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Minerals 2014, 4(2), 293-312; https://doi.org/10.3390/min4020293

Long-Term Acid-Generating and Metal Leaching Potential of a Sub-Arctic Oil Shale

1
Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, VIC 3010, Australia
2
Department of Environment and Geography, Macquarie University, Sydney, NSW 2109, Australia
3
Central Science Laboratory, University of Tasmania, Hobart, TAS 7001, Australia
4
Australian Antarctic Division, Kingston, TAS 7050, Australia
*
Author to whom correspondence should be addressed.
Received: 19 February 2014 / Revised: 8 April 2014 / Accepted: 10 April 2014 / Published: 14 April 2014
(This article belongs to the Special Issue Mine Waste Characterization, Management and Remediation)
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Abstract

Shales are increasingly being exploited for oil and unconventional gas. Exploitation of sub-arctic oil shales requires the creation of gravel pads to elevate workings above the heaving effects of ground ice. These gravel pads can potentially generate acidic leachate, which can enhance the mobility of metals from the shale. To examine this potential, pyrite-bearing shale originating from sub-Arctic gravel pad sites were subjected to leaching tests for 600 days at initial pH values ranging from 2 to 5, to simulate potential real world conditions. At set times over the 600 day experiment, pH, oxidation reduction potential (ORP), dissolved oxygen and temperature were recorded and small liquid samples withdrawn and analysed for elemental concentrations using total reflection X-ray fluorescence spectrometry (TRXRF). Six of eight shale samples were found to be acid generating, with pH declining and ORP becoming increasingly positive after 100 days. Two of the eight shale samples produced increasingly alkaline leachate conditions with relatively low ORP after 100 days, indicating an inbuilt buffering capacity. By 600 days the buffering capacity of all samples had been consumed and all leachate samples were acidic. TRXRF analyses demonstrated significant potential for the leaching of S, Fe, Ni, Cu, Zn and Mn with greatest concentrations found in reaction vessels with most acidic pH and highest ORP. View Full-Text
Keywords: acid rock drainage; pH; oxidation reduction potential; metal concentration; total reflection X-ray fluorescence spectrometry (TRXRF) acid rock drainage; pH; oxidation reduction potential; metal concentration; total reflection X-ray fluorescence spectrometry (TRXRF)
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Mumford, K.A.; Pitt, B.; Townsend, A.T.; Snape, I.; Gore, D.B. Long-Term Acid-Generating and Metal Leaching Potential of a Sub-Arctic Oil Shale. Minerals 2014, 4, 293-312.

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