CoFe-based layered double hydroxide for high removal capacity of hydrogen sulfide under high humid gas stream

Although the adsorption method was considered as the most realistic way in the removal of gaseous hydrogen sulfide (H2S), finding an efficient sorbent at low temperature with the high humid condition is still desired. A layered double hydroxide (LDH) of CoFe bimetal was prepared by co-precipitation of bivalent cobalt and trivalent iron and applied to H2S gas stream treatment. CoFe-LDH was optimally synthesized under 3:1 of Co/Fe molar ratio, pH 10 of a mixing solution of precipitating reagents, and 60 °C of aging temperature, which allowed high breakthrough capacity (0.209 g H2S/g) in H2S removal. XPS and spectral analyses on spent CoFe-LDH proved that the H2S removal proceeded through two reaction processes: formed intermediate HS− from dissociated H2S which finally replaced with the hydroxide on the metal surface; and formed HS− through carbonate counter ion at interlayer. This resulted in the formation of CO2 as a gaseous product with CoFeS2 and CoFeSO4 as solid products after the treatment of H2S. Environmental application evidenced the prepared CoFe-LDH more efficient in high humid (90% relative humidity (RH) at room temperature) condition and even at high concentrated H2S source (3333 ppm).