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|1. (WO2014208509) METHOD FOR PRODUCING HIGH-CONCENTRATION TETRAALKYLAMMONIUM SALT SOLUTION|
|Title:||METHOD FOR PRODUCING HIGH-CONCENTRATION TETRAALKYLAMMONIUM SALT SOLUTION|
A method for producing a high-concentration tetraalkylammonium salt solution, said method comprising: (1) an adsorption step of allowing a solution containing tetraalkylammonium hydroxide to pass through an adsorption column filled with a hydrogen ion-type cation exchange resin, thereby adsorbing tetraalkylammonium ions onto the cation exchange resin; and (2) an elution step of allowing an aqueous acid solution having a hydrogen ion concentration of 4 to 6 mol/L to pass through the adsorption column as an eluent to elute the tetraalkylammonium ions adsorbed on the cation exchange resin as a salt of the acid, and then collecting an effluent that flows out from the adsorption column. In the method, such a series of steps that the adsorption step (1) is carried out and subsequently the elution step (2) is carried out are repeated multiple times; the volume expansion ratio of the cation exchange resin is 1.2 folds or less when all of hydrogen ions in the cation exchange resin are replaced by tetraalkylammonium ions; and the elution step (2) involves a step of separating a high-concentration collected solution (i) from the effluent and collecting the high-concentration collected solution (i).