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An anodic oxidation process with graphite anode coated with lead dioxide (G/β-PbO2) was optimized for the degradation of methylene blue (MB) and the treatment of real textile wastewater. The G/β-PbO2 anode was prepared by the electrochemical precipitation method. The scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analyses confirmed the successful coating of graphite substrate with the β-PbO2 film. The effect of four independent variables including pH, reaction time, current density, and electrolyte concentration of Na2SO4 on the performance of the electrochemical oxidation system was modeled by using a complete central composite design and was then optimized by genetic algorithm method. The accuracy of the proposed quadratic model by CCD was confirmed with p-value 0.9. The optimum conditions for solution pH, reaction time, current density, and Na2SO4 electrolyte concentration were obtained to be 5.75, 50 min, 10 mA/cm2, and 78.8 mg/L, respectively. In these conditions, the experimental removal efficiencies of MB using G/β-PbO2 and graphite anodes were 96.2% and 68.3%, respectively. The electrochemical removal of MB using both G/β-PbO2 and graphite anodes well followed the pseudo-first-order reaction (R2 > 0.9). Cyclohexane, cyclohexa-2,5-dien-1-ylium, and N-(sec-butyl) aniline were the most abundant intermediates identified by LC-MS analysis. However, the complete mineralization of MB was achieved in 60 min. The optimized anodic oxidation process successfully improved the biodegradability of real textile wastewater ( B O D / C O D > 0.4 ).

Based on thermodynamic calculations a potential/pH diagram for the Pb/H2SO4/H2O system is plotted. It defines the pH ranges of formation of the different phases and electrode systems, but the system Pb/H2SO4/H2O is kinetically controlled as well. During the anodic polarization of a lead plate immersed in sulfuric acid solution, the following electrode systems form: 1. Lead sulfate electrode (Pb/PbSO4) in the potential region from −0.97 to −0.40 V versus Hg/HgSO4 reference electrode; 2. Lead oxide/lead sulfate electrode (Pb/PbO/PbSO4) at potentials from −0.40 to +0.95 V; 3. Lead dioxide electrode (Pb/PbO2) at potentials above +0.95 V. Pb/PbO/PbSO4electrode: In the lead oxide/lead sulfate potential region, a PbSO4 crystal layer forms first. It acts as a semipermeable membrane, which causes alkalization of the solution at the boundary between Pb and PbSO4 and the solution in the pores of PbSO4 layer. The Pb/PbO/PbSO4 electrode has photoelectrochemical properties, and when exposed to electrochemical oxidation above +0.95 V, PbO is oxidized to α-PbO2 and PbSO4 to β-PbO2. Pb/PbO2electrode: Electrochemically obtained PbO2 contains crystal (PbO2) and hydrated (PbO(OH)2) (gel) zones. During discharge of the battery, the reduction of PbO2 proceeds in the gel zones by a proton–electron mechanism. On anodic polarization of the Pb/PbO2 electrode, oxygen is evolved. It penetrates through the PbO2 layer and oxidizes the lead, i.e., a corrosion layer of PbO and PbOn (1 2) forms. The lead alloy composition (i.e., Sb, Sn, Bi, Ag, As, and other additives) affects the rate of oxidation of PbO to PbO2 and the electrochemical properties of the corrosion layer. At high overvoltage of the Pb or PbO2 electrodes, hydrogen and oxygen evolve, and hydrogen (H+/H2) and oxygen (H2O/O2) electrode systems form. This chapter presents also general notes on lead–acid cell/battery design and on the technological schemes for battery manufacture.

Formation of 3BS paste. Depending on the phase and chemical compositions of the cured paste, the formation process can be divided in two stages: first stage: PbO and basic lead sulfates are oxidized to α-PbO2; the plate potential is low; second stage: PbSO4 is oxidized to β-PbO2; the plate potential under load is high. Based on the above changes in the phase composition of the paste during formation, a general scheme is proposed for the chemical and electrochemical reactions during the two stages of formation. Formation starts at the grid bars yielding a (PbO2 + PbSO4) zone, which grows toward the bulk paste volume. The direction of its growth is determined by the transport hindrances that the H+ and So4−So4− ion flows have to overcome between the reaction layer and the bulk electrolyte. Zonal processes are slow processes. To accelerate the formation, electroconductive additives are introduced in the paste. Formation of 4BS paste. Formation of 4BS crystals is influenced by the conditions of soaking, which determine the thickness of the PbSO4 layer formed on the surface of 4BS crystals. During the formation process, PbSO4 particles are oxidized to β-PbO2 aggregates. Formation of the interior of the 4BS crystals is completed only after three to five deep charge–discharge cycles. The matrix of the 4BS crystals is transformed to the PbO2 aggregates, which preserve the shape of the initial substance. PbO2 aggregates interconnect to form a skeleton with a structure similar to that of the initial cured paste (metasomatic processes). Structure of positive active material (PAM). The β/α-PbO2 ratio increases with increase of the H2SO4 versus LO content for PAM produced from both 3BS and 4BS pastes. With increase of the β-PbO2 content in PAM, the capacity of the positive plates increases. The strucutre of PAM comprises (1) particles and aglomerates with micropores in-between (microstrucure) and (2) numerous aggregates interconnected to form a skeleton with macropores between its branches (macrostructure). Structure of PbO2particles. PbO2 particles consist of hydrated (gel) and crystal zones. These zones are in equilibrium, which depends on the temperature and the ions in the solutions. Gel zones have electron and proton conductivity, and the discharge reactions proceeds in these zones. Sb ions increase the hydration of lead dioxide particles, i.e., the share of gel zones. Sb5+ ions have higher effect than Sb3+ ions.

The positive active-material of lead–acid batteries is lead dioxide. During discharge, part of the material is reduced to lead sulfate; the reaction is reversed on charging. There are three types of positive electrodes: Plante, tubular and flat plates. The Plante design was used in the early days of lead–acid batteries and is still produced today for certain applications. Tubular plates are chosen for heavy cycling operations. Most positive electrodes are flat plates and are employed in all starter batteries. The principal failure modes of the positive material are sulfation and premature capacity loss (PCL). In recent years, considerable progress has been made in enhancing the cycling performance of the positive plate. Nowadays, excellent cycling performance can even be achieved with positive plates that have grids made from lead–calcium alloys. Nevertheless, there is still scope for further improvement.

Gaston Plante invented the lead–acid battery by combing a lead/lead sulfate and lead dioxide/lead sulfate electrodes. He demonstrated it before the French Academy of Sciences in 1860. The battery had low capacity because the electrodes were produced by electrochemical cycling of lead plates in H2SO4 solution. Faure increased the capacity by coating the lead plates with lead oxide paste to form active masses. Volckmar and Sellon replaced the lead sheets with lead–antimony (PbSb) grids. Barton proposed a method of PbO manufacture by oxidation of molten pulverized Pb and Shimadzu by friction of lead balls in mills. The technology evolved into manufacturing pastes from tri- or tetrabasic lead sulfates, pasting of grids, and electrochemical formation of electrodes. Thanks to this technology, skeleton and energetic structures are formed in both active masses. The capacity of the negative plates was improved by adding lignosulfonates, BaSO4, and carbon to the paste. To reduce water loss during operation of the lead–acid battery, the PbSb grids were replaced with PbCa ones. This resulted in premature capacity loss on cycling, which was overcome by the addition of tin to the PbCa alloy. In batteries with PbSnCa grids, the polymer separator was replaced by absorptive glass mat, which transferred the oxygen evolved at the positive plates to the negatives, where it was reduced and the water was restored. Maintenance-free valve-regulated lead–acid batteries were created. Lead–acid batteries are produced for use in automobiles for starting, lighting, and ignition. Other applications include stationary batteries used for back-up power supply, traction batteries, special purpose batteries for aircrafts and submarines, reserve (stand-by) batteries, and batteries for hybrid electric vehicles.

Sulfuric acid is one of the three active materials that take part in the reactions in lead–acid batteries. As a result of the reactions of electric current generation and accumulation in the battery the concentration of H2SO4 in the electrolyte changes. The battery has the highest performance parameters when the variations in H2SO4 concentration on cycling are within the range from 1.10 to 1.28 specific gravity. In this acid concentration range, lead dioxide has the highest electrochemical activity, lead sulfate is highly soluble, and the H2SO4 solution is most electroconductive. Acid concentration determines open circuit battery voltage. This should be taken into account when selecting the upper charging voltage limit so as to guarantee fully charged battery. Temperature has a strong effect on the water loss from the cells of a lead–acid battery, which differs for the different battery types. Temperature exerts an influence also on the rate of the electrochemical reactions, on the corrosion of the positive grids, the softening and shedding of the active masses and on the sulfation of the negative plates. Battery performance depends on the utilization coefficients of the three active materials: Pb, PbO2, and H2SO4. When the utilization of H2SO4 is higher than that of Pb and PbO2, the battery has lower initial capacity, but longer cycle life. When Pb and PbO2 are the capacity-limiting active materials, the initial capacity is high, but its life is shorter. The sulfuric acid purity is very important for normal operation of the battery and is regulated by a H2SO4 purity standard. Tests with various additives to the electrolyte (phosphoric acid, boric acid, polymer emulsions, etc.) have proved that they have but limited applications. During battery cycling, vertical stratification of the H2SO4 electrolyte occurs. This creates local potential differences in height and leads to self-discharge and capacity loss of the cell. Gas evolution in the cell homogenizes the electrolyte concentration throughout the cell volume.

The electrocatalytic properties of the Ti–Ru–Sn ternary oxide anode (TiRuSnO2), lead dioxide (PbO2) and boron-doped diamond (BDD) anodes were compared for the electrochemical incineration of Methyl Orange (MO), an azo dye, using an electrolytic flow cell with parallel-plate electrodes. The effects of several operating parameters such as current density, hydrodynamic conditions and initial dye concentration on the degradation rate, mineralization and current efficiency were determined. The experimental data indicate that, on PbO2 and BDD anodes, MO was completely oxidized by reaction with hydroxyl radicals electrogenerated from water discharge and the removal rate was favored by high flow rates, meaning that the oxidation was a diffusion-controlled process. It was also observed that the Methyl Orange decay followed a pseudo-first-order kinetics. After 3 h the BDD and PbO2 anodes lead to almost complete MO degradation with comparable removal rate, but BDD enables higher COD removal than PbO2, with 96% and 79% of mineralization, respectively. On the contrary, on DSA only a partial oxidation of MO was obtained corresponding to 75% degradation of the initial substrate with 60% mineralization.

The present paper reports a new single flow acid battery, Cu–H2SO4–PbO2 battery, in which smooth graphite is employed as negative electrode, lead dioxide as positive electrode and the intermixture of H2SO4–CuSO4 as electrolyte. The reaction Cu⇌Cu2+ takes place on the negative electrode. The working process of the battery is only the circulation of H2SO4–CuSO4 intermixture by means of a single pump. No cationic membrane is needed. A miniature acidic copper single flow battery with a rated capacity of 2000 mAh can offer a discharge voltage of 1.29 V, an average coulombic efficiency of 97% and an energy efficiency of 83% during 450 cycles at a charge/discharge current of 1000 mA. Keywords: Single flow acid battery, Lead dioxide, Coulombic efficiency, Copper

The electrodeposition of lead dioxide (PbO2) onto Au and Ti substrates was anodically executed at 65°C and the electrochemical characteristics and the mechanism in the PbO2 films deposition were investigated by the using an in-situ electrochemical quartz crystal microbalance, cyclic voltammogram, and chronoamperometry experiments. An X-ray diffractometer and scanning electron microscope were also used for investigation of the formed lead dioxide films onto both substrates. Considering the experimental and theoretical mass/charge ratios, PbO2 deposition on Au by applying constant potential was in excellent agreement with the theoretical value, while relatively higher values of the mass/charge ratio due to film hydration were found when Ti was used as substrate. Analysis of X-ray diffractometer and scanning electron microscope show different film structures on each substrate, especially the additional hydration of the lead dioxide film deposited on Ti leads to some structural effects, identified as Sky-Lotus PbO2. Keywords: PbO2, EQCM, Electrodeposition

Ordered arrays of α-PbO 2 nanostructures were grown by galvanostatic anodic deposition into the channels of alumina templates. Electrodepositions were performed in an aqueous solution containing lead acetate and sodium acetate at pH 5.4. Bath temperature and electrodeposition time were varied to check their effect on the growth of nanostructures. It has been found that filling of alumina pores is independent of the time and electrodeposition temperature, whilst height and growth kinetics of nanostructures vary with both parameters. Temperature greatly influences morphology: wires grown at room temperature consisted of clusters of particles, leading to poorly compact structures, whilst at 40 °C the formation of compact wires was observed, some of them being partially hollow. Finally, nanowires with a very regular and dense structure were obtained at 60 °C. Also crystalline structure changes with temperature: polycrystalline nanostructures, with a preferential orientation and an average grain size of 21 nm, were obtained at room temperature, whilst at higher temperatures, wires grew almost exclusively along the plane (2 0 0) with an average grain size of approximately 28 nm. Real surface area of nanowires was evaluated from the FEG-SEM images, and it was found two orders of magnitude greater than the geometrical one.

The electrodes of a lead–acid battery consist of the active material and the grid. The active material is lead dioxide (PbO2) on the positive side and sponge lead on the negative side. Within the highly porous active materials, the electrochemical process – the conversion of chemical energy into electric energy during discharge and vice versa during charge – takes place. The grid has two functions: It serves as the current collector and it provides mechanical support for the active material. Flat plates have grids made either by book-mold casting or by a continuous process (expanded, punched, or drumcast). This design is used as the negative electrode for all battery types. On the positive side, the most commonly employed design is also with flat plates. This includes virtually all automotive batteries and also a significant number of industrial batteries. Positive flat plates are also used for all absorbent glass mat (AGM) batteries. The positive tubular plate design uses parallel connected tubes, which have a spine of lead inside. Around the spines there is the positive active material, and the tube serves to prevent shedding. Other electrode types are the positive Plante plate and the negative copper-stretch-metal (CSM) design.

Curing and formation have a significant impact on the performance and service life of lead–acid batteries. Curing renders crystalline structure to the highly porous active material, which acts like a skeleton for the microcrystalline structure that is established during formation. A good bonding of the active material to the grid is also achieved. Curing is used for all negative and positive flat plates. It is neither used for Plante plates because they are directly formed from cast lead plates, nor for tubular Plates that are filled with dry lead oxide or red lead. Curing involves two steps: the treatment of the plates at higher temperatures in an atmosphere with humidity close to 100% followed by a drying procedure. Formation refers to the electrochemical conversion of the cured material into lead dioxide at the positive plate and sponge lead at the negative plate. It is performed in tanks, and the charged plates, after washing and drying, are used for assembling cells or batteries. An alternative is the assembling of cells or batteries with cured plates followed by formation inside the container.

Redox flow batteries (RFBs) are constructed such that the electrolytes, containing the active redox species, are stored in external tanks. The cells are typically arranged into bipolar stacks, through which the electrolytes are circulated during charge and discharge. The storage capacity is then determined by the size of the electrolyte tanks and the concentration of reactants, while the power is determined by the number and configuration of cell stacks as well as the choice of components. The soluble flow battery promises a significant advantage over other systems in its ability to operate without the need for a cell-dividing membrane. This developmental battery operates with an aqueous methanesulfonic acid (CH3SO3H) electrolyte, in which Pb2+ ions are highly soluble. In addition to the factors that are important in RFBs, the storage capacity of soluble lead flow batteries is determined by the quantity of lead and lead dioxide that can be deposited in a controlled fashion on the electrode surfaces. A typical charge–discharge profile is provided with the cell operating with an electrolyte containing 1.1 mol L−1 Pb2+ ions, 0.03 mol L−1 (CH3SO3H) acid, and 0.005 mol L−1 C16H33(CH3)3N+ additive. The typical voltage efficiency is ≈75%.

During the reactions of current generation and accumulation in the lead–acid battery, the concentration of H2SO4 in the electrolyte changes. The battery has the highest performance parameters when the changes in H2SO4 concentration on cycling are within the window from 1.10 to 1.28 specific gravity (SG). In this acid concentration window, lead dioxide has the highest electrochemical activity, lead sulfate is highly soluble, and the H2SO4 solution is most electroconductive. Acid concentration determines battery voltage on open circuit, which should be taken into account when selecting the charge voltage so as to guarantee full charge of the battery. Battery performance depends on the utilization coefficients of the three active materials: Pb, PbO2, and H2SO4. When the H2SO4 utilization is higher than that of Pb and PbO2, the battery has lower initial capacity, but longer cycle life. When Pb and PbO2 are the capacity-limiting active materials, the initial capacity of the battery is high, but its cycle life is shorter.

This article covers studies of both the beneficial and the adverse effects of adding phosphoric acid to lead–acid batteries. The chemical mechanisms of these effects on the electrochemistry of the positive electrode are discussed. A thermodynamic model predicts the chemical lead oxides, sulfates, and phosphates that form on the positive electrode of a lead–acid battery when small quantities of phosphoric acid are added to the battery electrolyte.

The first amperometric biosensing method for the determination of L-fucose is described. L-Fucose is the objective of much current research, as it is considered as a potential marker for various pathologic disorders. Recombinant L-fucose dehydrogenase, having as cofactor beta-nicotinamide adenine dinucleotide phosphate (NAD(+)P), was cross-linked in a water-soluble photosensitive polymer matrix, that is, polyvinyl alcohol (PVA) modified with styrylpyridinium (SbQ), in the presence of BSA and glutaraldehyde. The resulting membrane was sandwiched between two polycarbonate membranes and was mounted in an amperometric cell. The oxidation of the enzymatically produced NADPH was monitored at a platinum anode at +0.25 V versus a silver pseudoreference electrode in the presence of ferricyanide. The system was fully optimized with respect to various analytical parameters. Regarding to the mechanical properties of the membrane and the storage stability of the immobilized enzyme, various parameters were also optimized. Several methods for the pretreatment of urine samples were investigated. Treatment of the samples with PbO2 found to eliminate the interference effect of various electroactive species exist in urine; optimum incubation time was determined since at prolonged incubation times L-fucose is also affected. Calibration curves for the direct and the mediated monitoring of NADPH were liner over the concentration ranges 0.04-1.0 mM (r(2) = 0.9995) and 0.03-3.0 mM (r(2) = 0.9997) fucose, respectively. The detection limits (S/N 3) were 2 and 1.5 muM fucose, respectively. The R.S.D. of the mediated biosensor is better than 1.5% (n = 10, 0.5 mM fucose). The proposed biosensor correlates well with a reference enzymatic method and exhibits very good working and storage stability. (C) 2004 Elsevier B.V. All rights reserved. Biosens Bioelectron

The influence of the ultrasonic intensity on the electrocrystallisation of lead dioxide on glassy carbon electrodes was studied in 1moldm−3HNO3+0.1moldm−3Pb(NO3)2. Chronoamperometry and numerical approximations of the current transients have been carried out in order to compare these results with those obtained in the absence of ultrasound. Results show different effects of the ultrasound power from those obtained with other variables like electrode potential. Keywords: Ultrasound, Lead dioxide, Glassy carbon electrodes, Sonoelectrochemistry, Electrodeposition nucleation

In lead-acid secondary batteries the negative plates have a spongy lead as their active material, while the positive plates of the lead-acid cell have an active material of brown lead dioxide. The plates are immersed in an electrolyte of dilute sulphuric acid. There are two types of pates available: tubular and flat. The tubular positive consists of rods of antimonial lead, which are surrounded by sleeves of an inert porous material, such as terylene. The annular spaces in the tubes of the sleeves and around the rods are filled with the active material lead dioxide. In the case of the flat plate design, the plate is made from lead alloy grids with lattices containing lead dioxide. The negative plate of the tubular cell, which must match the electrical capacity of the positive plate to enable efficient chemical reaction to take place, is of a similar design to that of the flat plate positive, but the lattices in this case are filled with a sponge of pure lead. The positive and negative plates are placed into a container, each positive being placed next to a negative and so on. Further, charging is done by A passing a direct current through the cell in the opposite direction to that during discharge, liberating the acid from the plates, i.e. the concentration of acid in the electrolyte increases. This reverses the action of the discharge and restores the battery to its original charged condition. The capacity of the battery varies according to the current at which it is discharged. The higher the current being taken out of the battery, the lower the available capacity.

The chapter describes the process of oxidation of alcohols, amines, and amides. Early electrochemical processes for the oxidation of alcohols to ketones or carboxylic acids used platinum or lead dioxide anodes, usually with dilute sulphuric acid as an electrolyte. The majority of amines show an irreversible oxidation wave on cyclic voltammetry in acetonitrite at a platinum electrode. An electron is lost from the nitrogen lone pair and the resulting radical-cation loses a proton from the α-position. Proton loss is assisted by overlap in the transition state between the p -orbital containing an unpaired electron on nitrogen and the stretching σ-orbital of the carbon-hydrogen bond. Amines are stable to electrochemical oxidation in acid solution because the nitrogen lone pair is protonated and inaccessible for reaction. However, this is not the case for N-acetylamines, which are oxidizable at a lead dioxide anode in aqueous sulphuric acid. The primary electron transfer step involves the amide function and leads to a radical-cation, which loses a proton from the carbon atom adjacent to nitrogen. Electrochemical oxidation of amides and urethanes in methanol containing an inert electrolyte has been developed into a useful procedure for the generation of α -methoxy derivatives.

The process of curing or conditioning pasted lead-acid battery plates made with uncalcined or leady Barton pot litharge is probed. Microscopy, wet chemistry and X-ray diffraction techniques are used to characterize the changes in crystal structure and chemical composition which take place in the material as it undergoes curing. A matched set of uncured positive plates is divided into groups each of which is then cured under different controlled conditions. At various times throughout the cure cycle, sample plates from each group are analyzed for composition and crystal structure. Photomicrographs used in conjunction with X-ray diffraction patterns illustrate the reactions which occur. The plates cured under various conditions are then formed or charged. Time-lapse photographic techniques are used to follow the conversion of divalent lead compounds into the various species of lead dioxide. The degree of completion of formation and the proportions and characteristics of the two polymorphs of lead dioxide present in the formed plates of varying cure history are discussed.

A method for making very thin optically transparent sections of lead dioxide deposits is described. A number of different types of crystal are noted and illustrated. Polarized light was used in a partially successful attempt to distinguish between α and β-PbO2. The presence of phosphorus, arsenic and antimony compounds in the forming electrolyte had a pronounced effect on the structure of the electrodeposits.

Oxygen overpotentials on smooth lead dioxide surfaces were measured in sulphuric acid. Little change in overpotential was detected as the acid concentration was raised from 1·76 to 8·80 molal. For 6·18 molal electrolyte, the temperature coefficient of the overpotential at 0·01 A/cm2 was —0·0035 V/°C. The transfer coefficient was found to be almost constant at 0·50 over the range 15 to 45°C, while the exchange current density increased from 6·92 × 10–11 A/cm2 to 135 × 10–11 A/cm2. The standard heat of activation for the rate-determining step at the reversible potential was calculated to be 23 kcal/mole. Arguments are presented suggesting that the rate-determining step is in fact the discharge of a water molecule.

The differential thermal analysis technique has been used to study the active material of the positive plate in the lead-acid battery. Results obtained on reference samples of lead dioxide showed that there were four different decomposition paths leading to lead monoxide. This work was used to explain the differences between the thermal analysis curves of the active material samples. It is shown that differences in the physical state of the active material are reflected in the differential thermal analysis curves.