Biochars derived from by-products of microalgae pyrolysis for sorption of gaseous H2S

KOH-modified biochars derived from by-products of microalgae pyrolysis were prepared to adsorb gaseous H2S. Influences of various parameters (e.g., mass ratio between KOH and biochars, and adsorption temperature) on desulfurization performance were investigated. Kinetics/mechanisms of H2S adsorption, and reutilization of spent adsorbents for capturing gaseous Hg0 were also explored. Results exhibited that KOH modification greatly improved the desulfurization performance of biochars via improving the pore structures of biochar and increasing the surfaces oxygen-containing group. The modified biochars (CK2 and SK2) achieve optimal desulfurization performance, with an adsorption capacity of 59.10 mg/g for CK2 and 42.30 mg/g for SK2, respectively. Adsorption temperature showed a double effect on desulfurization. S0 and sulfate were successfully detected on biochar surface after adsorption via XPS and XRD analysis, indicating that chemical adsorption occurred in the H2S adsorption. Kinetic study showed that physical adsorption governed the H2S adsorption process, and mass transfer was the main control step of the desulfurization process. The spent adsorbents (i.e., spent containing-sulfur biochars) could capture efficiently Hg0 in gas and shown good competitiveness as compared with commercial activated carbon.