Topic
Castner process
About: Castner process is a research topic. Over the lifetime, 32 publications have been published within this topic receiving 214 citations.
Papers
TL;DR: In this article, the authors investigated the effect of impurities, concentration of sodium hydroxide, temperature, agitation, and external current on the dissolution of a series of aluminum specimens ranging in composition from 99.2 to 99.998 per cent Al.
Abstract: In continuation of a previous study (1) of the dissolution of commercially pure aluminum (99.2% Al) in alkaline solutions, the effect of impurities, concentration of sodium hydroxide, temperature, agitation, and the effect of an external current on the dissolution of a series of aluminum specimens ranging in composition from 99.2 to 99.998 per cent Al was investigated. Increasing quantities of impurities (iron being the most effective) increase the rate of dissolution. The largest increase is at the concentration of iron representing the limit of solubility of iron in solid aluminum. During the dissolution process the impurities in aluminum accumulate on the surface and accelerate the rate of dissolution.An aluminum alloy containing 2.5 per cent Mg and 0.5 per cent Cr (52S) has a constant rate of dissolution. The impurities in this alloy, together with the alloying elements, drop to the bottom of the solution. They do not precipitate on the surface of the metal. The electrode potential for the alloy having a constant rate is constant, whereas the alloys whose rate of dissolution increases as the impurities precipitate on the surface reflect this increasing rate in electrode potential measurements, which change in the cathodic direction.The rate of dissolution of aluminum reaches a maximum value as the concentration of sodium hydroxide is increased to 5.5N. At concentrations greater than 5.5N the rate of dissolution decreases. The decrease is linear with the concentration of sodium hydroxide between 7 and 12N. The effect of temperature on the rate of dissolution may be represented by the Arrhenius equation. The "experimental energy of activation" of this equation increases as the concentration of sodium hydroxide is increased up to 12N. Agitation equivalent to a linear velocity of 188 cm/sec does not change the rate of dissolution of the alloy containing Mg and Cr in 0.30N solution.Making aluminum cathodic by means of an external current does not affect the electrode potential. The electrode potential changes observed on making aluminum anodic are correlated with measurements of the "difference effect."An attempt is made to correlate the effect of increasing concentration of sodium hydroxide on the rate of dissolution with the specific conductance of the solution and to interpret the experimental results in terms of various electrochemical theories.
31 citations
26 citations
17 citations
Patent•
16 Jul 1979TL;DR: In this paper, a process for selectively removing sodium sulfate and sodium hydroxide from an aqueous slurry containing sodium chloride, salt, and sulfate is described.
Abstract: A process for selectively removing sodium sulfate and sodium hydroxide from an aqueous slurry containing sodium chloride, sodium sulfate and sodium hydroxide, which comprises contacting the slurry in a countercurrent wash step with cool water to remove sodium sulfate and sodium hydroxide therefrom
17 citations
Patent•
2 Feb 1994
TL;DR: In this article, a process for the manufacture of pure amorphous silica from rocks containing non-crystalline silica is described, which comprises the steps of: (a) dissolution of said rock in an alkaline solution comprising of sodium hydroxide and sodium carbonate, obtaining a solution of sodium silicate; (b) precipitation, by adding sodium bicarbonate into said sodium silicates and co-producing sodium carbonates, the weight ratio between SiO 2 and Na 2 O in said dissolution step is in the range of between 0.5
Abstract: A process for the manufacture of pure amorphous silica from rocks containing non-crystalline silica is described. The process comprises the steps of: (a) dissolution of said rock in an alkaline solution comprising sodium hydroxide and sodium carbonate, obtaining a solution of sodium silicate; (b) precipitation of pure amorphous silica by adding sodium bicarbonate into said sodium silicate and co-producing sodium carbonate, the weight ratio between SiO 2 and Na 2 O in said dissolution step is in the range of between 0.5 to 3.0; and (c) the sodium carbonate solution is transformed into crystalline sodium bicarbonate, by a salting out reaction with sodium chloride, being recycled to the process. According to a preferred embodiment, the alkaline solution is obtained by the caustification of sodium carbonate with calcium hydroxide. The preferred concentration of sodium hydroxide in said dissolution step is in the range of 4% to 14% by weight.
17 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2014 | 1 |
| 2011 | 1 |
| 2006 | 2 |
| 2005 | 1 |
| 2004 | 2 |
| 2003 | 1 |