Abstract
SYNOPSIS To conserve fresh water resources and comply with environmental regulations, DRDGOLD, a South African gold producer re-treating surface tailings, has transitioned to a fully closed water circulation system. Consequently, the accumulation of contaminants, as well as addition of reagents, has led to changes in water composition that have compromised leach performance and overall gold recovery. A two-sample t-test confirmed a significant difference in gold recoveries between the use of Rand Water, which was used as a benchmark, and untreated process water. Atomic absorption analysis of ERGO's process water, confirmed the presence of iron, nickel, zinc, and manganese. A study of the effect of the identified contaminants on gold recovery showed that iron, nickel, and zinc have the largest negative effect on gold recovery, with iron and nickel being more detrimental than zinc. Sulphates were shown to have a possible passivation effect, which also influenced gold recoveries, although to a lesser extent than the heavy metals. Calcium, when present in excess, had a positive influence on gold recovery indicating the possible formation of a calcium aurocyanide complex. Lime softening successfully reduced the heavy metal and sulphate concentrations, and the gold recoveries obtained with the treated process water were similar to those as achieved with Rand Water. Keywords: gold tailings, re-processing, water quality, gold recovery.
Highlights
DRDGOLD is a South African gold producer and a world leader in the recovery of gold from the retreatment of surface tailings
The current study focuses on the ERGO plant operations in Brakpan, which predominantly reclaims tailings dams in the eastern regions of the Witwatersrand
This has led to a growing interest in research to determine the effect/s of recycled process water on gold recovery
Summary
DRDGOLD is a South African gold producer and a world leader in the recovery of gold from the retreatment of surface tailings. Since water is a strategic resource in water-scarce South Africa , several mining operations are at risk due to a limited supply of water. This has resulted in an increased utilization of recycled water, with the focus on recycling process water. ERGO’s metallurgical research department has, demonstrated improved gold recoveries when utilizing clean water compared with recycled process water in laboratory test work. This has led to a growing interest in research to determine the effect/s of recycled process water on gold recovery
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