Green preparation of carbon materials from biomass slag and steam as byproducts of power plants for efficient treatment of lead-containing wastewater

Green preparation of high-performance and cost-effective carbon materials using biomass slag and steam, which were the byproducts of power plants, for efficient treatment of lead (Pb(II))-containing wastewater was investigated. The optimum carbon material CH₅₀₀-800 (S_BET=818.8 m²/g and V_t=0.46 cm³/g) was produced by one-step steam activation at 800 ℃ for 1 h under a 500 mL/min stream with a heating rate of 5 °C/min. The obtained CH₅₀₀-800 greatly enhanced the efficiency of Pb(II) removal, achieving the maximum adsorption capacity of 191.1 mg/g. The removal of Pb(II) from wastewater was well described by the Pseudo-second-order, Elovich and Freundlich model, suggesting that it was predominantly governed by chemical adsorption and diffusion on heterogeneous surfaces. The adsorption process demonstrated a synergistic mechanism involving pore and surface adsorption, chemical interactions between oxygen-containing groups (C-O and -OH) and Pb(II), as well as Pb(II)-π interactions, which was responsible for the efficient removal of Pb(II) from wastewater. Moreover, CH₅₀₀-800 retained a potential for reusability with a high adsorption stability (only 2.5 % Pb(II) desorption after 48 h) and ion selectivity (>93.0 %) in the presence of K(I), Na(I) or Ca(II). Additionally, a circular economic model was proposed to valorize biomass slag and steam in situ for treating Pb(II)-containing wastewater effectively in biomass power plants. This approach provided an innovative solution for utilizing waste to treat hazardous substances within practical engineering applications.