Adding alkali solution to the acidic water stripping tower can effectively reduce the ammonia nitrogen content in the purified water. Could anyone explain its principle?

Ammonia dissociates in water; if an acid is present as well, the acid will also dissociate: ?? ?? ?? ???HA—H+ + A-. The H+ ions released from the acid’s dissociation combine with the OH- ions produced by ammonia’s dissociation to form H2O, which shifts the dissociation equilibrium of ammonia in the direction of forming NH4+. Since this portion of ammonia nitrogen cannot be removed by heating, it remains fixed in the solution. This is the main reason why acidic substances can fix ammonia. Conversely, if a base is added to the solution, the base dissociates to produce OH- ions. By shifting the dissociation equilibrium of ammonia in the direction of free ammonia formation, this portion of ammonia can be removed by heating. In this way, during the stripping process, fixed ammonia can be essentially removed. ??The greater the amount of alkali added, the more favorable it is

It actually involves the decomposition of fixed ammonium salts, with specific examples in coal chemical industry. Volatile ammonia is removed by stripping, while fixed ammonium requires the addition of alkali to be eliminated!