PURPOSE: To provide a removing method of hydrocarbon contaminants from air and water.

CONSTITUTION: An organic compound adsorbing clay prepared by ion-exchanging with quaternary ammonium ions containing four 1-4C short chain alkyl groups, or quaternary ammonium ions containing two or three 1-4C short chain alkyl groups and one or two substituted or unsubstituted cycloalkyl groups, or one or two substituted or unsubstituted aryl groups or one or two alkaryl groups, is brought into contact with air or water to adsorb and remove contaminants. Aromatic petroleum-based contaminants such as benzene, toluene, xylene (ortho-, meta and para-), ethylbenzene, naphthalene and other water-containing petroleum components and derivatives with pKa of ≥10 can be efficiently removed from water.