PVA-assisted CNCs/SiO₂ composite aerogel for efficient sorption of ciprofloxacin

Efforts to develop a green, inexpensive and effective adsorbent are crucial for eliminating antibiotics in polluted water. The sorption capacity of the as-prepared polyvinyl alcohol (PVA)-assisted cellulose nanocrystals/SiO₂ (CNCs/SiO₂) composite aerogel to ciprofloxacin (CIP) rises with the increase of temperature and initial concentration. Reverse trend of sorption capacity can be found when increasing the adsorbent dosage of adsorbent. The optimal pH value for the sorption is proved to be 4. It's found in the uniaxial compression test that the maximum load that PVA-assisted aerogels can withstand is nearly 100 times than that of non-PVA aerogels. Sorption results confirm that the Pseudo-second order (R² = 0.9885) and Langmuir models (R² = 0.9959) fit well to sorption kinetics and equilibrium data, respectively. The rate constant differs from the initial concentration of CIP according to the Pseudo-second order model. The composite aerogel sorption capacity of Langmuir (q_max) for CIP was 163.34 mg·g^-1. The thermodynamic studies showed that the sorption process is endothermic with the value of enthalpy change of 41.032 kJ/mol. Hydrogen bonding, π-π interaction, hydrophobic and electrostatic interactions are the dominant mechanisms of CIP sorption by the PVA-assisted CNCs/SiO₂ composite aerogel.