HEAP LEACHING & SX just like a carbon absorption system – with a full desorption and recovery system scaled to that absorption skid ,” Dr Gluckman explained .
While the pilot plant was a success in his eyes – “ we demonstrated we could use the beads over and over again , that they could be fully eluted with no residual metals left on them , that our projections for reagent consumption were accurate , etc ” – Kinross , at the start of this year , decided to defer further capital projects at Bald Mountain . Sixth Wave has since moved on . In September , it signed a pact with Rio2 Ltd to test its technology on ore samples from the mine developer ’ s heap leach gold project , in Chile .
The letter of intent will see Sixth Wave perform a combination of leaching and recovery tests using IXOS on ore samples consistent with the expected heap leach mining activity planned for Rio2 ’ s Fenix project .
Upon completion of the testing – and , pending positive results – the two companies will work to negotiate a definitive agreement to proceed to a complete on-site pilot ADR plant scaled to operate on a 400 t pilot leach pad .
Dr Gluckman says the company is also working with several other groups on IXOS projects , including another heap leach mine in Turkey and a project with Agnico Eagle Mines .
Most test work to date has been tied to cyanidation , but Sixth Wave , conscious of growing environmental , social and governance concerns in the industry , is also looking at alternatives .
It recently signed an agreement with Australiabased Mining and Process Solutions ( MPS ) on test work initiatives in North America and Australia integrating IXOS with the MPS GlyCat™ process , the latter of which aims to reduce cyanide consumption while maintaining gold recovery for gold ores from deposits containing nuisance copper .
The two companies are also working in collaboration with the Centre Technologique des Résidus Industriels and a top 10 gold producer in Canada to develop an environmentally friendly flowsheet for the gold mining industry , examining MPS ’ acidic and alkaline leaching technologies , together with Sixth Wave ’ s IXOS technology , for the extraction of gold from alternative lixiviants .
This follows a recent study published in the Hydrometallurgy Journal titled , ‘ Gold recovery from cyanide-starved glycine solutions ( GlyCat ) in the
presence of Cu using molecularly imprinted polymer IXOS-AuC ’. This study found that “ gold recovery increased , while copper recovery decreased with the increasing gold concentration ” during tests of the IXOS-GlyCat combination . The adsorption behaviour of IXOS-AuC had “ the best selectivity compared to three other gold selective resins ”, according to the study , while the IXOS-AuC polymer was proven to be very robust , allowing reuse without deterioration of the polymer or performance .
Dr Gluckman said IXOS has widespread appeal beyond the heap leach industry , with resin-in-pulp and resin-in-leach circuit applications also feasible .
“ We ’ ve also had a lot of interesting opportunities come our way in tailings remediation ,” he said . “ As gold prices remain high , these projects take on new potential life and , because our plant is much more compact than activated carbon plants , we have additional cost benefits in this type of application .”
The copper catalyst
Chalcopyrite is typically the problem child in the copper leaching family .
More than 70 % of copper reserves are contained in this primary sulphide mineral , which is traditionally processed through capital-intensive pyrometallurgical processes or hydrometallurgical processes .
Conventional leaching has typically had poor results on chalcopyrite as , when attempted , a hard , non-reactive coating known as a “ passivation layer ” develops around the ore , preventing contact between the leaching solution and the surface of the mineral , according to Mike Outwin , Co-founder and CEO of Jetti Resources , a technology-driven natural resources company .
Outwin and Jetti say they have come up with a technology that disrupts the sulphur metal bond of the mineral .
This catalyst allows for the leaching solution to contact the copper , enabling the extraction of the metal to take place unimpeded , according to Outwin .
The process sees Jetti ’ s soluble catalyst added to the leaching solution , which percolates through the ore . After percolation , copper from the copper-rich leachate is recovered using the industry standard processes of solvent extraction and electrowinning ( SX-EW ) to produce copper cathode .
Outwin says Jetti ’ s catalytic formulation is unique in that it integrates seamlessly with the existing heap leach SX-EW infrastructure already on site .
Jetti ’ s Mike Outwin ( pictured left , photo courtesy of Jetti Resources ) says the results from the commercial operation at Pinto Valley , ( photo courtesy of Capstone Mining Corp ) match very well with the outcomes from the pilot test programs the company has been operating
“ There are no new material preparation steps needed and the catalyst works across all crush sizes so it can be used on almost all run of mine material ,” he said .
This means limited levels of capex are required to implement the technology , which significantly increases copper yields and profitability .
The details of the chemical compounds used in Jetti ’ s catalyst are confidential , with Outwin saying the company has a comprehensive set of patents across relevant jurisdictions to protect this breakthrough technology , which could present a viable option for processing a significant worldwide copper resource .
“ Huge amounts of chalcopyrite and other sulphide ores are currently stockpiled as waste or left in the ground unmined , leaving vast resources of valuable copper unexploited ,” he told IM . “ By unlocking the value in this material , Jetti ’ s technology allows the conversion of waste into high-value product and can extend the life of existing mines and reduce the need to develop new operations .”
And , with the technology allowing for the use of leaching systems on low-grade sulphide ores , it also reduces the energy and water that would typically be used through a pyrometallurgical route , according to Outwin .
“ As a result , mine operators can increase production while reducing overall environmental impacts ,” he said .
Other technologies to treat chalcopyrite have emerged ( see ROL options below ), but none have been commercially proven or offer the same intensity advantages of Jetti ’ s process , according to Outwin .
“ Jetti ’ s catalyst does not require heating or grinding of ore to small sizes and , therefore , it can be applied directly to low-grade ores without concentration , he said . “ In this way , it integrates seamlessly with the existing heap leach SX-EW infrastructure already on site , meaning that it can be deployed rapidly and with very limited capex .
“ There is no other process that has been proven to leach chalcopyrite that is low intensity .”
In terms of capital outlay , the main item of consideration is the installation of an on-site catalyst addition facility like the one built at Capstone ’ s Pinto Valley operation in Arizona , in the US .
Capstone started using Jetti ’ s technology at the Pinto Valley leaching operation back in 2019 as part of its PV3 Optimization strategy and , within a year , cathode production per area irrigated had doubled .
NOVEMBER / DECEMBER 2020 | International Mining 59