Magnetic silica nanoparticles adorned with a metal-organic framework; a novel nanosorbent for elimination of aqueous Pb ions contaminant.

The annual growth of water pollution resulting from the uncontrolled entry of heavy metals, like Pb ions, is one of the most critical global concerns due to its direct and indirect effects on human life. The absorption of this component by the body could affect the nervous system via oxidative stress production or disturbing cellular biological mechanism. So, it is important to find an effective method for purifying the existing waters. This study aims to fabricate and compare the effect of two new nano-adsorbents (FeO@ZIF-8 and FeO@SiO@ZIF-8) on removing Pb ions from the aqueous solution. Accordingly, iron oxide nanoparticles were synthesized via co-precipitation method at first and then coated with a silica shell through the sol-gel method. Both nanoparticles were coated with a layer of metal-organic framework (MOF), ZIF-8, and analyzed with different physicochemical tests. In the following parts, the Pb ion removal capability of the nano-adsorbents was evaluated in the presence of different parameters, including nanosorbent concentrations, contact time, pH, and pollutant concentrations. Results confirmed preparation of nanoparticles with a mean size of about 110 ± 10 nm and 80 ± 10 nm for FeO@ZIF-8 and FeO@SiO@ZIF-8, respectively. Both nanoparticles showed the highest amount of pollutants removal (near 90% for both nanoparticles) at pH = 6 within 15 min of contact in the presence of 100 ppm Pb ions. Besides, in the case of real samples, with a concentration of about 150 ppm of Pb ions, they showed maximum adsorption of about 93.61% and 99.2% for FeO@ZIF-8 and FeO@SiO@ZIF-8, respectively. The presence of iron oxide nanoparticles in the structure of this adsorbent makes it easy to separate them in a user-friendly method. A brief comparison between these nanosorbents indicates that FeO@SiO@ZIF-8 nanoparticles have better performance due to their higher porosity and surface area ratio and so it could be used as a cost-effective ideal nanosorbent candidate for easy removal of heavy metals from water.