Highly efficient adsorption of antibiotic ciprofloxacin hydrochloride from aqueous solution by diatomite-basic zinc chloride composites.

The antibiotic ciprofloxacin (CIP) is used to treat a variety of bacterial infections, yet it poses significant health risks to aquatic environments. While adsorption is a promising technique for CIP removal, current adsorption capacities remain limited. In this study, we introduce a diatomite and basic zinc chloride composite (ZnHC-Dt) prepared using a straightforward deposition method, with the ability to achieve highly efficient ciprofloxacin removal. ZnHC-Dt is characterized using field emission scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and the Brunauer-Emmett-Teller method (BET). We also assess the zeta potential. The optimized ZnHC-Dt adsorbent, achieved at a mass ratio of 0.45 with ZnHC/(ZnHC+Dt), is adopted with a CIP adsorption capacity of 831.96 mg/g at 25 °C, broad pH adaptability (within 3.0-10.0), rapid adsorption rate (reaching equilibrium in 4 h), and stable performance under Na ionic strength. The CIP adsorption process follows pseudo-second-order kinetics and aligns well with the Langmuir adsorption model. The high adsorption capacity of ZnHC-Dt can be attributed to electrostatic attraction, hydrogen bonding, surface complexation, and available adsorption sites. During the desorption process, the CIP removal rate retains 65.33% effectiveness after five cycles. The results suggest that ZnHC-Dt holds significant potential for CIP removal in aqueous solutions.