Study of Properties of Cryolite – Lithium Fluoride Melt containing Silica

• Main Author: Thomas, Sridevi
• Other Authors: Barati, Mansoor
• Language: en_ca
• Published: 2012
• Subjects: cryolite; silica; lithium fluoride; dissolution; density; mass transfer coefficient; conductivity; electrolysis; 0794; 0743
• Online Access: http://hdl.handle.net/1807/34784

The ultimate goal of this study is to examine the feasibility of extracting silicon from silica through electrolysis. The objective of the thesis was to evaluate the physico-chemical properties of a cryolite-lithium fluoride mixture as an electrolyte for the electrolysis process. A study of 86.2wt%Cryolite and13.8wt%Lithium fluoride melt with silica concentration varying from 0-4wt% and temperature range of 900-1000°C was done. Three properties were measured using two sets of experiments: 1) Dissolution Behaviour Determination, to obtain a) solubility limit, b) dissolution rate (mass transfer coefficient) and 2) density using Archimedes’ Principle. The study concluded that solubility and dissolution rate increases with temperature and the addition of LiF to cryolite decreases the solubility limit but increases the rate at which silica dissolves into the melt. With addition of silica, the apparent density of electrolyte first increases up to 2-3wt% and the drops.