Synthesis and characterizations of a novel FeNi3/SiO2/CuS magnetic nanocomposite for photocatalytic degradation of tetracycline in simulated wastewater

In recent decades, application of magnetic nanocomposites as a catalyst to remove organic contaminants and antibiotics has attracted a great deal of attention on account of having production simplicity, stability and recyclability, operating under environmental conditions, high chemical stability and easier separation, as well as full degradability of organic materials. This experimental research was conducted at laboratory scale with the aim of investigating the efficiency of a new magnetic nanocatalyst (FeNi3/SiO2/CuS) for degradation of tetracycline-the second common group of antibiotics in terms of production and consumption in the world-in the presence of ultraviolet light in aqueous solutions. To this end, first, FeNi3/SiO2/CuS was synthesized. The morphology and other characteristics of the produced nanocatalyst were specified by X-ray diffraction, energy dispersive spectroscopy, field emission scanning electron microscopy, vibration sampling magnetometer, and transmission electron microscopy. The factors influencing tetracycline removal by the mentioned nanophotocatalyst, including pH (3, 5, 7, 9), contact time (5-200 min), contaminant concentration (10-30 mg L-1), and nanocomposite dose (0.005-0.1 g L-1), were studied. The results indicated that FeNi3/SiO2/CuS possess accumulation and agglomeration structure, good monodispersity, superior magnetic properties (Ms = 19.42 emu g(-1)). In addition, the findings showed that with elevation of pH, the percentage of degradation increased from 75.6 to 99.5%, and when the nanocatalyst dose and the initial concentration of the contaminant reduced, the removal percentage increased (95.54-57.7%) and (96.71-78.21%), respectively, so that under optimal conditions (tetracycline concentration: 10 mg L-1, time: 200 min, pH = 9, nanocatalyst dose: 0.005 g L-1), the efficiency of the photocatalytic process using FeNi3/SiO2/CuS in tetracycline degradation reached almost 100% and the mineralization rate was 64.96%. Furthermore, the kinetics of the rate of this pollutant degradation followed pseudo-first-order kinetics (R-2> 0.98) and the constant rate of degradation was obtained as 0.0257 min(-1). The findings suggested that after five cycles, the nanocatalyst efficiency did not decrease significantly, such that the removal efficiency showed a reduction of only 15% from the first to the last cycle. Eventually, based on the results obtained in the present study, it can be concluded that the FeNi3/SiO2/CuS photocatalytic process enjoys a suitable efficiency for the removal of tetracycline from aqueous solutions. (C) 2018 Elsevier Ltd. All rights reserved.