Synthesis of magnetized ZIF-8 and Ag2O nanocomposites as colloids for a designed magnetic column reactor for water treatment and enhanced removal of Escherichia coli

Abstract

Magnetic nanocomposite (MNC) colloids can be employed in guided systems under a magnetic field, as demonstrated in this work for the removal of Escherichia coli (E. coli) from water. Herein, we employed a magnetic reactor system incorporating an Fe₃O₄@ZIF-8@Ag₂O nanocomposite colloid with destructive power against bacteria, focusing on elucidating the influence of key parameters, including the applied magnetic field and the presence of the MNCs, on the efficiency of bacterial removal. To assess bacterial viability, experiments were conducted in both phosphate-buffered saline (PBS) and a standard aqueous solution. The experimental design aimed to optimize bacterial removal by employing a 2 mT magnetic field, generated by a solenoid coil-assisted tubular reactor, which contributed to the stabilization of the magnetic nanoparticle (MNP) colloids. As the bacterial suspension traversed the reactor, interactions between E. coli and the nanoparticles resulted in collisions that induced cellular disruption and subsequent cell death. Under magnetic field conditions, the removal efficiency of E. coli increased by 29.6% after 60 minutes relative to control experiments without a magnetic field, culminating in an overall removal rate of 99.83% within the same period. Additionally, kinetic modeling using the Weibull function in the absence of a magnetic field yielded a minimal root mean square error (RMSE) of 7%, while the maximum standard deviation in the average E. coli concentration reached 75% at 40 minutes under magnetic conditions. These findings suggest that using stable MNC colloids under a controlled magnetic field markedly improves bacterial removal from water.