Abstract: A method (10) for the separation of gases involving the method steps of: i) passing an exhaust gas stream (27) containing CO2 through a first membrane separation system (30) to produce a pre-concentrated gas stream (34) containing at least carbon dioxide; and a reject stream; and ii) directing the pre-concentrated gas stream to at least one purification step (50) to produce a purified CO2 stream (55); wherein, sulphur-containing gases (SOx) are also substantially separated from the exhaust gas (27) by the first membrane separation step (30) into the pre-concentrated gas stream (34), and the purified CO2 stream (55) is substantially free of nitrogen gas.