The structural characteristics of desiccants vary significantly depending on their type, primarily achieving efficient moisture absorption through physical adsorption or porous structures. The following is a systematic description of their structural characteristics, starting with common types:
1. Silica Gel Dessiccant: Hydrous Silica with a Highly Microporous Structure
Silica gel desiccants are composed of silica (SiO₂), appearing as transparent or translucent spherical particles with an extremely fine, open, porous network structure inside.
The micropore diameter is approximately 2–10 nanometers, resulting in a large specific surface area, enabling efficient adsorption of water molecules (approximately 0.3 nanometers in diameter).
The structure is stable, insoluble in water and solvents, and does not soften even when fully immersed in water.
Some products contain color-changing indicators (such as cobalt chloride), appearing blue when anhydrous and turning pink after absorbing moisture, facilitating the determination of saturation.
2. Montmorillonite Desiccant: Natural Layered Clay Mineral Structure
Montmorillonite, also known as bentonite, is a layered silicate mineral that forms porous particles after drying and activation.
The interlayers can hold water molecules, and the structure slightly expands when humidity increases, achieving physical adsorption.
It has stable moisture absorption performance, with a saturated moisture absorption rate of over 50% of its own weight, suitable for room temperature and general humidity environments.
It is natural, environmentally friendly, biodegradable, non-toxic, and non-corrosive, widely used in food and pharmaceutical packaging.
3. Calcium Chloride Desiccant: Strongly Hygroscopic Crystalline Structure
Calcium chloride desiccant is mainly composed of anhydrous calcium chloride (CaCl₂), appearing as white porous blocks or granules.
Through chemical adsorption and reaction with water to form hydrates (such as CaCl₂·6H₂O), its moisture absorption capacity can reach 200%–300% of its own weight.
After absorbing moisture, it forms a gel-like substance, often using double-layer packaging (water-locking and breathable materials) to prevent leakage and improve safety.
4. Molecular Sieve Desiccant: Artificially Synthesized Regular Microporous Structure
Molecular sieves are artificially synthesized crystalline aluminosilicates with uniform and controllable microporous channels (e.g., 3Å, 4Å).
The pore size is precise to the molecular level, selectively adsorbing water molecules and repelling larger molecules.
They maintain high moisture absorption capacity even in high-temperature or low-humidity environments, making them suitable for moisture protection in precision industries.