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:: DNI Extracts Metals from its Alberta Polymetallic Shales using CO2 as Leaching Agent
DNI Metals Inc. is pleased to announce encouraging preliminary results from its ongoing R&D work testing extraction (leaching) of metals from its Alberta polymetallic black shales using CO2 as a leaching agent.
DNI carried out a series of batch reaction experiments in 2010 to assess the CO2 uptake potential of its Alberta polymetallic black shales. The tests were conducted by Alberta Innovates Technology Futures (AITF - formerly the Alberta Research Council).
The experiments were intended to collect baseline data relating to CO2-shale chemical interaction from a series of tests which essentially entailed sparging (bubbling) of CO2 through samples of DNIís polymetallic black shale in a dilute electrolyte. An incidental discovery of this work was that metals contained in the black shale are partly solubilized (extracted from the shale) by the mild acidic conditions created by addition of CO2 to the shale.
Further tests conducted in 2011-2012 focused on assessing the potential of relying on CO2 as a pretreatment to bioleaching which has to date been the principal process being assessed by DNI for extraction of metals from its Alberta polymetallic black shales. Samples were tested over a 192 hour period, consisting of an initial 96 hours of equilibration with the mild electrolyte and subsequent 96 hours of CO2 sparging. Of 54 elements monitored, metal recovery was assessed for 11 elements (As, Co, Cd, Li, Mo, Ni, Sb, Se, U, V and Zn).
While, as expected, metals recoveries reported by the CO2 sparging tests are lower than those reported from DNIís bioleaching testwork (previously announced), the current experiments demonstrate that CO2 can be used to leach metals from the black shales, supporting a proposal that leaching with CO2 offers previously unrecognized possibilities as a pretreatment during bioleaching to reduce reagent consumption. Metal recoveries reported by the CO2 sparging tests ranged 0.1% to 10.5% as follows: Mo-9.8%, Ni-3.3%, U-10.5%, V-0.1%, Zn-0.3%, Co-2.3%, Cd-0.8%, Li-5.7%.
The tests suggest that lower metal recoveries documented during the CO2 sparging are likely due to the mild acidic pH conditions generated by the CO2 (pH ~5.6) compared to higher acidities (pH ~1.6-2) typifying bioleaching testwork. It is of particular note that initial equilibration of shale samples in the mild electrolyte resulted in partial dissolution and recovery of metals (except Cd,V,Zn), an observation which is consistent with proposals from other testwork unrelated to the CO2 tests that the metals in the shale are not hosted within other minerals but rather occur as readily extractable charged ions adsorbed on clays in the shale (see DNI press Jan16/2012).
In a statement, Mr.S.Sabag, DNIís president & CEO, commented: "Öthe possibility of relying on CO2 as a partial leaching agent is an entirely new development and an exciting CO2 consumption sidebar to an otherwise metal mining story which might benefit adjacent oil sands operations by providing a practical use for CO2 emitted and captured from oil sands processing. This new development is synergistic with Provincial and industry led carbon capture and sequestration initiatives in the regionĒ.
DNI plans to broaden the above testwork per recommendations of the above study to expand on current findings. Considerable additional data are also on hand from the tests which might enable calculation of percentages of REE and Specialty Metals also extracted during the CO2 sparging testwork. Additional results will be announced at a later date once the data have been processed.
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