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3A molecular sieves, with a pore size of 3A (0.3 nm), exhibit excellent adsorption capacity for ammonia due to their well-defined structure and surface properties. The adsorption mechanism mainly involves physical adsorption, where ammonia molecules are trapped in the sieve's pores through van der Waals forces, avoiding strong chemical bonding. Key factors influencing adsorption performance include temperature, pressure, and ammonia concentration. Lower temperatures and higher pressures enhance adsorption, as they favor the condensation of ammonia molecules on the sieve surface. The adsorption isotherm typically follows the Langmuir model, indicating monolayer adsorption with a maximum capacity of ~8-10 mg NH3/g sieve at 25°C and 1 atm. Selectivity is a critical advantage: 3A sieves preferentially adsorb ammonia over other small molecules like N2 or O2, making them ideal for gas purification. Regeneration is feasible through heating (to 100-150°C) or pressure reduction, allowing repeated use. Applications span industrial gas purification (removing trace ammonia from synthesis gas), ammonia storage (via reversible adsorption/desorption cycles), and environmental protection (treating ammonia-contaminated emissions). This makes 3A molecular sieves a vital material for efficient ammonia management in diverse fields.
