a b s t r a c t
Extensive usage of tetracycline has resulted in its contamination in surface water and groundwater. The
adsorption of tetracycline on zeolite beta was systematically investigated for the decontamination of the
antibiotic polluted water in this study. Ninety percent of uptake by the zeolite beta occured in 0.25 h, and
the adsorption equilibrium was obtained within 3 h, which was well described by an intraparticle diffusion
model. The adsorption generally increased when pH was increased from 4.0 to 5.0, and then
decreased significantly as the pH was further increased, which was caused by the pH-dependent speciation
of tetracycline and surface charge of zeolite beta. Both Freundlich and Langmuir equations well
described the adsorption isotherm. A thermodynamic analysis showed that the sorption process was
spontaneous and endothermic. Aluminum atoms in the zeolite played a crucial role in the uptake; the
adsorption increased with the increasing aluminum content in zeolite. The UV–Visible spectroscopy
study showed that the spectra of tetracycline changed upon the interaction with zeolite beta, which could
be ascribed to the formation of complexes of tetracycline and aluminum atoms in the zeolite surface.
Nuclear magnetic resonance spectroscopy study further confirmed the participation of Al in the tetracycline
adsorption. Fourier transform infrared spectroscopy studies showed that the amino functional
groups in tetracycline were involved in the complexation with the zeolite surface.