The need for a reliable, cost effective method to produce solar grade silicon (>6N purity) for photovoltaic cells is imperative in the age of climate change. Boron and phosphorus are used to dope the silicon to make p- and n-junctions and require the strictest control; unfortunately, these are also the most difficult elements to remove during the purification of silicon. The relatively new path of combining of slag treatment and solvent refining is seen as a potential route to large scale and cost-effective refining of silicon. In this study, slag treatment of aluminum-silicon alloys using calcium aluminate slags with varying composition was investigated. Kinetics data was collected and used to calculate the mass transfer coefficient of B and P into the slag; a maximum of 47µm/s and 14µm/s respectively was reported at 35mol% Al2O3. Calculations showed mass transfer of boron was faster than phosphorus due to the smaller ionic radius. It was found that there was a linear correlation between the mass transfer coefficients and superheat of the slag; it is concluded that this is an artifact of the change in both slag and metal compositions as the experiment proceeds. Equilibrium data was used to compare the removal of phosphorus and boron from the alloy, showing significantly better performance for phosphorus removal as it was reduced into the slag as a phosphide ion. Boron removal, as borate ions, was less than ideal because of the very low oxygen potential provided by the slag. The maximum LB and LP reported in this study was 0.38 and 2.17 respectively at 40mol% Al2O3. Also calculated were the slag capacities for borate and phosphide ions. In addition to the fundamental data contributions to the field, a set of criteria were defined for future researchers should they want to pursue slag treatment and solvent refining. Also, a number of parameters that might prove useful when narrowing down potential alloy systems, that would benefit from slag refining, were provided and assessed.Ph.D
