Method for extracting and purifying calcium lactate

The invention discloses a method for extracting and purifying calcium lactate, and belongs to the technical field of biochemical engineering. The method comprises the following steps of removing impurities from a calcium lactate solution by centrifugation; adding a phase-separating solvent, mixing uniformly, standing for separating phases, taking an upper phase, crystallizing to obtain calcium lactate, wherein the phase-separating solvent is acetonitrile or a mixed solution formed by any one of acetonitrile, ethyl formate, methyl formate, methyl acetate, ethyl acetate, tetrahydrofuran and methyl ethyl ketone and any one of C1-C3 alcohol and C3-C5 alcohol. An extraction-crystallization method is adopted to extract and purify calcium lactate; calcium lactate can be crystallized naturally in the phase-separating solvent; a re-extraction step is omitted; and the process is simple and practicable. The phase-separating solvent has a low boiling point, can be recycled easily, has no toxicity or low toxicity, and is safe and environment-friendly. By adopting the method provided by the invention to extract and purify calcium lactate, a removal rate of impurities is high; a removal rate for pigment, protein and total sugar can reach 97%, 98% and 98% respectively; and the calcium lactate can be used for preparing high-purity lactic acid. The method is particularly suitable for calcium lactate fermentation broth prepared by straw hydrolysate with high impurity content.