Adsorption method and apparatus

A gas containing NOx at a low concentration is contacted with an adsorbent comprising a copper salt supported on zeolite whereby the NOx is adsorbed and removed efficiently. The copper salt is preferably selected from copper chloride, double salt of copper chloride and ammine complex salt of copper chloride. An apparatus for purifying an NOx-containing gas comprises an adsorptive dehumidifier 1 for dehumidifying the gas with a dehumidifying agent and regenerating the agent with a purified gas, and an adsorptive denitration unit 2 for denitrating the dehumidified gas. The denitration unit has an adsorbent regenerating zone provided with a channel 9 for recycling an NH3- containing regenerating gas and with a channel 10 for withdrawing a portion of the regenerating gas from the recycling channel, passing the withdrawn gas through a denitration reactor 5 and then releasing the denitrated gas into the atmosphere.