Adsorptive Effect of Corn Silk-Loaded Nickel Oxide and Copper Oxide Nanoparticles for Elimination of Ciprofloxacin from Wastewater

Ciprofloxacin (CIP) is one of the most reported antibiotic pollutants in hospital and industrial wastewater systems. The inclusion of nanosized transition metal oxides in adsorbent materials is able to improve the affinity and aqueous phase uptake of CIP from water. In this study, we report for the first time composites of corn silk with impregnated nanoparticles of NiO (NiONPs-CS) and CuO (CuONPs-CS) for the removal of CIP from water. The adsorbent was characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), energy-dispersive X-ray spectroscopy (EDX), an adsorption/desorption analyzer, and X-ray diffractometer (XRD) to study the morphology, surface functionality, elemental composition, textural properties, and crystal phases. The monolayer adsorption capacities of NiONPs-CS and CuONPs-CS were 108.3 and 120.2 mg/g, which were over 2 times higher than the capacity for unloaded corn silk. The kinetics of the adsorptive uptake followed the pseudo-second-order kinetics, revealing that both adsorption site density and CIP aqueous concentration control the removal rate. NiONPs-CS and CuONPs-CS were reusable for five cycles, with the uptake efficiency being 63.1 and 66.9%, respectively. This dropped to 47.8% for the unloaded corn silk. The mechanism of uptake was mainly by electrostatic attraction, pi-pi interaction, hydrogen bonding, and hydrophobic interaction. Based on our findings, the adsorbents have proven to be an efficient, cheap, and reusable material for CIP uptake.