Biochar prepared by fish feces residue: properties and its application for removing antibiotics in aquaculture tail water

Fish feces and residues are a kind of common waste in aquaculture system to require timely handling while aquaculture wastewater generally contains antibiotics to require efficient treatment. This study prepared biochar by using fish feces and residues to investigate the removal of typical fluoroquinolone enrofloxacin by biochar. Biochar showed the sheet-dot mixed structure with multiple elements on surface. The content of carbon/nitrogen/hydrogen of biochar made of fish feces and residues reached 46.5%/3.1%/2.5%. The removal efficiency of enrofloxacin reached 94.7% with biochar dosage of 1 g/L. The adsorption capacity of biochar at pH of 2 or 10 was higher than that at the other pH values. Adsorption capacity of biochar increased by 10.6% from 15°C to 25°C to reach 9.47 mg/g at 25°C while that slightly increased from 25°C to 35°C. Pseudo-first-order model was the best model with R 2 = 0.9982 for describing adsorption kinetics of enrofloxacin by biochar. Langmuir model could better fit results of isotherm for enrofloxacin by biochar with Langmuir constant of 0.38–1.65 L/mg. Biochar used 3–4 times still kept good removal efficiency for enrofloxacin. The prepared biochar exhibited good application potential. The findings of this study provide new idea for treating aquaculture solid wastes and wastewater.