Determination Method of Water Capacity of Activated Carbon

Determination Method of Water Capacity of Activated Carbon

Activated carbon is a specially treated porous carbon material mainly composed of carbon. It features a well-developed pore structure and a large specific surface area (ranging from 500–1700 m²/g), which can effectively remove harmful substances from gases or liquids through physical and chemical adsorption.

It is manufactured from carbon-containing raw materials such as wood, nut shells and coal via carbonization and activation processes. It is generally black in powder, granular or columnar form, and widely applied in water treatment, air purification, food decolorization, pharmaceutical purification and other fields.

Experimental Purpose

The purpose of testing the water capacity of activated carbon is to evaluate its adsorption capacity for water molecules, so as to reflect the development degree of its pore structure and surface hydrophilicity. This index serves as an important reference for judging its performance in applications such as water treatment and air purification.

Reflect total pore volume: Water molecules mainly fill the micropores and mesopores of activated carbon. A higher adsorption capacity indicates a more developed pore structure and generally a larger specific surface area.

Predict practical application performance: In scenarios of air purification, humidification and sewage treatment, water capacity can quickly indicate the adsorption potential of activated carbon for polar substances.

Assist quality control: As a rapid testing method in production, it is used to monitor product consistency and batch stability.

Experimental Samples and Instruments

Sample: Activated carbon

Instrument: ST-62 Activated Carbon Water Capacity Tester, compliant with GB/T 7702.5

Experimental Procedures

1. Sample Pre-treatment and Drying

Sample according to GB/T 7702.1. Place the activated carbon sample evenly in a clean weighing bottle with the sample thickness no more than two-thirds of the container. Put the uncovered bottle into a drying oven at 105℃±5℃ and dry for 2 hours. Take it out, cover tightly, transfer to a desiccator, and cool to room temperature for no less than 30 minutes to prepare the absolutely dry test sample.

• Weighing of Absolute Dry Sample

Preheat, calibrate and zero the analytical balance. Accurately weigh the mass of the absolute dry activated carbon sample as m₁ to an accuracy of 0.0001 g and record the data. Prepare two parallel samples for simultaneous testing to ensure the test repeatability meets national standard requirements.

3.Saturated Water Immersion of Activated Carbon

Place the weighed absolute dry activated carbon into a clean beaker. Add sufficient distilled water to fully submerge the sample, with the liquid level at least 20 mm above the sample surface. Allow it to stand and soak at room temperature and atmospheric pressure until full pore water saturation. Gently stir 2–3 times during soaking to ensure uniform and sufficient water adsorption.

4.Vacuum Filtration to Remove Surface Free Water

Transfer the water-saturated activated carbon to a Buchner funnel lined with filter cloth. Turn on the vacuum pump for stable negative-pressure filtration until no continuous dripping occurs. Remove free water on the particle surface while retaining only the adsorbed water inside the pores to ensure test accuracy.

5.Weighing of Saturated Sample

After filtration, quickly transfer the saturated activated carbon back into the original weighing bottle and seal it to prevent moisture evaporation. Use the same calibrated balance to accurately weigh the total mass of the saturated sample as m₂ to 0.0001 g, and completely record all parallel sample data.

Experimental Result

The measured water capacity of this batch of coal-based granular activated carbon is 37.0%, which complies with the relevant product technical specifications. The water absorption and water retention performance of the sample is qualified.