4A Molecular Sieve Can Adsorb Low Molecular Weight Compounds
4A Molecular Sieve can adsorb small molecules such as water, methanol, ethanol, hydrogen sulfide, sulfur dioxide, carbon dioxide, ethylene, propylene, etc., and does not adsorb any molecule with a diameter greater than 4A (including propane). It has high selective adsorption performance for water than any other molecule.
4A molecular sieve is one of the commonly used molecular sieve varieties in the industry
Molecular sieve type 4A can evaporate water in a large space at 110℃, but it is impossible to remove the water in the pores. Therefore, in the laboratory, dehydration can be activated by drying in a Muffle furnace at a temperature of 350℃ and drying for 8 hours under atmospheric pressure (if there is a vacuum pump, it can be dried for 5 hours at 150℃). The activated molecular sieve is cooled in air to about 200℃ (about 2 minutes) and immediately stored in a dryer.
If conditions permit, use dry nitrogen to protect during the cooling and storage process to prevent moisture in the air from being adsorbed. Old molecular sieves produce pollutants after use. The activation temperature is not only up to 450℃ but also introduces water vapor or inert gas (such as nitrogen) to replace other substances.
Each oxygen atom in the 4A molecular sieve framework is shared by two adjacent tetrahedrons
This structure forms large crystal pockets that can be occupied by cations and water molecules, and these cations and water molecules have greater migration rates. It can perform cation exchange and reversible dehydration. Ion exchange is performed on the framework containing aluminum ions, and each aluminum ion carries a negative charge, which can not only bind sodium ions but also calcium ions and magnesium ions. They can enter the large crystal pores previously occupied by sodium ions in the molecular sieve type 4A, which means that sodium ions can undergo ion exchange and can combine with Ca2+ and Mg2+ ions in hard water.
The 4A molecular sieve binds calcium and magnesium ions slower than sodium tripolyphosphate and has weaker binding ability with magnesium ions
The molecular sieve type 4A can easily and quickly remove a small amount of harmful heavy metal ions in water solutions, which is of great significance for purifying water quality. For non-ionic surfactant adsorption, the molecular sieve type 4A is 3 times that of NTA (nitrilotriacetic acid) and sodium carbonate and 5 times that of sodium tripolyphosphate (STPP) and sodium sulfate. This property is significant for producing high-concentration laundry detergents in bulk polymerization by adding more surfactants, making detergency and flow better. In experiments, the liquid carrying capacity of the 4A molecular sieve is ≥30%. Adding the 4A molecular sieve in the laundry detergent production process can increase material flow, adjust viscosity, and produce products with a good appearance, flowability, and anti-caking ability.
The role of the molecular sieve type 4A as a detergent additive is mainly to exchange calcium ions in water to produce softened water, remove dirt, and prevent dirt from redepositing. The 4A molecular sieve is currently a mature product in replacement of sodium tripolyphosphate as a detergent additive, which is significant for solving environmental pollution. The molecular sieve type 4A can also be used as a molding agent for soap, and a friction agent for toothpaste.