Study on the adsorption performance and regeneration of lignin-derived graphitic carbon for H2S

In pursuit of effective adsorption materials for malodorous gases such as H2S and to broaden the utilization avenues of lignin waste, this study employed the direct pyrolysis method to synthesize three types of alkali lignin graphitized carbons, namely C-800, KC-700, and KEC-700. Among them, KEC-700 exhibits a high specific surface area of 1672.9 m2/g, significantly superior H2S adsorption performance compared to other materials, an adsorption breakthrough time of up to 220 min, and a sulfur capacity of 67.1 mg/g. Structural analysis showed that the more oxygen-containing functional groups of lignin charcoal and the larger specific surface area facilitated the adsorption of H2S. After reaching adsorption saturation, the degree of graphitization of lignin carbon diminishes. The H2S adsorption products primarily manifest as elemental sulfur and sulfate within the pores of lignin carbon measuring less than 2 nm. Through thermal regeneration, the charcoal effectively eliminates the elemental sulfur adsorption product. Nevertheless, sulfate removal proved unsatisfactory, as the adsorption efficiency of KEC-700 following two thermal regenerations was approximately 41% of that observed for fresh samples.