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A multi-functionalized Na-Y/ZnO/NH2/SH composite adsorbent was synthesized for Pb2+ and Ni2+ removal from single and binary aqueous systems. The prepared composites were characterized by FTIR, FESEM, XRD, BET, and N2 adsorption–desorption techniques. The effect of ZnO nanoparticles, amine, and thiol functional groups on the adsorption performance was studied in a batch system. The adsorption behavior of Pb2+ and Ni2+ ions was evaluated as a function of initial metal concentration, contact time, pH, and temperature. The adsorption process of both Pb2+ and Ni2+ ions followed the double-exponential kinetics model. Also, the investigation of isotherm models exhibited a monolayer adsorption onto the synthesized composite. The maximum adsorption capacity of Na-Y/ZnO/NH2/SH composite was found to be 177.9 mg/g for Ni2+ ions and 295.4 mg/g for Pb2+ ions. The synthesized Na-Y/ZnO/NH2/SH composite was regenerated multiple times showing a promising adsorbent with high regeneration efficiency. In a binary system, the inhibitory influence of Pb2+ ions on the Ni2+ adsorption was greater than the inhibitory influence of Ni2+ ions on the Pb2+ adsorption. [ABSTRACT FROM AUTHOR]

Recently, the use of nanoparticles in extraction columns has gained increasing attention due to their potential to enhance mass transfer processes. Most of the reported work, however, has been concerned with mass transfer enhancement in gas–liquid systems in the presence of nanoparticles, while limited studies of liquid–liquid systems have been reported. Liquid–liquid extraction is an extensively employed separation method that has taken on a substantial role in engineering and industrial applications for recovery processes. Therefore, the aim of this review article is to provide an overview of the state-of-the-art from the available literature on the effect of nanoparticles on the hydrodynamic behavior and mass transfer performance of liquid–liquid systems. Attention is also given to providing an understanding of the mechanisms responsible for the improvements in mass transfer with the use of nanoparticles. In the majority of studies, the presence of nanoparticles was found to be beneficial and to lead to improved mass transfer, although a few investigations reported a detrimental impact of nanoparticles. The literature does not clearly describe the conditions under which the addition of nanoparticles would be unfavorable. Moreover, the addition of nanoparticles always introduces potential drawbacks, such as sedimentation, accumulation, or clogging inside extraction columns, as well as the need to separate the nanoparticles at the outlets. These drawbacks have not been considered in the literature, limiting the practical employment of nanoparticles in this industry. [ABSTRACT FROM AUTHOR]

This study presents the application of a modified single-phase method by thermal dispersion model incorporating heterogeneous distribution of nanoparticle concentration for evaluating thermal performance of a nanofluid in a circular porous metal foam tube. Numerical approach was conducted for Re = 200–1000, mean concentration of 0.5–2%, and metal foam porosity of 0.7–0.9. It is observed that the predicted data by application of the thermal dispersion approach are in satisfactory agreement with those obtained experimentally, whereas applying the general homogeneous model results in an underestimation. The results reveal that the heterogeneity of the concentration distribution is directly proportional to nanoparticle mean concentration, Reynolds number, and the metal foam porosity. The velocity and temperature profiles at a cross section have been found to be flatter in dispersion model compared to those obtained from the homogeneous model. Furthermore, it is achieved that the Nusselt number varies directly relative to mean concentration and Reynolds number, whereas it inversely alters relative to the porosity. This reduction is found to be more profound at lower porosities. [ABSTRACT FROM AUTHOR]

Recently, it has been observed that the use of magnetic nanoparticles and the magnetic field would result in heat and mass transfer intensification. But most of the investigations have been devoted to the enhancement of heat transfer. However, the investigations on the applicability of magnetic nanoparticles for mass transfer improvement are still in the developing stage. In the present study, the effect of MnFe 2 O 4 nanoparticles on the mass transfer performance of a packed extraction column is evaluated in the presence of constant and alternating magnetic fields. The column is filled with Penta-Pak TM PS-500M1 structured packing; while four identical bar electromagnets made from zinc ferrite cores are used to generate the quadrupole magnetic field. The (toluene-acetic acid)-water system is employed. Spinel-type manganese ferrite nanoparticles are added to the organic dispersed phase (toluene + acetic acid) to intensify solute transfer. The quadrupole magnetic field is applied from 100 to 500 G intensity and 100 to 500 Hz frequency, accompanied with different nanoparticle concentrations from 0.001 wt% to 0.005 wt%. According to our observations, mass transfer performance increases remarkably in the presence of magnetic nanoparticles under the influence of magnetic field. Compared with no magnetic field, maximum improvements of 115% and 43% in overall mass transfer coefficient and extraction fraction are observed under alternating magnetic field with 300 Hz frequency and 500 G intensity for 0.003 wt% nanoparticle concentration. That is, by using the magnetic nanoparticles and the magnetic field, one can considerably improve the performance of a liquid-liquid extraction system. [ABSTRACT FROM AUTHOR]

In this work, the evaluation of thermal conductivity of MnFe 2 O 4 /water nanofluids in attendance of magnetic field is conducted. The MnFe 2 O 4 /water is synthesized and prepared in different nanoparticles concentrations, from 0.25% to 3%. The thermal conductivity of nanofluids has been determined at various nanofluid concentrations and temperatures with and without magnetic field. It is found that the thermal conductivity of nanofluid remarkably improves with augmentation of solid volume fraction. Moreover, by incrementing the nanofluid temperature, the thermal conductivity improves under no magnetic field, while it decreases at higher temperatures in attendance of magnetic field. The highest thermal conductivity improvement is achieved 26.4% at 60 °C and 3 vol.% of nanoparticles under no magnetic field and 36.5% under 400 G magnetic field which occurs at 20 °C and 3 vol.% of nanoparticles. Furthermore, an empirical correlation is derived to estimate thermal conductivity of MnFe 2 O 4 /water nanofluid in terms of magnetic field intensity, volume concentration, and temperature. [ABSTRACT FROM AUTHOR]

Abstract It has been more than two decades since the discovery of nanofluids-mixtures of common liquids and solid nanoparticles less than 100 nm in size. As a type of colloidal suspension, nanofluids are typically employed as heat transfer fluids due to their favorable thermal and fluid properties. There have been numerous numerical studies of nanofluids in recent years (more than 1000 in both 2016 and 2017, based on Scopus statistics). Due to the small size and large numbers of nanoparticles that interact with the surrounding fluid in nanofluid flows, it has been a major challenge to capture both the macro-scale and the nano-scale effects of these systems without incurring extraordinarily high computational costs. To help understand the state of the art in modeling nanofluids and to discuss the challenges that remain in this field, the present article reviews the latest developments in modeling of nanofluid flows and heat transfer with an emphasis on 3D simulations. In part I, a brief overview of nanofluids (fabrication, applications, and their achievable thermo-physical properties) will be presented first. Next, various forces that exist in particulate flows such as drag, lift (Magnus and Saffman), Brownian, thermophoretic, van der Waals, and electrostatic double layer forces and their significance in nanofluid flows are discussed. Afterwards, the main models used to calculate the thermophysical properties of nanofluids are reviewed. This will be followed with the description of the main physical models presented for nanofluid flows and heat transfer, from single-phase to Eulerian and Lagrangian two-phase models. In part II, various computational fluid dynamics (CFD) techniques will be presented. Next, the latest studies on 3D simulation of nanofluid flow in various regimes and configurations are reviewed. The present review is expected to be helpful for researchers working on numerical simulation of nanofluids and also for scholars who work on experimental aspects of nanofluids to understand the underlying physical phenomena occurring during their experiments. [ABSTRACT FROM AUTHOR]