Abstract
In this work we propose a facile method of preparing cost-effective clay-metaloxide/metal (CuO/Ag and ZnO/Ag) composite pellets for an efficient water purification technique. Clay, with intrinsic antibacterial activity, served as a membrane support for different metaloxide/Ag nanoparticles (NPs) concentrations (2.5, 5 and 10 wt.%), as the active fillers. The effect of time (24 and 48 h) on the bactericidal activity of these pellets was also monitored. The clay–nanocomposite pellets were characterized using: X-ray diffraction, X-ray fluorescence, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible (UV–Vis) spectrophotometry and nitrogen desorption analysis. The antibacterial activity performance was tested using E. coli and S. aureus strains of ATCC25922 and ATCC25923, respectively, in two aqueous media (nutrient broth and nutrient-free) by the colony-forming unit method. The results showed that the clay-CuO/Ag composite with a bandgap (1.24 eV) exhibited overall best performance under all conditions and time factors of ~100% efficiency in nutrient-free medium for all concentrations and times and 20–40% efficiency in nutrient broth for 24 h. The clay-ZnO/Ag with a bandgap of 2.88 eV showed no bactericidal activity in both media, except for that with 10 wt.% ZnO/Ag which showed 100% efficiency in nutrient-free medium after 24 h. All the synthesized composites showed 100% bactericidal efficiency in nutrient free medium after 48 h. These results indicate that, the clay/metaloxide/Ag could serve as efficient water purification technique, with a potential for large-scale commercialization.
Highlights
Pathogen-contaminated water source is a predominant problem in remote and rural communities, especially in poorer countries [1]
These results indicate that, the clay/metaloxide/Ag could serve as efficient water purification technique, with a potential for large-scale commercialization
The X-ray Diffraction (XRD) analysis was to of study dry nanocomposite powders were studied with nanocomposite an X-ray diffractometer prioranalysis to the formation the crystalline microstructure of the respective samples.(XRD)
Summary
Pathogen-contaminated water source is a predominant problem in remote and rural communities, especially in poorer countries [1]. The introduction of nanoparticle powder into water sample causes a quick release of its ions in solution which becomes difficult to control. The ionic release is highly unrestrained and it is difficult to predict the ionic time kinetic release [6] Nanoparticle dissolution and their fast uncontrolled ionic release cause them to be used-up shortly. This phenomenon is responsible for the lack of the reuse of powdered nanoparticles for water purification [7]. Powdered nanoparticles in solution are Materials 2020, 13, 3793; doi:10.3390/ma13173793 www.mdpi.com/journal/materials
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