BHP Billiton Cannington Mine, an underground silver-lead-zinc operation, has found that a significant amount of silver is not recovered in the current flotation process. Application has been made to investigate the recovery of this silver, as well as the lead and zinc, using a variety of hydrometallurgical methods.
The methods under investigation include cyanide, thiourea, and ferric chloride leaching. Ferric chloride leaching is the topic of this thesis.
This leaching method is a potentially attractive method of processing due to:
● Preliminary test work indicating recovery of silver (>80%)
●Ferric chloride leaching has been well researched in the past ,
● Ferric ion is a good oxidant of sulphides.
The literature research also indicated the promise of increased recovery and rate of reaction when using sodium chloride or brine leaching. This information as well as information on additional studies allowed the identification of the variables and respective ranges for the experiments.
The variables selected were temperature, time, ferric chloride concentration, sodium chloride concentration and solid-liquid ratio.
Statistical analysis by backward, backward/forward elimination and best subsets methods has been completed using the statistical package MINITAB 13. Models for silver, lead and zinc recovery have been analysed. The models for silver lead and zinc were found to be statistically adequate.
Overall safety and risk analysis is complete. Hazard identification, probability and consequences have been reported and analysed for control
Of the experiments, a single experiment produced maximum values of 82% silver, 99% lead and 99% zinc recovery. Optimum parameters are expected to be near these values.
Ferric chloride leaching appears to be a promising method for recovery of the valuable methods but recommendations are for alternative methods to be assessed and compared. Further investigation may also examine a cost analysis of this leaching method.