The　application　of　sludge-based　biochar　and　its　derivatives　to　remove　antibiotics　from　aquatic　media　has　long　been　recognized　as　an　environmentally-friendly　approach　since　it　delivers　the　scenario　of　waste　treatment　by　wastes.　Despite　the　existence　of　various　proposed　adsorption　mechanisms,　a　comprehensive　analysis　that　combines　macroscopic　and　microscopic　perspectives　remains　insufficient.　Herein,　surface　modification　(Fe3O4)　and　spherization　(chitosan)　were　employed　to　improve　the　adsorption　capacity　of　sludge-based　biochar　toward　tetracycline　hydrochloride　(TC).　The　as-prepared　gel　pellets　(FeB-11)　exhibited　high　adsorption　capacity　toward　TC　in　aqueous　with　maximum　uptake　of　206.98　mg　&　BULL;g　�　1　under　298K.　The　combination　of　characterization-based　and　approximate　site　energy　distribution　(ASED)　methods　concluded　that　surface　complexation　played　the　primary　role　in　enhancing　the　adsorption　capacity　of　FeB-11　for　TC,　while　space　filling,　hydrogen　bonding,　7c-7c　interaction,　electrostatic　interaction　and　ion　exchange　also　contributed　to　the　adsorption　process.　The　introduction　of　chitosan　and　Fe3O4　weakened　physisorption　but　strengthened　chemisorption,　and　Fe3O4　was　proposed　as　the　primary　promoter　for　TC　adsorption　due　to　the　better　affinity　between　TC　molecules　and　FeB-11　which　Fe3O4　brought.　Concentrated　and　high　distribution　frequency　of　adsorption　sites　with　high　adsorptive　energy　were　the　primary　surface　property　responsible　for　the　remarkable　TC　adsorption　capacity　exhibited　by　FeB-11　in　the　macroscopic　perspective.　These　findings　underscored　the　importance　of　combining　macroscopic　and　microscopic　perspectives　to　understand　the　prioritization　among　various　adsorption　mechanisms,　other　than　solely　proposing　various　mechanisms,　which　was　useful　to　help　design　efficient　adsorbents.