A method for quantitatively evaluating the coordination ability of complex components in an alkali-free accelerator with aluminum ions

Abstract

The application discloses a method for quantitatively evaluating the coordination ability of complex components in an alkali-free quick-setting agent to aluminum ions, and relates to the technical field of concrete quick-setting agents.The application verifies whether a certain complex component can be complexed with aluminum ions through conductivity determination, and then adopts complex component titration of supersaturated aluminum sulfate suspension to further obtain the coordination ratio of the complex component to the aluminum ions to form a complex.The method can quickly determine whether the complex component can increase the solubility of aluminum sulfate, and the coordination molar ratio of the complex component to the aluminum ions can be obtained through calculation, so that the coordination ability of the complex component in the alkali-free quick-setting agent to the aluminum ions can be quantitatively evaluated, thereby providing a theoretical basis for the selection and dosage of the complex component in the production process of the alkali-free liquid quick-setting agent.

Description

Technical Field

[0001] This invention relates to the field of concrete accelerator technology, and in particular to a method for quantitatively evaluating the coordination ability of complexing components with aluminum ions in alkali-free accelerators. Background Technology

[0002] Shotcrete is a core engineering material used in tunnel construction, with a large market demand and broad application prospects. Accelerators are the core admixtures of shotcrete, and aluminum sulfate is the main rapid-setting and early-strength component in alkali-free accelerators. To improve the rapid-setting and early-strength effect, the aluminum ion content in the accelerator needs to be increased. Under the target setting and hardening performance requirements, the aluminum sulfate dosage needs to reach 4.5% of the cement content. Differences in solubility lead to precipitation and stratification of the accelerator, and blindly increasing the amount of aluminum sulfate will also increase costs.

[0003] To address the aforementioned issues, incorporating aluminum ion complexing components to increase the solubility of aluminum sulfate through complexation with aluminum ions is a primary approach. Commonly used aluminum ion complexing agents include alkanolamines, phosphoric acid, EDTA, and fluorides. Based on coordination mechanisms, components with stronger coordination ability and higher coordination numbers exhibit more significant solubilizing effects on aluminum sulfate and demonstrate better stability after dissolution. For some simple complex ions, studying equilibrium states and kinetics using chemical methods can provide information on the existence form, compositional distribution, and formation mechanism of the complexes. However, aluminum sulfate readily undergoes hydrolysis and polymerization in water, forming polynuclear aluminum (III) complexes, the specific composition of which is difficult to ascertain. Therefore, to study the existence form, compositional distribution, and formation mechanism of aluminum (III) complexes, it is necessary to utilize modern separation and analytical techniques such as GFC, GPC, GE, IEC, HPLC, UV, and IR. 27 Methods such as Al-NMR and XRD, along with chemometrics and computer-aided equilibrium calculations, are used to address this issue. However, these testing methods are technically challenging, data analysis and processing are difficult, and testing costs are high, making it difficult to practically guide the industrial production of alkali-free quick-setting agents. Summary of the Invention

[0004] The purpose of this invention is to provide a method for quantitatively evaluating the coordination ability of complexing components with aluminum ions in alkali-free quick-setting agents, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a method for determining the coordination ability of a complexing component with aluminum ions, comprising the following steps:

[0007] A method for evaluating the coordination ability of a complexing component with aluminum ions, characterized by comprising the following steps:

[0008] (1) Conductivity determination: The complexing component is added to the aluminum nitrate solution system, or aluminum nitrate is added to the complexing component solution system, and the degree of change in the conductivity of the solution system is used to determine whether the complexing component has complexed with aluminum ions;

[0009] When it is determined that the complexing component cannot complex with aluminum ions, the determination of the coordination ability of the complexing component with aluminum ions is completed.

[0010] When it is determined that the complexing component has complexed with aluminum ions, proceed to step (2).

[0011] (2) Titration of supersaturated aluminum sulfate suspension with complexing components:

[0012] a. Add excess aluminum sulfate octahydrate to a saturated aqueous solution of aluminum sulfate octahydrate, and record the mass of the excess aluminum sulfate octahydrate added as m1;

[0013] b. Titrate the supersaturated aluminum sulfate suspension with the complexing component. When the supersaturated aluminum sulfate suspension becomes clear and transparent, record the mass m2 of the added complexing component. Calculate the coordination molar ratio of aluminum ions to the complexing component according to the following formula, and then quantitatively determine the coordination ability of the complexing component with aluminum ions:

[0014] ;

[0015] In the formula: M1—the molecular weight of aluminum sulfate octahydrate;

[0016] M2 — Molecular weight of the complexed component.

[0017] Furthermore, when the complexing component in the reaction system is added dropwise to the aluminum nitrate solution, compared with the addition of deionized water, the conductivity of the system first decreases rapidly, and then the rate of decrease tends to level off. When a clear inflection point appears on the conductivity change curve, it indicates that the complexing component has undergone a complexing reaction with aluminum ions, and step (2) is carried out.

[0018] The present invention also provides the application of the above method in evaluating the coordination ability of complexing components with aluminum ions in alkali-free quick-setting agents.

[0019] The present invention has the following advantages:

[0020] (1) By measuring conductivity, a certain concentration of the analyte complexing component is slowly added dropwise to an aluminum nitrate solution. If the analyte can undergo a complexation reaction with aluminum ions, the number of free ions in the solution decreases, and therefore the conductivity of the solution decreases rapidly until all aluminum ions in the solution are complexed. The change in conductivity then tends to level off. Throughout the process, a clear inflection point appears in the change in conductivity of the aluminum nitrate solution. If the analyte cannot undergo a complexation reaction with aluminum ions, the change in conductivity of the aluminum nitrate solution is not significant. Based on the change in conductivity, it can be preliminarily determined whether a certain component can be used as a complexing agent for aluminum ions.

[0021] (2) Use complexing components to titrate supersaturated aluminum sulfate suspension. Slowly add aluminum ion complexing components to supersaturated aluminum sulfate suspension of known concentration. By complexing with aluminum ions in the solution, aluminum sulfate can be further dissolved. Continue until the milky white suspension becomes a clear and transparent solution. Record the mass of the added complexing components and calculate the coordination molar ratio of aluminum ions to complexing components.

[0022] (3) Compared with complex electroanalysis and optical and spectroscopic analysis techniques, the measurement process of this invention is simple and easy to operate, easy to repeat and verify, and the final calculated results are in high agreement with the results of literature research.

[0023] (4) The method of the present invention can quickly determine whether a component has the ability to complex aluminum ions, and can also calculate the coordination ratio of aluminum ions and their complexes. This has important guiding significance for the selection of aluminum ion complexing components and the determination of dosage in the industrial production process of alkali-free quick-setting agents.

[0024] The present invention discloses the following technical effects:

[0025] The method of this invention can quickly determine whether the complexing component can increase the solubility of aluminum sulfate, and calculate the coordination molar ratio between the complexing component and aluminum ions. This invention can quantitatively evaluate the coordination ability of the complexing component and aluminum ions in alkali-free quick-setting agents, thus providing a theoretical basis for the selection and dosage of complexing components in the production process of alkali-free liquid quick-setting agents. Attached Figure Description

[0026] 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.

[0027] Figure 1 The effect of adding different alkanolamine solutions on the conductivity of aluminum nitrate solution;

[0028] Figure 2 The effect of adding aluminum nitrate solution dropwise on the conductivity of different alkanolamine solutions. Detailed Implementation

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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 readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0033] 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.

[0034] This invention verifies whether a certain complexing component can complex with aluminum ions by measuring conductivity, and then further determines the coordination ratio of the complexing component to aluminum ions by titrating a supersaturated aluminum sulfate suspension with the complexing component.

[0035] (1) Conductivity determination: A solution of a certain concentration of the analyte is slowly added dropwise to an Al(NO3)3 solution. Due to the complexation of Al... 3+This leads to a decrease in free aluminum ions in the aluminum nitrate solution, causing a rapid drop in conductivity. Once the complexing component becomes saturated with aluminum, the change in conductivity is mainly caused by the dilution of the complexing component solution, thus the decreasing trend will level off. A distinct inflection point will appear on the conductivity change curve throughout this process.

[0036] The specific steps are as follows:

[0037] a. Prepare solutions of the complexing components to be tested and Al(NO3)3 solutions of different concentrations in advance;

[0038] b. Measure the conductivity of the above solution or reference (deionized water) after it has been added to the analyte using a conductivity meter (Mettler). The difference between the conductivity trend and the reference value can prove that Al 3+ The reaction with the analyte complex.

[0039] (2) Titration of supersaturated aluminum sulfate suspension with complexing components:

[0040] ①The main raw material of the alkali-free liquid quick-setting agent is industrial-grade aluminum sulfate octadechydrate. First, the solubility of aluminum sulfate octadechydrate is tested at room temperature and used as a benchmark.

[0041] ② Add excess aluminum sulfate octahydrate (m1) to this standard and stir vigorously for several hours to obtain a milky white supersaturated aluminum sulfate suspension;

[0042] ③ Slowly add the complexing component to be tested dropwise, continue stirring and observe the changes in the solution. Since the complexing component will complex with the aluminum ions in the solution after being added, it can further promote the dissolution of aluminum sulfate, until the milky white suspension completely becomes a clear and transparent solution, and record the mass m2 of the complexing component added;

[0043] ④ The coordination molar ratio of aluminum ions to complex components can be calculated using the following formula.

[0044]

[0045] In the formula: M1—the molecular weight of aluminum sulfate octahydrate;

[0046] M2 — Molecular weight of the complexed component.

[0047] Example 1

[0048] Alkylamines are not only commonly used complexing components for aluminum ions, but they can also be used as early strength components in cement. Therefore, in this embodiment, alkylamines were selected as complexing components for determination.

[0049] 1. First, we verified whether alkanolamines could complex aluminum ions through conductivity tests:

[0050] (1) Aluminum nitrate nonahydrate, triethanolamine, and diethanolamine were prepared into solutions with different molar concentrations, and their conductivity values ​​were measured using a conductivity meter. The results are shown in Table 1.

[0051] Table 1. Conductivity values ​​of different substances at different concentrations (temperature approximately 27~28℃)

[0052]

[0053] (2) Titrate aluminum nitrate solution with 0.1 mol / L alkanolamine solution.

[0054] Take three 50 mL portions of 0.001 mol / L aluminum nitrate solution. Add 0.1 mol / L triethanolamine and 0.1 mol / L diethanolamine solutions dropwise to each portion in 0.5 mL increments, respectively. Simultaneously add deionized water as a reference. Observe the changes in conductivity values ​​as follows: Figure 1 As shown.

[0055] Depend on Figure 1 It can be seen that after adding deionized water, the aluminum nitrate solution is diluted, and the ion concentration decreases slowly, resulting in a slight decrease in the solution's conductivity, but the overall change in conductivity is very small. However, after adding triethanolamine and diethanolamine solutions, the conductivity of the aluminum nitrate solution decreases rapidly, and then the rate of decrease tends to level off, indicating that triethanolamine and diethanolamine react with Al... 3+ Complexation occurs, leading to a decrease in the number of free aluminum ions in the solution, thus reducing the solution conductivity. After a certain amount, the conductivity change tends to level off, suggesting that all aluminum ions in the solution have been complexed at this point. The change in conductivity is mainly due to the dilution effect of triethanolamine and diethanolamine solutions. A clear inflection point will appear on the conductivity change curve throughout the process.

[0056] (3) Titrate the alkanolamine solution with 0.01 mol / L aluminum nitrate solution.

[0057] Take 50 mL each of 0.1 mol / L triethanolamine solution, 0.1 mol / L diethanolamine solution, and deionized water. Slowly add 0.01 mol / L aluminum nitrate solution dropwise in 0.5 mL increments. The change in conductivity is shown below. Figure 2 As shown.

[0058] Depend on Figure 2 It can be seen that when aluminum nitrate solution is slowly added dropwise to deionized water, as the Al in the solution increases... 3+ NO3 - With the increase of ions, the conductivity of the system gradually increases; when aluminum nitrate solution is slowly added dropwise to triethanolamine and diethanolamine solutions, the conductivity increases with the increase of Al in the solution. 3+ NO3 - The increase in ions will increase the solution conductivity, but due to the effect of alkanolamines on Al... 3+Due to the complexation effect, the number of free aluminum ions in the solution is less than that in deionized water, resulting in a much slower increase in conductivity compared to deionized water. However, once a certain amount is consumed, the rate of increase in conductivity will increase.

[0059] The above conductivity tests confirmed that triethanolamine and diethanolamine can complex aluminum ions, but the coordination ratio of the complexes could not be quantified.

[0060] 2. To investigate the coordination ratio of aluminum ions to form complexes with alcoholamines by titrating a supersaturated aluminum sulfate suspension with complexing components:

[0061] ① At room temperature, industrial-grade aluminum sulfate octadechydrate was dissolved. The experiment showed that 50% (w / w) aluminum sulfate octadechydrate could be completely dissolved into a clear solution at room temperature, but a turbid suspension was formed after the concentration exceeded 50 wt.%. Therefore, a 50 wt.% aluminum sulfate octadechydrate solution was selected as the reference standard.

[0062] ② Take 50g of 50wt.% aluminum sulfate solution, add 12.5g, 20g and 30g of aluminum sulfate octahydrate solid respectively, and stir thoroughly for several hours to obtain 60wt.%, 64.3wt.% and 68.75wt.% supersaturated milky white suspensions of aluminum sulfate respectively.

[0063] ③ Slowly add different types of analytical grade alcohol amines to the suspension while stirring until the suspension becomes clear, and record the amount of alcohol amine added and the corresponding phenomena.

[0064] As various alkanolamines were slowly added, the milky white suspension gradually turned into a clear solution. The final amounts of different alkanolamines added are shown in Table 2 below.

[0065] Table 2. Titration results of different alcoholamines

[0066]

[0067] As shown in Table 2, the coordination abilities of the various alkanolamines with aluminum ions are not significantly different. The molar ratios of the complexes formed by aluminum ions and the various alkanolamines range from 1:1.04 to 1:1.39; and the higher the concentration of the supersaturated aluminum sulfate suspension, the closer the calculated ratio is to 1:1.

[0068] According to literature reports, metal ions form 1:1 or 1:2 complexes with alkanolamines. Taking TEA as an example, the structure of the complex formed by TEA and metal ions is shown below:

[0069]

[0070] Besides the molar ratio, the type of metal atoms is also a factor influencing the structure of different coordination compounds. In the study by Naiini et al., monovalent alkali metal ions readily form the structure of formula I, while divalent metal ions readily form the structure of formula II. Furthermore, Al... 3+ and Fe 3+ It is considered easy to form the structure in Formula I.

[0071] The results obtained using the method of this invention are consistent with those obtained in the literature, and the experimental method is simple, easy to operate, and readily reproducible. Based on the above results, a theoretical basis can be provided for the dosage of alkanolamines in the industrial production of alkali-free liquid quick-setting agents; it can also provide experimental methods for the selection of other solubilizing components.

[0072] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for evaluating the coordination ability of alkanolamine complex components with aluminum ions, characterized in that, Includes the following steps: (1) Conductivity determination: The alkanolamine complexing component is added to the aluminum nitrate solution system, or aluminum nitrate is added to the alkanolamine complexing component solution system, and the change in conductivity of the solution system is used to determine whether the alkanolamine complexing component has complexed with aluminum ions; When it is determined that the alkanolamine complex component cannot form a complex with aluminum ions, the determination of the coordination ability of the alkanolamine complex component with aluminum ions is completed. When the alkanolamine complex component is added dropwise to the aluminum nitrate solution in the reaction system, an inflection point appears on the conductivity change curve of the system, indicating that the alkanolamine complex component has undergone a complexation reaction with aluminum ions, and step (2) is carried out. (2) Titration of supersaturated aluminum sulfate suspension with alkanolamine complex components: a. Add excess aluminum sulfate octahydrate to a saturated aqueous solution of aluminum sulfate octahydrate to obtain a supersaturated aluminum sulfate suspension. Record the mass of the excess aluminum sulfate octahydrate added as m1. b. Titrate the supersaturated aluminum sulfate suspension with the alkanolamine complexing component. When the supersaturated aluminum sulfate suspension becomes clear and transparent, record the mass m2 of the added alkanolamine complexing component. Calculate the coordination molar ratio of aluminum ions to the alkanolamine complexing component according to the following formula, and then quantitatively determine the coordination ability of the alkanolamine complexing component with aluminum ions: ； In the formula: M1—the molecular weight of aluminum sulfate octahydrate; M2 – Molecular weight of the alcohol amine complex component.

2. The application of the method as described in claim 1 in evaluating the coordination ability of alkanolamine complex components with aluminum ions in alkali-free quick-setting agents.

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