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The current study involves a synthesis of a composite of nickel oxide nanoparticles (NiONPs) with a chromium dopant to yield (Cr/NiONPs). Synthesis of nickel oxide was performed by the co-precipitation method. The synthesis of the composite was conducted by the impregnation method. FTIR, EDX, SEM, and XRD were used to characterize the synthesized materials. The synthesised materials’ point zero charges (PZC) were performed using the potentiometric titration method. The obtained results show that the PZC for neat nickel oxide was around 5, and it was around 8 for Cr/NiONPs. The adsorption action of the prepared materials was examined by applying them to remove Reactive Red 2 (RR2) and Crystal Violate (CV) dyes from solutions. The outcomes demonstrated that Cr/NiONPs were stronger in the removal of dyes than NiONPs. Cr/NiONPs achieved 99.9% removal of dyes after 1 h. Adsorption isotherms involving Freundlich and Langmuir adsorption isotherms were also conducted, and the outcomes indicated that the most accurate representation of the adsorption data was offered by Langmuir adsorption isotherms. Additionally, it was discovered that the adsorption characteristics of the NiONPs and Cr/NiONPs correspond well with the pseudo-second-order kinetic model. Each of the NiONPs and Cr/NiONPs was reused five times, and the results display that the effectiveness of the removal of RR2 dye slightly declined with the increase in reuse cycles; it lost only 5% of its original efficiency after the 5 cycles. Generally, Cr/NiONPs showed better reusability than NiONPs under the same conditions.

Magnesium hydroxide nanoparticles (Mg(OH)2NPs) have recently attracted significant attention due to their wide applications as environmentally friendly antimicrobial nanomaterials, with potentially low toxicity and low fabrication cost. Here, we describe the synthesis and characterisation of a range of surface modified Mg(OH)2NPs, including particle size distribution, crystallite size, zeta potential, isoelectric point, X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). We explored the antimicrobial activity of the modified Mg(OH)2NPs on the microalgae (C. reinhardtii), yeast (S. cerevisiae) and Escherichia coli (E. coli). The viability of these cells was evaluated for various concentrations and exposure times with Mg(OH)2NPs. It was discovered that the antimicrobial activity of the uncoated Mg(OH)2NPs on the viability of C. reinhardtii occurred at considerably lower particle concentrations than for S. cerevisiae and E. coli. Our results indicate that the antimicrobial activity of polyelectrolyte-coated Mg(OH)2NPs alternates with their surface charge. The anionic nanoparticles (Mg(OH)2NPs/PSS) have much lower antibacterial activity than the cationic ones (Mg(OH)2NPs/PSS/PAH and uncoated Mg(OH)2NPs). These findings could be explained by the lower adhesion of the Mg(OH)2NPs/PSS to the cell wall, because of electrostatic repulsion and the enhanced particle-cell adhesion due to electrostatic attraction in the case of cationic Mg(OH)2NPs. The results can be potentially applied to control the cytotoxicity and the antimicrobial activity of other inorganic nanoparticles.

Antimould agents are widely used in different applications, such as specialty paints, building materials, wood preservation and crop protection. However, many antimould agents can be toxic to the environment. This work aims to evaluate the application of copper oxide nanoparticles (CuONPs) surface modified with boronic acid (BA) terminal groups as antimould agents. We developed CuONPs grafted with (3-glycidyloxypropyl) trimethoxysilane (GLYMO), coupled with 4-hydroxyphenylboronic acid (4-HPBA), which provided a strong boost of their action as antimould agents. We studied the antimould action of the 4-HPBA-functionalized CuONPs against two mould species: Aspergillus niger (A. niger) and Penicillium chrysogenum (P. chrysogenum). The cis-diol groups of polysaccharides expressed on the mould cell walls can form reversible covalent bonds with the BA groups attached on the CuONPs surface. This allowed them to bind strongly to the mould surface, resulting in a very substantial boost of their antimould activity, which is not based on electrostatic adhesion, as in the case of bare CuONPs. The impact of these BA-surface functionalized nanoparticles was studied by measuring the growth of the mould colonies versus time. The BA-functionalized CuONPs showed significant antimould action, compared to the untreated mould sample at the same conditions and period of time. These results can be applied for the development of more efficient antimould treatments at a lower concentration of active agent with potentially substantial economic and environmental benefits.

Polycyclic aromatic hydrocarbons (PAHs) represent a large class of persistent organic pollutants in an environment of special concern because they have carcinogenic and mutagenic activity. In this paper, we focus on and discuss the effect of different parameters, for instance, initial concentration of Anthracene, temperature, and light intensity, on the degradation rate. These parameters were adjusted at pH 6.8 in the presence of the semiconductor materials (TiO2) as photocatalysts over UV light. The main product of Anthracene photodegradation is 9,10-Anthraquinone which isidentified and compared with the standard compound by GC-MS. Our results indicate that the optimum conditions for the best rate of degradation are 25 ppm concentration of Anthracene, regulating the reaction vessel at 308.15 K and 2.5 mW/cm2 of light intensity at 175 mg/100 mL of titanium dioxide (P25).

The multiwall carbon nanotubes (MWCNTs)/titanium dioxide (P25) composite in different ratios was prepared using simple evaporation and drying process. The composite was characterized by Raman spectroscopy, X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy, and scanning electron microscopy (SEM). The photocatalytic activity of this composite was investigated using degradation of the Bismarck brown R dye (BBR). An optimal MWCNTs/TiO2 ratio of 0.5% (w/w) was found to achieve the maximum rate of BBR degradation. It was observed that the composite exhibits enhanced photocatalytic activity compared with TiO2. The enhancement in photocatalytic activity performance of the MWCNTs/P25 composite is explained in terms of recombination of photogenerated electron-hole pairs. In addition, MWCNTs act as a dispersing support to control the morphology of TiO2 particles in the MWCNTs/TiO2 composite.

We explored the factors and mechanisms of the adsorption and photocatalytic activity of iron oxide nanoparticles (Fe 2 O 3 NPs) coated with poly(sodium 4-styrenesulfonate) sodium salt (PSS), and poly(allylamine hydrochloride) (PAH) polyelectrolytes using the layer-by-layer technique. We synthesized Fe 2 O 3 NPs using the precipitation method at two calcination temperatures, 200 ℃ and 500 ℃. We studied the activity of bare and surface modified Fe 2 O 3 NPs toward fluorescein sodium salt (FSS) dye upon illumination with UV light compared with that under dark conditions to assess the effect of the oxidative stress because of the reactive oxygen species (ROS). The bare and surface modified Fe 2 O 3 NPs display excellent adsorption and photocatalytic activity for FSS dye. The Langmuir isotherm and the pseudo-second order kinetic model fit well with the adsorption properties of the Fe 2 O 3 NPs. The nanoparticles of the anionic surface (Fe 2 O 3 NPs/PSS) showed much lower adsorption and photocatalytic activity than the ones with a cationic surface functionality (Fe 2 O 3 NPs/PSS/PAH and bare Fe 2 O 3 NPs). The impact of the Fe 2 O 3 NPs surface coating was discovered to be much stronger than the ROS impact because of irradiation with UV light. This indicates that the nanoparticles attachment to the FSS dye is much more important for their adsorption and photocatalytic action than the ROS generation alone. This could be explained by the poor adhesion of Fe 2 O 3 NPs/PSS to the FSS dye due to electrostatic repulsion. In contrast, the particle-FSS dye electrostatic adhesion in the case of cationic Fe 2 O 3 NPs/PSS/PAH and bare Fe 2 O 3 NPs led to enhanced adsorption and photocatalytic action. Additionally, it was discovered that the Fe 2 O 3 NPs/PSS/PAH and bare Fe 2 O 3 NPs were extremely selective for anionic FSS over cationic crystal violet (CV) dye, making it simple to separate the two dyes from aqueous solutions of dye mixtures. The data also displays that bare and surface modified Fe 2 O 3 NPs have good recyclability, showing that they would be an economical material with significant potential in water treatment. Graphical abstract

In this study, we have developed a simple technique to prepare cationic chitosan hydrogel with interconnected porous structure using freeze–thaw process and the obtained hydrogel was named FCS hydrogel. Scanning electron microscopy (SEM) imaging discovered that the synthesized hydrogel demonstrated interconnected porous structure in the scope of 5–20 μm. We also showed that the FCS hydrogel exhibits pH responsiveness behavior, and demonstrated reversible swelling and de-swelling behaviors maintaining their mechanical stability. We demonstrate that the FCS hydrogel swelling capacity decreased at alkaline pH and rose with a decline in pH value. Besides, the FCS hydrogel presented specific surface area of 78.25 ± 8.75 m2 g−1, due to the cryogenic treatment of glutaraldehyde cross-linked chitosan hydrogel could increase the surface area and permeability of composite hydrogel and then strongly increasing the adsorption capacity. Subsequently, the FCS monolithic hydrogel tested dyes removal, which provides a high removal efficiency towards anionic dyes including congo red (CR) and sodium fluorescein (SFL) dyes. Significantly, we show that the FCS hydrogel could be regenerated and reused as an adsorbent for wastewater treatment without significant loss of pollutants removal efficiency over a number of adsorption and washing cycles. This study offers a promising environmental friendly and sustainable interconnected porous hydrogel for anionic dye removal from wastewater.

The photocatalytic decolorization of cobalamin was carried out in aqueous solution of different types of catalysts including ZnO, TiO2 (Degussa P25), TiO2 (Hombikat UV100), TiO2 (Millennium PC105), and TiO2 (Koronose 2073) by using UVA source of irradiation. The effect of various parameters such as photocatalyst amount, cobalamin concentration, type of catalyst, pH of aqueous solution, light intensity, addition of H2O2, flow rate of O2, type of current gas, and temperature on photocatalytic oxidation was investigated. The results indicated that the photocatalytic decolorization of cobalamin was well described by pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. The effect of temperature on the efficiency of photodecolorization of cobalamin was also studied in the range 278–298 K. The activation energy was calculated according to Arrhenius plot and was found equal to 28±1 kJ·mol−1 for ZnO and 22±1 kJ·mol−1 for TiO2 (Degussa P25). The results of the total organic carbon (TOC) analysis indicate that the rate of decolorization of dye was faster than the total mineralization. Decolorization and mineralization of cobalamin in the absence of light and/or catalyst were performed to demonstrate that the presence of light and catalyst is essential for the decolorization of this cobalamin. The results show that the activity of different types of catalysts used in this study was of the sequence: ZnO > TiO2 (Degussa P25) > TiO2 (Hombikat UV100) > TiO2 (Millennium PC105) > TiO2 (Koronose 2073).

The current work involves preparation of neat vanadium oxide and cobalt oxide. Likewise, various percentage from their mixed forms were prepared in various ratios: 25%, 50%, 75% and 100% from CoO were precipitated with fixed weight of V2O5 2.0 g. In addition, the above percentage from V2O5 were precipitated with fixed weight of CoO, 2.0 g. The individual metal oxides and their mixtures with various ratios were prepared from the solution of sulphate and nitrate of both metals respectively by co-precipitation process by adding sodium carbonate. All metals carbonates transfer to corresponding oxides by calcification at 773 K. Spectroscopic studies for metal oxides and their mixtures with various ratios using X-rays diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Some of physical properties of these oxides and their mixtures were studies such as pore size, density, porosity and electrical conductivity. The activity of these materials were investigated by following photocatalytic oxidation of 1-octanol over a suspension of these materials. The obtained results showed that photocaatalytic oxidation of alcohol was achieved when using each of catalyst, light, air and 1-octanol.

The current work involves preparation of neat vanadium oxide and cobalt oxide. Likewise, various percentage from their mixed forms were prepared in various ratios: 25%, 50%, 75% and 100% from CoO were precipitated with fixed weight of V 2 O 5 2.0 g. In addition, the above percentage from V 2 O 5 were precipitated with fixed weight of CoO, 2.0 g. The individual metal oxides and their mixtures with various ratios were prepared from the solution of sulphate and nitrate of both metals respectively by co-precipitation process by adding sodium carbonate. All metals carbonates transfer to corresponding oxides by calcification at 773 K. Spectroscopic studies for metal oxides and their mixtures with various ratios using X-rays diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Some of physical properties of these oxides and their mixtures were studies such as pore size, density, porosity and electrical conductivity. The activity of these materials were investigated by following photocatalytic oxidation of 1-octanol over a suspension of these materials. The obtained results showed that photocaatalytic oxidation of alcohol was achieved when using each of catalyst, light, air and 1-octanol.