Search

The electrochemical oxidation of the urea in near neutral pH is investigated on platinum electrode. It is shown that oxidation reaction is practically inhibited up to the potentials of â¼0.9Â V. The same reaction is investigated onto electrochemically obtained titanium dioxide nanotubes modified by hematite using facile, low-cost successive ion layer adsorption and reaction (SILAR) method. It is shown that such system possesses electrocatalytic activity at very low potentials, and activity can be further improved by the illumination of the electrode in the photo-assisted reaction. The possible application of the photoactive anode is considered in the application of urea based water electrolysis and urea based fuel cell. Keywords: Photoelectrochemical cell, Water electrolysis, Fuel cell, SILAR

An environmentally friendly cell using polypyrrole-air regenerative cathode and zinc as anode is investigated in the 3% sodium chloride solution. The cell can operate in different charge and discharge mode. Polypyrrole can be reoxidized (doped) with chloride anions either by using dissolved oxygen or by an external power supply, e.g., small photovoltaic cell. In that way, after discharge, capacity retaining can be achieved by using seawater as the electrolyte. During low discharge rate, the delicate balance between solid state diffusion-controlled dedoping and chemical oxidation of polypyrrole produced by hydrogen peroxide is achieved, generating stable voltage plateau. The cell is proposed to operate as a power supply for different sensor devices in two modes. In the low discharge mode (10-20 mA g(-1)), it can be used for data acquisition, and at the fast discharge mode (up to 2 A g(-1)) for collecting data transmission.

Polypyrrole (PPY) electrode was obtained by electrochemical oxidative polymerization of pyrrole on graphite electrode from aqueous electrolyte containing 0.1 mol dm–3 pyrrole monomer and 1.0 mol dm–3 HCl. Polymerization was achieved at the constant current density of 2 mA cm–2 during 1 h. The estimated active mass of PPY (assuming that the maximal doping degree of 0.33 was achieved and the polymerization efficiency of 100%) was 14 mg. Electrochemical characterization of PPY electrode was performed by galvanostatic experiments of charge (doping) and discharge (dedoping) with different current densities in the range between 0.5 and 1.5 mA cm–2. The experiments were performed in aqueous electrolyte containing 2.0 mol dm–3 NH4Cl and 1.1 mol dm–3 ZnCl2. Based on galvanostatic charge/discharge curves, following parameters of PPY electrode were evaluated: discharge capacity, specific discharge capacity, charge capacity, specific charge capacity, and Columbic efficiency. Both charge and discharge capacities were dependent on charge/discharge currents. The values decreased by increasing charge/discharge current, except for the lowest current density where Columbic efficiency exceeded 100%, which was explained by involvement of cations, from the electrolyte, in the doping process. An electrochemical cell in which PPY electrode served as a cathode and zinc electrode as the anode with an aqueous electrolyte containing 2.0 mol dm–3 NH4Cl and 1.1 mol dm–3 ZnCl2, was formed and relevant electrochemical and electrical parameters of the cell were estimated and discussed. Charge of the Zn|PPY cell was dependent on the charge/discharge current. Charge of the cell started between 0.5 and 0.7 V and proceeded up to 1.5 V, while the open circuit voltage of the fully discharged cell was 1.3 V. Specific discharge capacity of Zn|PPY cell, calculated based on discharge times, ranged from 95 to 70 mA h g–1, decreasing linearly with increasing discharge current density. On the other hand, calculated values of the theoretical capacity of the Zn|PPY cell was 105 mA g–1, meaning that practically 90% of the theoretical capacity can be achieved by discharging the cell with low current densities, while 67% of the theoretical capacity was obtained with the highest used current density. Based on Ragon parameters, the estimated values of specific energy that ranged between 46 and 68 W h kg–1, and the specific power between 125 and 380 W kg–1, Zn|PPY cell might be classified as a “supercapattery”. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON172046]

The fast reaction of forced hydrolysis of iron(III) nitrate in hypochlorite solution at room temperature, leads to the formation of mainly hematite, α-Fe2O3. Successive ion adsorption and reaction (SILAR) is applied to decorate an electrochemically formed TiO2 nanotube electrode. The anodic photoelectrochemical behavior of pure TiO2-NT’s and modified electrodes are investigated in a sulfate containing solution at pH = 9.2. It is shown that such a modification leads to an increase of anodic photoactivity, as well as that at the same current density, the photoelectrochemical cell with a modified electrode operates at a voltage lower by 0.7 V. The band gap and flat band potentials are estimated, and the structure of the band gap and possible charge transfer reactions and mechanism are discussed.

The electrochemically synthesized polypyrrole (PPy) is investigated as a possible active material of the low-cost aqueous based secondary power sources in combination with zinc, lead oxide, and lead sulfate. The discharge capacity of the polypyrrole in the chloride-based electrolyte (for the Zn|PPy cell) is in the range 110 mAh g −1 of PPy, while in the sulfate-based electrolyte ∼150 mAh g −1 of PPy (for the PbSO 4 |PPy and PPy|PbO 2 cells), which is close to the theoretically calculated values. Electrochemical and electrical parameters, reactions in the cells, specific capacity, specific capacitance, energy, and power, for the Zn|PPy, PPy|PbO 2 and PbSO 4 |PPy cells are determined. In addition, the energy efficiency, for the considered systems is estimated. Obtained values of the specific power and energy, could classified investigated systems as a battery type hybrid superacapacitors or “supercapattery”. Published version: [http://technorep.tmf.bg.ac.rs/handle/123456789/4221] This is the peer-reviewed version of the following article: Grgur B, Janačković M, Jugović B, Gvozdenović M. The initial characteristics of the polypyrrole based aqueous rechargeable batteries with supercapattery characteristics. in Materials Science and Engineering B-Advanced Functional Solid-State Materials. 2019;243:175-182. [https://doi.org/10.1016/j.mseb.2019.04.013]

The electrochemical characteristics of zinc–polyaniline (PANI) secondary cell in the electrolyte containing 0.8 M Na citrate, 0.3 M NH4Cl and 0.3 M ZnCl2 is investigated. Based on the measurements of potentials and voltage of the cell during charge/discharge for the currents in the range of 18 to 45 mA, the specific electrode capacity of 85 to 55 mA h g-1, the specific energy of 60–40 mW h g-1 and the specific power of 150–350 mW g-1, is determined. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON172046: Electrochemical synthesis and characterization of nanostructured functional materials for applications in new technologies]

Due to unique properties of intrinsically conducting polymers (ICP) such as: electrical conductivity, reversible electrochemistry, optical activity, biocompatibility, environmental and corrosion stability, they still represent a base for both theoretical and practical studies. The mentioned properties open up possibilities for practical application in the field of electrochemical systems for energy storage and conversion, sensors, biosensors, antistatic coatings, magnetic shielding, active corrosion protection etc. Bearing in mind that nanostructurization of materials lead to improvement of physical and chemical properties, there is a growing interest in the development of nanosized ICP. Nanosized ICP can be prepared by both chemical and electrochemical procedures. Although chemical synthesis is a common approach, there are also not a few studies of electrochemical synthesis of ICP. The aim of this paper is to review literature dedicated to electrochemical formation of nanostructured ICP with special attention dedicated to polyaniline and polypyrrole as the most popular ICPs.

The copper sulfide is successfully deposited onto electrochemically formed polypyrrole, by successive ion-adsorption and reaction (SILAR) processes. The photoelectrochemical behavior of the polypyrrole, copper sulfide and copper sulfide modified polypyrrole are investigated in the sulfide based solution, under cathodic and anodic polarization. The improvement of the photooxidation stability, as well as activity of copper sulfide modified polypyrrole is achieved. Such behavior is explained by recombination of electrons from Cu2-xS conducting band with the holes of the PPy LUMO. © 2015 Elsevier B.V. All rights reserved.

Corrosion protection using conventional coatings is the most used method. Application of polyaniline (PANI) as an inhibitor in conventional coating is based on its proven and well examined protective nature, with motivation for replacement of hazardous materials used as inhibitors. Experimental procedures for investigation of the influence of PANI in coatings are focused both on evaluation of physical properties of the coatings studied by FTIR, Raman and UV spectroscopy, thermogravimetric analysis, SEM and TEM microcopies, while the protective nature of the coating, applied at the first place on steel, is studied by accelerated corrosion testing using humidity and salt chamber, electrochemical impedance spectroscopy and polarization measurements upon immersion in corrosion media. Primena sistema klasičnih organskih prevlaka za zaštitu metala i legura od korozije je najrasprostranjeniji vid zašte. Primena inhibitora korozije na bazi polianilina (PANI) je zasnovana na njegovom eksperimentalno potvrđenom zaštitnom dejstvu. Osnovni motiv za primenu PANI je zamena ekološki neprihvatljivih materijala koji se korite kao inhibitori. Eksperimentalna istraživanja u ovoj oblsti bazirana su na proučavanju fizičkih svojstava prevlaka primenom spektoskopskih tehnika: FTIR, Ramanske spektroskopije i UV spektroskopije, termogravimetrijske analize, SEM i TEM mikroskopija, dok se ispitivanja zaštitnih svojstava prevlaka na baziraju na ubrzanim korozionim testovima primenom slane i vlažne komore, eksperimentima spektroskopije elektrohemijske impedancije i polarizacionim merenjima.

The aim of this paper was to investigate the possibility of using the copper anodes with high nickel content for electrolytic treatment of waste sulfuric acid copper electrolyte. Nickel content in each anode was about 10 wt. %. Lead, antimony, and tin content was within the limits ranged from 0.1 to 1.4 wt. %. Copper mass content in anodes was in the range from 86 to 90 wt. %, and was mathematical deference to 100 wt. %. Electrolytic processing was done in galvanostatic conditions at the current density of 250 A/m2, electrolyte temperature of 63 ± 2 ° C, duration of each test of 72 h. The mass of each anode was about 7 kg. The waste sulfuric acid electrolyte with concentration of 30 g dm3 Cu2+ ions and 225 g/dm3 SO4 2- ions was used as the working solution. Changing the anode mass, changing the content of copper and nickel ions in the working solution and the mass of obtained cathode deposit were the subject of discussion in this paper. The difference in weight of anode at the beginning and end of the process confirmed that the anodes are dissolved during the process. A significant reduction of Cu2+ ions concentration was achieved as well as an increase in concentration of Ni2+ ions in the working solution. Mass of cathode deposit, obtained during electrolytic refining of anode with the smallest impurity content, was greater than the mass of dissolved correspondent anode for about 2%. Mass of cathode deposit, obtained by refining the anode with the content of Pb + Sn + Sb from 1.5 to 3.5 wt. %, was less than the mass of dissolved correspondent anode by about 2 %.

Electroconducting polymers from the group of synthetic metals are extensively investigated due to numerous properties perspective in practical application. These materials may be synthesized by both chemical and electrochemical procedures. Chemical synthesis is suitable when bulk quantities of the polymer are needed and up to date it presents dominant commercial method of producing electroconducting polymers. Nevertheless, electrochemical synthesis has its advantages; it avoids usage of oxidants since conducting polymeric material is obtained at anode upon application of positive potential, leading to increased purity. On the other hand, since the polymer is deposited onto electrode, further electrochemical characterization is facilitated. Owing to actuality of the research in the field this texts aims to describe important aspects of electrochemical synthesis of electroconducting polymers, with special emphasis to polyaniline and polypyrrole. [Projekat Ministarstva nauke Republike Srbije, br. 172046]

The corrosion process of mild steel in the presence of benzoate-doped polyaniline coatings exposed to different environments (3% NaCl, atmosphere, and the Sahara sand) has been investigated. This system was also tested for cathodic protection and it has proven more efficient comparing to mild steel alone. Possible mechanisms of the corrosion protection of mild steel in the presence of a polyaniline-based coating in different corrosion media were also proposed. This is the peer-reviewed version of the article: Elkais, A.R., Gvozdenović, M.M., Jugović, B.Z., Grgur, B.N., 2013. The influence of thin benzoate-doped polyaniline coatings on corrosion protection of mild steel in different environments. Progress in Organic Coatings 76, 670–676. [https://doi.org/10.1016/j.porgcoat.2012.12.008]

Poly(aniline-co-(m-aminobenzoic acid)) was synthesized electrochemically at graphite electrode under galvanostatic conditions. Aqueous electrolyte for synthesis was consisted of HCl and different amount of aniline and m-aminobenzoic acid. The presence of the meta positioned carboxylic group in m-aminobenzoic acid influenced higher co-polymerization potential, different morphology and electrochemical behavior of copolymers compared to polyaniline. Electrochemical activity is achieved by proton exchange in neutral environment that can result in a faster charge/discharge process, which is in the case of PANI limited by slow anion exchange, making this material promising for consideration in super-capacitors and in biological system.

Electrochemically synthesized polyaniline (PANI) and lead dioxide have been investigated as electrode materials for PANI/1.1 M H 2 SO 4 ; 0.5 M (NH 4 ) 2 SO 4 /PbO 2 rechargeable cell. At constant current charge/discharge of the cell, the average discharge potential of 1.1 V, specific capacity of 50 mA h g −1 , specific energy of 55 W h kg −1 , and self discharge rate of 2.2% per day have been obtained.

The aim of this study is synthesis of copper-sulfate pentahydrate from the waste sulfuric acid solution-mother liquor generated during the regeneration process of copper bleed solution. Copper is removed from the mother liquor solution in the process of the electrolytic treatment using the insoluble lead anodes alloyed with 6 mass pct of antimony on the industrial-scale equipment. As the result of the decopperization process, copper is removed in the form of the cathode sludge and is precipitated at the bottom of the electrolytic cell. By this procedure, the content of copper could be reduced to the 20 mass pct of the initial value. Chemical characterization of the sludge has shown that it contains about 90 mass pct of copper. During the decopperization process, the very strong poison, arsine, can be formed, and the process is in that case terminated. The copper leaching degree of 82 mass pct is obtained using H2SO4 aqueous solution with the oxygen addition during the cathode sludge chemical treatment at 80 A degrees C +/- A 5 A degrees C. Obtained copper salt satisfies the requirements of the Serbian Standard for Pesticide, SRPS H.P1. 058. Therefore, the treatment of waste sulfuric acid solutions is of great economic and environmental interest. DOI: 10.1007/s11663-012-9721-8

This study is concerned with the partitioning of cellulolytic activity in the polyethylene glycol/dextran two-phase systems. In the system of 10% (w/w) polyethylene glycol 1500/5% (w/w) dextran 500,000/80% (w/w) crude enzyme at the pH 5, 100%, yield of cellulolytic activity from Penicillium sp. in the top phase was achieved in a single extraction step. Addition of KH2PO4 to this system at a concentration of 15 mmol/L improved the purification factor in the top phase for cellulolytic activity from crude preparation to a value of 2.6, although it had an adverse effect on the yield in the same phase. U radu je ispitana raspodela celulolitičke aktivnosti u vodenim dvofaznim sistemima polietilenglikol/dekstran. Maksimalno moguć 100% prinos celulolitičke aktivnosti dobijene kultivacijom Penicillium sp. postignut je u dvofaznom sistemu sastava 10% (m/m) polietilenglikol 1500/5% (m/m) dekstran 500000/ 80% (m/m) sirovi enzim na pH 5 u samo jednom koraku ekstrakcije. Dodatak KH2PO4 u koncentraciji 15 mmol/l u ovaj sistem, iako je smanjio raspodelu celulolitičke aktivnosti iz sirovog enzimskog preparata u gornju fazu sistema, poboljšao je faktor prečišćavanja u toj fazi na vrednost 2,6. Razlike u odzivu između celulolitičkih aktivnosti iz dva ispitivana izvora na promene faktora koji utiču na raspodelu mogu se objasniti različitom kompleksošću njihovih matriksa - komercijalnog, delimično prečišćenog, i sirovog neprečišćenog preparata dobijenog kultivacijom. Naime, i prisustvo samih kontaminenata može dodatno uticati na raspodelu enzimske aktivnosti.

Polyaniline (PANI) enzyme electrode was formed by immobilisation of Glucose oxidase (GOx) via glutaraldehyde into electrochemically polymerised PANI on graphite electrode. Electrochemical polymerisation of PANI on graphite was performed from aqueous solution of 1.0 mol dm(-3) HCl and 0.25 mol dm(-3) aniline at constant current density of 2.0 mA cm(-2). Hronopotentiometric curves of the PANI enzyme electrode obtained at current density of 10 mu A cm(-2) were recorded in different glucose concentrations. The linearity response range was between 1.0 and 5.0 mmol dm(-3) of glucose concentration. The estimated apparent Michaelis-Menten constant, was K-m(') = 0.30 mmol dm(-3), which is significantly lower than that of free enzyme.

The electrochemical synthesis of polyaniline (PANI) on mild steel, aluminum and copper from the sodium benzoate solutions has been investigated. It has been shown that thin, highly adherent, polyaniline films on the investigated metals could be obtained by anodic oxidation with current densities in the range of 0.5 and 1.5 mA cm-2. The corrosion behavior of mild steel, aluminum and copper with polyaniline coating in 0.5 mol dm-3 NaCl (pH 3) solutions, has been investigated by polarization technique. The corrosion current densities, porosity and protection efficiency was determined. It has been shown that polyaniline coating provided corrosion protection of all mentioned metals. U radu je ispitivana elektrohemijska sinteza polianilina (PANI) na mekom čeliku, aluminijumu i bakru iz rastvora natrijum-benzoata i monomera anilina. Ustanovljeno je da se tanki, dobro adherentni, filmovi polianilina mogu formirati na svim ispitivanim metalima pri anodnim gustinama struja od 0,5-1,5 mA cm-2. Ispitivano je koroziono ponašanje metala sa prevlakom polianilina u rastvoru 0,5 mol dm-3 NaCl (3%). Ustanovljeno je da ove prevlake pružaju korozionu zaštitu svim ispitivanim metalima u datoj korozionoj sredini.

Electrochemical synthesis of polyaniline (PANI) on aluminum electrode from aqueous Solution Of 0.25 mol dm(-3) aniline and 0.2 mol dm(-3) sodium benzoate has been investigated under potentiodynamic and galvanostatic conditions. Initial corrosion behavior of aluminum and PANI coated aluminum electrode exposed to 3% NaCl has been investigated using electrochemical potentiodynamic and impedance spectroscopy technique (EIS). It was shown that PANI coating initially provide corrosion protection of aluminum, decreasing the corrosion current density at least 15 times.

The influence of light of the mild steel corrosion in 3% NaCl solution with polyaniline coating based on the possibilities that polyaniline can generate photoelectrons, even in the laboratory conditions has been investigated. Ispitivan je uticaj svetlosti na koroziju mekog čelika sa prevlakom polianilina u 3% rastvoru NaCl sa pretpostavkom da polianilin može generisati fotoelektrone čak i u uslovima laboratorijskog osvetljenja.

Novel TiO2-PANI core-shell nanocomposite, prepared by in situ oxidative polymerization of aniline in the presence of TiO2 nanoparticles surface modified with vitamin B6, was used to reinforce epoxy resin. The size of prepared TiO2 nanoparticles and TiO2-PANI nanocomposite were determined by a transmission electron microscopy (TEM). The surface modification of TiO2 nanoparticles was confirmed by FTIR and UV-vis spectroscopy, while the morphology of PANI and TiO2-PANI nanocomposite was investigated by scanning electron microscopy (SEM). The influence of TiO2-PANI nanocomposite on glass transition temperature, dielectric and dynamic mechanical properties, thermooxidative stability, mechanical and anticorrosion properties of epoxy based nanocomposites was investigated and compared to the properties of epoxy/PANI nanocomposites. It has been observed that the glass transition temperature of epoxy resin increases after introduction of PANI and TiO2-PANI nanocomposite, as well as with increasing their content. Prepared nanocomposites exhibited higher value of dielectric constant than pure epoxy resin. Epoxy based coating containing TiO2-PANI nanocomposite showed lower dielectric loss, higher hardness and better anticorrosion properties than pure epoxy resin and epoxy/PANI nanocomposite. (C) 2016 Elsevier B.V. All rights reserved.

The most common disinfectants for water treatment are based on chlorine and its compounds. Practically, water treatments with chlorine compounds have no alternative, since they provide, in comparison to other effective processes such as ozonization or ultraviolet irradiation, high residual disinfection capacity. Unfortunately, all of chlorine-based compounds for disinfection tend to degrade during storage, thus reducing the concentration of active chlorine. Apart from degradation, additional problems are transportation, storage and handling of such hazardous compounds. Nowadays, a lot of attention is paid to the development of electrochemical devices for in situ production of chlorine dioxide or sodium hypochlorite as efficient disinfectants for water treatment. The most important part of such a device is the electrochemical reactor. Electrochemical reactor uses external source of direct current in order to produce disinfectants in electrochemical reactions occurring at the electrodes. Construction of an electrochemical device for water treatment is based on evaluation of optimal conditions for electrochemical reactions during continues production of disinfectants. The aim of this study was to develop a low-cost electrochemical device for the production of disinfectant, active chlorine, at the place of its usage, based on newly developed technical solutions and newest commercial components. The projected electrochemical device was constructed and mounted, and its operation was investigated. Investigations involved both functionality of individual components and device in general. The major goal of these investigations was to achieve maximal efficiency in extreme condition of elevated room temperature and humidity with a novel device construction involving coaxial heat exchanger at the solution inlet. Room operation of the proposed device was investigated when relative humidity was set to 90% and the ambient temperature of 38°C. The obtained results in such extreme operation conditions reveled that it was possible to obtain required concentration of 0.85% of active chlorine with maximal temperature of outlet electrolyte of 35.3°C, which is within the limits of optimal temperatures. [Projekat Ministarstva nauke Republike Srbije, br. 172046]

The potential characteristics of graphite felt electrodes, modified by iron oxide, for oxygen reduction are evaluated. Modification is carried out by Successive Ion Layer Adsorption and Reaction (SILAR) method, using a solution of ferric nitrate in methanol for the adsorption of ions, and a solution of sodium hypochlorite for reaction. The reaction activity of the oxygen reduction from the air, in sodium sulfate based solution varying the number of SILAR cycles, as well as the influence of pH is investigated. By comparing the activity with pure platinum, similar activity is obtained at pH = 9.2, as well as good electrode stability. Possible mechanism of the oxygen reduction on the graphite felt modified by iron oxide is discussed.

The electrochemically synthesized polypyrrole and lead-lead sulfate is examined as a potential electrodes for battery-type hybrid supercapacitors in acidic solution. The device exhibits battery-type behavior at low discharge rate, e.g. lt 0.5 A g(-1), and supercapacitors-type behavior at a higher discharge rate. Discharge in the specific current range of similar to 0.6-2.27 A g(-1) based on the active masses, can deliver capacity of 90-72 Ah kg(-1), energy of 58-40 Wh kg(-1) and power of 40-1350 W kg(-1), with the specific capacitance of the cell in the range of 300-250 F g(-1). The experimentally obtained values are compared with theoretical.

The potential application of electrochemically formed copper sulfide as horseradish peroxidase mediator in the enzymatic biofuel cell and anthraquinone AV109 dye as a fuel is investigated. The open circuit voltage of 0.52 V and short circuit current of similar to 3.6 mu A/cm(2) are obtained, with the maximum specific power of similar to 1 mu W/cm(2). The influence of internal resistance of the cell is discussed. Decolorization is investigated under open circuit potentials, and under external load of 3.31 k Omega conditions. In both cases, 40% of decolorization is achieved, but are three times faster under external load conditions. Specific energy during decolorization in such cell is estimated to 5 mWh/m(2). The possible mechanism of the power generation during decolorization of AV 109 dye is discussed.

The corrosion behavior and thermal stability of epoxy coatings electrodeposited on mild steel and on mild steel with electrochemically deposited polyaniline (PANI) film were investigated by electrochemical impedance spectroscopy (EIS) and thermo gravimetric analysis (TGA). The aim of the paper was to present new findings on the corrosion protection of mild steel by a duplex PANI/-epoxy coating in 3% NaCl solution and to determine the effect of thin PANI film on the protective properties of the coating. PANI film was deposited electrochemically on mild steel from an aqueous solution of 0.5 mol dm-3 sodium benzoate and 0.1 mol dm-3 aniline at a constant current density of 1.5 mA cm-2. Non-pigmented epoxy coatings on mild steel and on mild steel with PANI film were obtained by cathodic electrode position at constant voltage and stirring conditions. The resin concentration in the electrode position bath was 10 wt.% solid dispersion in water at pH 5.7. The applied voltage was 250 V, the temperature 26°C and the deposition time 3 min. It was shown that thin PANI film could be used to modify the surface of mild steel prior to epoxy coating deposition, due to the increased corrosion protection of a duplex PANI/epoxy coating comparing to an epoxy coating on mild steel in 3% NaCl solution. Koroziono ponašanje i termička stabilnost epoksidnih kataforetskih prevlaka na mekom čeliku i mekom čeliku sa elektrohemijski taloženim polianilinom (PANI) ispitivani su primenom metoda spektroskopije elektrohemijske impedancije i termogravimetrijske analize. PANI film na mekom čeliku je dobijen elektrohemijskim taloženjem iz vodenog rastvora 0,5 mol dm-3 Na-benzoata I 0,1 mol dm-3 anilina pod galvanostatskim uslovima, gustinom struje od j = 1,5 mA cm-2. Epoksidne prevlake na mekom čeliku I mekom čeliku sa PANI dobijene su elektroforetskim taloženjem u uslovima konstantnog napona uz mešanje. Pokazano je da dvoslojna PANI/epoksidna prevlaka na mekom čeliku ima značajno veću korozionu stabilnosti u 3% rastvoru NaCl u odnosu na epoksidnu prevlaku.

The objective of this research was to design an efficient continuously operated membrane reactor with a separation unit for egg white protein (EWP) hydrolysis and production of hydrolysates with improved antioxidant properties. For this purpose, a mechanically stirred tank reactor coupled with the polyethersulfone ultrafiltration module with a molecular weight cutoff of 10 kDa was employed. Several proteolytic enzymes have been tested in order to obtain the best quality of peptide-based formulations intended for human consumption. Among protease from Bacillus licheniformis (Alcalase), protease from Bacillus amyloliquefaciens (Neutrase), and protease from papaya latex (papain), the highest degree of hydrolysis (DH), as well as the best antioxidant properties of obtained hydrolysates, was achieved with Alcalase. The effects of operating variables such as enzyme/substrate ([E]/[S]) ratio, impeller speed, and permeate flow rate were further studied using response surface methodology (RSM) and Box–Behnken experimental design. Results obtained in RSM analysis confirmed that over the studied range [E]/[S] ratio, impeller speed and permeate flow rate had the significant effect on the DH and reactor capacity. The effects of different impeller geometries were also studied and four-bladed propeller stirrer enabled the highest DH. Antioxidant properties were analyzed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), by the 2,2′-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) radical scavenging activity, and by the linear voltammetry methods. Results show that the use of Alcalase in the membrane reactor system is of potential interest for the EWP hydrolysis and obtaining value-added egg products. © 2014, Springer Science+Business Media New York.

The protective abilities of composite coatings based on electrochemically and chemically formed polyaniline powder against the corrosion of mild steel were investigated. A polyaniline powder has been prepared in the form of an emeraldine base and benzoate salt through chemical dedoping and doping. The composite coatings using polyaniline powders, which were obtained through different routes, and base coatings, which were not corrosion-resistant, with different formulations were prepared and applied on mild steelsamples. The corrosion was investigated using an electrochemical impedance technique in 3% NaCl, andthe atmospheric corrosion was assessed in a humidity chamber. Emeraldine-benzoate salts, which area chemically synthesized polyaniline, offer the best protection with an optimal polyaniline concentration of approximately 5 wt%. The different corrosion behaviors were assessed relative to the presence of aniline oligomers in the samples after characterization using UV-vis spectrophotometry. Upon comparison between the corrosion behavior in 3% NaCl with commercial primer paint for iron and that with apaint containing 5 wt% PANI, the composite coating has superior anticorrosion characteristics. The mech-anism for the protection of mild steel from corrosion through composite polyaniline coatings was also considered. © 2014 Elsevier B.V. All rights reserved.

Immobilized lipase from Candida antarctica (Novozyme 435) was tested for the synthesis of various phenolic acid esters (ethyl and n-butyl cinnamate, ethyl p-coumarate and n-butyl p-methoxycinnamate). The second-order kinetic model was used to mathematically describe the reaction kinetics and to compare present processes quantitatively. It was found that the model agreed well with the experimental data. Further, the effect of alcohol type on the esterification of cinnamic acid was investigated. The immobilized lipase showed more ability to catalyze the synthesis of butyl cinnamate. Therefore, the process was optimized for the synthesis of butyl cinnamate as a function of solvent polarity (logP) and amount of biocatalyst. The highest ester yield of 60.7 % was obtained for the highest enzyme concentration tested (3 % w/w), but the productivity was for 34 % lower than the corresponding value obtained for the enzyme concentration of 1 % (w/w). The synthesized esters were purified, identified, and screened for antioxidant activities. Both DPPH assay and cyclic voltammetry measurement have shown that cinnamic acid esters have better antioxidant properties than cinnamic acid itself.

In recent years, great focus has been placed upon polymer thin films. These polymer thin films are important in many technological applications, ranging from coatings and adhesives to organic electronic devices, including sensors and detectors. Electrochemical polymerization is preferable, especially if the polymeric product is intended for use as polymer thin films, because electrogeneration allows fine control over the film thickness, an important parameter for fabrication of devices. Moreover, it was demonstrated that it is possible to modify the material properties by parameter control of the electrodeposition process. Electrochemistry is an excellent tool, not only for synthesis, but also for characterization and application of various types of materials. This book provides a timely overview of a current state of knowledge regarding the use of electropolymerization for new materials preparation, including conducting polymers and various possibilities of applications.

The polyaniline thin film electrode and powder have been synthesized on graphite electrodes from 0.5 M hydrochloric acid solution under galvanostatic conditions. The water insoluble and acetone soluble polyaniline mass fractions of the powder, as well as the polymerization efficiency, based on the emeraldine salt have been determined. The morphology of the obtained emeraldine salt powder has been investigated by the optical microscopy.

Electrochemical polymerization of polyaniline (PANI) coating on copper electrode was performed galvanostatically in the current density range between 0.50 and 1.25 mA cm(-2), from aqueous solution of 0.3 mol dm(-3) sodium benzoate and 0.2 mol dm(-3) aniline. The corrosion behavior of PANI coated copper and copper electrode exposed to 0.5 mol dm(-3) sodium chloride solution was investigated by potentiodynamic and electrochemical impedance spectroscopy techniques. It was observed that thin PANI (5 mu m) coating had provided efficient protection (similar to 96%) to copper in 0.5 mol dm(-3) sodium chloride solution. Unusual initial impedance behavior to that normally observed with conventional organic coatings was attributed to dedoping of benzoate anions from the polymer coating.

Electrochemical synthesis of polyaniline support for enzyme immobilization provides easier control over the properties of obtained polymer and reduced risk of biocatalyst inactivation with residues of toxic compounds. In the present study, immobilization of lipase from Candida rugosa on electrochemically synthesized PANI (activated with glutaraldehyde) resulted with high lipase loadings up to 93.7 mg of proteins per gram of dry support. The activation of support and immobilization were optimized, with respect to activity yield. The optimum concentration of glutaraldehyde was 2% (w/v) and optimum concentration of enzyme was 4 mg ml −1 . Modification of enzyme surface with carbodiimide and ethylenediamine was performed in order to increase concentration of amino groups. Aminated lipase exhibited higher specific activity (52%) and thermal stability (3 times) after immobilization, compared with non-modified lipase. Also, reusability of immobilized enzyme was significantly increased with amination, especially if immobilization was performed at pH 10, so in such a way obtained derivative retained 91% of activity after 15 reaction cycles.

Electrochemically formed thin film polyaniline (PANI) anode and lead dioxide (PbO2) cathode, obtained from sulfuric acid solution, for potential applications as electrode materials in PANI|H2SO4|PbO2 aqueous based rechargeable power sources, have been studied using cyclic voltammetry and galvanostatic techniques. Based on the investigations of half cell reactions, the simulation of the charge/discharge characteristic of the possible cell has been done. © 2008 Elsevier B.V. All rights reserved.

The corrosion behavior, sorption characteristics and thermal stability of epoxy coatings electrodeposited on mild steel (MS) and mild steel with electrochemically deposited polyaniline (PANI) film were investigated in 3% NaCl solution using electrochemical impedance spectroscopy (EIS) and thermogravimetric analysis (TGA). Electrochemical deposition of PANI film on mild steel was performed from aqueous solution of 0.5 M sodium benzoate and 0.1 M aniline at constant current density of 1.5 mA cm −2 . Epoxy coatings on mild steel and mild steel with PANI film were deposited at constant voltage. It was shown that during initial time of exposure to 3% NaCl, PANI/epoxy coating system on mild steel has lower values of pore resistance (obtained from EIS), greater amount of absorbed water and lower thermal stability (obtained from TGA) which indicate more porous structure comparing to epoxy coating on mild steel. During prolonged exposure to 3% NaCl, PANI/epoxy coating system exhibited increased corrosion protection of mild steel comparing to epoxy coating due to the barrier effect of PANI film and the influence of the dissolved molecular oxygen on cathodic and anodic reaction. Differences between corrosion behavior of epoxy coated and PANI/epoxy coated mild steel in acid and neutral solutions has been discussed.

The kinetics of the oxidation Of D-glucose to D-gluconic acid by bromine in aqueous solution were studied using potentiometric techniques and theoretical considerations of complex bromine-bromide-pH equilibria. The pH has a strong influence on reaction rate. At pH lt 8 the reaction is very slow, while in the pH range pH 8-9.5 the reaction is sufficiently fast and seems optimal for the reaction. The proposed active species at that pH region is hypobromous acid. At pH gt 9.5, the reaction is further accelerated due to the formation of hypobromite. The proposed kinetics expression for gluconic acid formation, based on the determined kinetic parameters at pH 9.24, is of the form dc(GA)/dt = 160c(2)(G)c(0)(HOBr)c(0)(H+)c(0)(Br)