Abstract
The present study aims to investigate adsorptive removal of molecular ciprofloxacin using protein-modified nanosilica (ProMNS). Protein was successfully extracted from Moringa seeds while nanosilica was synthesized from rice husk. Fourier-transform infrared (FTIR), ultraviolet visible (UV-Vis) and high-performance liquid chromatography (HPLC) were used to evaluate the characterization of protein. Adsorption of protein onto nanosilica at different pH and ionic strength was thoroughly studied to modify nanosilica surface. The removal efficiency of antibiotic ciprofloxacin (CFX) increased from 56.84% to 89.86% after surface modification with protein. Effective conditions for CFX removal using ProMNS were systematically optimized and found to be pH 7.0, adsorption time 90 min, adsorbent dosage 10 mg/mL, and ionic strength 1 mM KCl. A two-step model was successfully used to fit the adsorption isotherms of CFX onto ProMNS at different ionic strength while a pseudo-second-order model could fit adsorption kinetic of CFX onto ProMNS very well. Maximum adsorption capacity was very high that reached to 85 mg/g. Adsorption of CFX onto ProMNS decreased with increasing KCl concentration, suggesting that adsorption of CFX onto ProMNS is mainly controlled by electrostatic attraction between positively charged ProMNS surface and anionic species of CFX. Adsorption mechanisms of CFX onto ProMNS were discussed in detail based on adsorption isotherms, the change in surface charge by zeta potentail and the change in functional groups by FT-IR. The removal of CFX after three regenerations was greater than 73% while CFX removal from an actual hospital wastewater using ProMNS reached to 70%. Our results suggest that ProMNS is a new and eco-friendly adsorbent to remove antibiotics from aqueous solutions.
Highlights
Antibiotics, which are synthetic chemicals or natural products, are a powerful medicine to bacterial infections
For the first time, we report adsorptive removal of CFX using nanosilica fabricated from rice husk with surface modification by adsorption of MO seeds protein
It implies that high positive protein, which is good for surface modification of nanosilica
Summary
Antibiotics, which are synthetic chemicals or natural products, are a powerful medicine to bacterial infections. Application of adsorption of protein MO seeds for antibiotic removal has not been reported. Surface modification of nanosilica by protein adsorption may be useful to remove of antibiotic. Protein adsorption onto nanosilica to enhance removal of antibiotic CFX has not been studied. An understanding of adsorption mechanisms of antibiotic onto protein-modified nanosilica (ProMNS) is needed for further application to a real system in the presence of many interferences. For this purpose, adsorption isotherms by different modes is often evaluated. For the first time, we report adsorptive removal of CFX using nanosilica fabricated from rice husk with surface modification by adsorption of MO seeds protein. The application of the optimum condition for CFX removal for actual hospital wastewater is investigated in the present study
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