The primary aim of this study is to develop a recovery process for PhSO3K from the industrial waste of Qpe (quizalofop-p-ethyl) production. The solubility data for the PhSO3K-K2CO3-H2O system at 15, 25, 35, 45, and 55 degrees C were determined to obtain the phase diagram of the system. Moreover, the different crystallization fields in the phase diagram of 25 degrees C were analyzed. The separation technology of PhSO3K from the PhSO3K-K2CO3-H2O system was designed based on the phase diagram. Furthermore, the PhSO3K and K2CO3 in a wastewater from Qpe production were crystallized in sequence by evaporation according to the designed method. The organic impurities precipitated concomitantly with PhSO3K were washed out by ethanol. Finally, the purified PhSO3K was converted to (R)-ethyl O-bezenesulfonyl lactate, the intermediate of Qpe production.