Effects of binary chemical reaction and Arrhenius activation energy in Darcy–Forchheimer three-dimensional flow of nanofluid subject to rotating frame

Darcy–Forchheimer three-dimensional rotating flow of nanoliquid in the presence of activation energy and heat generation/absorption is examined. Heat and mass transport via convective process is considered. Buongiorno model has been employed to illustrate thermophoresis and Brownian diffusion effects. Adequate transformation procedure gives rise to system in terms of nonlinear ODE’s. An efficient numerical technique namely NDsolve is used to tackle the governing nonlinear system. The graphical illustrations examine the outcomes of various sundry variables. Heat and mass transfer rates are also computed and examined. Our results indicate that the temperature and concentration distributions are enhanced for larger values of porosity parameter and Forchheimer number.

     

Effect of Temperature on Cd2+ Sorption by Mixed Oxides of Iron and Silicon

The current study focuses on the synthesis and sorption properties of two mixed oxides of iron and silicon prepared by physical mixing (M₁) and sequential precipitation methods (M₂). Both the mixed oxides were synthesized from equimolar ratios of Fe(OH)₃ and SiO₂ and characterized for surface area, EDX, XRD and PZC. The surface area, micropore volume and average pore width of the oxide M₁ were higher as compared to the oxide M₂. However, potentiometric titrations revealed that mixed oxide synthesized by this method had a very high capacity towards Cd²⁺ ions as compared to the mixed oxide M₁. Sorption of Cd²⁺ ions at pH 5 on mixed oxide, M₂ was found to increase with temperature in the range 288 to 318 K. Langmuir equation was found applicable to the sorption data with R²>0.99. Entropy (ΔS^?), enthalpy (ΔH^?) and free energy changes (ΔG^?) were calculated which revealed the process to be endothermic and spontaneous in nature.     

Ion chromatograph with three-dimensional printed absorbance detector for indirect ultraviolet absorbance detection of phosphate in effluent and natural waters

An ion chromatography system employing a low-cost three-dimensional printed absorbance detector for indirect ultraviolet detection towards portable phosphate analysis of environmental and industrial waters has been developed. The optical detection cell was fabricated using stereolithography three-dimensional printing of nanocomposite material. Chromatographic analysis and detection of phosphate were carried out using a CS5A 4 × 250 mm analytical column with indirect ultraviolet detection using a 255 nm light-emitting diode. Isocratic elution using a 0.6 mM potassium phthalate eluent combined with 1.44 mM sodium bicarbonate was employed at a flow rate of 0.75 mL/min. A linear calibration range of 0.5 to 30 mg/L PO₄³⁻ applicable to environmental and wastewater analysis was achieved. For retention time and peak area repeatability, relative standard deviation values were 0.68 and 4.09%, respectively. Environmental and wastewater samples were analyzed with the optimized ion chromatography platform and the results were compared to values obtained by an accredited ion chromatograph. For the analysis of environmental samples, relative errors of <14 % were achieved. Recovery analysis was also carried out on both freshwater and wastewater samples and recovery results were within the acceptable range for water analysis using standard ion chromatography methods.     

Peristaltic radiative flow of Sisko nanomaterial with entropy generation and modified Darcy’s law

Journal of Thermal Analysis and Calorimetry - Nanomaterials are quite significant in the physiological and engineering processes. Such materials have motivated the recent scientists in view of...     

Complexation of radionuclide <Superscript>152+154</Superscript>Eu(III) with alumina-bound fulvic acid studied by batch and time-resolved laser fluorescence spectroscopy

To contribute to the understanding of Eu(III) interaction preperties on hydrous alumina particles in the absence and presence of fulvic acid (FA), the complexation properties of Eu(III) with hydrous alumina, FA and FA-alumina hybrids are studied by batch and time-resolved laser fluorescence spectroscopy (TRLFS) techniques. The continuous increase in the fluorescence lifetime of Eu-alumina and Eu-FA with increasing pH indicates that the complexation is accompanied by decreasing number of hydration water in the first coordination sphere of Eu(III). Eu(III) is adsorbed onto alumina particles as outer-sphere surface complexes of ≡(Al?O)?Eu· (OH)· 7H₂O and ≡(Al?O)?Eu· 6H₂O at low pH values, and as inner-sphere surface complexes as ≡(Al?O)₂?Eu⁺· 4H₂O at high pH. In FA solution, Eu(III) forms complexes with FA as (COO)₂Eu⁺(H₂O) _x and the hydration water number in the first coordination sphere decreases with pH increasing. The formation of ≡COO?Eu?(O?Al≡)· 4H₂O is observed on FA-alumina hybrids, suggesting the formation of strong inner-sphere surface complexes in the presence of FA. The surface complexes are also characterized by their emission spectra [the ratio of emission intensities of ⁵ D ₀→⁷ F ₁ (λ=594 nm) and ⁵ D ₀→⁷ F ₂ (λ=619 nm) transitions] and their fluorescence lifetime. The findings is important to understand the contribution of FA in the complexation properties of Eu(III) on FA-alumina hybrids that the clarification of the environmental behavior of humic substances is necessary to understand fully the behavior of Eu(III), or its analogue trivalent lanthanide and actinide ions in natural environment.     

Interaction of radionuclides with natural and manmade materials using XAFS technique

The X-ray absorption fine structure (XAFS) technology has exhibited a very unique application in the study of sorption mechanism, chemical species and microstructures of radionuclides at the natural solid-water interfaces. In this review, the interaction mechanism of radionuclides with clay minerals and nanomaterials under different environmental conditions are summarized from the XAFS spectroscopy analysis. The coordination number and the bond distances of radionuclides, the oxidation-reduction reactions, the influence of humic substances and microorganisms on the species and structures of radionuclides at molecule level are reviewed and compared. This review is helpful to understand the interactions of radionuclides with oxides, natural clay minerals and nanomaterials, which is also crucial to evaluate the physicochemical behaviors of radionuclides in the natural environment.     

Determination of Phenolic Compounds in Various Propolis Samples Collected from an African and an Asian Region and Their Impact on Antioxidant and Antibacterial Activities

The biological activities of propolis samples are the result of many bioactive compounds present in the propolis. The aim of the present study was to determine the various chemical compounds of some selected propolis samples collected from Palestine and Morocco by the High-Performance Liquid Chromatography–Photodiode Array Detection (HPLC-PDA) method, as well as the antioxidant and antibacterial activities of this bee product. The chemical analysis of propolis samples by HPLC-PDA shows the cinnamic acid content in the Palestinian sample is higher compared to that in Moroccan propolis. The results of antioxidant activity demonstrated an important free radical scavenging activity (2,2-Diphenyl-1-picrylhydrazyl (DPPH); 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and reducing power assays) with EC₅₀ values ranging between 0.02 ± 0.001 and 0.14 ± 0.01 mg/mL. Additionally, all tested propolis samples possessed a moderate antibacterial activity against bacterial strains. Notably, Minimum Inhibitory Concentrations (MICs) values ranged from 0.31 to 2.50 mg/mL for Gram-negative bacterial strains and from 0.09 to 0.125 mg/mL for Gram-positive bacterial strains. The S2 sample from Morocco and the S4 sample from Palestine had the highest content of polyphenol level. Thus, the strong antioxidant and antibacterial properties were apparently due to the high total phenolic and flavone/flavonol contents in the samples. As a conclusion, the activities of propolis samples collected from both countries are similar, while the cinnamic acid in the Palestinian samples was more than that of the Moroccan samples.     

Interaction mechanisms of U(VI) and graphene oxide from the perspective of particle size distribution

Graphene oxide (GO) is an ideal adsorbent due to excellent physicochemical properties. Humic acid (HA) is ubiquitous in aquatic and soil environment, which can affect the migration of metal ions. In this study, we investigated the sorption mechanisms of U(VI) onto GO surfaces in the presence of HA. pH dependent and ionic strength independent sorption process were observed and the concentration of HA is positively proportional to U(VI) sorption capacities. Results also suggest that a pre-mixing HA + U(VI) gave better results than a pre-mixing of GO + HA, which can be explained by the size distribution of different GO systems.

     

Modulating opto-electronic and magnetic responses of Mo- and Zn-adsorbed LiNbO3 (1 1 1) surface for advanced energy harvesting applications: A comprehensive study

This study aimed to comprehensively investigate the optoelectronic and magnetic properties of Mo, Zn/LiNbO₃ (1 1 1) material. The primary objectives were to understand the potential for manipulating the material's magnetism and to elucidate the origin of spin-polarized states and magnetic moments, particularly with respect to the unpaired d orbitals of Nb, Mo, and Zn atoms. To achieve these objectives, we employed the Pardew–Burke–Ernzerhof (PBE) method within the Generalized Gradient Approximation (GGA + U) framework. This computational approach allowed us to examine the optoelectronic and magnetic characteristics of the material in detail. Our research yielded several key findings that enhance our understanding of Mo, Zn/LiNbO₃ (1 1 1) material. We observed a modest improvement in the material's absorption capacity within the visible spectrum, accompanied by a discernible red-shift. Notably, our study involved the calculation of the dielectric function and refractive constant of the material, revealing a strong correlation between absorption trends and the dielectric constant. Furthermore, our investigation uncovered that Mo, Zn/LiNbO₃ (1 1 1) exhibits distinct conduction and valence bands, with p and d orbitals predominantly contributing to each, respectively. The energy gap of the material falls within a range of 0.30–1.04 eV. A particularly significant finding was the narrower band gap of Mo, Zn/LiNbO₃ (1 1 1) material, which can be attributed to the superposition of Mo-d and Zn-p orbit energy levels with O-p orbit energy levels, ultimately forming a covalent bond. Importantly, our research demonstrated the material's heightened optical absorption within the visible spectrum, suggesting its suitability for various photonic and optoelectronic applications. Additionally, we calculated a wide range of optical characteristics, including the dielectric function, absorption coefficient, energy loss, reflectivity, refractive index, extinction coefficient, and optical conductivity, providing a comprehensive assessment of the material's optical properties.