PURPOSE: To recover iminodiacetic acid(IDA) and sodium sulfate, by adjusting the temperature of a solution containing IDA and sodium sulfate to form a slurry containing a solid mixture of IDA and sodium sulfate and separating the solid mixture therefrom.

CONSTITUTION: Waste water in the production of IDA from nitrilotriacetic acid(NTA) and an aqueous recycled solution containing IDA and sodium sulfate are cooled to form a slurry comprising a solid mixture of IDA and sodium sulfate decahydrate and the mother liquor. The solid mixture is separated from the motor liquor preferably by centrifuge. The aqueous solution is kept at about 40°C and cooled to about 5°C at cooling rate of 5.8°C/hour, wherein seed cystals of IDA and sodium sulfate and added preferably at a saturation temperature for IDA and sodium sulfate, respectively. In advance to the above procedure, it is preferred to adjust the pH of the aqueous solution to about 2.1 and to remove the precipitated NTA.