Synthesis of TiO2 Photoelectrode Nanostructures for Sensing and Removing Textile Compounds Rhodamine B

The study of the sensing and removal of Rhodamine B (RhB) textile compounds is the photoelectrocatalytic system applications development. RhB was used as a model to study the performance of TiO2 (NTiO2) photoelectrode nanostructures as environmentally friendly sensors. The synthesis of NTiO2 was carried out on the surface of the Titanium electrode by applying a potential bias of 25.0 V. The NTiO2 formed on the surface of the Titanium electrode (NTiO2/Ti) was characterized using SEM, XRD, FTIR, and Cyclic Voltammetry (CV). The formation of NTiO2 is characterized by the formation of a honeycomb-like tube on the Ti electrode surface. In addition, it is strengthened by diffractogram peaks at 2ϴ = 25 o and 48 o and IR absorption at wavenumbers of 3441.01 cm-1 (-OH groups) and 1629.85 cm-1 (Ti-O group). As for the results of sensing RhB using CV, it is known that RhB is oxidized on the surface of NTiO2/Ti with a value of Ea = 1.54 V. The oxidation process that occurs is controlled by the diffusion rate. Based on the results of photoelectrocatalytic RhB removal for 60 minutes, it was shown that using 0.10 M NaCl support electrolyte effectively increased the RhB removal rate. The decrease in RhB concentration during the photoelectrocatalytic removal process was 74.21%.

Electrochemical Polishing of Extruded and Laser Powder-Bed-Fused Inconel 718

ABSTRACT Electro-chemical polishing (ECP) was utilized to produce sub-micron surface finish on Inconel 718 parts manufactured by Laser Powder-Bed-Fusion (L-PBF) and extrusion methods. The L-PBF parts had very rough surfaces due to semi-welded powder particles, surface defects, and difference layer steps that were generally not found on surfaces of extruded and machined components. This study compared the results of electro-polishing of these differently manufactured parts under the same conditions. Titanium electrode was used with an acid-based electrolyte to polish both the specimens at different combinations of pulsed current density, duty cycle, and polishing time. Digital 3D optical profiler was used to assess the surface finish, while optical and scanning electron microscopy was utilized to observe the microstructure of polished specimens. At optimal condition, the ECP successfully reduced the surface of L-PBF part from 17 µm to 0.25 µm; further polishing did not improve the surface finish due to different removal rates of micro-leveled pores, cracks, nonconductive phases, and carbide particles in 3D-printed Inconel 718. The microstructure of extruded materials was uniform and free of processing defects, therefore can be polished consistently to 0.20 µm. Over-polishing of extruded material could improve its surface finish, but not for the L-PBF material due to defects and the surrounding micro-strain.

Dissolution of iron in sodium chloride solution during alternating current polarization

Iron compounds are widely used in many industries and engineering, and even in medicine. The existing methods of obtaining iron compounds are multi-stage and complex. The purpose of this work is to obtain iron (II) hydroxide and oxide from metal waste under alternating current action using one and two half-cycles. For the first time, the electrochemical behavior of iron electrode was studied by electrolysis method during alternating current polarization of industrial frequency in sodium chloride solutions. The iron polarization was carried out in pair with titanium, while the current density on the iron electrode varied in the range of 200-1200 A/m2, and on the titanium is in the range of 20-100 kA/m2. It is established that in the anode half-cycle of alternating current, iron is oxidized to form divalent ions. At this moment, the titanium electrode is in the cathode half-cycle, hydrogen is released on it, hydroxyl ions are formed in the cathode space. In the solution, ions interact with iron (II) ions to produce iron hydroxide. At temperatures above 600C, iron (II) hydroxide is dehydrated with the production of iron (II) oxide. The electrolysis was carried out in two electrolyzers connected to each other in parallel with the immersion of pair of “titanium-iron” electrodes into each electrolyzer. The iron dissolution occurs simultaneously in two half-cycles of alternating current and this approach is proposed for the first time. The process productivity increases by more than 1.5 times.

Electrochemiluminescence at 3D Printed Titanium Electrodes

The fabrication and electrochemical properties of a 3D printed titanium electrode array are described. The array comprises 25 round cylinders (0.015 cm radius, 0.3 cm high) that are evenly separated on a 0.48 × 0.48 cm square porous base (total geometric area of 1.32 cm2). The electrochemically active surface area consists of fused titanium particles and exhibits a large roughness factor ≈17. In acidic, oxygenated solution, the available potential window is from ~-0.3 to +1.2 V. The voltammetric response of ferrocyanide is quasi-reversible arising from slow heterogeneous electron transfer due to the presence of a native/oxidatively formed oxide. Unlike other metal electrodes, both [Ru(bpy)3]1+ and [Ru(bpy)3]3+ can be created in aqueous solutions which enables electrochemiluminescence to be generated by an annihilation mechanism. Depositing a thin gold layer significantly increases the standard heterogeneous electron transfer rate constant, ko, by a factor of ~80 to a value of 8.0 ± 0.4 × 10−3 cm s−1 and the voltammetry of ferrocyanide becomes reversible. The titanium and gold coated arrays generate electrochemiluminescence using tri-propyl amine as a co-reactant. However, the intensity of the gold-coated array is between 30 (high scan rate) and 100-fold (slow scan rates) higher at the gold coated arrays. Moreover, while the voltammetry of the luminophore is dominated by semi-infinite linear diffusion, the ECL response is significantly influenced by radial diffusion to the individual microcylinders of the array.

ELECTROCHEMICAL BEHAVIOR OF CUPRONICKEL ELECTRODE IN ACIDIC MEDIA

The electrochemical properties of the cupronickel electrode polarized by an alternating current in an aqueous solution of hydrochloric acid were studied for the first time. The electrochemical dissolution of cupronickel was carried out in a polarization mode with a frequency of 50 Hz in pairs with a titanium electrode. The current efficiency of dissolution of Cu-Ni alloys dependence on the current density at the titanium (20-120 kA/m2) and cupronickel (200-1200 A/m2) electrodes, the concentration of a hydrochloric acid solution (0.5-5.0 M), the electrolysis duration (0.5-1.75 h) and the alternating current effect (50-300 Hz) were considered. It was observed that the current efficiency of the alloy dissolution decreases linearly with increasing current density at the cupronickel electrode, while the current density at the titanium electrode passes through a maximum value at 60 kA/m2. The dependence of the alloy dissolution on the acid concentration was studied, and the reaction order was calculated. The reaction orders for the formation of copper (I) and nickel (II) ions accounted for 0.95 and 0.85, respectively. As the frequency of the alternating current increased, the current efficiency of the cupronickel electrode dissolution changed significantly. It has been shown that high current frequencies do not provide the required anodic half-cycle duration for the oxidation reaction of the metals, as the periods change very rapidly. It was found that electrolysis is effective at a frequency of 50 Hz AC. It was observed that the dissolution rate of the copper-nickel alloy increases with increasing solution temperature. It was found that the dissolution of cupronickel in an aqueous solution of hydrochloric acid by the temperature-kinetic method takes place in the diffusion-kinetic mode. Ideally, the current efficiency values were 59% for Cu (I) ions and 15% for Ni (II) ions.

Generation of active Co(III) and peroxodiphosphate by synergistic electrocatalytic system with phosphate and the mediator cobalt(II) and its degradation performance

The promising synergistic electrocatalytic system of phosphate (PO43−) with the mediator cobalt(II) (for short E-Co(II)-PO43−) was employed to degrade cationic dye methylene blue (MB). The exploration in the electrocatalytic process revealed that the main intermediate active oxidation products were Co(III), accompanied with hydroxyl radicals and peroxodiphosphates (P2O84−). Their synergistic electrocatalytic degradation rate to MB and total organic carbon (TOC) was up to 100 and 60% in 40 min, respectively, which was 5 times and 2.6 times that in a direct electrocatalytic system, correspondingly. The degradation process of the E-Co(II)-PO43− system on MB started with the bond being broken at the N-C junction of the MB molecule and intermediate active oxidation substances being generated, such as phenothiazine, 2-amino-5-(N-methylformamide) benzene sulfonic acid and N1,N1-dimethyl-1,4 diaminobenzene. Then, the intermediates were degraded into aniline, phenol and benzene sulfonic acid, and eventually decomposed into inorganic substances like CO2 and water. The electrocatalytic degradation mechanism of E-Co(II)-PO43− system on MB was the combination of indirect oxidation of the intermediate oxidants like Co(III), P2O84− and the hydroxyl radical with direct electrocatalysis on the platinum titanium electrode, where the electrocatalytic oxidation of Co(III) was dominant.

Wireless electrochemiluminescence at functionalised gold microparticles using 3D titanium electrode arrays

Wireless electrochemiluminescence is generated from functionalised gold microparticles using interdigitated, 3D printed, titanium arrays as feeder electrodes. Active transport and intense electric fields leads to bright electrochemiluminescence.

Recovery of Copper and Cyanide from Copper-cyanide Solution by Direct Electrolysis

Using direct electrolysis method, the recovery of copper and cyanide from high concentration copper cyanide solution was researched. The distribution of copper cyanide species was calculated by stability constants and balance equation. The results showed that the cupric ion was confirmed to generate at low potential (<0.4V) on the titanium electrode coated with iridium and tantalum oxides during the electrolysis process, which led to the oxidation of cyanide and the precipitate obtained on the anode was proved to be cupric hydroxide by XRD at high potential. The copper was recovered by direct electrowinning, the recovery of copper increased with increasing temperature, which reached 80% at 70°C; but the loss of cyanide was serious, the free cyanide concentration was significantly lower than original value.

Electrochemical Degradation of Reactive Red 195 from its Aqueous Solution using RuO2/IrO2/TaO2 Coated Titanium Electrodes

The electrochemical oxidation of reactive red 195 from aqueous solution was carried out using titanium electrode in an electrochemical cell reactor. The effect of different operating parameters such as dye concentration, current density, electrolyte concentration, pH and stirring speed were investigated. The UV-visible spectroscopy confirmed the removal and degradation of reactive red 195. Three different supporting electrolytes such as NaCl, NaNO3 and Na2SO4 were used for electrolysis and NaCl were found to be effective for the removal of reactive red 195 dye from its aqueous solution. The maximum percentage of colour removal was 94%, under the optimum operating conditions with electrolyte (NaCl) concentration 0.075 M, current density 25 mA/cm2, pH 5 and stirring speed of 250 rpm. This method was found to be relatively more effective to the conventional treatment techniques.

ELECTROCHEMICAL BEHAVIOR OF SILVER IN A SULPHURIC ACID SOLUTION

In recent years, alternating current has been widely used in various fields of chemical and electrochemical technology. When a symmetric alternating current passes through an electrochemical cell, in principle there should be no visible changes, since the product restored to the cathode half-period should be oxidized back to the anodic half-period. However, depending on the conditions of electrolysis, electrode material, etc. a purposeful course of the electrochemical process is possible. The paper shows the distinctive features of electrochemical processes occurring on a silver electrode during electrolysis by industrial alternating current in a solution of sulfuric acid by the method of rational mathematical planning. The optimal conditions for the dissolution of silver are determined by studying the effect of current density at the electrodes, the concentration and temperature of the electrolyte, the duration of the electrolysis and the frequency of the alternating current. It is shown that when polarized with an alternating current of silver in a pair with a titanium electrode, the process of passivation of the silver electrode is eliminated, and the rate of dissolution of the metal increases.