The evolution of removal mechanism of tetracyclines by nano scale iron particles from aques solution

In this study the removal mechanism of TCs by nanoscale zero valent iron (nZVI) was evaluated. Therefore, nZVI was prepared by using chemical reduction method in the laboratory. Experimental variables such as solution pH, nZVI dosage, contact time and reaction temprature were systematically studied. Moreover, the degradation products of TCs were determined at optimum operating conditions which were provided to maximum TCs removal percentages. The adsorption behavior was pH-dependent and favored at pH: 6 regardless of tetracycline considered which was probably due to electrostatic attraction between nZVI and TCs. In addition to the influence of reaction temperature on TCs removal was insignificant. nZVI dosages between 0.4 and 0.6 were enough to efficient TCs adsorption. TCs adsorption kinetics were found that equilibrium was reached within 2 h following the pseudo-second order model. The results from LC-MS-MS analysis showed that main degradation product was 4-epi-tetracycline for TC while by-products of OTC were insignificant. On the other hand, nZVI could adsorb not only parent compounds but also degradation products of these compounds which was obtained from the desorption process with hydrochloric acid. The removal mechanism was mainly due to the adsorption of TC and OTC on nZVI surface. Key Words: Tetracycline, Adsorption, Nanoscale zero valent iron.