Abstract
In this study, the objective was to evaluate the recovery of gold from the Witwatersrand gold
tailings using cyanide-free reagents namely, glycine and thiosulphate. The leaching of goldcontaining
ores in prior studies have investigated the use of conventional cyanidation processing
followed by detoxification of the waste or pre-conditioning the ore prior to leaching. Not much work
has focused on the recovery of gold from waste material using cyanide-free reagents, considering
its possible effects on the Witwatersrand gold tailings. The studied samples were obtained from
the West, East and Central Rand gold tailings. These were classified using XRD, and MLA
techniques before leaching. The analysis showed that the tailings contained silicates, sulphides,
iron oxides with minor concentrations of sulphates and phosphate minerals. The highest gold
recovery, which is from the East rand gold tailings, was achieved with glycine and potassium
permanganate concentrations of 0.857g/L. The processing of these tailings produced recoveries
of up to 56 wt.%. Analysis with the MLA identified that the East Rand tailings contained the least
amount of preg-robbing minerals such as those belonging to the mica group minerals with a
greater degree of locked gold grains amenable to leaching with all three applied reagents. The
recoveries with cyanide-free reagent were found to be below that of conventional cyanidation,
with instances were recoveries were better than current gold plant recoveries. The study also
found that a maximum of 83% gold recovery can be achieved with cyanidation at set leaching
conditions of 30% solids percentages at a pH 10.5 at ambient temperature using the bottle roll
experiment. The study determined that the Witwatersrand gold tailing are amenable to alternative
reagents, however, conducting a process mineralogy study before leaching assists in
understanding the material and development of a plan for an effective processing route to deal
with possible challenges during leaching.