Response surface methodology for optimization of operational parameters to remove tetracycline from contaminated water by new magnetic Ho₂MoO₆/Fe₂O₃ nano adsorbent

World-wide, tetracycline is among the most commonly used and produced antibiotics. The entry of these chemicals into domestic sewage can result in water pollution. The purpose of this study is to evaluate a new nano-adsorbent for separating tetracycline from aquatic environments. Lab-scale and batch experiments were conducted. Tetracycline removal parameters, such as temperature, adsorbent amount, and initial concentration of antibiotic, as well as contact time, were investigated. Using Response Surface Methodology (Central Composite Design), effective parameters were optimized and the appropriate model was developed for predicting tetracycline removal. We determined the structure and morphological properties of nano absorbents by using Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), diffuse reflectance spectroscopy (DRS) and Brunauer-Emmett-Teller (BET) analysis. Data obtained from practical tests were compared with Langmuir and Freundlich isotherms. Furthermore, the adsorption kinetics of this new adsorbent were studied. Results showed that the best absorption, which was equal to 99.96 %, occurred at 30 °C, with 1000 mg of nano-adsorbent per liter, 20 mg of tetracycline per liter, and 90 min of incubation. According to RSM, the quadratic model is the most appropriate equation to calculate tetracycline separation by this new nano adsorbent with R² = 0.9931. Furthermore, the results of the studies related to adsorption kinetics and isotherms demonstrate that this process follows pseudo-second-order kinetics and Langmuir isotherms. The high ability of this nanocomposite to absorb tetracycline as well as its ease of separation due to its magnetic properties make this nano adsorbent an ideal choice for removing tetracycline from water.