A simple chemical precipitation route was utilized for the synthesis of ZnO nanoparticles (NPs), CdS NPs and ZnO–CdS nanocomposites (NCs). The synthesized nanostructures were examined for the crystal structure, morphology, optical properties and photodegradation activity of rhodamine B (RhB) dye. The ZnO–CdS NCs showed a mixed phase of hexagonal wurtzite structure for both ZnO NPs and CdS NPs. Pure ZnO NPs and CdS NPs possessed bandgaps of 3.2617 and 2.5261 eV, respectively. On the other hand, the composite nanostructures displayed a more narrow bandgap of 2.9796 eV than pure ZnO NPs. When compared to bare ZnO NPs, the PL intensity of near-band-edge emission at 381 nm was practically suppressed, suggesting a lower rate of photogenerated electron–hole (e−/h+) pairs recombination, resulting in enhanced photocatalytic activity. Under solar light, the composite nanostructures displayed a photodegradation efficiency of 98.16% towards of RhB dye. After four trials, the structural stability of ZnO–CdS NCs was verified.
In this study, a low-cost bioadsorbent aluminum metal blended with groundnut shell activated carbon material (Al-GNSC) was used for Cr(VI) adsorption from aqueous solutions. Al-GNSC was prepared and characterized using Fourier transform infrared spectrometer (FT-IR), scanning electron microscopic (SEM) and X-ray diffraction (XRD) to determine its surface morphology. Batch studies were performed and the optimum conditions for maximum Cr(VI) removal (of 94.2%) were found at pH 4.0, initial concentration 100 mg/L, adsorbent dosage 8 g/L of Cr(VI) solution, and time of contact 50 min. Moreover, the Langmuir isotherm model (maximum adsorption capacity of 13.458 mg/g) was the best fit and favored the mono-layered Cr(VI) adsorption. The kinetic studies reveal that the pseudo-second-order model was the best fit and favored chemisorption as the rate-limiting step. The desorption study revealed that Cr(VI) leached with sodium hydroxide solution acted as a regenerating agent. It is proved that Al-GNSC removes the Cr(VI) content in groundwater samples. The methodology developed using the Al-GNSC adsorbent as an alternative for the adsorption of Cr(VI) ions is remarkably successful in this study.
Nanomaterials with collective optical and magnetic properties are called smart or functional materials and have promising applications in many fields of science and technology. Undoped and Co-doped ZnAl2O4 were prepared using a co-precipitation-assisted hydrothermal method. A systematic investigation was carried out to understand the effects of the Co concentration on the crystalline phase, morphology, and optical and magnetic properties of Co-doped ZnAl2O4. X-ray diffraction confirmed the cubic spinel structure with the Fd3m space group, and there was no impurity phase. X-ray photoelectron spectroscopy of Co-doped ZnAl2O4 confirmed the existence of Zn, Al and O, and the Co in the optimized sample of ZAO-Co-3 confirmed the oxidation state of cobalt as Co2+. Transmission electron microscopy of pure and Co-doped ZnAl2O4 revealed micro-hexagons and nanosheets, respectively. The optical absorption results showed that the bandgap of ZnAl2O4 decreased with increasing Co concentration. The hysteresis loop of Co-doped ZnAl2O4 revealed clear ferromagnetic behavior at room temperature. The as-prepared materials are suitable for energy storage applications, such as in supercapacitors and fuel cells. This work aims to focus on the effect of cobalt ions in different concentrations on structural, optical and magnetic properties.
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