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Title: New chemical methods for the processing of low grade cassiterite concentrates
Author: Nixon, Philip John
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1971
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A theoretical and practical investigation of ways of processing low-grade cassiterite concentrates has been made. A wide range of methods were assessed theoretically and four were chosen for a preliminary practical examination. These were (i) a segregation process, (ii) leaching the concentrate in an autoclave with a sulphide solution under an over-pressure of hydrogen sulphide gas, (iii) volatilizing a tin fluoride by reaction with calcium fluoride, silica and carbon, and (iv) processing, by heat treatment and physical separation or by acid leaching, a glass made from the concentrate. It was found that the segregation process did not have significant advantages over a direct reduction process. The sulphide leach dissolved the cassiterite but also any silica present. Iron and aluminium were not, however, dissolved. The fluoride volatilization appeared unpromising because of a side reaction between the calcium fluoride and silica. Heat treatment of a glass did not give a product suitable for subsequent physical processing but an acid leach was successful in taking tin into solution. Further investigation of the last mentioned method showed that, in preparing the glass, the tin was probably reduced to the stannous state. The composition of the glass was found to be critically important in determining the ease with which the tin would be dissolved. At the optimum glass composition and leaching conditions all metal ions present in the glass could be dissolved without the disintegration of the silica framework. Methods of recovering tin from the leach solution were considered theoretically and two, electrowinning and hydrolysis, were shown by experiment to provide practicable routes. Examination of three of the glasses by electron microscopy suggested a connection between the ease of acid attack and phase separation on a submicroscopic scale in the glass structure.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available