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In this study, we examine the movement of ions that are in a water solution which flows along a duct, due to the existence of an electric field, taking into account the size of the ions, a phenomenon known as the steric effect. We compare the results from the above model with the classical one (the one that uses the Boltzmann distribution where ions are considered dimensionless) for various parameters such as surface charge density, electric field and differential capacitance. It is shown that for dilute water solutions (1019–1024 ions/m3 final concentration at the center of the duct), with ions of valence z = 1 (let us say saline water), steric effects become important for potentials greater than 1 V, and the phenomenon is more pronounced at higher concentrations. Furthermore, the steric effect model is applied to the calculation of the percentage of reduction in ion concentration in the main volume of the solution as a function of duct width for various electrode potentials and initial ion concentrations. Removal times are also calculated using Modified PNP equations which take into account steric effects. It is found that with a potential of 2.6 V, a 96% reduction in ions is achieved in the main volume of the solution for duct width 0.1 mm for 1021 ions/m3 final concentration at the center of the duct within approximately 1.6 s, while the percentage drops to 80% for duct width 1 mm. For smaller potentials, no noticeable decrease in concentration is observed, while for higher potentials, there are more impressive results, but we must be very careful because there is the case of other electrochemical phenomena taking place. The results are better when reducing the width of the duct, but relatively large widths are considered for the method to be practically applicable. With the increase in the concentration of the ions, their reduction percentage in the main volume of the solution decreases but remains significant up to 1023 ions/m3 final concentration at the center of the duct. In addition, the completion time is shown to be proportional to the duct width. Therefore, for example, with the other parameters the same (2.6 V, 1021 ions/m3) but with L ~ 1   mm , the completion time can be estimated to be approximately 16 s. This observation enables us to estimate the completion time for different duct widths, eliminating the need for repeated numerical computation of the MPNP equations. [ABSTRACT FROM AUTHOR]

The article discusses the issue of water scarcity and the need for energy-efficient desalination systems to provide potable water to populations facing water shortages. It explores various physical and chemical methods of desalination, including distillation, membrane processes, and chemical treatments. The article also highlights a special issue focused on small-scale technologies for desalination and water purification, which includes articles on topics such as slow sand filtration, solar distillation, evaporation-assisted humidification-dehumidification cycles, electric field force for ion removal, and a self-regenerating solar evaporation system. These technologies offer potential solutions for individual or small group usage, as well as emergency scenarios. [Extracted from the article]

The recovery of anthocyanins from winery wastewater constitutes an attractive option for both environmental and commercial valorization, as food colorants and nutraceutical ingredients. In this study, the electric field induced ion drift method is proposed as a promising technique for the purification of wastewater solutions as well as for the accumulation of anthocyanins. The cation of the anthocyanidin malvidin (C17H15O7+) was selected as the most representative of winery waste, in order to develop a theoretical model. The main principle of the model is based on the displacement of charged anthocyanin ions, under the influence of an electric field vertical to the flow of the solution, and their accumulation on the side walls of a conductor. Apparatus inducing an electric field drift is described, and critical parameters (i.e., final spatial distribution of concentration, electric field intensity, surface charge density, and potential) were calculated. The proposed model succeeded in reducing anthocyanin concentration by more than 90%, for duct widths smaller than 1 mm in the bulk of the solution, for applied potentials φ(0) in the range of 0.2–0.4 V and target concentrations equal to 1.2 × 10−3 mol/m3. [ABSTRACT FROM AUTHOR]

A water purification method using a static electric field that may drift the dissolved ions of heavy metals is proposed here. The electric field force drifts the positively charged metal ions of continuously flowing contaminated water to one sidewall, where the negative electrode is placed, leaving most of the area of the duct purified. The steady-state ion distributions, as well as the time evolution in the linear regime, are studied analytically and ion concentration distributions for various electric field magnitudes and widths of the duct are reported. The method performs well with a duct width less than 10−3 m and an electrode potential of 0.26 V or more. Moreover, a significant reduction of more than 90% in heavy metals concentration is accomplished in less than a second at a low cost. [ABSTRACT FROM AUTHOR]

Desalination and water purification through the ion drift of salted water flow due to an electric field in a duct is perhaps a feasible membrane-free technology. Here, the unsteady modulation of ion drift is treated by employing the Poison–Nernst–Plank (PNP) equations in the linear regime. Based on the solution of the PNP equations, the closed-form relationships of the charge density, the ion concentration, the electric field distribution and its potential are obtained as a function of position and time. It is found that the duration of the ion drift is of the order of one second or less. Moreover, the credibility of various electrical circuit models is examined and successfully compared with our solution. Then, the closed form of the surface charge density and the potential that are calculated without the linear approximation showed that the compact layer is crucial for the ion confinement near the duct walls. To test this, nonlinear solutions of the PNP equations are obtained, and the limits of accuracy of the linear theory is discussed. Our results indicate that the linear approximation gives accurate results only at the fluid's bulk but not inside the double layer. Finally, the important issue of electric field diminishing at the fluid's bulk is discussed, and a potential method to overcome this is proposed. [ABSTRACT FROM AUTHOR]