The invention belongs to the technical field of L-
lactic acid production, and particularly discloses a method for purifying and refining L-
lactic acid. The method for purifying and refining L-
lactic acid comprises the following steps: removing thalli in a
fermentation liquor through separation to obtain
thallus residues which can be used as a feed
raw material; decolorizing an acidolysis filteredclear liquid by using
activated carbon, feeding the decolorized acidolysis filtered
clear liquid into a first
ion exchange column, carrying out cation and anion exchange to obtain a primary
ion exchange liquid, filtering the primary
ion exchange liquid by using a
nanofiltration membrane, carrying out pre-concentration, and sequentially carrying out cation and anion exchange to obtain a secondary
ion exchange liquid; decolorizing the secondary
ion exchange solution by adopting an
activated carbon decolorizing column, and then concentrating to obtain a lactic acid concentrate with the L-lactic
acid content of 80-90%; and carrying out short-path
distillation and purification on the lactic acid concentrate to obtain high-purity food-grade lactic acid or produce
polylactic acid. According to the L-lactic acid purification and refining method provided by the invention, the finished product quality of the L-lactic acid is improved, and the finally obtained L-lactic acid is good in quality andhigh in yield and particularly meets the quality requirement of the L-lactic acid serving as a PLA
raw material.