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Procedure Acid Leaching Potential Testing (3 replies)

Maya Rothman
11 months ago
Maya Rothman 11 months ago

For an acid drainage study I need a Procedure for ARD AMD Leach Test for Assessing Water Reactivity and Leaching Potential of Mine Wastes. My project requires the assessment of the selective copper extraction from a waste material (AMD Sludge) in Alkaline-Ammonia media. Does anyone have a laboratory procedure to do extraction tests (Agitated leach tests). I hear it was a good idea to extract Cu from slurry so that copper can be recovered and metal content in slurry is therefore reduced.

Victor Bergman
11 months ago
Victor Bergman 11 months ago

i've been doing a bit of work over the past 12-18 months using leaching method USEPA 1316 for determining leach-ability of various metals (including copper) mainly for environmental assessment/impact purposes. It's an end-over-end bottle leach, but at several different Liquid:Solid (LS) ratios. I find it particularly useful to see what metals leach (partition) at what LS ratios. Logic would suggest that the lower the LS ratio, the greater the concentration of a metal leaching, but for some metals under some circumstances this assumption doesn't hold. Doing a leach at a single LS ratio (such as 20:1 or 5:1 or whatever) misses this possibility. Arsenic is one element that exhibits this behavior.

You may want to consider the U.S. Geological Survey Field Leach Test for Assessing Water Reactivity and Leaching Potential of Mine Wastes, Soils, and Other Geologic and Environmental Materials at http://pubs.usgs.gov/tm/2007/05D03/pdf/TM5-D3_508.pdf

John Koenig
11 months ago
John Koenig 11 months ago

On a mineral processing route basis and very simplistically, assuming you have determined the optimal liberation grind size:

  • 3-necked Kontes flask w/overhead agitator, immersed in a water bath; 
  • 20-wt% solids (dry basis); 
  • Add sufficient DI followed by 28-wt% NH3 to achieve pH ~10.8; 
  • Sufficient rpm's to avoid slurry vortexing; 
  • Continuously monitor pH & add NH3 to pH 10.8; 
  • Kinetic samples every 1/2 hour for Cu AAS. 
  • Leach for 4-hours under ambient conditions.

Depending on results, you can increase temp to 60C to improve kinetics Note that NH3 loss, as vapor, will be exacerbated at higher temps.

Helena Russell
11 months ago
Helena Russell 11 months ago

Regardless if you are wanting to use the method to assess the extraction process or conduct the extraction itself, you would be best to use rotary end-over-end extraction at 29+/-2 rpm which is the standard used except in a few European methods and the old LEP previously used in the Province of Ontario. Liquid-to-solid ratio should be determined based on whether you want maximum concentration in the extract (low L/S down to 3), or to maximise the mg/kg extraction efficiency (higher L/S of 20) without the possibility of reaching the solubility limitation.
It would also be best to go with an identifiable method such as the ASTM D3987 20:1 L/S DI extraction. There can be much added confusion when researchers add modified to a method where they have changed the method of agitation, L/S ratio and the leachant. If you were to supply a better idea of what needs to be determined we could give some appropriate suggestions.

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