Electrochemical reactions at PbO2 electrodes. Part I. The passivation of β-PbO2 in perchloric acid

1967 ◽  
Vol 45 (18) ◽  
pp. 2039-2044 ◽  
Author(s):  
N. A. Hampson ◽  
P. C. Jones ◽  
R. F. Phillips
Keyword(s):  
Diffusion Equation ◽  
Current Density ◽  
Perchloric Acid ◽  
Electrochemical Reactions ◽  
Perchlorate Ion ◽  
Two Parameters ◽  
Pbo2 Electrodes

The cathodic passivation of β-PbO2 electrodes in electrolytes based on perchlorate ion has been studied as a function of current density and electrolyte composition.Before passivation the electrode remains free of films based on Pb(II).Passivation results are correlated in the form of a modified diffusion equation incorporating two parameters kp and i1. [Formula: see text]

Phosphate removal from source separated urine by electrocoagulation using iron plate electrodes

2009 ◽  
Vol 60 (11) ◽  
pp. 2929-2938 ◽  
Author(s):  
Xiang-yong Zheng ◽  
Hai-Nan Kong ◽  
De-yi Wu ◽  
Chong Wang ◽  
Yan Li ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Current Density ◽  
High Current Density ◽  
Tap Water ◽  
Complete Removal ◽  
Phosphate Removal ◽  
Electrolysis Time ◽  
Two Parameters ◽  
Hydrolysis Of ◽  
P Removal

The aim of this study was to investigate the effects of current density, gap between electrodes, urine dosage, dilution and hydrolysis on phosphate removal from human urine by electrocoagulation technique using iron as electrodes. It was shown that, although a high current density and a long electrolysis time favored the removal of phosphate, an appropriate value for these two parameters can be obtained by taking into account the consumption of energy and iron in addition to P removal. In this study, current density 40 mA/cm2 and electrolysis time 20 min were shown to be optimal for 1.0 L pure urine to achieve nearly a complete removal (98%) efficiency of phosphate under the conditions of electrode area 160 cm2, the stirring speed 150 rpm, and the gap between electrodes 5 mm. Increase of gap between electrodes had little effect on phosphate removal, although it increased the energy consumption dramatically. The use of a high urine dosage reduced the efficiency of phosphate removal but increased the amount of removed phosphate. When pure urine was diluted with tap water, use of a higher tap water proportion for dilution expedited the electrolysis to achieve a nearly complete removal of phosphate in solution, but dilution caused the increase in energy consumption. It was also revealed that the hydrolysis of urine prior to electrocoagulation treatment impeded phosphate removal.

scholarly journals Application of Schwarz–Christoffel mapping to the analysis of conduction through a slot

2015 ◽  
Vol 471 (2181) ◽  
pp. 20150292 ◽  
Author(s):  
Ehud Yariv ◽  
John D. Sherwood
Keyword(s):  
Current Density ◽  
Plate Thickness ◽  
Slow Decay ◽  
Slot Length ◽  
Conducting Plate ◽  
Implicit Equations ◽  
Generic Problem ◽  
Two Parameters ◽  
Christoffel Transformation ◽  
Excess Resistance

We consider the generic problem of steady conduction through a slot traversing a non-conducting plate that separates two semi-infinite conducting regions. The current-density field is conservative; the dimensionless problem governing its potential depends upon a single geometric parameter, h , the ratio of the slot length (i.e. the plate thickness) to its width. We construct a Schwarz–Christoffel transformation to handle this two-dimensional transport problem. The transformation is expressed in terms of two parameters which are related to h through two implicit equations; in the limit h →0, it becomes explicit. Because of the slow decay of the current density at large distances from the slot, the integral representing the slot resistance diverges. The excess resistance of a finite-length slot relative to that of a zero-length slot is, however, finite. This excess resistance depends only upon the asymptotic behaviour of the potential far from the slot; it may therefore be directly obtained as a function of the two transformation parameters. Asymptotic approximations are found for the excess resistance at small and large h , respectively, scaling as h ln ⁡ h and h . The single-slot solution is used to analyse conduction through a periodic array of widely spaced slots.

Electrochemical reactions at Pbo2 electrodes. Part III. β-PbO2 electrodes in acid perchlorate electrolytes at high overpotential

1968 ◽  
Vol 46 (8) ◽  
pp. 1325-1335 ◽  
Author(s):  
N. A. Hampson ◽  
P. C. Jones ◽  
R. F. Phillips
Keyword(s):  
Electron Transfer ◽  
Reaction Mechanism ◽  
Kinetic Data ◽  
Lead Dioxide ◽  
Slow Step ◽  
Electrochemical Reactions ◽  
Single Electron Transfer ◽  
Hydrogen Ions ◽  
Logarithmic Region ◽  
Pbo2 Electrodes

The mechanism of exchange between β-lead dioxide and plumbous ions in solution has been investigated using the galvanostatic technique. Interpretation of the ηD vs.i data is consistent with a change in mechanism from a single two-electron transfer step to two successive single-electron transfer steps as the magnitude of the potential excursion from equilibrium is increased.Analysis of the slopes obtained from the linear-logarithmic region indicates that the slow step in the reaction is that leading to the formation of a Pb(III) intermediate.The orders of reaction with respect to the plumbous and hydrogen ions have been obtained from the dependence of the rate of the reaction on the concentration of the electro-reactive species.A reaction mechanism is suggested on the basis of the kinetic data.

Optimization on Self-Ordering Process of Electropolishing Surface on High-Purity Aluminum

2014 ◽  
Vol 1053 ◽  
pp. 56-60
Author(s):  
Di Ma ◽  
Shu Bai Li ◽  
Xiu Ying Hu ◽  
Xing Hong Zhao ◽  
Xu Hong Chen
Keyword(s):  
Propylene Glycol ◽  
Current Density ◽  
Perchloric Acid ◽  
High Purity ◽  
Volume Ratio ◽  
Limiting Current ◽  
Mixed Solution ◽  
Salt Film ◽  
Limiting Current Density ◽  
High Purity Aluminum

The electropolishing behavior of high-purity aluminum in perchloric acid ethanol electrolytes is studied by the electrochemical methods. The morphologies of electropolished surface are examined by SEM. The results of anodic polarization shows that the limiting current density was decreased with the 1,2-propylene glycol and perchloric acid volume ratio increasing and the temperature decreasing. The results of SEM show that A salt film with porous pores on the electropolishing surface was formed on high-purity aluminum in the mixed solution of 1, 2 propylene glycol and perchloric acid at the volume ratio of 4:1 and 6:1, porosity of film increases from 12.3 % to18.4%, and the pore diameter of film increases from 19 nm to 23 nm with the current density increased from 120 mAcm-2 to 140 mAcm-2.

scholarly journals Exact equivalence at cyclic steady state between isothermal diffusion and linear driving force models for linear adsorption systems

Adsorption ◽  
2020 ◽  
Author(s):  
Stefano Brandani
Keyword(s):  
Steady State ◽  
Diffusion Equation ◽  
Driving Force ◽  
Practical Importance ◽  
Response Analysis ◽  
Force Model ◽  
Separation Processes ◽  
Active Volume ◽  
Linear Driving Force ◽  
Two Parameters

Abstract To match the dynamics of a linear driving force model and the diffusion equation is of great practical importance in the design and optimization of adsorption separation processes. A frequency response analysis is applied to show that it is not possible to arrive at an equivalence based on a single parameter. Using this as the basis, a universal equivalence for the linear problem is constructed and closed form analytical expressions for the two parameters are derived for the sphere and slab geometries. The two parameters represent the increased effective mass transfer coefficient and a reduction in the active volume of the particle, both corresponding to the internal concentration profiles of the diffusion equation at cyclic steady state.

Dislocation Structures in Deformed Tin Single Crystals

1982 ◽  
Vol 40 ◽  
pp. 468-469
Author(s):  
G.W. Qiao
Keyword(s):  
Plastic Deformation ◽  
Electron Beam ◽  
Low Temperature ◽  
Single Crystals ◽  
Current Density ◽  
Perchloric Acid ◽  
Room Temperature ◽  
High Mobility ◽  
Tetragonal Structure ◽  
Methanol Mixture

Although β-tin is a familiar metal with tetragonal structure, its dislocation structures in bulk specimens after plastic deformation or irradiation have not been reported with observations by TEM probably because of difficulties in preparing specimens and the relatively high mobility of dislocations under electron beam illumination at room temperature (T/Tm~0.7). It proved possible to prepare specimens of β-tin for TEM observation using low temperature, double-jet electro-polishing techniques using 8% perchloric acid in methanol mixture at -30 °C under 80 volts and a typical current density of 0.7 Acm-2.

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