Synthesis of Fe3O4@SiO2–branched polyethylenimine nanospheres for removal of Cr(VI) and anionic dyes

Abstract

There is a need to design and prepare new sorbents for the effective elimination of toxic metal ions and textile dyes from the environment. In the presented study, the preparation of magnetic functionalized silica composite nanospheres for the removal of inorganic and organic pollutants from aqueous solutions is reported. Firstly, the surface of silica coated magnetic nanospheres was functionalized with epoxy groups via a reaction of 3-glycidoxypropyltriethoxysilane. Then, the branched polyethylenimine (BPEI) was attached to generate positive functional charged groups on the on the Fe3O4@SiO2. The performance of the Fe3O4@SiO2-BPEI nanospheres for the removal of Cr(VI) and Congo Red (CR) and Trypan Blue (TB) dyes was studied under various experimental conditions. The optimum pHs values for adsorption of Cr(VI) ions, CR and TB dyes on the Fe3O4@SiO2-BPEI nanospheres were found to be at pH 2.0, and at pH 4.0, respectively. The maximum adsorption capacities of the Fe3O4-@SiO2-BPEI nanospheres for Cr(VI), CR, and TB were obtained as 356.7, 395.3, and 561.8 mg/g within 90 min equilibrium time, an initial concentration of 500 mg/L, and at 25 ºC, respectively. The adsorption of the tested pollutants were well described by the Langmuir isotherm model and second-order kinetic model. After ten reuse cycles, the adsorption capacity of Fe3O4-@SiO2-BPEI nanospheres was not significantly changed for the tested pollutants. The adsorption mechanism of Cr(VI), CR, and TB by the Fe3O4-@SiO2-BPEI nanospheres was evaluated to be related to ion exchange and ion exchange and/or hydrogen bonding interactions, respectively. The results also suggested that the presented adsorbent may serve as a multi-functional adsorbent for the remediation of industrial effluents. In addition, compared to the unmodified Fe3O4@SiO2, the Fe3O4@SiO2-BPEI nanospheres have antibacterial activities against Escherichia coli (American Type Culture Collection (ATCC) 12435), Pseudomonas aeruginosa (ATCC 10145), Listeria monocytogenes (ATCC 7644), and Staphylococcus aureus (ATCC 43300). Based on the obtained results from this work, the branched polyethylene functionalized magnetic silica nanospheres with antibacterial properties can be used as a potential adsorbent for the removal of metal ions and anionic dyes from wastewater. © 2024 Elsevier B.V.