Synthesis of magnetic activated carbon from industrial waste: characterization, tetracycline removal and interpretation of its mechanism

Tetracycline is the second most widely used antibiotic, and its presence in wastewater is increasing with the increasing use of TC, which is of global concern. For the removal of TC from wastewater, magnetic activated carbon (MAC) was produced from activated carbon obtained using potassium-rich wine stones in previous studies. In this study, MAC synthesis was carried out in order to obtain a cost-effective, environmentally friendly, and high-quality adsorbent for TC adsorption using the activated carbon (AC) obtained in the previous study. In the production process of MAC, chemical precipitation and hydrothermal methods were used together. To produce MAC, FeCl2.4H2O and FeCl3.6H2O solutions were mixed with AC in a 1/2 w/w ratio. Tetracycline (TC) adsorption of both MAC and AC investigated the physicochemical properties with the help of analyses such as BET, SEM, EDX, FTIR, VSM, and pH at point eo charge (pHZPC). Pseudo-first-order model and pseudo-second-order model kinetic models and Langmui, Freundlich, Temkin, and Dubinin-Radushkevich kinetic isotherms were investigated for TC adsorption of MAC and AC. With an R2 value of 0.9895, it was concluded that the Langmuir isotherm is the most suitable adsorption, which indicates that the adsorption is monolayer; 3 desorption studies were performed for both TC and MAC. It was observed that MAC had better desorption capacity in the results obtained. According to the results obtained, MAC was tested to show higher TC adsorption, although it has a lower surface area than AC, which is 1086.45 m2/g and 1814.16 m2/g, respectively. However, the average pore diameter of MAC was 4.009 nm, while that of AC was 2.2483 nm. The reason for this is thought to be that magnetite clogs the pores on the surface of the AC, reducing the surface area but increasing the active sites, resulting in better adsorption. These results indicate that the obtained MAC is an environmentally friendly and cost-effective magnetic adsorbent for TC removal.