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).