A METHOD FOR IMPROVING POLYIMIDE HOLLOW FIBER MEMBRANE

A method of reforming a polyimide hollow fiber membrane and a polyimide hollow fiber membrane reformed by the method are provided, wherein the reformed polyimide hollow fiber membrane has an effect of recovering CH4 with a high purity by improving selectivity of CO2/CH4 of biogas, thereby removing CO2 from the biogas. A method of reforming a polyimide hollow fiber membrane comprises the steps of: submerging a polyimide hollow fiber membrane into a cross-linking agent to cross-link the polyimide hollow fiber membrane; and annealing the cross-linked polyimide hollow fiber membrane. The cross-linking agent is a mixture of N-(1-naphthyl)ethylenediamine and dihydrochloride. A reformed polyimide hollow fiber membrane for the separation of CO2 gas from biogas is characterized in that a polyimide hollow fiber membrane that has been reformed and annealed by the method has a CO2/CH4 selectivity range of 62 to 106 according to an annealing temperature of the membrane which has been increased as high as approximately 50% as compared to that of a non-reformed polyimide hollow fiber membrane, and a polyimide hollow fiber membrane that has been reformed by cross-linking and annealing has a CO2/CH4 selectivity range of 112 to 188 which has been incrased according to the annealing temperature of the polyimide hollow fiber membrane.