Removal of gaseous H2S using microalgae porous carbons synthesized by thermal/microwave KOH activation

Abstract

H2S has strong toxicity and corrosivity, which can endanger human health and corrode equipment. This article used the two types of activation methods as a comparison to activate raw biochar from microalgae pyrolysis to prepare microalgae porous carbon for removal of gaseous H2S. The difference in textural properties and functional group of the prepared microalgae porous carbon using two types of activation methods is studied emphatically. Then physicochemical property of microalgae porous carbons was characterized and effect of activation methods, KOH/raw biochar mass ratio and sorption temperature on desulfurization was tested. Sorption products, mechanism, kinetics and thermodynamics were studied. Reuse of deactivated adsorbents was also explored. Research revealed that both activation methods substantively improved pore structure and increased active functional group contents of raw biochar, greatly promoting desulfurization. Compared to thermal activation, active functional groups of microalgae porous carbons prepared by microwave-assisted activation had no obvious difference, but pore structure was greatly improved, leading to higher H2S sorption capacity. Results of product characterization, thermodynamics and kinetics demonstrated that in the H2S sorption process, physical sorption was major and chemical sorption was auxiliary. Spent containing-sulfur microalgae porous carbons showed good Hg0 capture ability, far exceeding commercial activated carbon.