Influence of Protonation-Deprotonation Reactions on the Diffusion of Ammonium Chloride through Anion-Exchange Membrane

Electrodialytic concentration of ammonium-containing liquid products of biochemical processing of municipal, industrial, and livestock wastewater is a promising method for obtaining cheap liquid fertilizers for agriculture. At the same time, it is known that electrodialysis of NH4Cl solutions fails to achieve the same high brine concentrations as in the case of other chlorides, for example, KCl. We show that the reason is high diffusion permeability of anion-exchange membranes (AEMs) to NH4Cl, which is due to the protonation-deprotonation reactions of ammonium coions during their transfer from an external solution to an internal AEM solution and vice versa. For the first time, a mathematical model of NH4Cl diffusion through AEM was proposed with allowance for these reactions. The experimental values of the diffusion permeability of an anion-exchange membrane AMX and a cation-exchange membrane CMX in NH4Cl and KCl solutions have been compared. between The results of calculating the diffusion permeability of the membrane AMX in NH4Cl solutions are in qualitative agreement with the experiment data.

Automated summary

Electrodialytic concentration is a promising method for obtaining cheap liquid fertilizers, but NH4Cl solutions do not achieve high concentrations as efficiently as other chlorides. The high diffusion permeability of anion-exchange membranes to NH4Cl is attributed to protonation-deprotonation reactions of ammonium coions.