Abstract: Nitrogen oxides are removed from a waste gas stream by contacting the waste gas stream with ammonia, thereby reducing the nitrogen oxides to nitrogen. Residual nitrogen oxides and unreacted ammonia in the waste gas stream leaving the nitrogen oxides reducing step are oxidized to nitrogen pentoxide or nitric acid by contacting this gas stream with ozone. Contact of the ozone and waste gas is preferably carried out in the presence of an aqueous solution at a pH above about 9 and at a temperature above about 75° C., and this step is preferably carried out in the presence of an ammonia-oxidizing catalyst.

Abstract: An ozone-oxygen gas stream produced by passing oxygen into an ozone generator is introduced into a membrane separation unit containing an ozone-permeable membrane. Ozone-enriched gas passes through the membrane and is recovered or it contacts a liquid or gas stream which contains ozone-reactive substances, thereby oxidizing the substances. The oxygen-enriched gas stream produced on the feed side of the membrane by permeation of ozone through the membrane is recycled to the ozone generator. Prior to being recycled, the oxygen-enriched stream may be purified to remove gaseous impurities which permeate through the membrane from the liquid or gas stream being treated.

Abstract: An ozone-oxygen gas stream is introduced into feed side of a membrane separation unit containing an elastomeric polymer membrane. Ozone-enriched gas passes through the membrane to a permeate zone and is contacted with an ozone-reactive substance-containing gas stream in the permeate zone, thereby oxidizing the substances or is removed from the permeate zone. Removal of the ozone-enriched gas from the permeate zone may be effected by purging the permeate zone with an inert gas and/or evacuating the permeate zone. Ozone-enriched gas removed from the permeate zone may be mixed with a liquid or gas stream which contains ozone-reactive substances in, for example, a venturi device, thereby oxidizing the substances.