Preparation, characterization, adsorptive and antimicrobial properties of Fe3O4@SiO2@ZnO nanocomposite

Abstract

A wide range of toxic contaminants, including hydrocarbons, mercaptans, phenol, ammonia and sulfide found in the wastewater from petroleum refineries have diverse health effects on human and aquatic species. In this work, the sequestration of COD and BOD from petroleum refinery wastewater by Fe3O4@SiO2@ZnO nanoabsorbent prepared at different mole ratios (1:1:1, 1:1:2, 1:2:1 and 2:1:1) was carried out via the batch adsorption method. The nanomaterials synthesized by a combination of sol-gel and wet impregnation techniques were characterized using FTIR, HRSEM, EDS, XPS, XRD, DLS and BET. The HRSEM result revealed a rod-like formation with little spherical shapes on the surfaces regardless of the mixing ratios. Based on the XRD analysis SiO2 and ZnO maintained their phases while that of Fe3O4 nanoparticles changed with respect to the mixing ratios. BET analysis confirmed higher surface area for Fe3O4@SiO2@ZnO prepared with a mixing ratio of 1:2:1 (35.469 m2 /

g) as compared to 24.918, 30.685, 15.751 m2

/g obtained for other mixing ratios (1:1:1, 1:1:2 and 2:1:1). The maximum removal efficiencies of COD and BOD at a contact time of 15 min, a dosage of 0.08 g, at 30 ◦C and a stirring speed of 250 rpm were 98.19% and 92.19%. The adsorption of COD and BOD at different temperatures using all the nanoadsorbent irrespective of the mixing ratios were endothermic in nature and Langmuir isothermand pseudo-second-order kinetic model provided the best description of the experimental data, indicating the chemical adsorption process. The regeneration studies after ten adsorption-desorption cycles indicated that the adsorbent could successfully remove COD (51.06%) and BOD (45.56%). The Fe3O4/SiO2/ZnO nanocomposites (1:2:1) nanoparticles was found to exhibit the greatest antimicrobial activity with 29.50 mm zone of inhibition against Salmonella typhi, 25.00 mm, 26.00 mm zone of inhibition obtained for Escherichia coli and Klebsiella

pneumoniae compared to others prepared with different mixing ratios. This study demonstrated that Fe3O4@- SiO2@ZnO nanocomposites with a mixing ratio (1:2:1) possesses excellent adsorptive, antimicrobial and recy- clability properties