Enhanced removal of sulfonamide antibiotics from water by phosphogypsum modified biochar composite

• PMBC was prepared from phosphogypsum and biomass for antibiotics removal. • PMBC produced from 70 wt% phosphogypsum and wood chips showed the best performance. • Acidic conditions facilitated the adsorption of SD and SMT by PMBC. • PMBC showed good removal efficiency for SD and SMT in a fixed bed column. • Hydrogen bonding, π-π, hydrophobic, and electrostatic interaction contributed to adsorption. Antibiotic pollution has become a global eco-environmental issue. To reduce sulfonamide antibiotics in water and improve resource utilization of solid wastes, phosphogypsum modified biochar composite (PMBC) was prepared via facile one-step from distillers grains, wood chips, and phosphogypsum. The physicochemical properties of PMBC were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Zeta potential, X-ray diffraction (XRD), etc. The influencing factors, adsorption behaviors, and mechanism of sulfadiazine (SD) and sulfamethazine (SMT) onto PMBC were studied by batch and fixed bed column adsorption experiments. The results showed that the removal rates of SD and SMT increased with the increase of phosphogypsum proportion, while decreased with the increase of solution pH. The maximum adsorption capacities of modified distillers grain biochar and wood chips biochar for SD were 2.98 and 4.18 mg/g, and for SMT were 4.40 and 8.91 mg/g, respectively, which was 9.03–22.30 times that of pristine biochar. Fixed bed column results demonstrated that PMBC had good adsorption capacities for SD and SMT. When the solution flow rate was 2.0 mL/min and the dosage of PMBC was 5.0 g, the removal rates of SD and SMT by modified wood chips biochar were both higher than 50% in 4 h. The main mechanisms of SD and SMT removal by PMBC are hydrogen bonding, π-π donor-acceptor, electrostatic interaction, and hydrophobic interaction. This study provides an effective method for the removal of antibiotics in water and the resource utilization of phosphogypsum.