Directional Preparation of Duckweed-Based Porous Carbon and Adsorptive Removal of Volatile Organic Compounds

In this reported study, a porous biochar adsorbent based on duckweed biomass was prepared by KOH impregnation activation and pyrolysis. The preparation process parameters were optimized through single-factor and orthogonal experimentation. The experimental results showed that the biochar AC-1.0-740-90, using 1.0 mol/L KOH and a pyrolysis temperature of 740 °C, with a pyrolysis time of 90 min, exhibited the best adsorption performance for toluene, with a saturated adsorption capacity of 910.97 mg/g. Characterization test results indicated that the biochar AC-1.0-740-90 had a high specific surface area (SSA, 2202.6 m²/g), a high proportion of micropores to the total pore volume (74%), abundant oxygen-containing functional groups, and highly dispersed heteroatoms N, P, and Fe. All these properties contributed to its excellent toluene adsorption performance. The multicomponent adsorption results showed that this sample had excellent adsorption performance for the ternary mixture of benzene, toluene, and chlorobenzene, with an adsorption capacity of 863.20 mg/g. During four toluene adsorption-desorption cycle tests, the adsorption capacity remained at around 90%. The toluene adsorption performance of sample AC-1.0-740-90 mainly involved pore filling and surface adsorption (such as n-π interaction, π-π interaction, and the complexation of metal iron with toluene).