Bamboo derived activated carbon as a highly efficient catalyst for the oxidation and adsorption of hydrogen sulfide at room temperature

Abstract

A series of bamboo derived activated carbon (BAC) catalysts with different activation degrees were prepared and tested for H₂S catalytic oxidation–adsorption at room temperature. It was found that the specific surface area, pore size and defect level increased with the increase in activation degree. The highest sulfur capacity (Q_s) can be obtained for Na/BAC-8, which can attach 0.73 g g⁻¹. And the Q_s was directly related to the total pore volume and specific surface area. Meanwhile, the final sulfate and elemental sulfur products were mainly formed in small micropores (<0.7 nm) and mesopores, respectively. The competitive adsorption of excess water with H₂S did not occur even under high RH conditions due to the highly hydrophobic nature and the partial consumption of water. Moreover, the diffusion process and adsorption kinetics of the sulfur containing products were explored for the first time. Diffusion in the pores rather than between the pores was the rate-determining step during the diffusion process of sulfur-containing products. The adsorption kinetics are dominated by internal diffusion. The reaction mechanism was investigated by using in situ DRIFTS and DFT methods. SO₃ was the important intermediate species during the reaction. And the polymerization of sulfur atoms to form stable S₈ clusters and the formation of SO₂ were the rate determining steps for the generation of elemental sulfur and sulfate, respectively.