disclosed herein is a method of separating carbon dioxide from a gas mixture using a biopolymer , including : introducing hemocyte or extrapallial fluid , extracted from shells , into a reactor filled with 1 l of a solution containing a calcium source , and then dissolving the hemocyte or extrapallial fluid in the solution to form a mixed solution ; and mixing carbon dioxide or a gas mixture containing carbon dioxide into the mixed solution to separate carbon dioxide from the gas mixture .