Box–Behnken design, kinetic, and isotherm models for oxytetracycline adsorption onto Co-based ZIF-67

Nowadays, some antibiotics including oxytetracycline have been widely consumed over the world due to the increasing demands for essential activities such as human therapies, and agricultural farming. However, a residual amount of antibiotics could accumulate, and cause many negative impacts on aquatic environments. Therefore, the removal of antibiotics from wastewater has paid greatly attention. Herein, we reported the use of cobalt-based zeolite imidazolate framework (Co-ZIF-67) crystals by the microwave-assisted method, and their application for oxytetracycline mitigation. Co-ZIF-67 was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy analysis. For adsorption experiments, the effect of oxytetracycline concentration (10–50 mg/L), Co-ZIF-67 dose (10–30 mg/L), and pH (3–9) was studied using Box-behnken design, combined with response surface methodology. An optimum finding was proposed with concentration of 10 mg/L, dose of 24.9 mg, and pH of 6.4, which tested for 88.26% removal efficiency. Nonlinear kinetics and isotherms were applied to more insight into the essence of oxytetracycline adsorption. Monolayer maximum adsorption capacity was measured, at 122.9 mg/g. Intraparticle diffusion model suggest a two-stage adsorption process, which first 30-min stage was very fast. The outcomes indicated the uptake of oxytetracycline controlled by chemisorption, in which proposed the role of hydrogen bonding. Through a comparative study, Co-ZIF-67 is recommended as a competitive adsorbent for the treatment of oxytetracycline adsorption.