Adsorption of bisphenol A and ciprofloxacin by palygorskite-montmorillonite: Effect of granule size, solution chemistry and temperature

Adsorption and desorption studies of the endocrine-disrupting compound, bisphenol A (BPA), and the antibiotic ciprofloxacin (CIP) with palygorskite-montmorillonite (Pal-Mt) granules (0.3–0.6mm, 1.7–2.0mm and ≈2.8mm), were done as a function of solution chemistry, temperature, and particle size. The data best fit the Langmuir adsorption model with the smallest and the largest granule sizes, respectively, exhibiting the highest (in mgkg−1, qm=77.3 for BPA; qm=107,000 for CIP) and the lowest (qm=41.0 for BPA; qm=81,000 for CIP) adsorption capacities. CIP adsorption was strongly pH dependent, while BPA adsorption was slightly pH and ionic strength dependent. Thermodynamic parameters indicated BPA and CIP adsorption were spontaneous. Net-adsorption-desorption hysteresis were indicative of irreversible adsorption. FTIR and thermogravimetric analysis (TGA) data corroborate the mechanisms and the level of adsorption for CIP but not for BPA. The smallest and the medium granule sizes, respectively, are appropriate for potential BPA and CIP removal.