Lead Dioxide Anode Research Articles

Improved Electrolytic Processes for the Production of Iodic Acid, Periodic Acid, and Their Salts Using a Special Lead Dioxide Anode

A special type of lead dioxide anode was found to be the most suitable anode material to produce iodate from iodide, periodic acid from iodine, and also to regenerate periodic acid (periodate) from iodic acid (iodate). This anode could be used in the absence of sulfate with a very slight loss. The yields of the products were almost quantitative with good current efficiency. Improved processes for the production of periodic acid from iodine and iodate from iodide using this anode and also those concerning the regeneration of periodic acid (periodate) from iodic acid (iodate) are covered in this paper.

Lead Dioxide Anode in the Preparation of Perchlorates

Lead dioxide deposited on graphite or carbon was used to make anodes suitable for the preparation of sodium perchlorate from sodium chlorate. This type of anode has been used successfully in the presence of certain addition agents as a replacement for platinum anode. The influence of anodic current density, temperature, pH, current concentration, and duration of electrolysis on the current efficiency of perchlorate formation was studied. Current efficiency was found to depend on anode surface transformation, which occurred with repeated use. Such changes could be observed visually and were confirmed by anode potential measurements. High current efficiency could be obtained even under slightly alkaline conditions of electrolysis, but addition of fluoride improved results. Addition of fluoride together with sulfate (as sulfuric acid) had the maximum effect on current efficiency under acidic conditions of pH.

The effect of Cobalt on the Kinetics of Oxygen evolution at a Lead Dioxide anode in Sulphuric Acid

The overpotential (n)-log current density (log i) curves for the evolution of oxygen at a lead dioxide anode in 2N H2SO4 both in the absence and presence of cobaltous sulphate in solution have been used to determine the electrode kinetic constants α ; i0 for a series of temperatures and also ΔH0*:. At 25 �C in the absence of cobalt α=O.59, i0= 10-11, and ΔH0*= 15 kcal mole-1 When 13 mg/l cobaltous sulphate is added α= 1.0, i0= 10-15, and ΔH0*:=29 kcal mole-1. Possible mechanisms for the reaction are discussed on the basis of these values and the rate determining steps suggested (where M represents the PbO2 surface) are M +H2O =MOH +H+ +e in the absence of cobalt and 2CoOH++ = 2Co++ +H2O + O in its presence.

Electrolytic Production of Sodium Perchlorate Using Lead Dioxide Anodes

Lead dioxide was investigated as an anode substitute for platinum in the production of sodium perchlorate. Rod shaped deposits were prepared on nickel and platinum clad tantalum wires. The plate was dense, heavy, metallic‐like in appearance and not too fragile for ordinary handling. The first phase of experimentation was performed in small laboratory cells to determine approximate electrolyses data. Larger bench‐scale production cells were also run simulating plant operating conditions. Lead dioxide anodes produce sodium perchlorate at high cumulative current efficiencies. One lead dioxide anode was used in cell operation for 3,000 hr. Cumulative current efficiency for a given anodic current density is a function of the cathode material, cathodic current density, and the additive used. Perchlorate can be produced using nickel, copper, stainless steel, and carbon steel cathodes. Energy requirements, under identical experimental conditions, indicate that stainless steel and nickel are the best cathode materials. A current efficiency of 91.5% was obtained with a stainless cathode at anodic and cathodic current densities of 15.5 amp/dm2 and of 7.25 amp/dm2, respectively. No unusual metallic contamination could be detected in the ammonium perchlorate prepared from the sodium perchlorate.

Lead Dioxide Anode for Commercial Use

Results are presented on one phase of a research carried out under an Office of Naval Research contract for the development of an electrode to replace platinum in the perchlorate cell. Electrodeposition of massive lead dioxide is preferably carried out from a lead nitrate bath. Uniquely, anodic deposition on tantalum is possible without polarization or erosion of the base. In the subsequent anodic process use, this tantalum acts as a polarized, inert filler. Sprayed silver permits the formation of an operable, low resistance current contact to the lead dioxide. Operation of a 100 amp perchlorate cell with a lead dioxide anode is described. Current efficiency of the lead dioxide anode is compared to platinum, and the effect of addition is shown.

The Electrolytic Oxidation of α-Pinene, Terpinolene and Dipentene

It is shown that the electrolytic oxidation of three terpene hydrocarbons, namely, α‐pinene, terpinolene and dipentene, can be carried out efficiently at a lead dioxide anode in dilute aqueous sulfuric acid as electrolyte. The addition of an emulsifying agent is not necessary, provided mechanical emulsification is maintained by agitation. The efficiency of oxidation is increased by raising the temperature, but is markedly decreased by making the electrolyte neutral or alkaline. Inorganic oxygen carriers, e.g., ceric ions, increase the current efficiency for the oxidation of the terpene hydrocarbons.