Diaphragm Electrolysis Research Articles

Clean recovery of copper from waste printed circuit boards using ceric ammonium nitrate

A clean approach was proposed to recycle copper from waste printed circuit boards (WPCBs), which involved leaching, purification, and electrolysis. Ceric ammonium nitrate (CAN) was used as the leaching agent to dissolve copper from WPCBs, due to its strong oxidizing property and recyclability through electrolytic oxidation. The results showed that the copper leaching rate was 99.9 % under the optimized conditions.The leaching process of copper was in accordance with the mixed control model, and the apparent activation energy was 47.56 kJ/mol. After the leaching, the solution was purified to remove Ag and Sn by activated carbon, and the removal behaviors of Ag and Sn followed the pseudo-second-order model. Using the purified solution as the electrolyte to conduct the diaphragm electrolysis, copper with a purity of 99.998 % was produced at the cathode, and Ce3+ ions were simultaneously oxidized into Ce4+ ions at the anode. By using this process, copper was recycled from WPCBs, and CAN was regenerated.

INFLUENCE OF ELECTROCHEMICALLY ACTIVATED SOLUTIONS ON THE FATTY ACID PROFILE OF FOOD SYSTEMS

The emergence of new types and methods of food processing requires studying the impact on the compo-nents of food systems. Fish products are an important part of the human diet, but as a result of storage, their quality and safety indicators are reduced. An effective way to ensure the biological safety of fish raw materials is the use of electrochemically activated solutions (ECAS) obtained by high-voltage diaphragm electrolysis. The aim of the study was to study the effect of various concentrations of ECAS on the fatty acid profile of food systems using the example of fish oil from Atlantic salmon (Salmo salar) fillet during the shelf life. In the experiments, a ready-made ECAS with an active chlorine concentration (hereinafter Cach) of 500 mg/l (0.05%) was used, from which working ECAS were prepared with a dilution of 50% and 15%, which corresponds to Cach – 250 mg/l (0.025%) and Cach – 75 mg / l (0.0075%). The concentration of ECAS was selected experimentally in order to determine the optimal concentration at which the de-struction of fatty acids (hereinafter FA) of the studied samples did not occur. The determination was car-ried out by gas chromatography using a Crystal-2000M chromatograph. Comparison was made with con-trol samples. Identification of the peaks of FA methyl esters of the tested samples made it possible to de-termine the recommended working concentration of active chlorine ECAS equal to 75 mg/l, at which the content of polyunsaturated fatty acids does not statistically decrease. The research results can be used to ensure the quality and biological safety of fish fillets, taking into account the specific effects of ECAS on individual components of food systems.

Utilizing 3D Electrolysis Models to Link Transport to Cell Design and Performance

Computational fluid dynamics (CFD) has been employed extensively for modeling fuel cells, but electrolysis has lacked this degree of attention in literature. As electrolysis commercialization advances, the desire to use numerical methods to aid the engineering process grows. The work described in this presentation aims to link channel/manifold geometry, porous media design, and operating conditions to cell performance in the context of mass transport and identify important unknown input quantities to which models are particularly sensitive. CFD is applied to electrolysis systems to quantify the impact of two-phase flow patterns and porous media properties on energy losses, primarily those linked directly to the presence of the gas phase.3D models for proton exchange and alkaline electrolysis devices are summarized. For proton exchange electrolysis, a homogeneous two-phase model was built in order to estimate the species composition at the anode and how operating conditions and porous transport layer (PTL) properties influence distributions. The model suggests that cell performance is particularly sensitive to the evaporation rate and PTL permeability when the contribution of the gas-phase reaction is considered. A similar model was applied to alkaline diaphragm electrolysis to study effects of the manifolds on the flow distribution and thereby local performance. Current and gas crossover were correlated with cell geometry and altered by the cell potential and feed rate. Figure 1

Cyclobis(paraquat-p-phenylene) – mediated electrosynthesis of new-type nanocomposite of palladium nanoparticles with designated macrocyclic organic compound

A new type nanocomposite of palladium nanoparticle (PdNP) with macrocyclic organic compound cyclobis(paraquat-p-phenylene) (CBPQT4+) was obtained by CBPQT4+- mediated electrosynthesis in the MeCN/ 0.05 М Bu4NPF6 and MeCN (50 vol%) – H2O/ 0.05 М Bu4NCl media. The nanocomposite has a pseudorotaxane structure formed due to the donor-acceptor binding of an electron-donor metal particle inside the cavity of an electron-acceptor CBPQT4+. Theoretical calculations have shown that up to 10 Pd atoms can fit into the CBPQT4+ cavity and the energy of such interaction is ∼500 kJ/mol in the gas phase. In addition to the target process, dispersion of the Pd-anode (current efficiency ∼ 170%) to form PdNPs in solution occurs in electrolyses in a diaphragmless cell. The resulting particles combine together with CBPQT4+to form aggregates, the size of which in solution is 80–900 nm. In the absence of stabilizer cetyltrimethylammonium chloride (CTAC), particles with an average size of PdNPs equal to 6.1 ± 1.8 nm and size of Pd crystallites of 4.1 – 8.2 nm are formed. The addition of CTAC leads to increased binding of PdNP with CBPQT4+and a decrease in the size of PdNPs and Pd crystallites (4.9 ± 2.9 nm, 3.0 – 5.9 nm, respectively). Nanocomposites obtained in a diaphragm electrolysis process contain PdNPs and Pd crystallites (3.2 ± 1.3 nm, 2.2 – 3.8 nm) of the smallest size. Binding with CBPQT4+causes slow activation and a decrease in the catalytic properties of PdNPs in the test reaction of p-nitrophenol reduction with sodium borohydride compared to larger PdNPs (5.9 ± 1.4 nm, Pd crystallite size is 2.9 – 5.6) obtained in the MV2+- mediated electrosynthesis under the same conditions.

Effect of processing parameters on the properties of electrolytically prepared Mg(OH)2 powders

In this paper, Mg(OH)2 was prepared by the diaphragm electrolysis method using bischofite (MgCl2·6H2O). The influence of electrolysis process conditions such as current density, electrolysis temperature and electrolyte concentration on powder particle size is discussed. The electrolytic product Mg(OH)2 powder was characterized by laser particle size analysis, XRD, SEM, BET, XRF, and DSC-TGA. The results show that the particle size of Mg(OH)2 powder first increases and then decreases with increasing current density and reaches a maximum D50 value of 20.1 μm at a current density of 0.04 A cm−2. The Mg(OH)2 powder particle size first decreases, then increases and then decreases with increasing electrolysis temperature, at an electrolysis temperature of 60 °C and 70 °C, the particle size reaches a maximum D50 value of 23.8 μm and a minimum D50 value of 7.7 μm, respectively. The Mg(OH)2 powder particle size first increases and then decreases with increasing electrolyte concentration and reaches a maximum D50 value of 22.3 μm at an electrolyte concentration of 0.7 mol l−1. The Mg(OH)2 powder prepared at a current density of 0.3 A cm−2, electrolyte concentration of 0.3 mol l−1 and an electrolysis temperature of 30 °C shows an average particle size of 13.8 μm, a purity higher than 98.66%, and a sheet-like structure. The surface area is 58 m2 g−1. The Mg(OH)2 powder can be decomposed at 300 °C–400 °C and calcined at 400 °C for 2 h, through SEM and Scherrer formula calculation, the calcined product is nano-MgO powder with good crystallinity.

Effective metal-free electrooxidative thiocyanation of anilines

An original anodic C–H thiocyanation of anilines with NH4SCN has been developed, allowing to obtain the products in 88–98% yields under potentiostatic diaphragm electrolysis on glassy carbon electrodes at Eanode = 0.60 V and moderate consumption of electricity. The preliminary voltammetric analysis included the assessment of the changes in the thiocyanate ion curve after the addition of aniline, as well as the measurements of the potentials of the reagents and products, which gave insight into mechanisms of the process (formation of thiocyanate radical and thiocyanogen) and was necessary for its optimization.

Выбор коррозионностойких конструкционных материалов для оборудования получения каустической соды

The article considers the corrosion resistance of domestic and foreign materials, both the base metal and welded joints in the media of concentration of electrolytic alkalis in the range of NaOH concentrations from 12% to 99.5% and temperatures from 115 to 395°С. For testing, specimens of 2080 mm in size with transverse welds with two drilled holes were made from the material under study. polished and assembled into cassettes using nickel alloy rods. For the first time, comparative data on the corrosion state of structural materials during evaporation of electrolytic slits obtained by diaphragm electrolysis and electrolysis using a mercury cathode were obtained. The results of corrosion studies are quite well corrected with the experience of operating nickel pipes at the first stage of alkali concentration. The electrochemical heterogeneity of welded joints of alloys 33 and 201 was evaluated. The conducted studies of the corrosion resistance of alloys 201 and 33 under conditions of evaporation of NaOH obtained by mercury electrolysis confirmed the high corrosion resistance of nickel alloy 201 at the main stages of alkali concentration. The research results can be used as recommendations for the development of structural materials.

Electrochemical Degradation of Phenol by MnO2- Pd/C Gas-Diffusion Electrode

MnO2/C and Pd/C catalysts used for the MnO2- Pd/C gas-diffusion cathodes were prepared by redox, and characterized by transmission electronmicroscopy (TEM), X-ray photoelectron spectroscopy (XPS). The electrochemical degradation of phenol was surveyed in a diaphragm electrolysis system and a connected electrolysis system, feeding with air, making the most of four kinds of self-made gas-diffusion cathodes. It turns out the MnO2- Pd/C cathodes was better than other cathodes, and the degration efficiency reached 96.95% and 99.3% in two kinds of electrolysis systems, respectively, after reaction for 100min.

Effects of Co2+ in diaphragm electrolysis on the electrochemical and corrosion behaviors of Pb[sbnd]Ag and Pb anodes for zinc electrowinning

In this study, the influence of Co2+ (2 g/L) on the electrochemical behavior of cast Pb−Ag (0.6 wt%) anode and cast Pb anode was investigated in diaphragm electrolysis by galvanostatic polarization, cyclic voltammetry, and anodic polarization and with Tafel curves. In addition, analyses of the anodic weight loss, metal ion concentration, phase analysis, and scanning electron microscopy images of the oxide layer and substrate were also conducted. The results show that the diaphragm electrolysis cell completely prevented the metal ions in the anode chamber from penetrating into the cathode chamber. The Co2+ in the solution was gradually oxidized to Co3+ during the oxygen evolution reaction (OER), which facilitated the reduction of the potential of the OER, decreased the time for the potential of the Pb−Ag (0.6 wt%) anode and Pb anode to stabilize, and improved the corrosion resistance of the Pb−Ag (0.6 wt%) anode and Pb anode by weakening the oxidation of the anodic metal substrate during the OER.

Process control system based on a fuzzy controller

The object for the control system is an electrolysis plant for the production of chlorine, hydrogen and electrolytic alkali by the method of diaphragm electrolysis. It is necessary to develop an improved system for controlling the process of diaphragm electrolysis. To create a control system for the electrolysis process, a fuzzy controller with the following output parameters was developed: the percentage of opening of the electromagnetic valve for supplying NaCl solution to the electrolyzer, the percentage of opening of the actuator for supplying asbestos suspension, the percentage of opening of the control valve for draining NaCl solution through a special device, voltage value. Control output parameters control input parameters: anolyte level and caustic concentration. Controlling of the output parameters is based on the information received from the input sensors of the concentration of caustic and the level of anolyte. The control algorithm modeling is performed in the Matlab package. The programming of the Modicon M340 controller and its connection is made using the Unity Pro CASE system. An automated workstation for controlling the electrolysis process is performed in the Vijeo Citect SCADA system. The introduction of a multidimensional automated control system that controls the entire electrolysis process allowed us to solve the problem posed: optimal control of the process output parameters.

Effects of Ag+ in diaphragm electrolysis on oxygen evolution and corrosion behaviors of Pb and Pb[sbnd]Ag anodes

In this study, the effects of Ag+ (140 mg/L) in an electrolyte on the oxygen evolution and corrosion behaviors of Pb and PbAg (0.6 wt%) anodes in diaphragm electrolysis were investigated by utilizing a variety of tests and analyses, including galvanostatic polarization, mass increment, ion concentration, anodic polarization curve, phase analysis, and scanning electron microscopy of the oxide layer and substrate. The results show that an ion exchange membrane can effectively prevent Ag+ and Pb2+ from penetrating into the cathode chamber and depositing on the cathode. The addition of Ag+ in diaphragm electrolysis significantly lowers the overpotential of oxygen evolution reaction and improves the corrosion resistance of Pb and PbAg (0.6 wt%) anodes. This is mainly attributed to the formation of Ag2O2 on the surface of the anode, which provides good catalytic activity for the oxygen evolution reaction (Ag2O2 can form Ag2O2 hydrate in sulfuric acid solution, Ag2O2 hydrate loses electrons and H+ during electrification, and then Ag2O2 is formed again after electron rearrangement).

Characteristic analysis of a diaphragm electrolysis reactor with different electrode materials and concentrated degrees of brine

Characteristic analysis of a diaphragm electrolysis reactor with different electrode materials and concentrated degrees of brine

Performance evaluation of diaphragm electrolysis cell for alkali production

AbstractSeawater desalination technology is important for solving water shortage problems. RO desalination is the most frequently used process for obtaining fresh water from salt water. Electrolysis is also one way of reusing the enriched brine. Alkali-activated products can be made by producing NaOH after electrolysis. There are three kinds of brine electrolysis methods including diaphragm, membrane, and mercury methods. This study was conducted using a 200 mL electrolysis diaphragm cell. Tedlar bags were used in order to gather gases such as Cl2, O2, and H2. The head was less than 10 mm when a diaphragm with a 10 μm pore size was used. The data in this study was collected to analyze the relationships between concentration, chloride removal, and current density (CD). Our results showed that pore size influenced the head at the anode. Chloride removal was not high even when a high CD was applied. When the CD was 200 mA/cm2, the maximum NaOH concentration was 1.85%. However, the NaOH concentration was just...

Preparation for CeO2/Nanographite Composite Materials and Electrochemical Degradation of Phenol by CeO2/Nanographite Cathodes.

CeO2/nanographite (CeO2/nano-G) composite materials were got by chemical precipitation method with nanographite (nano-G) and cerous nitrate hexahydrate as raw materials. The microstructures of CeO2/nano-G composite materials were characterized by means of SEM, XRD, XPS and Raman. The cathodes were made by nano-G and CeO2/nano-G composite materials, respectively. The electrolysis phenol was conducted by the diaphragm cell prepared cathode and the Ti/RuO2 anode. The results indicated that the Cerium oxide is mainly in nanoscale spherical state, uniformly dispersed in the nanographite sheet surface, and there are two different oxidation states for elemental Ce, namely, Ce(III) and Ce(IV). In the diaphragm electrolysis system with the aeration conditions, the degradation rate of phenol reached 93.9% under 120 min's electrolysis. Ceria in the cathode materials might lead to an increase in the local oxygen concentration, which accelerated the two-electron reduction of O2 to hydrogen peroxide (H2O2). The removal efficiency of phenol by using the CeO2/nano-G composite cathode was better than that of the nano-G cathode.

Preparation for Mn/nanographite materials and study on electrochemical degradation of phenol by Mn/nanographite cathodes.

Mn/nanographite (nano-G) materials were got by chemical redox reaction and using nano-G, potassium permanganate and manganese acetate as raw materials. The microstructures and properties of nano-G and Mn/nano-G sheets were characterized by means of SEM, XPS, XRD and Raman. The results showed that manganese oxide nanoscale rod inlaid on the graphite layer surface, the manganese valence of Mn/nano-G was +4 and existed in the form of the mix crystal of α-MnO2 and γ-MnO2. Moreover, Mn/nano-G represented the preferable electro-catalysis performance. The electrolysis of phenol was conducted by using self-made cathode and the Ti/IrO2/RuO2 anode in the diaphragm cell. In the diaphragm electrolysis system with the aeration conditions, under 120 min's electrolysis, the degradation rate of 100 mg/L phenol of Mn/nano-G cathode reached 97.2%. Compared with the nano-G cathode, the Mn/nano-G had higher catalytic activity and better degradation rate of phenolic organics.

Electrocatalytic reduction of CO2 to formic acid on palladium-graphene nanocomposites gas-diffusion electrode.

Palladium-graphene nanocomposites catalysts for the conversion of CO2 to formic acid were prepared by means of sodium borohydride reduction of K2PdCl4 in a graphite oxide suspension, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV) technologies. The characterization results showed that graphene with a d-spacing of 3.82 Å was fabricated, and palladium nanoparticles with an average size of 3.8 nm were highly dispersed in the graphene sheets with amorphous structure. The cyclic voltammogram analyses indicated palladium-graphene nanocomposites catalysts posed high catalytic activity for the CO2 reduction and the rate-determining step was the CO2 diffusion process from bulk solution to electrode surface. Then the electrocatalytic reduction of CO2 was investigated in a diaphragm electrolysis device, using Pd/graphene gas-diffusion electrode as a cathode and a Ti/RuO2 net anode. The reduction process was optimized by the application of factorial design 2(3) (voltage, reaction time and electrolyte concentration) and response surface methodology (RSM). Optimum conditions for the production of formic acid were given as following: voltage: 5.1 V, reaction time: 50.4 min and electrolyte concentration: 0.5 mol L(-1). The yield of formic acid formation was 3157.7 mg L(-1) and Faraday efficiency was 86.9% under the optimum operation condition.

Electrochemical Degradation of Phenol by the Nanographite and Foam-Ni Composite Cathode

The degradation of phenol was demonstrate with a novel two-layer type cathode (TTC). For the fabrication of TTC, chitosan was firstly deposited on foam nickel, then one piece of the resulting foam-Ni film and one piece of nanographite(Nano-G) composite film were fasten to obtain the two-layer type nano-G︱foam-Ni cathode. The electrolysis phenol was conducted by self-made cathode and the Ti/IrO2/RuO2 anode in the diaphragm cell. The results showed that in the diaphragm electrolysis system with the aeration conditions, the degradation rate of phenol reached 97.15% under 120min’s electrolysis, when current density was 39 mA/cm2, initial pH value was 12 and electrolyte concentration was 0.1 mol/L. This two-layer type cathode could be reused without catalytic activity decrease, suggesting its potential application in the wastewater treatment.

Electrochemical Reduction of CO2 to Organic Acids by a Pd‐MWNTs Gas‐Diffusion Electrode in Aqueous Medium

Pd-multiwalled carbon nanotubes (Pd-MWNTs) catalysts for the conversion of CO2 to organic acids were prepared by the ethylene glycol reduction and fully characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) technologies. The amorphous Pd particles with an average size of 5.7 nm were highly dispersed on the surface of carbon nanotubes. Functional groups of the MWNTs played a key role in the palladium deposition. The results indicated that Pd-MWNTs could transform CO2 into organic acid with high catalytic activity and CO2 could take part in the reduction reaction directly. Additionally, the electrochemical reduction of CO2 was investigated by a diaphragm electrolysis device, using a Pd-MWNTs gas-diffusion electrode as a cathode and a Ti/RuO2 net as an anode. The main products in present system were formic acid and acetic acid identified by ion chromatograph. The selectivity of the products could be achieved by reaction conditions changing. The optimum faraday efficiencies of formic and acetic acids formed on the Pd-MWNTs gas-diffusion electrode at 4 V electrode voltages under 1 atm CO2 were 34.5% and 52.3%, respectively.

Preparation of multifunctional gas-diffusion electrode and its application to the degrading of chlorinated phenols by electrochemical reducing and oxidizing processes

Multifunctional gas-diffusion electrode with electrochemical reduction and oxidation properties was achieved based on the palladium-modified activated carbon (Pd/C). Pd/C catalysts were prepared using the formaldehyde reduction from nitric acid treated activated carbon and fully characterized by Boehm titration method, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and cyclic voltammetry (CV) techniques. The electrochemical degradation of three typical chlorinated phenols (4-chlorophenol, 2,4-dichlorophenol and pentachlorophenol) was investigated in a diaphragm electrolysis system with the Pd/C gas-diffusion electrode as a cathode, feeding firstly with hydrogen gas and then with air. The electrolysis system with 15% mass fraction nitric acid pretreated activated carbon showed better electrocatalytic activity compared to those from other mass fractions nitric acid, due to the active organic function groups increased on the surface of the activated carbon. When the ratio of Pd/C was low, Pd particles with an average size of 3.5nm were highly dispersed in the activated carbon with an amorphous structure. The Pd/C gas-diffusion cathode cannot only reductively dechlorinate chlorinated phenols by feeding hydrogen gas, but also accelerate the two-electron reduction of O2 to H2O2 by feeding air. Therefore, the removal efficiency of chlorinated phenols reached almost 100%, conforming to the sequence of 4-chlorophenol, 2,4-dichlorophenol and pentachlorophenol. The dechlorination of three chlorinated phenols exceeded 80% after 100min. For H2O2 and HO existed in the catholyte, the mineralization of organic pollutants in the cathodic compartment was better than that in the anodic compartment. Finally, chlorinated organic pollutants were efficiently degraded by the combined processes of reduction and oxidation in the present system.

Degradation of 4-chlorophenol by the anodic–cathodic cooperative effect with a Pd/MWNT gas-diffusion electrode

Pd/multi-walled carbon nanotubes (MWNTs) catalyst used for the gas-diffusion electrode was prepared by ethylene glycol (EG) reduction and characterized by the X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicated that Pd particles with an average size of 8.0 nm were highly dispersed in the MWNTs with amorphous structure. In a diaphragm electrolysis system with a Ti/RuO(2)/IrO(2) anode and the Pd/MWNT gas diffusion cathode, the degradation of 4-chlorophenol was performed by a combination of electrochemical reduction and oxidation. The combined process was in favor of improving 4-chlorophenol degradation efficiency. The optimum reaction conditions were as following: initial pH 7, aeration with hydrogen and air. Under the optimized electrolysis conditions the removal of 4-chlorophenol in the anodic and cathodic compartments were 98.5 and 90.5%, respectively. Additionally, based on the analysis of electrolysis intermediates using high performance liquid chromatography (HPLC) and ion chromatography (IC), the electrolysis degradation of 4-chlorophenol was proposed containing the intermediates, such as phenol, hydroquinone, benzoquinone, maleic acid, fumaric acid, succinic acid, malonic acid, oxalic acid, acetic acid and formic acid.