Recent advances in simultaneous removal of SO₂ and NO_x from exhaust gases: Removal process, mechanism and kinetics

SO₂ and NO_x, major gaseous pollutants in exhaust gas, can exert adverse effects on human health and environmental disaster. Therefore, numerous desulfurization (de-SO₂) and denitrification (de-NO_x) technologies have been designed to reduce SO₂ and NO_x emissions. Compared to traditional multi-step removal processes, simultaneous removal of SO₂ and NO_x has been attracting significant attention recently. This paper timely reviewed available literature focused on simultaneous de-SO₂ and de-NO_x methods, which are classified into four pathways as oxidation, reduction, adsorption/absorption and microbial purification. The removal process, basic mechanism and kinetics of each pathway are systematically reviewed in consideration of reactants, catalyzers, temperatures and atmosphere. Moreover, the main challenges and potential breakthroughs in developing novel simultaneous de-SO₂ and de-NO_x methods are critically discussed to provide a roadmap for prospective research activities. Therefore, this review provides a deeper insight in understanding the mechanisms of de-SO₂ and de-NO_x, and then helps to develop innovative simultaneous removal methods or improve the efficiency of available abatement methods.