Abstract: A process is described for the removal of nitrogen oxides from waste gases with the recovery of nitric acid or a nitrate solution. The waste gas is reacted with hydrogen peroxide in an amount appropriate to the desired degree of removal of nitrogen oxides, on a catalyst, at a temperature of less than 800.degree. C., preferably in the range of 20.degree. to 100.degree. C., to give the valuable product, nitric acid or a nitrate solution. This may be done in accordance with the invention by bringing the hydrogen peroxide as a solution, i.e., in the liquid phase, into contact with the catalyst through which the waste gas is flowing. The reaction product is either utilized in a gaseous form or processed to nitric acid or a nitrate solution. Alternatively, the hydrogen peroxide may be introduced in a gaseous form, using a honeycombed catalyst, and wherein the hydrogen peroxide is present in at least one half of the stoichiometrically determined amount.

Abstract: A process for removing halogenated organic compounds from waste gases optionally containing NO.sub.x, in which the waste gas is optionally supplemented with SO.sub.2, optionally led through a fixed bed or fluidized bed of a solid and contacted with Caro's acid or one of its salts. The Caro's acid can be produced in situ by adding H.sub.2 O.sub.2 and optionally H.sub.2 SO.sub.4.