The high efficiency of Al2O3–SiO2–CuO nanocomposites as an adsorbent: synthesis and dye removal efficiency

Ag2O-adorned ZnO nanostructures: cooperative and sustainable nanomaterial system for effective reduction and mineralization of hazardous water pollutants

Organic water pollutants like nitroaromatics and synthetic dyes are causing serious threats to water. Ever-growing urban and industrial activities along with population explosion are rapidly contributing severe level of water contamination. Semiconducting nanomaterial-based photocatalysis has been proven to be an effective process for degradation of organic water pollutants. In the current study, visible light active Ag₂O-adorned ZnO nanostructures were fabricated by a simple two-step hydrothermal method and the prepared nanostructures were utilized for the photocatalytic mineralization of rhodamine B (RhB) dye with visible light radiation. The catalytic potential of as-synthesized nanostructures was also investigated for the reduction of nitroaromatics (4-NP and 4-NA) and RhB dye in the presence of NaBH₄. The Ag₂O-adorned ZnO nanostructures prepared with 5% of silver nitrate denoted as ZnO/Ag₂O (5%) demonstrated stupendous photomineralization activity against RhB dye as almost 100% degradation of RhB dye was achieved within 100 min of reaction time at pH = 6. The kinetic study revealed that the degradation reaction followed the pseudo-first-order kinetics and the kinetic rate constant (k) of photodecolorization reaction for optimal catalyst was calculated to be 61.4 × 10^-3 min^-1. The nanostructures revealed excellent recyclability and photostability as 95% activity of the catalyst was preserved even after the fifth cyclic run. The catalytic reduction of the 4-NP, 4-NA, and RhB dye was completed in 21, 12, and 40 min, respectively, in the presence of ZnO/Ag₂O (5%) and NaBH₄ solution. The kinetic rate constant values for the reduction reactions were determined to be 229.6 × 10^-3, 454.2 × 10^-3, and 105.5 × 10^-3 min^-1 for 4-NP, 4-NA, and RhB dye, respectively. Thus, the obtained results suggest that the components of the prepared nanosystem help in mutually strengthening the catalytic and photocatalytic abilities of each other, indicating the development of a cooperative and sustainable nanomaterial system in the current study.

Grapefruit Extract-Mediated Fabrication of Photosensitive Aluminum Oxide Nanoparticle and Their Antioxidant and Anti-Inflammatory Potential

Aluminum oxide nanoparticles (Al₂O₃ NPs) were synthesized using a simple, eco-friendly green synthesis approach in an alkaline medium from the extract of grapefruit peel waste. The pre-synthesized, nano-crystalline Al₂O₃ NPs were characterized by using spectroscopic (UV-vis, FTIR, XRD, and EDX) and microscopic (SEM and TEM) techniques. The formed Al₂O₃ NPs exhibited a pronounced absorption peak at 278 nm in the UV-vis spectrum. The average particle size of the as-prepared Al₂O₃ NPs was evaluated to be 57.34 nm, and the atomic percentages of O and Al were found to be 54.58 and 45.54, respectively. The fabricated Al₂O₃ NPs were evaluated for antioxidant, anti-inflammatory, and immunomodulatory properties. The Al₂O₃ NPs showed strong antioxidant potential towards all the four tested assays. The anti-inflammatory and immunomodulatory potential of Al₂O₃ NPs was investigated by measuring the production of nitric oxide and superoxide anion (O₂^•-), as well as proinflammatory cytokines tumour necrosis factor (TNF-α, IL-6) and inhibition of nuclear factor kappa B (NF- κB). The results revealed that Al₂O₃ NPs inhibited the production of O₂^•- (99.4%) at 100 μg mL^-1 concentrations and intracellular NO^•- (55%), proinflammatory cytokines IL-6 (83.3%), and TNF-α (87.9%) at 50 μg mL^-1 concentrations, respectively. Additionally, the Al₂O₃ NPs inhibited 41.8% of nuclear factor kappa B at 20 μg mL^-1 concentrations. Overall, the outcomes of current research studies indicated that Al₂O₃ NPs possess anti-inflammatory and immunomodulatory properties and could be used to treat chronic and acute anti-inflammatory conditions.

Photocatalytic Degradation of Methylene Blue and Metanil Yellow Dyes Using Green Synthesized Zinc Oxide (ZnO) Nanocrystals

In this work, ZnO nanocrystals (NCs) have been effectively synthesized by a simple, efficient and cost-effective method using coconut husk extract as a novel fuel. The synthesized NCs are characterized by UV-Vis, XRD, FT-IR, SEM, EDX, Raman and PL studies. The obtained ZnO were found to be UV-active with a bandgap of 2.93 eV. The X-ray diffraction pattern confirms the crystallinity of the ZnO with hexagonally structured ZnO with a crystallite size of 48 nm, while the SEM analysis reveals the hexagonal bipyramid morphology. Photocatalytic activities of the synthesized ZnO NCs are used to degrade methylene blue and metanil yellow dyes.

Hybrid functionalized chitosan-Al2O3@SiO2 composite for enhanced Cr(VI) adsorption

In this study, we prepared a novel hybrid functionalized chitosan-Al₂O₃@SiO₂ composite (FCAS) for removing hexavalent chromium [Cr(VI)] from aqueous system. Spectroscopic studies like Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and energy dispersive spectroscope (EDS) were characterized. The effects such as dosage of adsorbent, pH, contact time and initial Cr(VI) concentration were evaluated. It has been illustrated that a wide acidic condition in the pH range of 2-6 was conducive to Cr(VI) adsorption and only 10 min was required to reach about 80% adsorption. Also, the adsorption properties of prepared adsorbent such as kinetics, thermodynamics and isotherms were comprehensively studied. Additionally, the adsorption capacity barely declined even after five cycles. Studies found that FCAS with characteristics of high performance of adsorption rate and capacity and better reusability would be a potential adsorbent for wastewater treatment.