Adsorption And Kinetic Studies Of The Removal Of Ciprofloxacin From Aqueous Solutions By Diatomaceous Earth

Pharmaceutical derivatives have been reported to affect several water bodies around the world. Therefore, developing treatments that remove them from the environment is a significant need. The main goal of this work was to use powdered diatomaceous earth (DE) as a low-cost natural adsorbent for ciprofloxacin (CIP) in aqueous solutions, employing synthetic CIP solutions of pure water and treated domestic wastewater. The influences of adsorption time, initial pH, CIP concentration, and DE dosage were evaluated after DE structure characterization using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Diatomaceous earth was shown to have significant capabilities to remove CIP in aqueous phase, achieving pollutant equilibrium adsorption in 24 h. The best CIP removal efficiency was 97% (19.4 mg L-1) using 2 g of DE, 20 mg L-1 of CIP, and pH = 2.0. The experimental results were fitted using second-order rate kinetics, with rate constant values in the 0.0077 <= k(2) (g mg(-1) h(-1)) <= 0.1984 range and correlation coefficients above 0.95. The adsorption results were fitted to the Freundlich and Langmuir isotherm equations and isotherm constants were estimated. The maximum adsorption capacity was assessed to be 105.1 mg CIP g(-1) DE, suggesting good affinity between the pharmaceutical drug and the adsorbent.