Information about 4A molecular sieves
User：admin AddDate：2015/1/31 Read：4811Times
4A Molecular Sieves
Chemical Formula: Na2O*Al2O3*2SiO2*9/2H2O
4A Molecular Sieve is a kind of synthetic, with micropore cubic lattice of alkali metal aluminosilicate salt. It also called Sodium A molecular sieve, its structure is similar to NaCl. Due to its effective pore diameter is 0.4nm, so it is called 4A molecular sieve, its space network structure is staggered by silicon-oxygen tetrahedron (SiO4) and aluminium-oxygen tetrahedron (AlO4). 4A molecular sieve decides the adsorption order according to the polarity of different molecules, adsorbs only those with a molecular diameter of less than 4A. For small polar molecules and unsaturated molecules, the greater polarity, the higher degree of unsaturation, the stronger of selective absorption.
In the skeleton of 4A molecular sieve each oxygen atom is shared by two adjacent tetrahedrons, these structures formed a large crystal cave, positive ions and water molecules can be exchanged and reversible dehydration in the crystal cave. The ion-exchange of 4A molecular sieves is in crystals which have aluminium ions, each of aluminum ions with a negative charge, which can be combined with cations such as sodium, calcium and magnesium. Calcium ions and magnesium ions can replace sodium ions and enter crystal caves which were occupied by the sodium ions. It shows that sodium ions can be exchanged by Ca2+, Mg2+ ions in hard water, so 4A molecular sieve can soften water. 4A molecular sieve also can remove a small amount harmful heavy metal ions (such as Pb2+, Cd2+, Hg2+) in water, it is very important for purifying water.
4A molecular sieve adsorbs those substances which molecular diameter is less than 4A, such as water methanol, ethanol, hydrogen sulfide, sulfur dioxide, carbon dioxide, ethylene, ethane, propylene, ammonia, doesn’t adsorb molecules which diameter are greater than 4A (include propane), the selective adsorption performance to water than any other molecules.
4A molecular sieve is nonpoisonous and tasteless, no irritations to eyes and skin, does not cause allergies. 4A molecular sieve deposition in the soil after washing will not cause pollution, furthermore can improve soil, so it is a natural and environment-friendly product.
4A molecular sieves application:
(1) Argon gas making and purifying
(2) Detergent Builder: 4A molecular sieve as a detergent builder mainly used to exchange of calcium ions in water to soften water, remove dirt and prevent dirt deposition. 4A molecular sievesubstitute trisodium phosphate as detergent builder is a significant role on solving environmental pollution. 4A molecular sieve also is used for SOAP plasticizer, toothpaste abrasive, etc.
(3)Sewage Disposal: 4A molecular sieve as a softening agentinstead of domestic widespreadsulfonated coal, thereby reducing costs. In sewage 4A molecular sieves can remove ammonia nitrogen, Pb2+, Cu2+, Zn2+, Cd2+, etc. In addition to ensure water quality qualified, but also can recycle heavy metal.
(4) Metallurgical Industry separating agent:separation, extraction of potassium, rubidium and cesium in brine. In the industry it is used for collection, separation and extraction of metals and other processes.
(5) Petrochemical industry as catalyst, drying agent, adsorbent: depth drying gas and liquid such as air, natural gas, LPG, inert gas, hydrocarbons, saturated hydrocarbons, refrigerant; dehydrating agent for paint, polyester, dyesand coatings.
(6) For agricultural soil conditioner.
(7) Medicine forsilver zeolite antibacterial agent
(8) Static desiccant for household refrigerating systems, pharmaceutical packaging, automotive air conditioning, electronic components, easy to wet and deteriorate material, perishable chemicals.
(9) Used in the R-12 and R-22 system, molecules adsorbed by 3A molecular sieve can all be adsorbed by 4A molecular sieve.