Potential removals of tetracycline and sulfamethoxazole by iron-loaded sludge biochar

In this study, the potential of iron-loaded sludge biochar (ISBC) to remove tetracycline (TC) and sulfamethoxazole (SMX) was investigated. Under the optimized conditions (initial pH of 4 and 5, ISBC dose of 1.0 g/L, contact time of 720 min, and temperature of 298 K), the maximum removal capacity of ISBC for TC and SMX was 81.04 mg/g and 80.19 mg/g, respectively. The better simulations of TC and SMX removal by Langmuir model and pseudo-second-order kinetic model indicated that monolayer chemisorption dominated their removal. Their removal rates depended on liquid film diffusion, intraparticle diffusion and chemical reactions. Moreover, their removal was a spontaneous and endothermic process with increasing randomness between the solid-liquid interfaces. Besides, their removal likely included two simultaneous pathways: adsorption/surface degradation and degradation/adsorption/surface degradation. Furthermore, ISBCs could be effectively desorbed and regenerated by ultrapure water and NaOH. In summary, ISBCs had the potential to be practically applicable for TC and SMX removal.