Evaluation of Photocatalytic, Antioxidant, and Antibacterial Efficacy of Almond Oil Capped Zinc Oxide Nanoparticles

In this study, ZnO nanoparticles (NPs) were synthesized in the presence of almond oil at various molar ratios of zinc acetate and sodium hydroxide, including 0.5:1, 0.75:1, 1:1, 1.25:1, and 1.5:1, to obtain pH values of 11, 10, 9, 8, and 7, respectively. The XRD results revealed that ZnO NPs exhibit a hexagonal structure, with high crystallinity. SEM results showed that dense and large sized ZnO NPs were formed at pH 11, and relatively small (~30-40 nm) NPs were obtained at pH 9. The size distribution can be explained in terms of the presence of OH- ions at different pH levels. However, the larger size of the NPs at pH 7 compared to those at pH 8-11 were due to the coalescence of NPs suitable for antioxidant/antibacterial activities. ZnO NPs demonstrated a high degradation efficiency (~93%) in 90 min, with a high rate constant for Methyl Orange (MO), which is better than the previously reported rate. The larger sized almond oil capped ZnO NPs also showed excellent radical scavenging activity (94%) and are proven to be good carriers to resist Escherichia coli (E. coli) bacteria.

Recent Advances in the Removal of Organic Dyes from Aqueous Media with Conducting Polymers, Polyaniline and Polypyrrole, and Their Composites

Water pollution by organic dyes, and its remediation, is an important environmental issue associated with ever-increasing scientific interest. Conducting polymers have recently come to the forefront as advanced agents for removing dye. The present review reports on the progress represented by the literature published in 2020-2022 on the application of conducting polymers and their composites in the removal of dyes from aqueous media. Two composites, incorporating the most important polymers, polyaniline, and polypyrrole, have been used as efficient dye adsorbents or photocatalysts of dye decomposition. The recent application trends are outlined, and future uses also exploiting the electrical and electrochemical properties of conducting polymers are offered.

Green synthesis of microalgae-based carbon dots for decoration of TiO2 nanoparticles in enhancement of organic dye photodegradation

TiO₂ is a well-known semiconductor used widely in the photocatalyst field, but its photocatalytic applications are hampered by a fast electron-hole recombination rate and low visible light absorption due to a wide-band-gap energy. Herein, we present a simple, low cost, and green approach to obtain carbon dots from microalgae, namely microalgae-based carbon dots (MCDs), using an unprecedented microwave-assisted treatment. The MCDs were successfully decorated on the surface of TiO₂ nanoparticles. The as-prepared composite exhibited a superior photodegradation of methylene blue, compared with pristine TiO₂ (83% and 27%, respectively) under visible light irradiation. The MCDs in TiO₂-MCDs serve as electron reservoirs to trap photoinduced electrons and as photosensitizers for the improvement of visible light absorption; both factors play an important role in the improvement of the TiO₂ photocatalytic activity. Furthermore, the as-prepared composite photocatalyst also exhibits high photostability and recyclability during the photodegradation of methylene blue. Therefore, this work provides an original approach to the development of environmentally friendly and highly effective photocatalysts for the treatment of various organic pollutants, which can go a long way toward ensuring a safe and sustainable environment.

Preparing Biomass Carbon Fiber Derived from Waste Rabbit Hair as a Carrier of TiO2 for Photocatalytic Degradation of Methylene Blue

In the past few years, biomass carbon materials have gained wide attention from many scholars as TiO₂ carrier materials to improve photocatalytic activity due to their renewable, green, low-cost, and high-efficiency advantages. In this study, TiO₂/carbonized waste rabbit fibers (TiO₂/CRFs) nanocomposites with the hierarchical microporous/mesoporous structure were fabricated by a combination of carbonization, immersion, and calcination methods using tetrabutyl titanate as the titanium source and waste rabbit hair as the carbon source. The properties and catalytic activity of TiO₂/CRFs composite were evaluated based on several characterization techniques and methylene blue (MB) photodegradation studies. The results showed that the degradation of MB by TiO₂/CRFs could reach 98.1% after 80 min of solar irradiation. Moreover, TiO₂/CRFs still maintained high photocatalytic activity after five cycles of degradation tests, exhibiting good stability and reusability. The improved photocatalytic performance of TiO₂/CRFs materials is attributed to the natural carbon and nitrogen element doping of TiO₂/CRFs and its morphology, which reduces the compounding of photogenerated electron-hole pairs and narrows the TiO₂ band gap, while the multiple reflections of visible light in the pore channels enhance the visible light absorption of the materials. Furthermore, the large specific surface area provides abundant reaction sites for adsorbed reactants. This paper provides the experimental basis for the application of waste rabbit biomass carbon composites in photocatalytic degradation field.