Document Type

Thesis

Date of Award

6-30-1962

Degree Name

Master of Science in Chemical Engineering - (M.S.)

Department

Chemical Engineering

First Advisor

C. L. Mantell

Second Advisor

James A. Bradley

Third Advisor

Jerome J. Salamone

Abstract

The purpose of this investigation was to obtain new and to extend existing information on the method or methods used to produce high purity Tellurium using electrolytic refining methods. All available methods were investigated, in order to substantiate or disprove the available procedures. The main concern of this investigation is the outlined procedure to produce a metallic Tellurium product of 99.9999% purity. Any information which proved to be correct was used in attaining the ultimate goal of this thesis.

A literature search revealed only one good source of information. A United States patent, No. 2,258,963, dated October 14, 1941, issued to W. G. Woll and R. J. Gore, who in turn assigned the patent to International Smelting and Refining Company, New York. It concerns itself directly with a process for the refining of Tellurium dioxide to the metal using an electrolytic process.

The above patent mentions a purity of "The production obtained has exceptional purity, analyzing in the neighbor—hood of 99.9% Tellurium."

This investigation has substantiated the majority of the claims made in the previously mentioned patent. By determining optimum cell operating conditions it was easy to exceed the purity stated in the patent. In an effort to increase product purity the use of a membrane separator was also investigated with good success, With the introduction of a second refinement step it was necessary to investigate such things as, melting apparatus, proper atmospheres for melting, adequate container shape and container material for melting* The most desirable container and handling materials being glass or stainless steel. An investigation showed that on melting a further refinement had taken place. This opens the door to an entirely new approach, zone refining* A discussion of its possibilities is given. A procedure for the second refinement using a consumable anode method is investigated. Other investigations include determining the alkaline solution with the greatest solubility for Tellurium dioxide, solubility data for the aqueous sodium hydroxide, Tellurium dioxide system, and a compiled list of physical properties of Tellurium.

The maximum purity of Tellurium obtained was 99.9996%. This purity was not obtained solely by electrolytic refining* From the work in this thesis it would appear that the employment of electrolytic refining methods alone could not yield a purity of material over 99.999%

The main use of such a high purity material is in Tellurium rectifiers, semiconductors, thermoelectric devices, and general laboratory experimentation and investigation.

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