Electrooxidation of 4-clorphenol on modified lead dioxide anodes

The electrochemical oxidation of 4-chlorophenol on lead dioxide anodes micromodified by ions of iron group has been investigated. As follows from the data obtained, the rate of oxidation of organic substances on the anode materials involved is proportional to the number of reactive oxygen species in the near-electrode zone (OH–radicals) formed during the electrolysis as intermediates in water oxidation and participating in subsequent homogeneous chemical reactions with organic substrates in the bulk. The O1s peak on X– Ray photoelectron spectra was used to evaluate the amount of inert and labile oxygencontaining particles on undoped and doped PbO2 . Doping of lead dioxide with nickel leads to a significant increase in the number of labile oxygen-containing particles on the surface of the electrode, while iron modification leads to the opposite effect – an increase in the amount of inert oxygen-containing particles. The anodic oxidation of 4-chlorophenol yields a rather large number of intermediate products. The main intermediates include benzoquinone and maleic acid which was confirmed by high-performance liquid chromatography. The micromodification of lead dioxide with metal ions of iron group leads to a significant change in the electrocatalytic activity of oxide materials. The activity grows in the following sequence of modifying ions: PbO2<Co–PbO2<Fe–PbO2<Ni–PbO2

Pharmacological evaluation and preclinical studies of hypochlorous acid solution

The article presents materials on the electrochemical synthesis of hypochlorous acid and its pharmacological and toxicological evaluation. In the market of veterinary drugs, special attention has been paid to long-known, potent detoxifying antimicrobial agents based on active oxygen obtained by the electrolysis method. In addition to a broad spectrum of antimicrobial action, such drugs have several other advantages, especially the biogenic nature, which causes the absence of allergic reactions. New electrocatalysts were proposed for the electrochemical synthesis of hypochlorous acid, which was produced according to the following method using a combined electrochemical-pyrolytic method. VT1-0 technical titanium was used as a current collector. The current collectors were subjected to several preliminary preparation steps, such as NaOH degreasing and etching in 6 M HCl. Initial nanotubes were obtained by anodizing Ti foil in ethylene glycol with 0.3 wt.% ammonium fluoride and 2 vol.% water for 4 hours. The electrochemical reduction was carried out in 1 M HClO4 by cathodic polarization for 1 hour. Later, a thin discontinuous layer of platinum or consecutive layers of platinum-palladium were applied to the base by electrodeposition. Nitrite electrolytes for platinization and phosphate-palladation were used for this purpose. Depending on the task, platinum, and palladium on the ground's surface varied from 0.1 to 2.0 mg/cm2. The obtained material was heat-treated in an air atmosphere. At this stage, the surface layers of composites were formed due to the oxidation of the base and encapsulation of platinum and palladium particles in titanium oxide. It was established that the solution of hypochlorous acid, obtained by the electrolysis method, is a low-hazard substance that belongs to the fourth class of toxicity. Its half-lethal dose (DL50) is not determined. The fact that, in nature, hypochlorite acid is formed by granulocytes of neutrophils involved in the last link of phagocytosis confirms that the resulting solution is low-toxic, environmentally safe, and incapable of causing side effects and distant consequences. The obtained results proved the perspective of using new technology for producing hypochlorite acid for veterinary medicine; its development is highly relevant, clinically expedient, and economically justified

The comparative study of electrocatalytic activity of various anode materials in respect to the oxidation of nitroanilines

The comparative study of electrocatalytic activity of DSA, lead dioxide and F-PbO2 has been performed. It has been shown that the processes of electrochemical oxidation of nitroanilines on investigated materials occur qualitatively the same and differ only in the rate. This suggests the invariability of the mechanism of their oxidation on different materials that allows one for a correct comparison of their electrocatalytic activity. The maximum interest for the electrochemical destruction of nitroanilines represents lead dioxide electrodes modified by fluorine to which a rate constant of p-nitroaniline oxidation increases in 3 times compared with nonmodified electrodes

Мaterial selection and optimization of conditions for electrooxidation of nitrofurazone: a comparative study of tin and lead dioxides

The electrochemical oxidation of nitrofurazone with SnO2, doped by platinum group metals, and pure PbO2 has been investigated. Тhe oxidation rate of nitrofurazone with PbO2-anode is 5.3 times higher compared to doped SnO2 anodes. It was found that the presence of 1; 2 and 3 g l−1 NaCl in electrolyte affects the efficiency of the electrooxidation process in the case of doped SnO2 anodes, the oxidation rate of nitrofurazone increases by 2.3; 3.7; 5.8 times, respectively. Using of doped SnO2 in chloride-containing media allows one to achieve the same rate of destruction of nitrofurazone as when using lead dioxide. Moreover, SnO2 doped electrodes are characterized by the production of a large number of hypochlorous acid and have a higher service life compared to PbO2 in such harsh condition

Розробка методів контролювання якості розчину гіпохлоритної кислоти, отриманої методом електрохімічного синтезу

The article presents materials on developing quality control methods for hypochlorite acid obtained by electrochemical synthesis. Electrochemical synthesis of hypochlorous acid was carried out using a combined electrochemical-pyrolytic method. The electrocatalytic activity of the obtained materials in the hypochlorite acid synthesis reaction was evaluated under the electrolysis of 0.05 M NaCl solutions in a duct cell with a Ti cathode at 25 ºС. The cathode area was varied, so the cathode current density was 40 mA/cm2. The pH of the solutions was monitored with a pX-150MI universal ionometer. The volumetric current density in the channel cell was 2.4 A/dm3, and the volumetric rate of solution supply was 9.5 l/h. The authors developed an original method of iodometric titration, which is based on the sequential determination of the content of hypochlorite ions, their total content with chlorite ions, and the total content simultaneously with chlorite and chlorate ions. The content of individual components of the mixture is determined as the difference between the total content of ions and the content of hypochlorite ions. The iodometric method of titration of oxidants is based on the reaction of replacing oxygen-containing compounds of chlorine with elemental iodine with its subsequent titration with standard solutions of sodium thiosulfate. It is proposed to fix the endpoint of the titration potentiometrically, which allows you to speed up the analysis, and it is also relatively easy to automate it using an automatic titrator. The content of oxygen-containing compounds in the solutions depends on the oxidation conditions and the specified operating modes of the electrochemical catalyst. The solution's acidity determines the presence of hypochlorous acid and can be calculated based on the equilibrium constant of its dissociation. The developed analysis methods will allow the control of the quality of veterinary drugs based on hypochlorous acid obtained by electrochemical synthesis.У статті подано матеріали щодо розробки методів контролю якості гіпохлоритної кислоти, отриманої методом електрохімічного синтезу. Електрохімічний синтез гіпохлоритної кислоти проводили за використання комбінованого електрохімічно-піролітичного методу. Електрокаталітичну активність одержуваних матеріалів у реакції синтезу гіпохлоритної кислоти оцінювали в умовах електролізу 0,05 М розчинів NaCl у протоковій комірці з Ti-катодом за температури 25 ºС. Площа катоду варіювалася таким чином, щоб катодна щільність струму складала 40&nbsp;мА/см2. рН розчинів контролювали іономіром універсальним pX-150МІ. Об’ємна густина струму в протоковій комірці була 2,4 А/дм3, об’ємна швидкість подачі розчину – 9,5 л/год. Авторами розроблена оригінальна методика йодометричного титрування, що ґрунтується на послідовному визначенні вмісту гіпохлорит-іонів, їх сумарного вмісту з хлорит-іонами та сумарного вмісту одночасно з хлорит- та хлорат-іонами. Вміст окремих компонентів суміші визначають як різницю між сумарним вмістом іонів та вмістом гіпохлорит-іонів. Йодометричний метод титрування окисників ґрунтується на реакції заміщення кисневмісних сполук хлору елементарним йодом з його подальшим титруванням стандартними розчинами тіосульфату натрію. Кінцеву точку титрування запропоновано фіксувати потенціометрично, що дозволяє прискорити аналіз, а також порівняно легко автоматизувати його за використання автоматичного титратора. Вміст кисневмісних сполук у розчинах залежить від умов окиснення та заданих режимів роботи електрохімічного каталізатору. Присутність гіпохлоритної кислоти визначається кислотністю розчину і може бути розрахована на основі константи рівноваги її дисоціації. Розроблені методи аналізу дозволять контролювати якість ветеринарних препаратів на основі гіпохлоритної кислоти, отриманої методом електрохімічного синтезу

Electrodeposition of Ce-doped PbO2

An investigation is reported on lead dioxide electrodeposition from methanesulfonate electrolytes, that addnl. contg. Ce3+ ions. It is shown, that the ion additive influences on kinetics of PbO2 formation without changing of process mechanism. During the deposition lead dioxide electrodes are formed micromodified by cerium with different physico-chem. properties as compared to traditional PbO2-anodes. Electrocatalytical reactivity of the electrodes in respect to oxygen evolution was investigated

Bi-doped PbO2 anodes: Electrodeposition and physico-chemical properties

The influence of bismuth ions on kinetics of lead dioxide electrodeposition from methanesulfonate elec-trolytes and physico-chemical properties of obtained coatings were studied. Experimental results areconsistent with a mechanism previously proposed in the literature for lead dioxide electrodeposition.The presence of bismuth ions in the electrodeposition solution causes a decrease of rate constants oflead dioxide formation due to co-adsorption phenomena. Deposits from solutions containing bismuthions appear shiny dark grey, and show good adhesion to metal support. SEM images reveal a compactstructure with spindle-shaped submicron and nanosized crystals and X-ray diffractograms demonstratedthat incorporation of bismuth diminishes the size of crystal particles. Oxygen evolution was investigatedto test electrocatalytic activity. It is shown, that oxygen overpotential on modified electrodes is signifi-cantly higher than on non-modified PbO2-electrode, which depends on bismuth content in deposit andsegregation of bismuth that induces surface heterogeneity due to sites with different electroactivity forwater oxidation. © 2013 Elsevier Ltd