In this work we have studied the absorption of H2S and CO2 in NaOH solutions (0.01, 0.1, 0.5, 1 and 2 M), in order to treat these acid gases coming from sour gas sweetening process. Our results show that gas dissolution/neutralization is faster at the lowest NaOH concentrations tested in consequence a compromise must be reached between bisulfide-sulfide yield and reaction fastness. (c) 2012 Elsevier Ltd. All rights reserved.