Abstract: A process is provided for the destruction of nitrogen oxides in sulfuric acid by adding a reducing agent, such as hydrazine, sulfamic acid or urea, and an oxidizing agent, such as hydrogen peroxide or persulfates, into the nitrogen oxides contaminated sulfuric acid. The nitrogen oxides contaminated sulfuric acid is treated at a temperature between 15.degree. C. and 100.degree. C.

Abstract: A process for the generation of chlorine dioxide from an alkali metal chlorate is provided that employs a waste sulphuric acid containing oxidizable organic material. Alkylation waste sulphuric acid from petroleum refining is particularly useful in this process. Conventional chlorate reducing agents used in the generation of chlorine dioxide can be partially or completely replaced by the organic material contained in the alkylation waste acid.

Abstract: An improved kraft pulping process is characterized by the addition of a spent concentrated sulphuric acid composition containing organic matter to a kraft recovery system to provide a mixture enriched in its total sulphur content that is subjected to dehydration, pyrolysis and reduction in a recovery furnace. The organic matter of the sulphuric acid composition is particularly beneficial as a source of thermal energy that enables high heat levels to be easily maintained to facilitate the oxidation and reduction reactions that take place in the furnace, thus resulting in the formation of sulphide used for the preparation of cooking liquor suitable for pulping.

Abstract: The present invention provides a stabilized concentrated sulphuric acid composition containing a chemical additive selected from a group of aminoalkylphosphonates that increases the precipitation threshold of impurities in solution, thereby suppressing the precipitation of said impurities and the formation of "cloudy acid".