Andrei Kolesnikov

The role of surfactants in the electroflotation extraction of copper, nickel, and zinc hydroxides and phosphates

The effect of various surfactants on the physicochemical parameters (particle size and zeta potential) of the disperse phase of copper, nickel, and zinc hydroxides at concentrations of cationic, anionic, and nonionic surfactants of 2, 10, 50, and 100 mg/L at pH of 9.5–10.5 was studied. The efficiency of their electroflotation extraction into a flotation froth was determined in a laboratory electroflotation module with antiwear oxide electrodes with efficiency of higher than 95% (initial concentration 50 mg/L, in the form of flotation sludge, processing time no more than 30 min, current density 0.2 A/L).

Nanopowders Production in the Plasmachemical Reactor: Modelling and Simulation

A mathematical model capable of determining suitable operating conditions to produce TiO2 nanoparticles with specified average diameter is presented. The model consists of mass, momentum and energy conservation equations. Particle dynamics processes under consideration include particle formation by nucleation, growth by both condensation and coagulation as well as the loss of the product particles due to deposition on the reactor wall. The aim of this model is to predict the effect of inlet temperature and reactants concentrations on the average diameter of TiO2 nanoparticle products taking into account particle deposition on the wall due to thermophoresis. Strong non-linear coupling between energy and mass balance equations makes numerical integration of the stiff ordinary differential equations (ODE) a problem. The simulation results obtained provide useful information about the influence of the operational conditions (initial temperature and TiCl4 concentration) and particle wall deposition rate on the average nanoparticle diameter at reasonable computational time. The performance of the present monodisperse model was validated by comparing its predicted results with previously published numerical data. Good correlations between the predicted and numerical results were achieved.

Microscopical characterizations of nanofiltration membranes for the removal of nickel ions from aqueous solution

The nanofiltration (NF) process is electrostatically governed and the surface free energy plays a key role in the separation of particulates, macromolecules, and dissolved ionic species. Streaming potential measurement and the surface charge mapping by Kelvin probe atomic force mircoscopy (AFM) have been carried out. Forces of interaction near the surface of nanofiltration membranes were further studied by a force spectroscopy using atomic force microscopy. The two membranes used are more negatively charged at high pH values; hence the higher the solution chemistry, the higher and faster will be adhesion of ions on the surface of the nanofiltration membranes. It was observed that the three acquired signals from non-contact AFM (contact potential difference, amplitude and phase) were rigorously connected to the surface structure of the nanofiltration membranes. In addition to the surface structure (roughness), electrostatic interactions can also enhance initial particle adhesion to surfaces of nanofiltration membranes. The performance of the NF membranes was further investigated for the removal of nickel ions from aqueous solution, and the results were correlated to the mechanical responses of the nanofiltration membranes obtained from AFM and the streaming potential measurement.

Theoretical performance of nanofiltration membranes for wastewater treatment

Abstract Mechanisms of ionic transport in nanofiltration are poorly known. Modelling can be used to predict membrane performance, to reveal separation mechanisms, to select appropriate membranes, and to design processes. Several models have been proposed to describe nanofiltration membranes. Some models rely on simple concepts, while other models are more complex and require sophisticated solution techniques. Here, we review predictive models used for characterizing nanofiltration membranes for the separation of wastewater. The most popular model uses the extended Nernst–Planck equation, which describes the ionic transport mechanisms in details. Results obtained by using the extended Nernst–Planck equation show that the performance of nanofiltration membranes is strongly dependent on charge, steric, and dielectric effects.

Electroflotation purification of wastewater from copper and nickel ions in the presence of surface-active compounds and oil products

This work is devoted to the electroflotation purification of wastewater from copper and nickel ions in the presence of surface-active compounds (SACs) and oil. The kinetics of these processes were studied. It was shown that the presence of oil decelerates the initial stage of the process of extraction of nickel(II) and copper(II) hydroxides. SACs do not affect the extraction of copper hydroxide and the process is intensified for nickel hydroxide. The possibility of extracting metal ions as phosphates was demonstrated.

Characterization of Two Nanofiltration Membranes for the Separation of Ions from Acid Mine Water

We evaluated nanofiltration for separation of ions from acid mine drainage (AMD), using two composite nanofiltration membranes (Nano-Pro-3012 and NF90) as examples of the polyamide class of acid-stable membranes. The structure of the NF membranes was characterized by scanning electron and atomic force microscopy. The NF90 displayed a higher permeate flux than Nano-Pro-3012, with higher relative roughness at both pH values. Both membranes suitably rejected most of the metals found in the AMD, but the Nano-Pro-3012 membrane proved unsuitable for sulphate removal.两种分离酸性矿山废水离子的纳米渗透膜用Nano-Pro-3012和NF90两种合成纳米膜作为酸稳定聚酰胺膜为例,评价了它们对酸性矿山废水(AMD)离子的分离效果。用扫描电镜和原子力显微镜观察NF膜结构。NF90膜比Nano-Pro-3012膜拥有更高渗透通量且在相同pH值条件下膜强度也更高。研究证明,两种膜都适于阻止酸性废水中多数金属离子通过,但Nano-Pro-3012膜更适于去除硫酸盐。ZusammenfassungWir bewerteten die Nanofiltration als Methode zur Abtrennung von Ionen aus saurem Grubenwasserunter Verwendung von zwei Komposit-Nanofiltrationsmembranen (Nano-Pro-3012 and NF90) als Beispiele für säurestabile Polyamid-Membranen. Die Struktur der Nanofiltrationsmembranen wurde durch Scanning-Elektronenmikroskopie und Atomkraftmikroskopie charakterisiert. NF90 zeigte einen höheren Permeatfluss als Nano-Pro-3012 mit höherer relativer Unschärfe bei beiden pH-Werten. Beide Membranen hielten hinreichend die meisten der im sauren Grubenwasser gefundenen Metalle zurück. Nano-Pro-3012 erwies sich allerdings als ungeeignet für die Rückhaltung von Sulfat.ResumenHemos evaluado la nanofiltración de iones de drenaje ácido de minas (AMD), usando 2 membranas de nanofiltración de composite (Nano-Pro-3012 y NF90) como ejemplos de membranas de poliamida resistentes a medio ácido. La estructura de las membranas NF fue caracterizada por microscopía electrónica de barrido y microscopía de fuerza atómica. La NF90 mostró un mayor flujo de permeación que Nano-Pro-3012, con mayor rugosidad relativa a ambos valores de pH. Ambas membranas rechazaron la mayoría de los metales presentes en el AMD, pero la membrana Nano-Pro-3012 mostró ser inadecuada para la remoción de sulfato.

Self-Healing Polymeric Composite Material Design, Failure Analysis and Future Outlook: A Review

The formation of micro-cracks and crack propagation is still an acute problem in polymer and polymer composites. These micro-cracks usually occur while the materials are manufactured or serviced. The development and coalescence of these cracks reduces the lifespan and brings about a catastrophic failure of the materials. Novel scientific research on polymeric self-healing is emphasised in a number of publications, which consist of contributions from many of the prominent researchers in this area. Progress in this field can eventually enable scientist to construct new flexible materials that both monitor the material’s integrity and repair the deformed material prior to the occurrence of any fatal failures. This report describes recent trends that have been used in material science and computational methods to mitigate the development of micro-cracks and crack propagation in polymer composites.

Metal Oxides: Promising Materials for Electrochemical Processes

The electrochemical behavior of electrodes with an active layer comprised of TiO2, IrO2, RuO2, and SnO2 is studied. The zero-current potentials are determined. Curves of the rates of chlorine and oxygen release at the anode versus the composition of the electrode are presented.

Performance Of An Acid Stable NanofiltrationMembrane For Nickel Removal FromAqueous Solutions: Effects Of Concentration,Solution PHAnd Ionic Strength

The performance of a nanofiltration membrane for the removal of the nickel ion was studied as a function of the nickel concentration, solution pH, and the background ionic strength of the solution. Nanofiltration is investigated as a means to determine to what extent the nickel ions could be removed from acid mine drainage; thus the effect of solution chemistry on nanofiltration performance is investigated. Higher fluxes (47.6l/m²/h) were experienced at the lower nickel concentration (10mg/l) than at the higher (28.9l/m²/h) nickel concentration (100mg/l). Higher nickel ion rejections (97.3%) were obtained at the higher nickel concentration (100mg/l) than at the lower nickel concentration (93.6%). Higher flux was obtained at the higher pH (pH 4) with a 0.01M NaCl background solution than at lower pH (pH 3) when a 0.05M NaCl was used as background solution. Higher nickel ion rejections were obtained at higher pH (pH 4) for the two ionic strength background solutions. Higher fluxes were also obtained with the lower NaCl background solution. Slightly higher ion rejections were obtained with the lower NaCl background concentration. It therefore appears that this nanofiltration membrane should be successfully applied for the removal of nickel ions from acid mine drainage.

Modeling of heat and mass transfer in LaNi5 matrix during hydrogen absorption-desorption cycle

Packed bed reactors using metal hydride are attracting a lot of attention as potential hydrogen storage systems. Some operational and design variables are major constraints to obtain a proper infl ow/outfl ow of hydrogen into a metal hydride reactor. These variables include packed bed thermal conductivity, porosity, pressure and temperature distributions in the reactor during the absorption/desorption cycle. They also cause a mechanical stress induced by temperature gradient. In this paper, two dimensional models are implemented in COMSOL multiphysics to simulate the hydrogen fl ow, pressure and temperature distributions in the packed bed reactor during absorption/desorption cycle. Also, stresses in porous metal hydride induced by temperature variation in the heating/cooling cycle were evaluated. A possible effect of stress induced, porosity changes on diffusion and heating of hydrogen in both radial and axial direction in packed bed is discussed. The model consists of a system of partial differential equations (PDE) describing structural mechanics of stress, heat and mass transfer of hydrogen in the porous matrix of the packed bed reactor.