Enhanced concentration of carbon dioxide, typically of carbon dioxide in the air, is advantageous in areas such as agriculture and horticulture involving raising of plants which utilize carbon dioxide for photosynthesis. Various carbon dioxide concentration apparatus have been developed, but the problems thereof are numerous. It is accordingly the purpose of the present invention to develop an adsorbent having exceptional adsorption of carbon dioxide, and to provide an apparatus for concentration of carbon dioxide in the air through the use thereof. Provided is a pressure swing concentration apparatus that uses ferrierite as the adsorbent, the ferrierite having been subjected to alkali treatment to give a pore diameter of 0.01-1 μm and a pore volume of 0.1 mL/g or above.
