Enhanced adsorption for the removal of tetracycline hydrochloride (TC) using ball-milled biochar derived from crayfish shell

Abstract Tetracycline hydrochloride (TC) is a broad-spectrum antibacterial widely used in the livestock and aquaculture industry. Entry of these into water body can bring serious threat to human health and it is difficult to degrade or remove by biodegradation due to bacterial resistance. Hence, non-biodegradation methods such as adsorption show advantages in TC treatment. In this study, pristine (CFS) and ball-milled (BCFS) crayfish shell biochar pyrolyzed at 400, 600, 800 °C were fabricated for TC removal. Results indicated that the ball milling enhanced the adsorption capacity (39.1 mg/g for CFS800 versus 60.7 mg/g for BCFS800) mainly by improving the structure properties of the obtained biochar (SBET=127.9 m2/g, Vmic=0.028 cm3/g, D50=50.56 μm for CFS800 versus SBET=289.7 m2/g, Vmic=0.061 cm3/g, D50=0.623 μm for BCFS800). The main adsorption mechanism of TC on biochar was physisorption via pore filling, followed by chemisorption including hydroxyl complexation, H-bonding and electrostatic interaction. Furthermore, the studied biochar had excellent reusability and environmental adaptability and thus proved its promising application potential in the treatment of TC laden wastewater.