A novel self-floating silica adsorbent for antibiotic ciprofloxacin and nickel (II) ion

Abstract A novel self-floating silica adsorbent was synthesized by introducing sulfonic acid groups onto the surface of hollow glass microsphere (HGM) through post-grafting technique. The obtained sulfonated HGM (SO3H-HGM) not only had satisfactory adsorption performance for ciprofloxacin (CIP) and heavy metal nickel (Ni2+), but also had stable self-floating capability. SO3H-HGM exhibited wide pH adaptability. Langmuir and Elovich models well fitted the adsorption isotherm and kinetic data, respectively. Under the optimal experimental conditions, the theoretical saturated adsorption capacities of SO3H-HGM for CIP and Ni2+ calculated by the Langmuir model reached 464.78 mg·g−1 and 19.65 mg·g−1, respectively. Thermodynamic calculation verified the spontaneous nature and feasibility of the adsorption processes. The saturated adsorbent could be easily desorbed and regenerated by the eluent, and after five adsorption cycles, there was no serious reduction in adsorption capacity, which proved the good reusability and stability of SO3H-HGM. The adsorption mechanism of CIP and Ni2+ by SO3H-HGM is mainly electrostatic interaction, followed by hydrogen bond, hydrophobic interaction and coordination. This research demonstrates that HGM is a potential and promising material for the adsorptive purification of water contaminated with CIP and Ni2+, and to realize self-floating solid–liquid separation.