Intercalation of ciprofloxacin accompanied by dehydration in rectorite

In this study, the interaction between ciprofloxacin (CIP), a fluoroquinolone antibiotic, and rectorite, a regular mixed-layer clay mineral, in aqueous solution was studied by X-ray diffraction, Fourier transform infrared, and thermal gravimetric analyses in conjunction with solution chemistry. The uptake of CIP by rectorite was mainly via a cation exchange mechanism as evidenced by quantitative desorption of exchangeable cations accompanying CIP adsorption. The dehydration of rectorite accompanying CIP adsorption as indicated by infrared and gravimetric analyses also pointed to the cation exchange mechanism between CIP and hydrated cations previously occupied in the interlayer. The intercalated CIP is thermally more stable in comparison to crystalline CIP, suggesting that the presence of swelling clay minerals in soil and wastewater treatment systems may provide a place for contaminant accumulation and shelter to protect CIP from thermal degradation.