The SAIMM is a professional institute with local and international links aimed at assisting members source information about technological developments in the mining, metallurgical and related sectors.
twitter1 facebook1 linkedin logo
 

News

The following comment was received on the December 2010 Journal paper on the retreatment by Mine Waste Solutions of residues at Buffelsfontein. If this comment is of interest to you, please visit the section on our website for the Johannesburg Branch events and Ms Mariette Liefferink’s presentation on acid mine drainage...

But the item that caught my attention in your December 2010 issue was the retreatment by Mine Waste Solutions of residues at Buffelsfontein.  Buffelsfontein was first and foremost a gold mine in Jack Scott’s Strathmore Group.  Production of uranium from the gold plant tailings was added in the late 1950s using sulphuric acid with manganese dioxide to provide the acid oxidising conditions at  elevated temperature to bring the uraninite in the ore into solution as uranyl sulphate.

At this time West Rand Consolidated Mines Ltd, the first mine to undertake uranium production in South Africa, was augmenting its uranium production by hosing down the stopes on a monthly basis, neutralising the “acid mine drainage” with lime then settling and pumping the uranium rich sludge to the uranium plant.  We are now familiar with what was happening.  Exposed to air and water, pyrite on the stope walls was being oxidised by a species of bacterium -thiobacillus ferro-oxidans- to ferric sulphate and sulphuric acid.   This led to the replacement of MnO2 in the uranium leach at Buffelsfontein by an integrated circuit in which ferrous ions in the barren liquor were bacterially reoxidised to ferric ions and fed back to the leach circuit. 

It was also common knowledge that long crushed gold ore lying at the edges and bottom of ore stockpiles tended to develop coatings of complex iron compounds which rendered the gold somewhat refractory to the alkaline cyanide leach process.  Building silos for the in-line storage of crushed ore provided a means of ensuring first in first out to the mills.  This led to the prediction that it would be better to leach the milled ore for uranium first followed by gold in a reverse leach operation that would polish any iron compounds from gold particles in the acid conditions of the uranium leach, allowing a better extraction of gold in the subsequent cyanidation process. This was confirmed first in pilot operations but it was still a brave decision in the late 1970s to stop the Buffelsfontein plants for a weekend while the piping was switched for the reverse leach.  It was certainly vindicated by improved gold recovery.

Back to Page 21 of your December 2010 issue and the statement that “it makes sense for us to bed down the TSF and the new gold module before embarking on the commissioning of the uranium plant”.    Agreed, but I would expect that gold particles in the material brought back from the slimes dams would be coated to some extent with iron compounds, somewhat refractory to alkaline cyanidation and would be more amenable to dissolution in the reverse leach situation.  I hope this is the intention.

John Freer.   Hon. Life FSAIMM 

SAIMM Advert button072017inner

SAIMM on twitter

Other mining news

Mining Weekly | Africa

The latest mining world news and project information from Africa.
  • Barrick silences its biggest critic by buying out Randgold
    For more than two decades, Mark Bristow has been a thorn in the side of Barrick Gold. Now he’s its closest partner. The 59-year-old South African will take the role of chief executive officer at Barrick after the Canadian company inked a $5.4-billion deal to buy out Randgold Resources. It’s a bigger stage for Bristow, known as an outsider for his sharp and frequent criticisms of the gold industry and a genius at running an African mine.
  • Barrick Gold to buy Randgold Resources in $18.3bn deal
    Canada's Barrick Gold has agreed to buy Randgold Resources in a $18.3-billion share deal to create the world's largest gold company in an industry under investor pressure to put capital to good use. The new Barrick company, which will be listed in New York and Toronto, will own five of the world's 10 lowest cost gold mines and will be valued at $24-billion including debt.
  • Bank of America sees gold topping $1 300 on fiscal deficit
    Gold is set to surge over the next year as concerns deepen about the widening US. budget deficit and a tariff-driven trade war starts to damage the country’s economy, according to Bank of America Merrill Lynch. Bullion could average $1 350/oz in 2019 as corporate tax reforms worsen the US fiscal balance, Francisco Blanch, head of global commodities and derivatives research, said in a phone interview last week. Spot gold traded at $1 196.23 on Monday and has averaged about $1 285 this year.