Tailoring the Surface Chemistry of Activated Carbon Cloth by Electrochemical Methods

This paper presents a systematic study of the effect of the electrochemical treatment (galvanostatic electrolysis in a filter-press electrochemical cell) on the surface chemistry and porous texture of commercial activated carbon cloth. The same treatments have been conducted over a granular activated carbon in order to clarify the effect of morphology. The influence of different electrochemical variables, such as the electrode polarity (anodic or cathodic), the applied current (between 0.2 and 1.0 A) and the type of electrolyte (HNO3 and NaCl) have also been analyzed. The anodic treatment of both activated carbons causes an increase in the amount of surface oxygen groups, whereas the cathodic treatment does not produce any relevant modification of the surface chemistry. The HNO3 electrolyte produced a lower generation of oxygen groups than the NaCl one, but differences in the achieved distribution of surface groups can be benefitial to selectively tune the surface chemistry. The porous texture seems to be unaltered after the electro-oxidation treatment. The validity of this method to introduce surface oxygen groups with a pseudocapacitive behavior has been corroborated by cyclic voltammetry. As a conclusion, the electrochemical treatment can be easily implemented to selectively and quantitatively modify the surface chemistry of activated carbons with different shapes and morphologies.

A continuous electrolytic process for the production of beryllium metal /

The continuous production of beryllium metal by low-temperature fused salt electrolysis into a continuously circulating mercury cathode has been demonstrated. The product is amenable to direct hot pressing or to powder preparation by distilling off the mercury. The production of pure beryllium chloride in good yield by direct chlorination of beryllium oxide has also been demonstrated.

Hawkins electrical guide. Questions, answers & illustrations; a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications; a practical treatise,

"Credit is largely due to Frank D. Graham ... for the authorship of the Guides, and for the original sketches illustrating electrical principles and construction."--Pref. to no. 1.

A method of studying electrode potentials and polarization,

Running title: Electrode potentials.

Thermodynamik und kinetik der körper,

Vol. 3 issued in 2 parts, 1905-08.

The oxidation states of the elements and their potentials in aqueous solutions,

"First printing November, 1938."

Electrochemical chloride extraction to halt corrosion of reinforcement

This thesis presents results of experiments designed to study the effect of applying electrochemical chloride extraction (ECE) to a range of different hardened cement pastes. Rectangular prism specimens of hydrated cement paste containing sodium chloride at different concentrations were subjected to electrolysis between the embedded steel cathodes and external anodes of activated titanium mesh. The cathodic current density used was in the range of 1 to 5 A/m2 with treatment periods of 4 to 12 weeks. After treatment, the specimens were cut into sections which were subjected to pore-solution expression and analysis in order to determine changes in the distribution of free and total ionic species. The effect of the ECE treatment on the physical and microstructural properties of the cements was studied by using microhardness and MIP techniques. XRD was employed to look at the possibility of ettringite redistribution as a result of the accumulation of soluble sulphate ions in the cement matrix near the cathode during ECE. Remigration of chloride which remains after the ECE treatment and distribution of other ions were studied by analysing specimens which had been stored for several months, after undergoing ECE treatment. The potentials of the steel cathodes were also monitored over the period to detect any changes in their corrosion state. The main findings of this research were as follows: 1, ECE, as applied in this investigation, was capable of removing both free and bound chloride. The removal process occurred relatively quickly and an equilibrium between free and bound chlorides in the specimens was maintained throughout. At the same time, alkali concentrations in the pore solution near the steel cathode increased. The soluble sulphate ionic concentration near the cathode also increased due to the local increase in the pH of the pore solution. 2, ECE caused some changes in physical and microstructural of the cement matrix. However these changes were minimal and in the case of microhardness, the results were highly scattered. Ettringite in the bulk material well away from the cathode was found not to increase significantly with the increase in charge passed.3, Remigration of chloride and other ionic species occurred slowly after cessation of ECE with a resultant gradual increase in the Cl-/OH- ratio around the steel.4, The removal of chloride from blended cements was slower than that from OPC.

Synthesis of hydrazine by the fixation process

A critical review of the literature concerning organic derivatives of hydrazine, the ammonia-chlorine reaction and the electrolytic formation of hydrazine has been carried out. Apparatus was constructed to study the electrolysis of liquid ammonia, the formation of chloramine and the fixation of chloramine with a ketone to form an isohydrazone. In the latter case the reaction was carried out in a 3" diameter stirred tank and also in a 1" diameter, 2' high column reactor where the liquid phase was continuously recirculated. Two methods of analysis of azines and isohydrazones in a ketone solution have been developed. One is a colorimetric technique using p-dimethylaminobenzaldehyde and the other involves the hydrolysis of the organic derivative to hydrazine sulphate. Hydrazine was detected in low concentration in some of the electrolytic experiments carried out but it was concluded that this method did not show sufficient promise to warrant further investigation. The gas phase formation of chloramine and acetone isohydrazone has also been studied but in this system difficulties were encountered with the chlorine jet blocking with ammonium chloride. The formation of isohydrazones in a stirred tank reactor has been investigated in some detail and the effect of several parameters was determined. The yield was found to be extremely sensitive to chlorine concentration and in order to obtain yields of more than 90 per cent, the molar concentration of chlorine in the gas phase had to be of the order of 5 per cent. An optimum temperature in the region of 0°C was also detected. These results disagree with those quoted in previous studies but extensive experimental work has confirmed the information presented in this thesis. It has also been shown that at high yields the chloramine formation reaction took place in the gas phase.

Electrocoating of carbon fibres:a route for interface control in carbon fibre reinforced poly methylmethacrylate?

A simple method of creating defined PMMA and poly (MMA-co-Cz) electrocoatings on carbon fibres is described. The electrodeposition of poly methylmethacrylate (PMMA) onto unsized, unmodified carbon fibres was performed by simple constant current electrolyses of methylmethacrylate (MMA) monomer in dimethylformamide (DMF) solutions and the 'pur' liquid monomer using sodium nitrate and lithium perchlorate as supporting electrolytes. The presence of polymeric coatings successfully attached to the carbon fibres was verified by scanning electron microscopy and photoelectron spectroscopy (XPS). Performing the electrolysis in dilute MMA in DMF solutions ([MMA]

Estudo da participação das espécies fortemente oxidantes produzidas durante a oxidação eletroquímica de corantes usando eletrodo de diamante dopado com boro: função das propriedades eletroquímicas do eletrodo e condições experimentais

The textile industry is one of the most polluting in the world (AHMEDCHEKKAT et al. 2011), generating wastewater with high organic loading. Among the pollutants present in these effluents are dyes, substances with complex structures, toxic and carcinogenic characteristics, besides having a strong staining. Improper disposal of these substances to the environment, without performing a pre-treatment can cause major environmental impacts. The objective this thesis to use a technique of electrochemical oxidation of boron doped diamond anode, BDD, for the treatment of a synthetic dye and a textile real effluent. In addition to studying the behavior of different electrolytes (HClO4, H3PO4, NaCl and Na2SO4) and current densities (15, 60, 90 and 120 mA.cm-2 ), and compare the methods with Rhodamine B (RhB) photolysis, electrolysis and photoelectrocatalytic using H3PO4 and Na2SO4. Electrochemical oxidation studies were performed in different ratio sp3 /sp2 of BDD with solution of RhB. To achieve these objectives, analysis of pH, conductivity, UV-visible, TOC, HPLC and GC-MS were developed. Based on the results with the Rhodamine B, it was observed that in all cases occurred at mineralization, independent of electrolyte and current density, but these parameters affect the speed and efficiency of mineralization. The radiation of light was favorable during the electrolysis of RhB with phosphate and sulfate. Regarding the oxidation in BDD anode with different ratio sp3 /sp2 (165, 176, 206, 220, 262 e 329), with lower carbon-sp3 had a longer favoring the electrochemical conversion of RhB, instead of combustion. The greater the carbon content on the anodes BDD took the biggest favor of direct electrochemical oxidation

Aplicação da tecnologia eletroquímica para a remoção e monitoramento de metais pesados em efluentes aquosos

Heavy metals are present in industrial waste. These metals can generate a large environmental impact contaminating water, soil and plants. The chemical action of heavy metals has attracted environmental interest. In this context, this study aimed to test t he performance of electrochemical technologies for removing and quantifying heavy metals. First ly , the electroanalytical technique of stripping voltammetry with glassy carbon electrode (GC) was standardized in order to use this method for the quantificatio n of metals during their removal by electrocoagulation process (EC). A nalytical curves were evaluated to obtain reliability of the determin ation and quantification of Cd 2+ and Pb 2+ separately or in a mixture. Meanwhile , EC process was developed using an el ectrochemical cell in a continuous flow (EFC) for removing Pb 2+ and Cd 2+ . The se experiments were performed using Al parallel plates with 10 cm of diameter (  63.5 cm 2 ) . The optimization of conditions for removing Pb 2+ and Cd 2+ , dissolved in 2 L of solution at 151 L h - 1 , were studied by applying different values of current for 30 min. Cd 2+ and Pb 2+ concentrations were monitored during electrolysis using stripping voltammetry. The results showed that the removal of Pb 2 + was effective when the EC pro cess is used, obtaining removals of 98% in 30 min. This behavior is dependent on the applied current, which implies an increase in power consumption. From the results also verified that the stripping voltammetry technique is quite reliable deter mining Pb 2+ concentration , when compared with the measurements obtained by atomic absorption method (AA). In view of this, t he second objective of this study was to evaluate the removal of Cd 2+ and Pb 2+ (mixture solution) by EC . Removal efficiency increasing current was confirmed when 93% and 100% of Cd 2+ and Pb 2+ was removed after 30 min . The increase in the current promotes the oxidation of sacrificial electrodes, and consequently increased amount of coagulant, which influences the removal of heavy metals in solution. Adsortive voltammetry is a fast, reliable, economical and simple way to determine Cd 2+ and Pb 2+ during their removal. I t is more economical than those normally used, which require the use of toxic and expensive reagents. Our results demonstrated the potential use of electroanalytical techniques to monitor the course of environmental interventions. Thus, the application of the two techniques associated can be a reliable way to monitor environmental impacts due to the pollution of aquatic ecosystems by heavy metals.

Tecnologia eletroquímica como tratamento alternativo de efluentes derivados da indústria têxtil e petroquímica

In this work, the treatment of wastewater from the textile industry, containing dyes as Yellow Novacron (YN), Red Remazol BR (RRB) and Blue Novacron CD (NB), and also, the treatment of wastewater from petrochemical industry (produced water) were investigated by anodic oxidation (OA) with platinum anodes supported on titanium (Ti/Pt) and boron-doped diamond (DDB). Definitely, one of the main parameters of this kind of treatment is the type of electrocatalytic material used, since the mechanisms and products of some anodic reactions depend on it. The OA of synthetic effluents containing with RRB, NB and YN were investigated in order to find the best conditions for the removal of color and organic content of the dye. According to the experimental results, the process of OA is suitable for decolorization of wastewaters containing these textile dyes due to electrocatalytic properties of DDB and Pt anodes. Removal of the organic load was more efficient at DDB, in all cases; where the dyes were degraded to aliphatic carboxylic acids at the end of the electrolysis. Energy requirements for the removal of color during OA of solutions of RRB, NB and YN depends mainly on the operating conditions, for example, RRB passes of 3.30 kWh m-3 at 20 mA cm-2 for 4.28 kWh m-3 at 60 mA cm-2 (pH = 1); 15.23 kWh m-3 at 20 mA cm-2 to 24.75 kWh m-3 at 60 mA cm-2 (pH 4.5); 10.80 kWh m-3 at 20 mA cm-2 to 31.5 kWh m-3 at 60 mA cm-2 (pH = 8) (estimated data for volume of treated effluent). On the other hand, in the study of OA of produced water effluent generated by petrochemical industry, galvanostatic electrolysis using DDB led to the complete removal of COD (98%), due to large amounts of hydroxyl radicals and peroxodisulphates generated from the oxidation of water and sulfates in solution, respectively. Thus, the rate of COD removal increases with increasing applied current density (15-60 mAcm-2 ). Moreover, at Pt electrode, approximately 50% removal of the organic load was achieved by applying from 15 to 30 mAcm-2 while 80% of COD removal was achieved for 60 mAcm-2 . Thus, the results obtained in the application of this technology were satisfactory depending on the electrocatalytic materials and operating conditions used for removal of organic load (petrochemical and textile effluents) as well as for the removal of color (in the case of textile effluents). Therefore, the applicability of electrochemical treatment can be considered as a new alternative like pretreatment or treatment of effluents derived from textiles and petrochemical industries.

Análise experimental de danos em pistões de motor à gasolina operando com adição de gás hidróxi

The addition of hydrogen gas as an alternative fuel source has been widely used, as well reported in scientific literature. Today, several experiments are underway for the use of hydrogen generators (electrolysers) demand for motor vehicles. In all these products their ads manufacturers claim that this provides a reduction of fuel consumption, reduces the emission levels of toxic gas by the discharge and improves engine life. This research analyzes the physical structure of engine components using electrolysis on demand. To this end, a stationary system was fitted with a power generator of electricity, drum roller and adapted two electrolyzers: a dry cell and wet cell other. In steps observation were consumption analyzes in four work load ranges and observing the piston engine, which has been cut and analyzed by Optical Microscopy (OM), Scanning Electron Microscopy and Dispersive Energy (SEM-EDS), X – Ray Diffraction (XRD) and Confocal Microscopy, the stationary system in each step. The results showed a considerable reduction in fuel consumption and a high corrosion in the original factory piston constituted of aluminum-silicon alloy. As corrosion barrier was made a plasma nitriding in the piston head, which proved resistant to attack by hydrogen, although it has presented evidence also, of having been attacked. It is concluded that the automotive electrolysers can be a good choice in terms of consumption and reducing toxic gas emissions, but the material of the combustion chambers of vehicles must be prepared for this purpose.

Avaliação do tratamento eletroquímico (direto e indireto) como alternativa de degradação do corante azul de metileno

Textile industry has been a cause of environmental pollution, mainly due to the generation of large volumes of waste containing high organic loading and intense color. In this context, this study evaluated the electrochemical degradation of synthetic effluents from textile industry containing Methylene Blue (AM) dye, using Ti/IrO2-Ta2O5 and Ti/Pt anodes, by direct and indirect (active chlorine) electrooxidation. We evaluated the influence of applied current density (20, 40 and 60 mA/cm2 ), and the presence of different concentrations of electrolyte (NaCl and Na2SO4), as well as the neutral and alkaline pH media. The electrochemical treatment was conducted in a continuous flow reactor, in which the electrolysis time of the AM 100 ppm was 6 hours. The performance of electrochemical process was evaluated by UV-vis spectrophotometry, chemical oxygen demand (COD) and total organic carbon (TOC). The results showed that with increasing current density, it was possible to obtain 100 % of color removal at Ti/IrO2-Ta2O5 and Ti/Pt electrodes. Regarding the color removal efficiency, increasing the concentration of electrolyte promotes a higher percentage of removal using 0,02 M Na2SO4 and 0,017 M NaCl. Concerning to the aqueous medium, the best color removal results were obtained in alkaline medium using Ti/Pt. In terms of organic matter, 86 % was achieved in neutral pH medium for Ti/Pt; while a 30 % in an alkaline medium. To understand the electrochemical behavior due to the oxygen evolution reaction, polarization curves were registered, determining that the presence of NaCl in the solution favored the production of active chlorine species. The best results in energy consumption and cost were obtained by applying lower current density (20 mA/cm2 ) in 6 hours of electrolysis.