“Making cutting edge, rapid kinetic test procedures routine”
Kinetic test-work provides a range of information used to validate static geochemical test work and assist in the development of appropriate acid and metalliferous drainage (AMD / ARD) prevention and management strategies.
The key purposes of kinetic test-work are to:
- Determine indicative AMD / ARD leachate quality / chemistry,
- Determine the rate that materials (ore, waste, tailings, wall rock) generate AMD / ARD,
- Determine lag time to the onset of AMD / ARD generation,
- Determine the longevity of AMD / ARD generation,
- Determine the key controls on AMD / ARD generation,
- Determine the likelihood of neutral metalliferous drainage (NMD) or metal leaching (ML) if AMD / ARD generation is unlikely,
- Quantify the magnitude of the impact of AMD / ARD generation, and
- Quantify the impact of saline drainage from sulfide oxidation.
The information gained from kinetic testwork can be used to manage sulfidic materials both during operations and post-closure. The outputs are routinely used for:
- Modelling pollution generation from waste rock piles, tailings dams and pit wallrocks,
- Used to assist the design of waste rock piles that offer AMD / ARD control,
- Facilitate the design of large scale test pads for waste rock piles,
- Quantify the full oxygen penetration depth into tailings deposits,
- Identify the most problematic lithologies in an open pit,
- Assist with the design and assessment of cover systems for both waste rock piles and tailings dams,
- Assist with the design of remedial activities and quantify the benefit of specific rehabilitation activities.
Using the advanced geochemical laboratory services of ES Analytical, Earth Systems can provide a range of standard kinetic test-work procedures for the determination of AMD/ARD risk under simulated site conditions, including:
- Column Leach Tests
- Benefits – Design flexibility; Indicative leachate chemistry.
- Limitations – Relatively expensive; Relatively slow (0.5-5 yrs); Potentially inaccurate; Poor simulation; Precipitates may impact leachate flow; No moisture control.
- Humidity Cell Tests
- Benefits – Relatively rapid (2-6 months); Indicative leachate chemistry.
- Limitations – Relatively expensive; Potentially inaccurate; Climatic conditions within cell can differ substantially to actual climate conditions; Poor simulation; No moisture control.
- Test Piles (Field Based)
- Benefits – Good simulation of site conditions; Indicative leachate chemistry.
- Limitations – High cost; Real time (2-10 yrs); Active irrigation often required.
Analytical work associated with the kinetic tests indicated above are conducted at NATA accredited laboratories.
Table below shows expected outputs from the various kinetic techniques.
|Output||Oxygen Consumption||Humidity Cell||Column Leach||Test Piles|
|Sulfate Generation Rate (SGR)||Yes||?||?|
|Acidity / Net Acidity Generation Rate||Yes||Yes||Yes||Yes|
|Lag Time to Onset of Acid Conditions||Yes||?||?||Yes|
|Oxygen Consumption Rate (OCR)||Yes|
|Pyrite Oxidation Rate (per kg – Waste Rock & Tailings)||Yes|
|Pyrite Oxidation Rate (per m2 – Wall rock & Tailings)||Yes|
|Estimate of Longevity of Sulfide Oxidation||Yes|
|Quantification of Carbonate Neutralisation||Yes|
|Carbon Dioxide Release Rate||Yes|
|Oxygen Depth Penetration Profile||Yes||?|
Note: Sulfide oxidation rates calculated from kinetic tests that rely on sulfate release rates can be underestimated if sulfate precipitates (eg. gypsum, schwertmannite, jarosite, alunite) or overestimated by progressive dissolution of residual sulfate or sulfate-bearing secondary minerals present in samples prior to commencement of the test work.