Improved Ciprofloxacin Removal by a Novel Organohalloysite Obtained by Phenylphosphonic Acid Intercalation

Ciprofloxacin (CIP) is extensively used to treat bacterial infections, however, its presence in water can lead to bacterial resistance in pathogens and affect human and animal health through the food chain. We addressed this issue by synthesizing innovative organoclays using Algerian halloysite (H) and phenylphosphonic acid (PA) solutions of varying concentrations, which were used in the adsorption of this ubiquitous emerging contaminant. A bibliographic search did not retrieve any articles on the intercalation of phenylphosphonic acid in clays and its use in the removal of emerging contaminants. The insertion of PA in the interlayer space led to an increase in basal distance from 7.6 to 15.2 angstrom with an intercalation degree of 60%. The uptakes of CIP at 55 degrees C were 75.0 and 37.2 mg g-1 for the best organohalloysite (HPA6) and H, respectively. The Redlich-Peterson isotherm showed close agreement with our experimental isotherms. The NaOH eluent was highly effective, desorbing 90.7% of CIP from HPA6 which maintained its adsorption performance for four cycles. Through cross-checking the results of intercalation characterization, CIP adsorption and Fourier transform infrared spectroscopy (FTIR) and Raman investigations, we elucidated the mechanism of the CIP-HPA6 interaction, which includes a hydrogen bond between the CIP carbonyl and the hydrogen of intercalated phenylphosphonic acid, along with a hydrophobic interaction between the CIP aromatic ring and the -Si-O-Si- species. The promising potential of this novel nanohybrid is evident, and we believe it could be a highly efficient solution for eliminating pharmaceuticals from wastewater.