Evaluation of performance of magnetized activated carbon in removal of antibiotics from contaminated waters

Abstract

The widespread use of antibiotics contributes to the discharge of a large amount of these pharmaceuticals into the environment worldwide. To address ever-increasing concerns about negative impacts of antibiotics in the environment, especially antimicrobial resistance, various treatments have been used to control the release of antibiotics. Among the applied treatments, adsorption with powder activated carbon has attracted great attention due to several advantages. Although activated carbon is a promising adsorbent, it suffers from difficulties in subsequent separation from the treated water, which can be considered the inherent disadvantage of the adsorption process. It can also cause turbidity in the treated effluent. To overcome these disadvantages, one possibility is the development of magnetized activated carbon. In contrast to traditional adsorbents, which are mostly removed by screening, magnetized activated can be effectively separated from waste streams by applying an external magnetic field. In this research, a commercial activated carbon was magnetized using a co-precipitation method. The physicochemical properties of the developed adsorbent were investigated using different characterization techniques. The performance of the prepared adsorbent in removing tetracycline and lincomycin as two different model antibiotics from water was studied. The obtained adsorption data were modelled by Langmuir and Freundlich isotherms. Additionally, some preliminary adsorption experiments were performed for direct removal of tetracycline from liquid manure supernatant. It is expected that the outcomes of this research will contribute to addressing the existing problems of adsorption process and make it a step closer to sustainable treatment of wastewater. The results of characterization techniques show that iron oxide nanoparticles (γ-Fe2O3) with an average particle size of 10.2 nm were deposited into commercial activated carbon. It was also found that the developed adsorbent was sufficiently magnetized to be separated from water using a simple magnet. Notably the prepared adsorbent possesses superparamagnetic properties. This confirms that the developed magnetic adsorbent can be easily re-dispersed in water after removing the magnetic field. The results of adsorption studies indicate that the initial concentration of the antibiotics in the single- or binary-solute adsorption process affected the adsorption uptake. Also, the adsorption capacity of activated carbon decreased after magnetization process, but it still has a relatively high adsorption capacity. Interestingly, the obtained results indicated that the adsorption capacity of magnetic activated carbon toward tetracycline (mg g-1) was up to 4 times higher than that of lincomycin at room temperature depending on the equilibrium concentration of antibiotic in the liquid phase. Moreover, the results indicated that tetracycline was preferably adsorbed when both antibiotics were present in water. In addition, the overall adsorption capacity in binary-solution adsorption was higher than that of the individual antibiotics. On the other hand, the presence of each of these two antibiotics in mixture decreased the adsorption capacity of the adsorbents toward the other one. The adsorption of tetracycline from liquid manure supernatant was studied at 60 mg L-1 manure solution using three dosages of adsorbents (1500, 2500 and 4000 mg L-1). The obtained adsorption data indicated that the effective removal of tetracycline from liquid manure supernatant requires around 15 times more adsorbent compared to adsorption in water.