High-selectivity sodium ion glass electrode

Abstract

The invention discloses a high-selectivity sodium ion glass electrode, relates to the technical field of electrochemical detection, and aims to solve the technical problem that a sensitive membrane of an existing sodium ion glass electrode is difficult to burn due to the fact that the sensitive membrane contains high-melting-point aluminum oxide. A sensitive film of the electrode adopts a specific formula and comprises the following components in percentage by mole: 60-65% of silicon dioxide, 12-15% of aluminum oxide, 0-5% of sodium oxide, 0-7% of tantalum pentoxide, 0-2% of niobium oxide, 3-5% of gallium oxide and 15-20% of lithium carbonate. Gallium oxide is used for replacing part of aluminum oxide, the sintering temperature of the sensitive film is reduced, preparation can be achieved through a common hot melting furnace, meanwhile, high selectivity to sodium ions is kept, the concentration of the sodium ions in a solution can still be accurately measured in the presence of high potassium ions or other cations, measured data are stable and reliable, and the method is suitable for large-scale popularization and application. The method is suitable for sodium ion monitoring of a solution or discharged water.

Description

Technical Field

[0001] This invention relates to the field of electrochemical detection, specifically to a highly selective glass electrode for measuring sodium ion concentration, which is particularly suitable for the accurate monitoring of sodium ion concentration or activity in solutions or effluent. Background Technology

[0002] Sodium ion concentration monitoring is of great significance in chemical production, environmental management, and water quality testing. Glass electrodes have become a commonly used tool for sodium ion detection due to their advantages such as direct measurement and ease of operation. The sensitive membrane of existing sodium ion glass electrodes is mainly composed of sodium oxide or lithium oxide, aluminum oxide, and network-forming oxides (such as silicon dioxide). Its sodium ion selectivity depends on a specific molar ratio of the components: when the molar ratio of aluminum oxide to sodium oxide is ≥1, the selective sensitivity of the electrode for sodium ions can reach 100-250 times that of potassium ions. British Patent 924,845 further discloses that when the molar ratio of Al2O3 to Li2O is ≥1:3, the selective sensitivity can be increased to 100-10000 times or even higher.

[0003] However, the aforementioned high-selectivity formulation has significant preparation defects: alumina has a melting point as high as 2050℃, while the maximum temperature of the commonly used industrial muffle furnace is only 1700℃, and ordinary hot-melt furnaces are also unable to reach the melting temperature of alumina. This results in the glass material being difficult to completely melt during the preparation of the electrode sensitive film. Even with extended firing time, it is still impossible to ensure sufficient fusion of the raw materials, which not only reduces the production efficiency of the electrode but also leads to uneven sensitive film structure, affecting measurement accuracy and stability. Therefore, there is an urgent need for a glass sensitive film formulation that can maintain high sodium ion selectivity while reducing the firing difficulty, as well as a corresponding sodium ion glass electrode.

[0004] To address this problem, a highly selective sodium-ion glass electrode is proposed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing sodium ion glass electrode sensitive films, which are difficult to fire, have low production efficiency, and poor measurement stability due to the presence of high-melting-point alumina. The invention provides a highly selective sodium ion glass electrode with an optimized formula, which reduces the firing temperature while maintaining high sodium ion selectivity, is compatible with conventional heating equipment, and ensures the feasibility of preparation and the reliability of measurement.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a highly selective sodium-ion glass electrode, comprising an electrode body and a glass sensitive membrane, wherein the glass sensitive membrane is composed of the following components by molar percentage: silicon dioxide (SiO2): 60-65%, aluminum oxide (Al2O3): 12-15%, sodium oxide (Na2O): 0-5%, tantalum pentoxide (Ta2O5): 0-7%, niobium oxide (Nb2O5): 0-2%, gallium oxide (Ga2O3): 3-5%, and lithium carbonate (Li2CO3): 15-20%.

[0007] The present invention is further configured such that the composition of the glass sensitive film, by molar percentage, is: 62.5% silicon dioxide, 14.5% aluminum oxide, 2% sodium oxide, 3% tantalum pentoxide, 3% gallium oxide, and 15% lithium carbonate.

[0008] The present invention is further configured such that the firing temperature of the glass sensitive film is 1580℃ and the total firing time is 48-50 hours.

[0009] The present invention is further configured such that: during the preparation of the glass sensitive film, the raw material mixing time is 1 hour, the pre-melting temperature is 1450℃, the pre-melting time is 2 hours, and the film is stirred once every 5 hours during the firing process.

[0010] The present invention is further configured such that the selective sensitivity of the glass sensitive membrane to sodium ions is 100-10000 times that to potassium ions.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. The invention significantly reduces the firing difficulty, and the firing temperature of the sensitive film can be controlled at 1580℃. Conventional industrial hot melt furnaces can meet the requirements without the need for special high-temperature equipment. Moreover, the glass material can be completely melted within 50 hours, increasing production efficiency by more than 30%. 2. This invention has high sodium ion selectivity, maintaining high selectivity for sodium ions, and its selectivity sensitivity for potassium ions can reach 100-10000 times, enabling accurate measurement of sodium ion concentration in environments with high potassium ion concentration or coexistence with other cations; 3. This invention exhibits good measurement stability, with sufficient glass melting, uniform sensitive film structure, small deviation in multiple measurements, and stable potential response; 4. This invention has a wide range of applications and is suitable for monitoring sodium ion concentration in various scenarios such as solutions and wastewater. It is easy to operate and highly practical. Detailed Implementation

[0012] The present invention will now be described in more detail by way of examples. These examples are merely illustrative and do not limit the scope of the present invention in any way.

[0013] This invention provides a technical solution: a high-selectivity sodium-ion glass electrode, comprising an electrode body and a glass sensitive film disposed at the end of the electrode body. The composition of the glass sensitive film, by molar percentage, is: silicon dioxide 60-65%, aluminum oxide 12-15%, sodium oxide 0-5%, tantalum pentoxide 0-7%, niobium oxide 0-2%, gallium oxide 3-5%, and lithium carbonate 15-20%. The glass sensitive film achieves the effect of lowering the firing temperature and maintaining high sodium-ion selectivity by introducing gallium oxide to replace part of the aluminum oxide. The composition of the glass sensitive film, by molar percentage, is: silicon dioxide 62.5%, aluminum oxide 14.5%, sodium oxide 2%, tantalum pentoxide 3%, gallium oxide 3%, and lithium carbonate 15%. The firing temperature of the glass sensitive film is 1580℃, and the total firing time is 48-50 hours. During the preparation of the glass sensitive film, the raw material mixing time is 1 hour, the pre-melting temperature is 1450℃, the pre-melting time is 2 hours, and every 5 hours during the firing process... Stirred once every hour, the glass sensitive membrane has a selective sensitivity to sodium ions that is 100-10000 times that to potassium ions.

[0014] The key technology of this invention lies in: Introducing gallium oxide to replace some aluminum oxide: Gallium oxide is widely used in the semiconductor industry and has excellent ionic conductivity, which can completely replace some of the functions of aluminum oxide, ensuring high selectivity of the electrode for sodium ions; at the same time, the melting point of gallium oxide is much lower than that of aluminum oxide (gallium oxide melting point is about 1740℃, aluminum oxide melting point is 2050℃), which significantly reduces the firing temperature requirements of the sensitive film.

[0015] Optimize component ratio: By adjusting the ratio of Li2O (provided by lithium carbonate decomposition) to alumina, and combining it with silica as a glass network former, tantalum pentoxide and niobium oxide to assist in improving selectivity and stability, a synergistic effect is formed, which not only ensures sodium ion selectivity, but also improves the melt flowability of the glass material.

[0016] Example 1: Preparation of a highly selective sodium-ion glass electrode Raw material ratio (by molar percentage): silicon dioxide: 62.5%, aluminum oxide: 14.5%, sodium oxide: 2%, tantalum pentoxide: 3%, gallium oxide: 3%, lithium carbonate: 15%; all the above raw materials are analytical grade, with a purity ≥99.5%.

[0017] Preparation steps: Step 1: Raw material mixing: Accurately weigh each powder raw material according to the above proportions, put them into a ball mill and mix evenly for 1 hour to ensure that each component is evenly dispersed; Step 2: Preheating the hot melt furnace: Set aside the mixed powder raw materials, and preheat the hot melt furnace to 1450℃ and keep it at that temperature for 30 minutes to ensure uniform temperature inside the furnace; Step 3: Pre-melting: Pour the mixed powder into the platinum crucible in batches, with each batch not exceeding 1 / 3 of the crucible's volume. Place it in a hot melt furnace at 1450℃ for pre-melting for 2 hours. After the previous batch of powder has partially melted, add the next batch. Complete the addition of all powder within 12 hours. Step 4: High-temperature firing: Raise the temperature of the hot melt furnace to 1580℃ and maintain this temperature for 48-50 hours. During this period, stir the mixture every 5 hours with platinum crucible tongs to ensure that the raw materials are fully melted and mixed evenly. Step 5: Forming and processing: After the glass material is completely melted, it is poured out of the crucible, cooled to room temperature and formed into a rod. Then, it is blown into a glass sensitive film on an Arnold machine and assembled and fixed with the electrode body to obtain a highly selective sodium ion glass electrode.

[0018] Example 2: Performance Testing

[0019] Standard solutions with the same pNa value (pNa=1-6, corresponding to sodium ion concentrations of 1mol / L-1μmol / L) were used, and potassium ions of equal concentration were added as interfering ions. The potential response of the electrode was measured, and the test results are shown in the table below: Test Result Analysis: 1. The electrode potential exhibits a good linear relationship with the change of sodium ion concentration, and the potential response is continuous and stable in the range of pNa=1-6; 2. A deviation of ≤0.008V in multiple measurements indicates good repeatability of the electrode measurements; 3. Under the interference of potassium ions of equal concentration, the electrode can still accurately respond to changes in sodium ion concentration, proving that it has high selectivity for sodium ions and meets the actual monitoring needs.

[0020] The above embodiments demonstrate that the high-selectivity sodium ion glass electrode prepared by the present invention, through the rational design of the component ratio and preparation process of the sensitive glass membrane, is significantly superior to the traditional PVC membrane electrode in terms of detection accuracy, service life, anti-interference ability and mechanical properties, and has broad practical application value.

[0021] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A highly selective sodium-ion glass electrode, characterized in that, The device includes an electrode body and a glass sensitive film disposed at the end of the electrode body. The composition of the glass sensitive film, in molar percentage, is: 60-65% silicon dioxide, 12-15% aluminum oxide, 0-5% sodium oxide, 0-7% tantalum pentoxide, 0-2% niobium oxide, 3-5% gallium oxide, and 15-20% lithium carbonate. The glass sensitive film achieves the effect of reducing the firing temperature and maintaining high selectivity for sodium ions by introducing gallium oxide to replace part of the aluminum oxide.

2. The highly selective sodium-ion glass electrode according to claim 1, characterized in that: The composition of the glass sensitive film, by molar percentage, is: 62.5% silicon dioxide, 14.5% aluminum oxide, 2% sodium oxide, 3% tantalum pentoxide, 3% gallium oxide, and 15% lithium carbonate.

3. The highly selective sodium-ion glass electrode according to claim 1, characterized in that: The glass sensitive film is fired at a temperature of 1580℃ for a total firing time of 48-50 hours.

4. The highly selective sodium-ion glass electrode according to claim 3, characterized in that: In the preparation process of the glass sensitive film, the raw material mixing time is 1 hour, the pre-melting temperature is 1450℃, the pre-melting time is 2 hours, and the film is stirred once every 5 hours during the firing process.

5. The highly selective sodium-ion glass electrode according to claim 1, characterized in that: The selective sensitivity of the glass sensitive membrane to sodium ions is 100-10000 times that to potassium ions.

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