Analysis of Potassium Exchange in Insulating Glass Desiccants Using Wayeal AAS

Acting as the "invisible guardian" of insulating glass, the desiccant's performance directly determines the risk of condensation and the service life of the glass unit. If its adsorption capacity fails to meet standards, it can lead to fogging or condensation between the glass panes, compromising thermal insulation and increasing building energy consumption.

Potassium exchange rate, specifically the potassium ion exchange rate, is a critical technical indicator for assessing the quality and performance of 3A molecular sieve powder. According to the Chinese National Standard "3A Molecular Sieve" (GB/T 10504-2017), 3A molecular sieves are classified into four categories based on application and form: extrudates, spherical, spherical for insulating glass, and powder. The standard specifies a technical requirement for potassium exchange rate (≥40%) only for the powder category, with no such requirement for the formed types (extrudates or spherical).

This study establishes an atomic absorption flame method for determining the potassium exchange rate in desiccants for insulating glass. Experimental results demonstrate that the linear correlation coefficients for both potassium oxide and sodium oxide are greater than 0.999. The method proves to be accurate, reliable, and highly sensitive, making it suitable for quality control testing of potassium exchange capacity in insulating glass desiccants.

Keywords: Atomic absorption, Flame, Insulate glass, Desiccants, Potassium, Sodium.

1. Experiment Method

1.1 Instrument Configuration

Table 1 Configuration List of Atomic Absorption Spectrophotometer

1.2 Reagents and Experiment Material

1.2.1 Sodium oxide standard solution(1mg/mL): Accurately weigh 1.5830g of potassium chloride (primary standard) previously dried at 150°C for 2 hours into a beaker, add water to dissolve it. Then transfer into a 1L volumetric flask, and dilute to the mark with water and mix thoroughly. The concentration of this standard solution is 1mg/mL.

1.2.2 Potassium oxide standard solution(1mg/mL): Accurately weigh 1.8859g of sodium chloride (primary standard), previously dried at 150°C for 2 hours into a beaker, add water to dissolve it. Then transfer into a 1L volumetric flask. dilute to the mark with water and mix thoroughly. The concentration of this standard solution is 1mg/mL.

1.2.3 Perchloric acid

1.2.4 Hydrofluoric acid

1.2.5 Hydrochloric acid: 1+1

1.2.6 Ammonia solution: GR

1.2.7 Methyl red indicator: 0.2%

1.2.8 Analytical balance with 0.1 mg readability

1.2.9 Digital hot plate

1.2.10 PTFE crucible

1.2.11 Chamber resistance furnace

1.3 Sample Pretreatment

Grind the sample until it can pass through a 100-mesh sieve. Transfer the ground sample into a porcelain crucible and place it in a chamber resistance furnace. Gradually heat the furnace from room temperature to 550°C, then maintain this temperature for 1 hour. After the process, immediately remove the crucible and place it in a desiccator to cool down to room temperature.

Accurately weigh approximately 0.2g (accurate to 0.0001g) of the processed sample into a PTFE crucible. Moisten with a small amount of water, then add 1mL of perchloric acid and 15mL of hydrofluoric acid. Place on a 120°C hotplate and evaporate until white fumes of perchloric acid appear. Remove and allow to cool. Add 25mL of hydrofluoric acid and continue evaporation until the sample is completely dissolved and white fumes cease. Remove and cool. Add 10mL of hydrochloric acid and 20mL of water, heat to dissolve, then transfer into a 250mL volumetric flask. Cool to room temperature, dilute to the mark with water, mix thoroughly, and set aside for analysis. Pipette approximately 80mL of this solution, add methyl red until a faint pink color appears, and boil gently for 30 minutes. Add ammonia solution until the color turns yellow, then maintain slight boiling for another 15 minutes. Filter quantitatively into a volumetric flask, cool to room temperature, dilute to the mark with water, and mix well. Follow the same procedure for analyzing the blank sample.

2. Result and Discussion

2.1 Spectral Conditions for Elements

2.2 Standard Curve Testing

Standard Curve for K

Standard Curve for Na

2.3 Analysis Result for the Sample

3. Attention

3.1 The hydrofluoric acid, perchloric acid, and hydrochloric acid used in the experiment are highly hazardous: hydrofluoric and perchloric acids are strongly oxidizing and corrosive, while hydrochloric acid is highly volatile and corrosive. All reagent preparation and sample digestion must be conducted inside a fume hood. Operators must wear appropriate personal protective equipment (PPE) to avoid inhalation or contact with the skin and clothing.

3.2 When detecting potassium and sodium, the burner head must be rotated to optimize alignment. For potassium measurement, rotate the burner head until a 0.1mg/L standard produces an absorbance of 0.0115 Abs. For sodium measurement, rotate the burner head until a 0.1 mg/L standard produces an absorbance of 0.0307 Abs.

4. Conclusion

This study establishes a flame atomic absorption spectrometry (FAAS) method for determining the potassium exchange rate in desiccants for insulating glass. Experimental results demonstrate that the linear correlation coefficients (R) for both potassium oxide (K₂O) and sodium oxide (Na₂O) exceed 0.999. The method proves accurate, reliable, and stable, making it suitable for quality control testing of potassium exchange capacity in insulating glass desiccants.