Tag Archives: arsenic

WEC Projects, Multotec combine for Mali gold mine modular wastewater treatment plant

WEC Projects, in conjunction with its partner, Multotec, has designed and custom engineered a wastewater treatment plant for a gold mine in Mali, West Africa.

The plant, used to remove arsenic from the mine’s wastewater stream, incorporates a modular design which simplifies the logistics and reduces the costs of transport and installation, according to WEC Projects.

The international mine operator is a client of Multotec, an engineering company specialising in mineral processing plant design and installation. The company approached WEC Projects, a local EPC contractor in the water and wastewater treatment industry, to jointly develop a customised solution to remove toxic arsenic from the mine’s wastewater. A multi-stage removal system was required to meet the strict standards for the mine’s discharge. However, the system also required a modular design which would facilitate the transportation, installation and commissioning of the plant.

Wayne Taljaard, Managing Director of WEC Projects, said: “The mining industry in Africa presents some very unique challenges, not the least of which are the remote locations of many of the mines and the difficulties experienced in getting staff and equipment to sites where road, power and water infrastructure is often lacking, hence the requirement by Multotec for a modular solution that would allow for rapid transport to site and to simplify its installation and commissioning.

“The COVID-19 pandemic added to the difficulties for us and the client, causing delays that reduced the time frame for delivery.”

In the treatment process, the mine’s wastewater undergoes primary solid/water separation using coagulation and flocculation and the primary clarifier. From there it enters a two-stage chemical precipitation and secondary clarification process to reduce the arsenic levels. The final stage sees the sludge undergo dewatering before disposal. The treated water, although not potable, is then reused by the mine for process applications.

The plant has a processing capacity of 150 cu.m/h and is capable of reducing the arsenic levels from around 13 mg per litre to less than 0.1 mg per litre.

Taljaard added: “The project, incorporates a number of unique features in addition to its modular design, including nine custom-designed, proprietary lamella clarifiers and a multi-stage arsenic removal process capable of treating the wastewater to the mine’s discharge standards. WEC Projects has completed a number of water and wastewater treatment projects throughout Africa. Our ability to provide a customised and modular solution for Multotec underscores our ability as a major player in the industry both in South Africa as well as across the continent.”

Gold industry ready to take action on cyanide use, DST’s Lemieux says

The move away from cyanide in gold processing has been talked of for many years, with words often not followed by actions, yet David Lemieux, President and CEO of Dundee Sustainable Technologies (DST), believes the industry is now starting to get serious about assessing alternative lixiviants.

His assertion comes on the back of one of the biggest gold miners in the world recently making such a move with the help of DST.

Back in December, Newmont signed a Technology Transfer Licensing Agreement with DST to use its cyanide-free gold extraction technology, known as the CLEVR Process™.

The CLEVR Process uses no cyanide, produces no toxic liquid or gaseous effluent and the solid residues are inert, stable and non-acid generating, according to the company. With fast leach kinetics of 1-2 hours, the ability to treat refractory ores and handle base metals, plus a competitive capital/operating expense, the solution has been gaining prominence in the gold market.

Having tested the process out on a variety of ores from various sources, DST is now in the commercialisation phase with CLEVR.

The pact with Newmont follows a successful test work program in the March quarter of this year, after which the gold miner expressed its interest in the execution of such an agreement. This led to Newmont conducting laboratory CLEVR leaching tests in its technical facilities in Englewood, Colorado.

As part of the agreement, DST and Newmont, agreed to:

  • A two-year, non-exclusive licence for the use of CLEVR at the laboratory scale in its Colorado technical facilities, with an option to renew for an additional two-year period under the same terms;
  • Technology implementation support by DST, including all technology laboratory protocols in addition to technical training sessions to initiate and support the technology transfer and practical operations;
  • Ongoing technology support, and for DST to review the laboratory test plans, execution and results conducted by Newmont; and
  • Any process scaling-up requirements resulting from positive applications of CLEVR will be conducted jointly with Newmont at DST’s technical facilities in Canada and/or on-site using DST’s technology and engineering group expertise.

Lemieux said the agreement should be viewed as an indication the gold industry is serious about assessing alternative processing approaches.

“DST’s CLEVR Process is a mature and developed novel gold processing technology that allows majors to properly assess how it can be implemented within a given project in terms of environmental benefits, operational efficiency, and operating and capital costs,” he told IM. “Such a level of detail then allows for properly integrated decision making.”

He said there had been increased interest over the years from the industry with regards to alternative processing approaches, which is likely to continue as more jurisdictions target cyanide operations and pressure operators to reduce their dependency on the lixiviant as the main and sole gold recovery mean.

CLEVR is one of two “novel metallurgical processes” DST has in its portfolio, the other being its GlassLock Process™.

GlassLock is a patented process for the sequestration and stabilisation of the arsenic often associated with copper, gold, silver or polymetallic deposits.

Dundee Sustainable Technologies GlassLock industrial demonstration plant on site at an operating copper smelter

In DST’s approach, the arsenic is incorporated into a highly stable and insoluble glass form that can contain up to 20% arsenic, while meeting or exceeding the requirements of the USA EPA’s toxicity characterisation leaching procedure and the Synthetic Precipitation Leaching Procedure, the company said.

Also in the commercialisation phase, GlassLock has been operating at an industrial scale thanks to a demonstration facility built and operated by DST.

According to Lemieux, the increased number of complex orebodies currently being developed means there is likely to be more interest in both CLEVR and GlassLock.

“The chemistry and conditions of the CLEVR process can allow for improved gold recoveries,” he said. “This, combined with DST’s ability to efficiently and permanently stabilise arsenic using GlassLock, is providing good opportunities for DST.”

The Glasslock process, he said, is equally targeting existing operations that have immediate arsenic production and stabilisation needs as well as operations/miners required to address and stabilise legacy arsenical material as part of their permitting requirements.

These abilities were recently recognised by engineering firm Hatch, which entered into a Technology Framework Agreement with DST that could see GlassLock used in combination with Hatch’s fluid bed reactor and arsenic dry scrubbing technologies on gold and arsenopyrite projects.

The objective of the agreement was to “synergise” Hatch’s extensive client base, commercialisation and marketing expertise, fluid bed reactor and arsenic dry scrubbing technologies, and large-scale equipment engineering, supply, procurement, and life cycle services capabilities with DST’s innovative technology to identify and develop potential gold and arsenopyrite projects using GlassLock, the companies said.

While they cannot point to specific results of these two technologies complementing each other, Lemieux said DST has continued and is currently working on testing programs where the roasting and vitrification approach is applied on complex gold concentrates.

“These programs were generated and originate from DST’s own development efforts, but we hope to see more similar opportunities coming from Hatch in the future,” he said.

Lemieux concluded: “Implementing novel metallurgical processes within the industry takes time and DST has progressed greatly, and continues to do so, on the design and operating parameters of specific on-site implementations of GlassLock and/or CLEVR facilities.”

Latest Kamoa-Kakula copper studies reaffirm project’s world-class status

The latest economic studies on Ivanhoe Mines and Zijin Mining Group’s majority-owned Kamoa-Kakula project in the Democratic Republic of Congo have indicated the asset could become the world’s second largest copper mining complex.

First production at Kamoa-Kakula is less than a year away, but the project partners have continued with a series of economic studies that emphasise the world-class nature of the orebodies within their control.

The headline maker is the results of a preliminary economic assessment that has evaluated an integrated, multi-staged development to achieve a 19 Mt/y production rate at the mine, with peak annual copper production of more than 800,000 t.

At the same time, a prefeasibility study (PFS) has been carried out to look at mining 1.6 Mt/y from the Kansoko mine, in addition to 6 Mt/y already planned to be mined from Kakula, to fill a 7.6 Mt/y processing plant at Kakula.

A definitive feasibility study (DFS) has also evaluated the stage-one, 6 Mt/y plan at Kakula, which is currently being constructed and is less than a year away from producing first copper, according to Ivanhoe Co-Chair, Robert Friedland.

While the operation looks to have the scale of a world-class asset, it will also have top ranking ‘green’ credentials, according to Friedland.

“The Kakula mine has been designed to produce the world’s most environmentally-responsible copper, which is crucial for today’s new generation of environmentally- and socially-focused investors,” he said.

“Zijin shares our commitment to build the new mines at Kamoa-Kakula to industry-leading standards in terms of resource efficiency, water and energy usage, and minimising emissions. We are blessed with ultra-high copper grades in thick, shallow and flat-lying orebodies – allowing for large-scale, highly-productive, mechanised underground mining operations; and access to abundant clean, sustainable hydro electricity to power our mines – providing us with a distinct advantage in our goal to become the world’s ‘greenest’ copper miner and be among the world’s lowest greenhouse gas emitters per unit of copper produced.”

The project recently retained Hatch of Mississauga, Canada, to independently audit the greenhouse gas intensity metrics for the copper that will be produced at Kamoa-Kakula.

The Kamoa-Kakula Integrated Development Plan (IDP) 2020, as the companies refer to it, builds on the results of the previous studies announced in February 2019.

DFS to 6 Mt/y

The new DFS incorporates the advancement of development and construction activities to date, and has once again confirmed the outstanding economics of the first phase Kakula Mine, Ivanhoe said.

It evaluates the development of a stage one, 6 Mtpa underground mine and surface processing complex at the Kakula deposit with a capacity of 7.6 Mt/y, built in two modules of 3.8 Mt/y, with the first already under advanced construction (see photo). It comes with an internal rate of return of 77% and project payback period of 2.3 years.

The first module of 3.8 Mt/y commences production in the September quarter of 2021, and the second in the March quarter of 2023. The life-of-mine production scenario provides for 110 Mt to be mined at an average grade of 5.22% Cu, producing 8.5 Mt of high-grade copper concentrate.

The Kakula 2020 DFS mine access is via twin declines on the north side and a single decline on the south side of the deposit. One of the north declines will serve as the primary mine access, while the other decline is for the conveyor haulage system, which was recently commissioned.

The primary ore handling system will include a perimeter conveyor system connected to truck load-out points along the north side of the deposit. The perimeter conveyor system will terminate at the main conveyor decline.

The mining method for the Kakula deposit is primarily drift-and-fill using paste backfill (around 99%); with the exception of a room-and-pillar area close to the north declines, which will be mined in the early years of production. The paste backfill system will use a paste plant located on surface connected to a distribution system that includes a surface pipe network connected to bore holes located at each connection drive on the north side of the orebody, the company says.

The Kakula concentrator design incorporates a run-of-mine stockpile, followed by primary cone crushers operating in closed circuit with vibrating screens to produce 100% passing 50 mm material that is stockpiled.

At the end of August, the project’s pre-production surface ore stockpiles totalled an estimated 671,000 t grading 3.36% Cu, including 116,000 t of high-grade ore grading 6.08% Cu.

The crushed ore is fed to the high pressure grinding rolls operating in closed circuit with wet screening, at a product size of 80% (P80) passing 4.5 mm, which is gravity fed to the milling circuit.

The milling circuit incorporates two stages of ball milling in series in closed circuit with cyclone clusters for further size reduction and classification to a target grind size of 80% passing 53 micrometres (µm).

The milled slurry is pumped to the rougher and scavenger flotation circuit where the high-grade, or fast-floating rougher concentrate, and medium-grade, or slow-floating scavenger concentrate, are separated for further upgrading. The rougher concentrate is upgraded in the low entrainment high-grade cleaner stage to produce a high-grade concentrate.

The medium-grade or scavenger concentrate together with the tailings from the high-grade cleaner stage and the recycled scavenger recleaner tailings are combined and further upgraded in the scavenger cleaner circuit. The concentrate produced from the scavenger cleaner circuit, representing roughly 12% of the mill feed, is re-ground to a P80 of 10 µm prior to final cleaning in the low entrainment scavenger recleaner stage.

The scavenger recleaner concentrate is then combined with the high-grade cleaner concentrate to form final concentrate. The final concentrate is then thickened and pumped to the concentrate filter. Final filtered concentrate is then bagged for shipment to market.

The scavenger tailings and scavenger cleaner tailings are combined and thickened prior to being pumped to the backfill plant and/or to the tailings storage facility. Backfill will use approximately half of the tailings, with the remaining amount pumped to the tailings storage facility.

Based on extensive test work, the concentrator is expected to achieve an overall recovery of 85%, producing a very high-grade concentrate grading 57% copper. Kakula also benefits from having very low deleterious elements, including arsenic levels of 0.02%.

7.6 Mt/y PFS

The PFS evaluating mining 1.6 Mt/y from the Kansoko mine envisages an average annual production rate of 331,000 t of copper at a total cash cost of $1.23/lb copper for the first 10 years of operations, and annual copper production of up to 427,000 t by year four. This comes with an internal rate of return of 69% and project payback period of 2.5 years, according to Ivanhoe.

Development would see Kakula-Kansoko benefit from an ultra-high, average feed grade of 6.2% Cu over the first five years of operations, and 4.5% Cu on average over a 37-year mine life.

There are currently two mining crews at Kansoko, in addition to the 10 mining crews (three owner crews and seven contractor crews) currently at Kakula, with the ability to increase this number to fast-track the development of Kansoko, Ivanhoe said.

19 Mt/y option

The Kamoa-Kakula 2020 PEA presents initial production from Kakula at a rate of 6 Mt/y, followed by subsequent, separate underground mining operations at the nearby Kansoko, Kakula West and Kamoa North mines, along with the construction of a 1 Mt/y of concentrate direct-to-blister smelter. The smelter section of the study saw China Nerin Engineering act as the main engineering consultant with Outotec providing design and costing for propriety equipment.

The Kamoa North Area comprises five separate mines that will be developed as resources are mined out elsewhere to maintain the production rate at up to 19 Mt/y, with an overall life in excess of 40 years, Ivanhoe says.

For this integrated 19 Mt/y option, the PEA envisages $700 million in remaining initial capital costs, with future expansion at Kansoko, Kakula West and Kamoa North funded by cash flows from the Kakula mine, resulting in an internal rate of return of 56.2% and a payback period of 3.6 years.

This shows the potential for average annual production of 501,000 t of copper at a total cash cost of $1.07/lb copper during the first 10 years of operations and production of 805,000 t/y of copper by year eight, Ivanhoe said.

“At this future production rate, Kamoa-Kakula would rank as the world’s second largest copper mine,” the company said.

Clean TeQ DESALX plant up and running at Kirkland Lake’s Fosterville gold mine

Clean TeQ Holdings Limited has formally handed over a Continuous Ion Exchange Desalination (DESALX®) plant to Kirkland Lake Gold’s Fosterville gold mine in Victoria, Australia.

Clean TeQ says it was engaged to design, supply and commission a two million litre-per-day Clean TeQ DESALX mine water treatment plant, with the plant designed to deliver a sustainable water management solution by treating mine process water.

The plant construction was completed in late 2019, with commissioning and operations commencing in early 2020. Now, Clean TeQ has confirmed the plant has passed the performance tests specified in the engineering, procurement and construction contract and the customer has issued a formal notice of acceptance and completion, it said.

Sam Riggall, Clean TeQ CEO, said: “After successfully demonstrating the world’s first ever commercial scale CIF plant in Oman late last year, this is yet another moment of great significance for Clean TeQ.

“Confirmation of the successful deployment of our innovative DESALX solution for this application, designed and delivered by Clean TeQ, is strong validation of our proprietary continuous ion exchange technology, and provides us with a firm foothold in the mining waste water treatment market from which we can continue to grow the business.”

The DESALX technology consists of two continuous ionic filtration (CIF®) modules in series removing divalent cations and anions present in the water through complementary processes. The modules contain ion exchange resins that are cycled between columns using air lifts, allowing for continuous operation and regeneration of the system. This system increases impurity removal efficiency, reduces chemical use, and provides protection against fouling, according to Clean TeQ.

The DESALX solution is well suited to purification of difficult to treat waste waters with high hardness, sulphate, and heavy metals as well as suspended solids which can foul reverse osmosis membranes. These types of waste waters are common in the mining industry, including acid mine drainage water, the company explained.

At Fosterville, the equipment provided by Clean TeQ includes a precipitation package to remove antimony and arsenic. The effluent from the clarifiers is treated by the DESALX plant to remove sulphate, calcium and magnesium with gypsum as the only by-product. The DESALX effluent is then further treated by reverse osmosis to produce water for re-use.

“The Clean TeQ system is a key enabling component of the customer’s overall water management strategy which includes a medium-term target of creating a true ‘zero liquid discharge’ solution that does not produce any saline brine and includes aquifer reinjection,” Clean TeQ said.

Clean TeQ Water is now focused on completing one additional key project at a copper-cobalt mine in the Democratic Republic of the Congo, and a number of pilot programs in China.

“This Clean TeQ system, as well as the plants recently completed in Oman and Australia, are the first of their type anywhere in the world and have been deployed as part of three different technical solutions,” the company said. “The successful delivery and commissioning of these plants provides strong demonstration of the efficacy of Clean TeQ’s suite of proprietary ion exchange technologies and their versatility for metal extraction and wastewater treatment. As commercial scale plants, the facilities provide a valuable platform from which to now rapidly grow Clean TeQ Water.”

Dundee’s GlassLock Process engineers an opening at West Africa gold mine

Dundee Sustainable Technologies (DST) and its proprietary GlassLock Process™ is to help a West Africa mine stabilise legacy arsenic-bearing material at its gold operation following a new mandate agreement.

The mandate agreement, entered on June 8, consists of delivering an engineering package for a plant using DST’s GlassLock Process. It follows a preliminary metallurgical test program with the same customer from back in the March quarter.

This program saw over 40 kg of arsenic- and gold-bearing material received at DST’s technical facilities in Canada, whereby DST successfully combined gold recovery with the stabilisation of arsenic using GlassLock, it said.

A glass product containing over 15% arsenic was generated and successfully met the requirements of the United States Environmental Protection Agency’s toxicity characterisation leaching procedure (TCLP, Method 1311), DST said.

“As a result, the customer awarded the engineering mandate to DST to perform process optimisation and an engineering study at the prefeasibility (+/-25%) level,” it said. “The agreement includes engineering fees in the amount of C$101,000 ($74,436) to be paid to DST for this work as per its business plan to generate revenues for the corporation while the technology is progressing toward implementation.”

The final report is due at the beginning of September 2020, DST said.

Back in May, DST announced it had entered into a commercial agreement to provide engineering services to a gold and copper producer for a full-scale plant of its GlassLock Process as part of a C$600,000 Class 4 engineering package.

Since the construction of its pilot plant in 2016, DST has continued to demonstrate the validity of its technology, moving from pilot level to the industrial demonstration scale, where arsenical material was processed to generate vitrified arsenical glass, containing up to 20% arsenic while meeting the TCLP Method 1311.

“GlassLock is becoming an effective and cost attractive technique to segregate arsenic and is therefore opening new opportunities for arsenic-bearing precious metals deposits, concentrates or contaminated sites considered to contain too much arsenic to be exploited,” the company said.

This agreement is another major achievement in DST’s commercialisation efforts, it added.

Dundee Sustainable Technologies makes CLEVR, GlassLock process progress with China

Dundee Sustainable Technologies says it has received a mandate from a Chinese customer to continue testing of the cyanide alternative CLEVR Process™.

The company has received a 30-kg sample of mineralised material from the customer and a payment for this work, DST said, explaining that the goal of the work is to demonstrate its proprietary CLEVR Process can extract gold at a rate of 95% or better.

Brian Howlett, President and CEO, said: “Management of DST is very excited to be developing our CLEVR Process technology into China at this time. China controls a key portion of the gold and base metals processing capacity in the world and will be a key market going forward for our technologies.”

DST, back in December, said it had completed analysis of the samples from this customer and had been able to increase recovery of the gold from the customer’s concentrate from 71% using cyanide to over 90% at a lab scale using its technology.

CLEVR uses no cyanide, produces no toxic liquid or gaseous effluent, and the solid residues are inert, stable and non-acid generating, according to DST.

DST Management has also submitted a 5-kg sample of glass from its GlassLock Process™ to Chinese authorities for regulatory testing with the goal of classifying the glass as non-hazardous waste product suitable for disposal in the Chinese market.

GlassLock is a patented process for the sequestration and stabilisation of the arsenic often associated with copper, gold, silver or polymetallic deposits.

Canada Cobalt Works moves to protect Re-2OX process following SGS testing

Canada Cobalt Works says it has made important breakthroughs in its proprietary and environmentally green Re-2OX process for the recovery of cobalt, precious metals and base metals, and will look to submit a patent application to protect the technology.

New testing using SGS Lakefield in Peterborough, Ontario, Canada, has highlighted further optimisation of Re-2OX can allow the recovery of silver and copper for the first time, while also increasing the recovery rates for cobalt and nickel.

“In refining the Re-2OX process through a one-step leach extraction, overseen by Canada Cobalt adviser Dr Ron Molnar, SGS has recovered >99% cobalt, >99% silver, 99% nickel and 99% copper while removing 99% of arsenic from a composite of gravity concentrates,” the company said.

The gravity concentrates tested at SGS were from the historic Castle mine, in Ontario, classified as waste material and grading 10.2% Co, 11,000 g/t Ag, 0.26% Cu, 1.49% Ni and 45.1% arsenic.

Re-2OX skips the normal smelting process to create battery-grade cobalt sulphate, according to Canada Cobalt Works. The company said nickel-manganese-cobalt (NMC) battery-grade formulations are also in the pipeline.

“In addition, the ability of Re-2OX to achieve exceptionally high recovery rates for both cobalt and silver, plus nickel and copper, while also removing 99% of arsenic, expands the potential of the Castle mine given Phase 1 underground results released February 19, 2019, and a second phase starting soon,” the company said. “Furthermore, Re-2OX is a value-driver for the company’s planned tailings programs at Castle and elsewhere in the district, and will also be used by Canada Cobalt to immediately build a new model of ‘streaming’ opportunities for the company with respect to other battery metal projects while protecting the process.”

Given the current optimisation level of Re-2OX, and the growing importance of this hydrometallurgical process to Canada Cobalt and its shareholders, the company has now initiated the process of submitting a patent application for this proprietary metal extraction method.

Frank J Basa, Canada Cobalt President and CEO, said: “The fact that SGS has demonstrated that Re-2OX can very efficiently recover a broad set of metals from arsenic-rich material, ranging from low grade to high grade, further de-risks the Castle mine project and expands opportunities to build shareholder value. Further Re-2OX optimisation will target the recovery of gold.”