NaOH‐Activated Mango Leaf Biochar for Tetracycline Removal From Wastewater: Adsorption Mechanism, Kinetic–Isotherm Modeling, Toxicity Mitigation, and Economic Feasibility

The present study investigates the adsorption performance of sodium hydroxide‐activated mango leaf biochar (ML–NaOH) for the removal of tetracycline (TC), an antibiotic from aqueous solutions. The synthesized biochar was systematically characterized, and the effects of key operational parameters, including solution pH, contact time, initial TC concentration, and adsorbent dosage were evaluated. Under optimal conditions (initial TC concentration: 30 mg L − 1 , sorption time: 60 min, adsorbent dosage: 1.0 g L − 1 ), a maximum removal efficiency of 99.1% was attained. Isotherm and kinetic studies indicated that the adsorption process adhered to Langmuir isotherm model, indicating monolayer adsorption and pseudo‐second‐order model, suggesting that chemisorption respectively. The adsorption mechanism was found to involve many interactions, such as hydrogen bonding, π–π interactions, electrostatic attraction, and surface complexation, at solution pH of 7. Furthermore, phytotoxicity investigation using Vigna mungo seeds demonstrated reduced toxicity, indicated by improved radicle growth after treatment. Economic analysis indicated that the production cost of ML–NaOH was approximately 14.94 USD per kg, highlighting its potential as a cost‐effective adsorbent. Overall, the results suggest that ML–NaOH biochar is an efficient, sustainable, and economically viable material for the removal of TC from contaminated water systems.