Adsorption of tetracycline on 2:1 layered non-swelling clay mineral illite

The removal of tetracycline (TC) from aqueous environment by illite (IMt-2) was studied in a batch system at different pH and ionic strength conditions. Adsorbent characterizations were determined by XRD and FTIR. The TC adsorption capacity on IMt-2 was 32 mg/g at pH 5–6 and the adsorption equilibrium data obeyed the Freundlich isotherm. The kinetics of TC adsorption was moderately fast and almost reached equilibrium in 8 h and the results followed pseudo-second-order kinetic model and Elovich model. The X-ray diffraction patterns before and after TC adsorption revealed no changes in basal spacing and intensity under two kinetic adsorption and a few initial TC concentration conditions, indicating that the adsorbed TC molecules were on the external surface of the mineral in contrast to intercalation of TC into swelling clay minerals, such as montmorillonite and rectorite. In spite of its low TC adsorption capacity, the results suggested that IMt-2 could be a good candidate to remove TC from wastewater containing higher amounts of TC and illite would be an important environmental sink for the fate and transport of TC in soils.

► Adsorption of tetracycline (TC) on illite reached to 32 mg/g.
► Adsorption of TC was mainly due to cation exchange.
► Adsorption sites were on the external surfaces of illite.
► Adsorbed TC may adopt flat-lying orientation on illite surfaces.