Abstract: A method of simultaneously removing sulfur dioxide and nitrogen oxides from an exhaust gas which comprises the steps of:contacting the exhaust gas with an aqueous absorbing solution containing an iron chelate complex and an alkali metal sulfite to form alkali metal sulfur oxides comprising an alkali metal dithionate in the aqueous absorbing solution;separating the alkali metal sulfur oxides formed and accumulated from part or the whole of the aqueous absorbing solution by crystallization; andsubjecting the alkali metal sulfur oxides separated together with a carbonaceous material to decomposition-reduction reaction at a temperature of at least about 700.degree. C. to form an alkali metal sulfide and a gas comprising sulfur dioxide and carbon dioxide.

Abstract: A method of removing NO.sub.x and SO.sub.2 from an exhaust gas containing NO.sub.x and SO.sub.2 which comprises contacting an exhaust gas containing NO.sub.x and SO.sub.2 with an aqueous solution containing M.sub.2 SO.sub.3, an iron ion and an aminopolycarboxylic acid to absorb NO.sub.x and SO.sub.2 in the aqueous solution and treating the resulting absorbing solution while preventing a contact of the solution with the exhaust gas, thereby to form M.sub.2 S.sub.2 O.sub.6 in the absorbing solution and reducing NO.sub.x to N.sub.2. The M.sub.2 S.sub.2 O.sub.6 formed in the absorbing solution can be easily removed by crystallization separation. With such method, NO.sub.x and SO.sub.2 can be removed from exhaust gases at high rates and the absorbing solution can be easily regenerated and recycled to the absorbing zone.