Mohamed A. Eltaher

With increasing global concerns about industrial wastewater treatment and the need for sustainable practices, this study explores the potential of softwood sawdust as an eco-friendly, cost-effective adsorbent for removing heavy metal ions, specifically zinc (Zn²⁺) and lead (Pb²⁺), from synthetic model solutions. Factors affecting adsorption include adsorbent particle size, pH, adsorbent dosage, and contact time. A remarkable removal efficiency of 98.2% for Zn²⁺ and 98.1% for Pb²⁺ under optimal adsorption conditions of −106 µm average particle size at 8 pH and 0.3 g of adsorbent dosage using 50 (mg/L) initial concentrations for 60 min at ambient temperature. Characterization of the adsorbent used by XRD, FTIR, SEM, and BET analysis confirmed the structural integrity and surface properties of wood sawdust. It is clear that there is a gradual decline in adsorption capacity over multiple reuse cycles due to the depletion of active functional groups. The results confirm wood sawdust’s effectiveness as a locally available, low-cost, and biodegradable option for treating wastewater, eliminating metal ions, supporting environmental conservation, and aligning with sustainability goals.

This investigation primarily focuses on addressing the challenges posed by the traditional use of carbon steel, which, despite its strength and cost-effectiveness, is prone to rapid corrosion in harsh chemical environments within the petrochemical industry. This issue constitutes a chronic operational vulnerability, exacerbated by extreme environmental stressors. The combined effect of corrosive atmospheres and rigorous EHSS (Environment, Health, Safety, and Security) mandates creates a significant fiscal burden, primarily driven by escalated lifecycle maintenance and the necessity for specialized regulatory compliance. Integrating Inconel, known for its exceptional corrosion resistance and durability, particularly at high temperatures, will significantly enhance the lifespan, safety, and operational efficiency of these vessels. This investigation aims to study the corrosion resistance of carbon steel specimens and carbon steel specimens clad with Inconel at thicknesses of 2 mm and 4 mm in different environments: acidic pH = 2 (HCl), neutral pH = 7 (distilled water), and alkaline pH = 12 (NaClO). All specimens were tested at the same immersion intervals of 5 and 10 days. Corrosion resistance was measured for the immersion corrosion tests. Weight loss in the specimens was measured before and after immersion to calculate the corrosion rate, and surface analysis was conducted using a scanning electron microscope (SEM). It was observed that at pH = 12 (NaClO), carbon steel corrosion reached a rate of 6.96 mm/year, while Inconel showed very low corrosion, 0.05 mm/year, indicating a resistance 139 times greater than that of carbon steel. At pH = 2 (HCl), carbon steel corrosion reached a rate of 1.29 mm/year, while Inconel showed a very low corrosion rate of 0.015 mm/year, indicating a resistance 86 times greater than that of carbon steel. In a neutral environment, all materials exhibited approximately the same corrosion rate between 0.0017 and 0.12 mm/year. This indicates that Inconel is highly resistant to corrosion in both acidic and alkaline environments, making it suitable for petrochemical plants.

This research conducts a nonlinear analysis of free vibrations in a cylindrical panel comprising auxetic metal metamaterials enhanced with graphene origami (GOri), subjected to thermal loading and supported by an elastic foundation. The integration of GOri particles is observed to markedly improve the panel’s mechanical characteristics, which are quantified through a micromechanical modeling approach. The investigation incorporates five distinct through-thickness schemes for distributing GOri particles within the structure. Governing equations for the panel are formulated using first-order shear deformation theory alongside Hamilton’s principle, while von Karman’s nonlinear kinematic assumptions are implemented to capture geometric nonlinearities. Once the nonlinear partial differential equations are established and simply supported boundary conditions applied, Galerkin’s procedure is utilized to condense the system into a single nonlinear equation describing transverse displacement. Perturbation analysis and the modified Poincaré–Lindstedt technique are then adopted to determine the structure’s nonlinear natural frequencies. A notable feature of nonlinear free vibrations, as opposed to the linear case, is the dependence of natural frequencies on initial system conditions. The roles of various factors such as the dimensionless magnitude of initial disturbance, temperature variations, GOri concentration and distribution styles, fold parameters, structural geometry and foundation stiffness are systematically explored. To ensure robustness and reliability, the analytical framework, solution process and computed results are cross-validated through comparative analysis. Findings indicate that the initial state significantly influences vibrational characteristics, and higher temperatures lead to a pronounced reduction in nonlinear frequency.

This paper introduces a novel analytical model to investigate the nonlinear supersonic flutter characteristics of auxetic metamaterial plates exhibiting a negative Poisson’s ratio (NPR). The plate consists of multiple layers through its thickness, each made from a copper (Cu) matrix reinforced with a specific weight fraction of Graphene Origami Auxetic metamaterial (GOAM). Three patterns of graphene origami (GO) distribution are considered. Utilizing classical plate theory with von-Kármán nonlinear strains and linear supersonic piston theory, the nonlinear governing equations of motion are presented. Bernstein polynomials are employed to formulate mode shapes that satisfy the boundary conditions within the spatial domain. Then, Galerkin approximation is used to transform the nonlinear partial differential equations of motion to nonlinear time-dependent ordinary differential equations. The Runge–Kutta method is employed to attain the nonlinear dynamic post-flutter behaviors of GOAM plate. Furthermore, linear flutter characteristics are obtained through eigenvalue analysis. To validate the accuracy of the proposed approach, comparisons are conducted with results available in published literature, demonstrating excellent agreement. The impacts of material parameters, GO distribution patterns, and boundary conditions on flutter behaviors of plate are examined. This model offers applicability in analyzing solid–fluid interaction studies relevant to aerospace, ocean engineering, and mechanical systems.

This work introduces the first analytical framework for size-dependent buckling of bidirectional functionally graded (2D-FG) cylindrical nanoshells with Hardcore (HC) and Softcore (SC) configurations. The nanoshells are engineered with a distinctive bidirectional material gradation, in which ceramic and metallic constituents vary simultaneously along both axial and radial directions, enabling tailored stiffness profiles. To accurately capture scale-dependent effects, microstructure size influences, and transverse shear deformation, the formulation fully integrates first-order shear deformation theory (FSDT) with nonlocal strain gradient theory (NSGT). The governing equations are solved using the Galerkin method for a wide range of boundary conditions, while complex elastic foundations (Winkler, Pasternak, Kerr) are incorporated to reflect realistic nanoscale support environments. The governing equations are rigorously established through the principle of virtual work, and an efficient solution scheme — capable of handling a wide range of boundary conditions — is developed using the Galerkin method. A key finding is that HC nanocylinders consistently exhibit significantly higher buckling resistance than their SC counterparts, attributed to their ceramic-rich core. Furthermore, the analysis reveals the competing nature of size effects: the critical buckling load decreases with an increasing nonlocal parameter (softening effect) but increases with the strain gradient parameter (stiffening effect). The results also demonstrate that the elastic foundation substantially enhances stability, with the Pasternak model providing the most pronounced reinforcing effect, followed by the Kerr and Winkler models. This study provides critical insights for the design and optimization of advanced nanoscale cylindrical structures in aerospace and nano-engineering applications.