Adsorption Kinetics and Isotherm Models: A Review

Adsorption Kinetics describes the rate at which solute is adsorbed and the resident time of the adsorbates on the solid-liquid interface. Adsorption isotherms play important role in determining the interaction between adsorbate and adsorbent and the optimum adsorption capacity of adsorbent. This article considered selected adsorption kinetics and isotherms models. Pseudo first order, Pseudo second order, Elovich, Bhattacharya and Venkobachar, and Natarajan and Khalaf were adsorption kinetics reviewed on the assumption that the process behaves as heterogeneous reaction at solid-liquid interface. Adsorption kinetics equation presented takes the form of straight line, the slopes and intercepts of the plots are used to determine adsorption capacity of adsorbent, rate constant, rate of adsorption and intraparticle diffusion. Value of correlation coefficient obtained is used in determining the adsorption kinetics model that best describe the adsorption process. Langmuir, Freundlich, Radlich-Peterson, Temkin and Dubinin-Radushkevic adsorption isotherms were presented. Their slopes and intercepts provide insight on adsorption affinity, mean free energy, whether the adsorption is physisorption or chemisorptions, single or multilayer. Adsorption kinetics and isotherms reviewed provide essential information required for understanding adsorption process. Keywords:   Adsorption; kinetics; isotherms; pseudo first order; Langmui

On the stability of triangular points in the relativistic R3BP when the bigger primary is oblate and the smaller one radiating with application on Cen X-4 binary system

In the framework of the relativistic R3BP, we examine the effects of oblateness of the primary body and radiation pressure of the secondary on the positions and stability of the triangular points L4,5. It is found that the parameters involved all affect the positions and increase in any of the parameters leads to a reduction in the size of the region of stability. Thus establishing their destabilizing tendencies. The presence of positive real roots or positive real part in complex roots affirms the instability of L4,5 of the problem when applied to Cen X-4. Keywords: R3BP, Relativity, Oblateness, Radiation, Cen X-4 star

Impacts of Poynting–Robertson Drag and Dynamical Flattening Parameters on Motion around the Triangular Equilibrium Points of the Photogravitational ER3BP

Using an analytical and numerical study, this paper investigates the equilibrium state of the triangular equilibrium points L4,  5 of the Sun-Earth system in the frame of the elliptic restricted problem of three bodies subject to the radial component of Poynting–Robertson (P–R) drag and radiation pressure factor of the bigger primary as well as dynamical flattening parameters of both primary bodies (i.e., Sun and Earth). The equations of motion are presented in a dimensionless-pulsating coordinate system ξ−η, and the positions of the triangular equilibrium points are found to depend on the mass ratio μ and the perturbing forces involved in the equations of motion. A numerical analysis of the positions and stability of the triangular equilibrium points of the Sun-Earth system shows that the perturbing forces have no significant effect on the positions of the triangular equilibrium points and their stability. Hence, this research work concludes that the motion of an infinitesimal mass near the triangular equilibrium points of the Sun-Earth system remains linearly stable in the presence of the perturbing forces

Spectroscopic Characterization of Acetylated Wood Flakes and Its High-Density Polyethylene Blends

Communication in Physical Sciences, 2022, 8(1): 109-120 Authors: Yakubu Azeh*, Fatima Abubakar, Monday Musah, John Tsado Mathew, Musa Tanko Umar, Yahaya Sayyadi Mohammad, Aliyu Turaki Ibrahim, Abdulkarim Mohammed Awwal, Hauwa Larai Muhammad Idris and Aishetu Ibrahim Muhammad Received: 26 March 2022/Accepted 25 April 2022 Acetylation is a useful reaction for the improvement of the surface properties of natural fibers in bend/composites fabrications, which are essential in the determination of their usefulness.  In this study, the effects of acetylation on wood flakes/fibers of Gmelina Arborea was investigated. Acetylation was carried out in batches using acetic anhydride as an acetylating agent and acetic acid as a catalyst at 120˚C for 1, 2, and 3 h under reflux. The efficiency of acetylation was evaluated in terms of weight percent gains (WPGs) due to acetylation. Polyethylene blends were prepared by the solution blending of acetylated/unacetylated wood flakes using casting-evaporation method in toluene. The effects of acetylated/unacetylated wood flakes on the biodegradability of blends were investigated. Acetylated wood and blends were characterized using Fourier transform infrared spectroscopy (FT-IR), Thermogravimetry analysis (TGA/DTGA) and scanning electron microscopy (SEM). Results obtained from the study revealed that modification was indicative based on the observation of C=O absorption peak at 1722 and 1640 cm-1 respectively. TGA results revealed blend composition of 0.5/0.5 g gave the best material’s stability. We also observed that the properties of the modified wood flakes/blends were enhanced by the lower equilibrium moisture content caused by acetyl groups. The modified wood flakes could find industrial applications in fiber and particles/plywood board products for various construction purposes while unmodified blends can be used in the production of polymer-based biodegradable products. Biodegradation results indicate that blending of acetylated wood flakes with polyethylene matrix enhanced its biodegradation. Thus, adding acetylated wood flakes into polyethylene could reduce the lifespan of PE in the environment