A process for treating a NOx-containing gas resulting from a leaching process wherein said leaching process includes the treatment of ores with nitric acid to separate materials contained in the ores, and said leaching process releases a diluted nitric acid solution and said NOx-containing gas and wherein the treatment of said NOx containing gas includes an absorption step in presence of make-up water and/or in presence of diluted nitric acid, obtaining a concentrated nitric acid and a tail gas containing residual NOx.

The technology includes a method for removing sulfur dioxide (SO.sub.2) from a gas stream, where SO.sub.2 gas is contacted by a diluted sulfuric acid (H.sub.2SO.sub.4) stream and absorption takes place in a quench tower. The dissolved SO.sub.2 reacts with the excess of oxygen in the gas stream, where the oxidation results in the formation of sulfurous acid (H.sub.2SO.sub.3) and dilute H.sub.2SO.sub.4. For the complete oxidation of the dissolved SO.sub.2, an electrolyzer and/or liquid injectants are used. This results in the formation of diluted H.sub.2SO.sub.4. The diluted H.sub.2SO.sub.4 is processed in an enrichment unit to produce concentrated H.sub.2SO.sub.4 and fresh water. A portion of the diluted H.sub.2SO.sub.4 and/or fresh water is recycled back to the quench tower for the continued acidic absorption of the incoming SO.sub.2 in the gas stream, thereby not relying on an external water source.

A gas scrubber may include an absorption apparatus configured for receiving a gas and absorbing the gas in an absorption medium, as well as an evaporation apparatus configured for evaporating at least a part of the liquid that is introduced. The absorption apparatus may have an introduction apparatus for the gas, an apparatus for circulating the absorption solution that has reacted with the gas, a discharge apparatus for at least a part of the absorption solution that has reacted with the gas, and a cooling system for the circulating absorption solution. The absorption apparatus and the evaporation apparatus can be connected via a heat exchanger such that heat content of the absorption solution that has reacted with the gas is used at least in part for the evaporation.