Removal of tetracycline with grape leaves-based biochar: adsorption properties and mechanism

Tetracycline (TC) was a low-cost, commonly used antibiotic that was widely used in everyday life. Its residues in wastewater may cause harm to human health and ecological environment. Adsorption was an effective method for the removal of TC from the waste water. Grape leaves-based biochar materials (GLBCs) were prepared using oxygen limited pyrolysis at different temperatures. The produced biochars were used to adsorb TC in wastewater. The good adsorption capacity for low concentration can be reached for the GLBC900. According to the fitted results of Langmuir isotherm model, the adsorption capacity of GLBC900 for TC was 52.858 mg/g. The adsorption of TC by GLBC900 may be caused by pore filling, electrostatic interaction, surface complexation and hydrogen bonding. The adsorption process of GLBC900 confirmed to the Langmuir isotherm model better (R2 = 0.9716), which was single-layer adsorption. Thermodynamics showed that adsorption was a spontaneous, endothermic and entropy increasing reaction. Grape leaves-based biochar was a low-cost and environmentally friendly adsorbent that can effectively remove TC from wastewater.