BMR Group announced on 1 June that in co-operation with Kupfermelt Metal Processing CC, its metallurgical partner, a recovery of 77.2% Zn had been achieved from the ISF Slag (ISFS), albeit at a cost of high sulphuric acid consumption.
Recognising that this stockpile potentially contains 120,000 tonnes of Zn metal, the company announced that test work would be continued in order to investigate ways of mitigating the high acid consumption by inter alia modifying the process route and blending it with either Leach Plant Residues (LPR) or Wash Plant Tailings (WPT).
BMR says the board has now announced that it has successfully completed laboratory scale test work, using a sulphating acid brine leach, on randomly selected LPR/ISFS samples composited in the ratio of 2:1, which approximates to the individual tonnages of the two assets.
The laboratory scale test work, whose assay results were verified by an independent accredited laboratory, generated recoveries from the composite of up to circa 85% Zn and 91% Pb at a leach temperature of 80oC, and 75% Zn and 80% Pb at ambient temperatures.
Importantly, the sulphuric acid consumption was more than halved, when compared to the September 2015 tests, to approximately 500kgs/tonne.
The Board is also pleased to report that the sulphating acid brine leach process also recovered approximately 90% of the contained vanadium from the ISFS/LPR composite. The ISFS potentially contains 9000 tonnes of Vanadium (V) which is expected to be recovered in the form of vanadium pentoxide, which has a current aggregate market price in excess of US$15,000 per tonne.
BMR's metallurgical partner has advised that the proposed Kabwe processing plant can in due course be modified to incorporate a sulphating acid brine leach circuit to process the ISFS/LPR composite. The Company's strategy remains however to treat first the WPT with the acid brine leach process.
In light of the success of the sulphating acid brine leach tests to recover Zn, Pb and now V, the Company now intends to commission a study to convert the ISFS stockpile into a JORC compliant resource.
Vanadium is also present in the pregnant liquor solution produced by the proposed WPT treatment process. Optimisation test work to ensure the selective recovery of V from the pregnant liquor solution will be completed shortly. The Board has therefore engaged Alfred Knight Laboratories in Kitwe, Zambia to investigate the inclusion of a vanadium recovery circuit in its proposed WPT acid brine treatment facility.
At 9:14am: (LON:BMR) Berkeley Mineral Resources PLC share price was +0.13p at 5.63p