Multi-application fennel-based composites for the adsorption of Cr(VI) ions from water and control of Escherichia coli and Staphylococcus aureus

Abstract

Ubiquitous toxic metal ions and pathogenic microbes in contaminated water affects the lives of millions of people globally. The synthesis of multifunction composites that can uptake metal ion from contaminated water and simultaneously inhibit the growth of microbes is a novel concept. This study developed composite substances from fennel seeds impregnated with binary nanoparticles of CuO-ZnO. These composites were used to remove Cr(VI) from water and inhibit the growth of Escherichia coli and Staphylococcus aureus. SEM analysis of the surface of the starting material showed various sizes and shapes of pores. In contrast, the composites showed unique surface morphology cavity features and a rough texture. FTIR spectra indicated that peaks for (–OH), (–C=O) and (–COOH) shifted in the composites. The Freundlich model and PSO described the uptake process. The highest adsorption capacity recorded at pH 2 and 308 K were 75.96 and 84.77 mg/g for FS/CuO-ZnO[1:2] and FS/CuO-ZnO[2:1], respectively. Cr(VI) uptake was due to different adsorption processes such as electrostatic attraction, weak hydrogen bond and Cr(VI)–π complexation. The values of ΔGo became more negative when the solution temperature was increased. Data for ΔHo revealed that adsorption was controlled by chemisorption. The antibacterial assays indicated that the materials are effective in preventing the growth of microbes. The incorporation of CuO-ZnO onto the fennel seeds improved their antimicrobial activity. PFS were ineffective against E. coli but effective (MIC- 50 μg/mL) against S. aureus. Furthermore, composites were more effective against S.aureus (MIC- 25 μg/mL) than E.coli (MIC- 50 μg/mL).

Keywords

• Fennel seeds
• Hexavalent chromium
• Adsorption
• Copper‑zinc nanoparticles
• E. coli
• S. aureus