Purpose  Efficiency of biochar made of spent corn straws in adsorbing sulfonamide residues in water solutions of various conditions was studied for aquacultural application.

  Methods  The biochar was made from stover after corn harvest. The physicochemical properties of the biochar were determined by FTIR, SEM, XRD, and elemental analyzer. In water solutions of varied conditions, including biochar addition, sulfonamide concentration, pH, and treatment time and temperature, the kinetics, thermodynamics, and efficiencies of the biochar adsorptions on sulfadiazine (SDZ) and sulfachlorpyridazine (SCP) were studied.

  Results  The sulfonamides removal rate significantly affected by the amount of biochar used, initial antibiotic concentration in solution, adsorption treatment time, and solution pH. At 25^oC and pH 5, 94.57% of 10 g·L⁻¹ initial concentration of SDZ in solution was removed by 8 g·L⁻¹ addition of the biochar in 4h, while 98.12% of SCP at 10 g·L⁻¹ initial concentration was adsorbed by 5 g·L⁻¹ biochar. The sulfonamide adsorption kinetics of the biochar was a pseudo-second-order function, and the isotherms fitted a Freundlich equation. The adsorption process is mainly controlled by rapid reaction. Since a greater than 40% removal rate on SDZ or SCP could still be achieved by a same biochar application after 3 cycles, repeated usage of the adsorption material seemed durable.

  Conclusion  The corn straws biochar exhibited a capacity in effectively adsorbing residues of sulfonamide antibiotics in water solutions. It suggested a potential utilization of the low cost, highly efficient, and easily available material in aquaculture ponds for mitigating the antibiotic contamination.