Preparation of organic potassium salts modified microalgae biochar and its high-efficient removal of tetracycline hydrochloride from water: Activation mechanism and adsorption mechanism

In this study, Microcystis aeruginosa was effectively transformed into high-surface-area biochar using four different organic potassium salts as activators, achieving a maximum specific surface area of 2933 m2·g−1. The resulting biochar exhibited an outstanding adsorption capacity for tetracycline hydrochloride, reaching up to 969.9 mg·g−1. Our findings reveal that a higher potassium content in the precursor correlates with an increased surface area of the biochar, while lower self‑carbonization temperatures or higher melting points of the organic potassium salts promote a greater proportion of mesopores. Hydrogen bonding was identified as the primary adsorption mechanism, with density functional theory providing further insights into its significant role. This research presents a controllable, efficient, and environmentally friendly strategy for biochar activation and offers a predictive framework for optimizing biochar properties through organic potassium salt modification, laying a solid theoretical foundation for the design of advanced adsorbents with enhanced performance. [Display omitted] •Modified biochar achieves a maximum surface area of 2933 m2·g−1.•Modified biochar shows an excellent adsorption of HTC, reaching 969.9 mg·g−1.•The potassium proportion in the precursor results in surface area for the biochar.•The properties of organic potassium salts affect modified biochar properties.•Carbonyl-O is the main adsorption site.