Access to safe drinking water is universally recognized as a fundamental human right; however, millions of people worldwide continue to face limited access to clean and safe water resources. The presence of contaminants such as heavy metals, organic compounds, dyes, pesticides, pharmaceuticals, and pathogenic microorganisms poses significant threats to human health and aquatic ecosystems. Conventional water treatment technologies, although effective in certain applications, are often associated with high operational costs, energy requirements, and limited efficiency toward emerging pollutants. Consequently, the development of sustainable, low-cost, and efficient water purification materials has gained increasing scientific attention. This review investigates the effectiveness of activated carbon as a promising adsorbent for drinking water purification and examines the principal mechanisms involved in pollutant removal. Various forms of activated carbon produced from agricultural waste-derived precursors were comparatively evaluated. Reported studies indicate that activated carbon exhibits a high specific surface area ranging from 300 to 2500 m2.g−1 and achieves removal efficiencies exceeding 90% for volatile organic compounds (VOCs), chlorine, dyes, and toxic heavy metals including Pb2+, Cd2+, and Cr6+. The adsorption capacities of activated carbon for different contaminants were reported to range from 50 to more than 500 mg.g−1, depending on precursor type, activation process, and operational conditions. Furthermore, regeneration efficiencies commonly remained within 70–85% after multiple adsorption–desorption cycles, highlighting the economic feasibility and environmental sustainability of activated carbon.
This work investigates the use of activated carbon in a batch system for the adsorption of cadmium from aqueous solutions. Two adsorbents were assessed: Commercially available activated carbon (CAC) and synthesized activated carbon (SAC) produced from walnut shell–derived agricultural waste. Adsorption efficiency increased with increasing pH, according to research on the impact of solution pH on cadmium removal. In the pH range of 7–12, maximum removal efficiencies of 81.9% for SAC and 80.5% for CAC were found at an initial cadmium concentration of 100 mg/L. Freundlich and Langmuir isotherm models were used to analyze the adsorption data. The Freundlich model provided a marginally better fit, suggesting heterogeneous adsorption sites on the activated carbon surfaces, while both models demonstrated good agreement with the experimental results. The highest adsorption capacities that were obtained from adsorption isotherms, under conditions of 4 h of contact time and 30 °C, were 69.5 mg/g for SAC and 81.2 mg/g for CAC.
This research considers the impact of a point/line heat source/sink on steady magnetohydrodynamic (MHD) natural convection flows in a vertical channel subjected to a transverse magnetic field with a thermal boundary condition of the third-kind thermal (Robin) boundary conditions. A constant point/line heat source/sink generates convection current within the flow. The governing dimensional equations regulating the physical situation at hand are presented in dimensionless form with the associated boundary conditions. Exact solutions are derived for the momentum and energy equations using the Laplace transform technique. The effects of key controlling parameters involved in flow formations are studied, such as the magnetic parameter, point/line heat source/sink parameter and Biot number on flow behaviour are analyzed. MATLAB software is employed to obtain line graphical and tabular results. The findings indicate that lower values of the Biot number account for reduced heat transfer to the surroundings, whilst higher values lead to higher surface heat transfer. Furthermore, the heat transfer rate, frictional drag force and mass flow rate retard as the line heat source/sink approaches a point heat source. In addition, the mass flow rate increases by almost 49% as the interval between the line heat source increases. for both equal and unequal values of the Biot number. There is remarkable agreement between the current results and the previously published studies.
This study estimates minimal entropy production, the corresponding distribution of heat exchange surfaces and contact temperatures for heat exchange systems with given total heat load and heat transfer coefficient. The analysis proves that an optimal heat exchange system requires constancy of the temperature ratio for the contact flows and equal heat flows’ output temperatures. The requirement that the entropy production in the system be greater than the minimum entropy generation marks the boundary of the reachable set of heat exchange systems.
Heat transfer fluids (HTFs) are critical in numerous industrial processes, enabling efficient heat exchange and precise temperature control. HTF degradation, primarily from thermal cracking and oxidation, negatively impacts system performance, reducing fluid lifespan and increasing operational costs, thus necessitating regular monitoring and proactive management. This review assesses optimal sampling frequencies for organic and synthetic HTFs, considering degradation mechanisms, relevant analytical parameters, and the economic advantages of proactive monitoring. The objective of this review is to examine HTF degradation mechanisms, compare organic and synthetic fluid properties and their impact on sampling frequency, and discuss strategies for optimising system performance and extending fluid life through effective HTF condition management. The article highlights the importance of fluid management, including appropriate fluid selection, to optimise system and fluid health, which is crucial for maximising their lifespans, ensuring safe operation, and minimising costs.
