One section of the steel bar was selected as the test surface, and a copper wire was welded to the other section. The rest of the surface, except for the test surface, was sealed with PVC pipe and epoxy resin. The test surface was then polished step by step with 600#, 1000#, 1500#, and 2000# sandpaper. Finally, it was ultrasonically cleaned in anhydrous ethanol and dried for later use.

[0094] (3) Test the changes in electrochemical impedance spectroscopy (EIS) of steel bars in SCPs to evaluate the corrosion inhibition performance of ZLO on steel bars.

[0095] A three-electrode system was used, with the pre-fabricated steel bar as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum electrode as the counter electrode. EIS tests were performed every 24 hours at room temperature. First, the open-circuit potential (OCP) was tested. The system was considered stable when the OCP variation was within ±2mV over 5 minutes. Then, the EIS test was performed using a sine wave as the excitation signal, with an amplitude of 10mV and a test frequency range of 0.01Hz-10Hz. 5 Hz.

[0096] The working electrodes were immersed in two groups of SCPs, A and B, respectively. Group A consisted of 350 mL of SCPs, and Group B consisted of 350 mL of SCPs with 0.5% ZLO (0.5% of the solution mass) added. Three working electrodes were placed in each group of SCPs. After the reinforcing steel was completely passivated, 0.02 mol / L Cl was added to both groups of SCPs every 24 hours. - Until the steel bars rust.

[0097] Figures 5 to 8 As can be seen from group A, the Nyquist plot shows a single capacitive arc, and the radius of the capacitive arc decreases rapidly with increasing erosion concentration; for group B, in Cl... - Under erosion, with Cl - The increase in capacitive arc radius did not significantly decrease, and it reached the passivation film Cl -After reaching the threshold, the capacitive arc radius decreased rapidly, but increased again at 4 days. This was attributed to a protonation reaction in the slightly acidic environment, which caused the release of imidazole molecules to repair corrosion sites. Furthermore, the capacitive arc radius in group B was significantly larger than that in group A. The experimental results demonstrate that the addition of ZLO significantly increases the chloride ion concentration threshold for steel corrosion, effectively delaying steel corrosion.

[0098] Electrochemical testing and analysis of the ZLOs prepared in Examples 2 and 3, and Comparative Examples 1 and 2, using the same method, revealed that the steel bars in the ZLOs prepared in Examples 2 and 3 corroded at a chloride ion concentration of 6 days, while the steel bars in the ZLOs prepared in Comparative Examples 1 and 2 corroded at chloride ion concentrations of 3 days and 4 days, respectively. Therefore, it can be seen that the ZLOs prepared in Examples 1-3 of this invention can significantly delay the corrosion of steel bars compared to the ZLOs prepared in Comparative Examples 1 and 2.

[0099] The method for synthesizing composite hydrotalcite with surface-grown rust inhibitors disclosed in this invention is relatively simple, and the control precision of the synthesis conditions is not strict. Furthermore, the synthesized ZLO exhibits excellent rust-inhibiting ability, and it not only possesses strong Cl-reinforcing properties within concrete... - Adsorption capacity, forming an obstacle to Cl on the surface of the steel reinforcement. - It forms a physical barrier to oxygen transport and can also release imidazole ions to form a protective film on the steel bars, greatly slowing down the corrosion process of the steel bars.

[0100] like Figure 9 As shown in the SEM image of ZLO, uniformly distributed rhombic dodecahedral ZIF-8 nanocrystals (particle size ~70 nm) are visible on the LDO particles, some of which are embedded in the LDO interlayers or attached to the surface. Some ZLO lamellar edges exhibit irregular wrinkles, which are attributed to structural stress caused by the expansion of interlayer channels during ZIF-8 growth.

[0101] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a composite hydrotalcite with a surface growth rust inhibitor, characterized in that, Includes the following steps; Step 1: Weigh out zinc nitrate hexahydrate, aluminum nitrate nonahydrate, and urea respectively, and dissolve them in water to prepare solutions; Step 2: Heat and stir the solution, wash with water, and centrifuge to obtain hydrotalcite; Step 3: Vacuum dry the centrifuged hydrotalcite to obtain zinc aluminum nitrate hydrotalcite; Step 4: Place the zinc aluminum nitrate hydrotalcite in a muffle furnace for calcination, and then cool it to room temperature to obtain calcined zinc aluminum hydrotalcite powder; Step 5: Weigh out di-methylimidazole and calcined zinc aluminum hydrotalcite powder separately and dissolve them in methanol to prepare solutions; wherein the molar ratio of Zn2+ in di-methylimidazole and calcined zinc aluminum hydrotalcite powder is 1.5:1 to 2:1; Step 6: Heat the solution, stir vigorously, centrifuge, and wash with water to obtain ZLO; Step 7: After centrifugation, ZLO is vacuum dried to obtain composite hydrotalcite ZLO.

2. The method for preparing a composite hydrotalcite with a surface growth rust inhibitor according to claim 1, characterized in that, In step 1, the molar ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate, and urea is 2:0.8-1:8.5-10, and the water mass is weighed according to 65%-75% of the preparation container. Stir continuously for 20-40 minutes. In step 1, the water required to prepare the solution is boiled deionized water.

3. The method for preparing a composite hydrotalcite with a surface growth rust inhibitor according to claim 1, characterized in that, In step 2, the solution is heated to 90-100°C, stirred vigorously for 2-3 hours, and then centrifuged and washed with water 3-5 times.

4. The method for preparing a composite hydrotalcite with a surface growth rust inhibitor according to claim 1, characterized in that, In step 3, the centrifuged zinc-aluminum hydrotalcite is placed in an environment of 65-95°C for vacuum drying for 12-24 hours.

5. The method for preparing a composite hydrotalcite with a surface growth rust inhibitor according to claim 1, characterized in that, In step 4, the heating rate is 6-9℃ / min, and after heating to 580-600℃, the mixture is calcined for 5-6 hours and then cooled to room temperature.

6. The method for preparing a composite hydrotalcite with a surface growth rust inhibitor according to claim 1, characterized in that, In step 5, the methanol solution required for preparing the solution is analytical grade and can be used directly without purification; the methanol mass is weighed according to 65% to 75% of the preparation container, and the mixture is stirred continuously for 20 to 40 minutes.

7. The method for preparing a composite hydrotalcite with a surface growth rust inhibitor according to claim 1, characterized in that, In step 6, the solution is heated to 40-50°C, stirred vigorously for 5-6 hours, and then centrifuged and washed with water 3-5 times.

8. The method for preparing a composite hydrotalcite with a surface growth rust inhibitor according to claim 1, characterized in that, In step 7, the centrifuged ZLO is placed in an environment of 65-95℃ and vacuum dried for 12-24 hours to obtain composite hydrotalcite ZLO.

9. A composite hydrotalcite containing a surface growth rust inhibitor prepared by the method according to any one of claims 1-8, characterized in that, Formed by wrapping LDO with ZIF-8 as the surface; The LDO particles have uniformly distributed rhombic dodecahedral ZIF-8 nanocrystals with a particle size of ~70nm. Some of these nanocrystals are embedded between LDO layers or attached to the surface. Some of the ZLO lamellar edges exhibit irregular wrinkles.

10. The application of a surface growth rust inhibitor prepared by the method according to any one of claims 1-8, characterized in that, Composite hydrotalcite is used in the corrosion protection of reinforced concrete by being added as an admixture during concrete mixing at a certain mass fraction of cementitious material.

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