Removal of metronidazole from aqueous solutions by different natural surfactant-modified zeolitic tuffs

Metronidazole (MNZ) is an antiparasitic that has been found in wastewater. In this paper, the removal of MNZ by using modified zeolitic tuffs with two different surfactants (hexadecyltrimethylammonium bromide and benzyl hexadecyl dimethyl ammonium chloride) was studied. These modified materials were characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy and Brunauer-Emmett-Teller analysis. The cation exchange capacities and the points of zero charge were determined. The sorption kinetics show that the equilibrium times for all systems were similar about 15 h, the experimental data were best adjusted to the Ho-McKay model. The isotherms were linear indicating partition mechanism and the maximum adsorption capacity was in the order of 0.5 mg/g with an initial concentration of 20 mg/L of MNZ; the adsorption behavior of MNZ data at different temperatures was exothermic and the maximum adsorption capacity was observed between pH 5 and 6. The results show that the sorption efficiency depends on the origin of the zeolitic tuff and the surfactant used for the modification. These modified materials are effective to remove MNZ from aqueous solutions.