Method for removing sulfate radical and calcium ion in lactic acid

The invention provides a method for removing sulfate radical and calcium ion in lactic acid. The method comprises the following steps of: decoloring lactic acid feed liquid by active carbon until the color intensity is 0-200 APHA, dewatering and concentrating until the concentration of lactic acid is 50-60%, then separating out calcium sulfate crystal, filtering and removing calcium sulfate crystal, diluting the filtrate until the concentration of the lactic acid is 30-50%, and finally removing residual sulfate radical and calcium ion by a nano-filtration membrane of which the molecular cut off is 100-200 Daltons. The method has the characteristics that the removal effect of the sulfate radical and calcium ion in lactic acid solution is good; the process is environment-friendly; the method is a pure physical method; and the production cost is low, and the method has good industrial application prospect.