Application of molybdenum disulfide nanosheets for adsorption of tetracycline in water samples

Molybdenum disulfide (MoS2) is a layered material with unique two-dimensional structure which has abundant electron density on edges and surfaces. These adsorption sites could interact with polycyclic aromatic compounds by pi-pi stacking. Therefore, MoS2 nanosheets will no longer be modified or functionalized. In this study, MoS2 nanosheets were prepared by a simple and low cost hydrothermal method, and characterized by using different techniques, such as field emission scanning electron microscopy, transmission electron microscopy, X-ray power diffraction, and energy dispersive X-ray. The resultant MoS2 nanosheets were applied for preconcentration of tetracycline (TC) as a model analyte in solid-phase extraction. Various experimental parameters (pH, adsorbent amount, contact time, type and volume of eluent and desorption time, sample volume, salt addition, interferences, and reusability) affecting the extraction process were studied. Under optimum conditions, the calibration graph was linear in the concentration range of 0.025-5 mg L-1 with a detection limit of 7.91 mu g L-1. The relative standard deviation values of the method were 3.3%. The reusability (five consecutive cycles) and adsorption capacity (57.47 mg g(-1)) of MoS2 nanostructures were favorable. The proposed method was successfully applied to the TC analysis in real samples, such as fish pond water, agriculture-influenced water, and river water. Good spiked recoveries over the range of 92.0%-103.0% were obtained.