Preparation of Granular Activated Carbon and Its Mechanism in the Removal of Isoniazid, Sulfamethoxazole, Thiamphenicol, and Doxycycline from Aqueous Solution

Agricultural waste-based activated carbon has been applied to the treatment of antibiotics-loaded wastewater recently. In this article, cornstalk was employed as a raw material to manufacture a kind of granular activated carbon (GAC), which was then used to remove four antibiotics, including isoniazid (IN), sulfamethoxazole (SMZ), thiamphenicol (THI), and doxycycline (DOX), from water. The as-prepared GAC had a rough and porous structure; the surface area and total pore volume were 944.71 m²/g and 0.56 cm³/g, respectively. Kinetic and isothermal models were established to analyze the sorption mechanism and evaluate the sorption performance. Pseudo-second-order kinetic model fitted the sorption of IN, SMZ, THI, and DOX on the GAC better than pseudo-first-order model. Based on the Langmuir isothermal model, the maximum sorption capacities (q_m) of the GAC toward IN, SMZ, THI, and DOX were 27.0172, 36.9301, 28.0637, and 32.3902 mg/g, respectively. According to the Weber-Morris intraparticle diffusion model and the Boyd kinetics model, film diffusion was preponderant in the sorption process. Moreover, two-dimensional correlation spectroscopy integrated with Fourier-transform infrared spectroscopy was used to give the sequence of the different functional groups binding to the four antibiotics. To our knowledge, this is the first report on the sorption of IN, SMZ, THI, and DOX by cornstalk-based GAC. This work not only evaluated the application potential of cornstalk in the field of water purification but also provided a technical way for removing IN, SMZ, THI, and DOX from aqueous solution.