Recycling　biomass　resources　for　conversion　to　biochar　absorbents　toward　pollutant　capturing　is　an　important　strategy　for　realizing　＂two　birds　with　one　stone＂.　The　lack　of　efficient　and　straightforward　conversion　processes　prompts　us　to　explore　double　chemical　(MnCl2/KOH)　activation　to　convert　banana　peels　to　highly　porous　bio-char,　BC-MK,　straightforwardly.　BC-MK　possesses　a　specific　surface　area　of　1276.63　m2/g,　much　higher　than　those　produced　through　single　chemical　activation　using　MnCl2　or　KOH　alone.　The　initial　MnCl2　solution　impregnation　of　biomass　is　essential　to　loosen　the　internal　structure　of　the　biomass,　which　makes　the　subsequent　KOH　activation　homogeneous.　Besides,　MnO2　formed　during　high-temperature　pyrolysis　can　serve　as　a　template　for　more　porous　structure　formation.　Experimental　evidence　indicates　that　7C-7C　stacking　interactions　play　a　more　critical　role　than　hydrogen　bonding　interactions　in　enabling　the　BC-MK-based　fast　adsorption　of　tetracycline　(TC).　The　maximum　monolayer　adsorption　capacity　of　the　BC-MK　adsorbent　toward　TC　exceeds　295　mg/g.