Abstract: A mixed gas consisting of carbon dioxide and nitrogen is separated into the component gases by a method which comprises treating sepiolite with nitric acid, subjecting the treated sepiolite to an ion-exchange treatment thereby exchanging the cationic metal present in the treated sepiolite with Mg ions, heating the sepiolite resulting from the ion-exchange treatment, and exposing the ultimately prepared sepiolite to the mixed gas.

Abstract: Separation of nitrogen and carbon dioxide is accomplished by a method using as a separating material one member selected from the group consisting of sepiolite in the unmodified form, sepiolite which has been heat-treated, and sepiolite which has had part or the whole of the exchangeable cation thereof replaced with zinc ion and which has been subsequently subjected to a heat treatment.

Abstract: An interlayer cross-linked smectite is produced by a method which includes the steps of preparing a smectite suspension containing a dissolved water-soluble macromolecular compound, adding a cationic hydroxide oligomer to the suspension thereby subjecting the exchangeable cation in the smectite to ion exchange, allowing the resultant smectite suspension to stand at a fixed temperature for a fixed time thereby allowing the cationic hydroxide oligomer of the smectite to age, separating a solid smectite from the resultant suspension, and heating the separated solid smectite. The interlayer interval of the produced smectite can be controlled by adjusting the amount of the cationic hydroxide oligomer.