Tag Archives: cyanide

Outotec addresses cyanide consumption with new BIOX refractory gold process

Outotec has introduced its new MesoTHERM BIOX process to significantly reduce cyanide consumption in refractory gold ore treatment.

Traditionally, cyanide consumption with conventional bio-oxidation residues is higher than with residues produced through other oxidative technologies. The Outotec MesoTHERM BIOX® process, based on Outotec’s existing mesophile BIOX process, offers an easy, cost-effective upgrade path that can cut cyanide consumption by as much as 50% compared with conventional bio-oxidation, the company claims.

The BIOX process, which has been in commercial operation for over 30 years, was developed for the pre-treatment of refractory concentrates ahead of conventional cyanide leaching for gold recovery.

“The Outotec MesoTHERM BIOX process enhances the established mesophile BIOX process by combining mesophile bio-oxidation technology with a higher-temperature thermophile oxidative stage to enable an even more effective overall sulphide oxidation step,” Outotec says.

On top of cutting cyanide consumption by as much as 50% compared with conventional bio-oxidation, MesoTHERM BIOX significantly reduces the formation of thiocyanate – a common and stable cyanide species traditionally formed as a further by-product, the company said.

Solubilised species prevalent in the mesophile stage are decanted off in an inter-stage thickening step between the two oxidative processes, simplifying operation of the thermophile stage, the company explained.

For existing BIOX customers, upgrading to BIOX MesoTHERM is a “relatively simple process”, Outotec says. It involves reconfiguring the circuit with the addition of Outotec’s High Rate Thickeners for inter-stage thickening and Outotec OKTOP® Atmospheric Reactors for the thermophile step.

Craig van Buuren, Senior Process Engineer, Outotec, said: “Our conventional mesophile BIOX process has enabled the production of over 25 Moz of gold to date. This novel process takes advantage of these proven technologies to help our customers achieve significant cost savings while also reducing their environmental footprint.”

GreenGold’s ReCYN processing pipeline continues to grow

GreenGold Technology has been making huge waves of late, with its biggest ReCYN resin-based technology build to date nearing completion and several new projects on the horizon.

ReCYN reduces cyanide consumption by up to 50% by capturing free cyanide from plant tailings and recycling it back into the leach circuit while recovering metal complexes and making them available for sale, according to the company. In the process, it detoxifies the tailings stream and guarantees 100%-compliant clean water discharge.

Such technology is in serious demand considering the industry’s operational cost focus, increased stakeholder pressure around the use of cyanide, the need to recycle and replace as much water as possible, and a necessity to improve project economics through the recovery of all payable metals.

On top of this, new and existing gold projects are becoming difficult to process through conventional means with problems around by-products such as copper often proving to be the difference between a sub-economic and economic mine development proposition.

The ReCYN process is based on the use of a functionalised resin bead, pre-treated to allow the dual duty of recovering free and complexed cyanide ions from solution with a high degree of efficiency. GreenGold works with local construction companies to customise treatment plants for each operation to match the various solution chemistries and throughputs, it says.

“The two areas of cyanide recovery and metal detoxification are balanced to achieve the desired compliance levels,” GreenGold says. “Equally applicable to slurries and solutions, the process is technically and economically superior to all others currently available for the detoxification of gold plant tailings.”

The company currently has four ReCYN options for clients, according to Commercial Director, Peter Mellor.

ReCYN I is for active (free) cyanide reduction, while ReCYN II has been devised to include detox applications to recover cyanide complexes such as copper. ReCYN III adds gold recovery as a “secondary function” to the mix.

The fourth option (ReCYN IV) includes gold recovery as a primary option, Mellor told IM, explaining that the development of a plant offering in this configuration could remove the need for a carbon in leach treatment plant in some applications.

It is a ReCYN II installation the company is currently putting the finishing touches to at PT Agincourt Resources’ Martabe gold-silver operation in Sumatra, Indonesia (graphic above).

This project, which will detoxify tailings and recover cyanide and copper, was previously estimated by Whittle Consulting to provide a $126.9 million upside to the project.

Speaking to IM from Australia, Mellor said the company was just over a month away from completing the plant at Martabe before COVID-19 restrictions hit progress. He was confident the company would be back completing plant commissioning before the end of the year.

By far the biggest ReCYN installation of the technology, the ReCYN II plant at Martabe will fit into the 5.5 Mt/y circuit and treat around 1.2 t/d of copper, Mellor said. It will also have benefits in terms of reduced cyanide consumption and improved water quality at the operation.

While work in Indonesia is currently not taking place, the company is making significant progress elsewhere.

Mellor said GreenGold had started detailed engineering for a plant in the Ivory Coast, while it had also completed an economic study on a legacy gold operation in Australia that showed compelling economics and the potential for a ReCYN IV installation for processing gold-bearing tailings.

The company also has some 40 projects it is working on in the laboratory – from Australia to the US – with client awards expected in the next few months.

CyanoGuard receives EU, investor backing for next gen cyanide monitoring solution

Switzerland-based chemtech startup CyanoGuard has completed a fundraising and been awarded a non-dilutive SME Instrument grant by the European Union’s Horizon 2020 program that, it says, will speed up market penetration and develop further applications for its next generation cyanide monitoring solutions.

Established in 2016, CyanoGuard has since developed and commercialised its solutions for gold mining operations, food safety testing and healthcare.

Co-Founders Benedikt Kirchgässler (CEO) and Mathias Cherbuin (CTO) transformed a chemical technology for rapid toxin detection from the labs of the University of Zurich into a “comprehensive digital solution package” that has found its first commercial application in the gold mining industry.

The company has now raised more than CHF3 million ($3.12 million) to help further develop the technology, which CyanoGuard says can minimise cyanide consumption by 12% while maximising extraction efficiency through real-time, instaneous measurement results.

Kirchgässler said: “These funds enable us to scale our ground-breaking monitoring solutions and roll them out to gold mines around the world.

“I am excited about the positive impact that our digital, artificial intelligence-based technology has on the global gold mining industry as well as the local communities and the environment.

“I believe that we will benefit from both the experience of leading venture funds…as well as the support of the European Union to speed up market penetration and develop further applications for our technology.”

With the newly raised capital from this seed round, CyanoGuard plans to accelerate its go-to-market strategy in the global mining industry.

Alex Stöckl, Founding Partner at Wingman Ventures, who has joined CyanoGuard’s Board of Directors following the funding round, added: “With its current offering, CyanoGuard has a unique value proposition for its mining clients that is beyond improved cyanide testing. This encompasses an efficiency-enhancing digitisation of process control and a more sustainable usage of cyanide in mining operations.

“We are convinced that Benedikt, Mathias and their team will drive CyanoGuard to become a globally leading provider of digital mining solutions.”

The freshly obtained funds are also intended to further expedite the development of CyanoGuard’s product offering for food safety and healthcare applications, the company said.

EnviroLeach test results bode well for gold market take-up

EnviroLeach Technologies has announced the successful completion of what it says is a comprehensive lab and bulk sample program using its patented cyanide-free formula on high-grade gravity table tailings material from a mid-tier gold producer.

Estimated gold recoveries from the bulk sample (2.7 t of material) averaged 97% and produced 277.8 oz of gold using the EnviroLeach process, which can effectively dissolve gold into aqueous solution with similar leach kinetics and economics to that of cyanide but is sustainable, safe and environmentally friendly, according to the company.

Following extensive lab and bench scale test programs, a locked cycle, bulk test program (leaching, filtering and electrowinning) was carried out on this 2.7 t bulk sample of table tails from the gold mining operation. The objective of the bulk test program was to determine the efficacy and recovery rates of gold from the host material using EnviroLeach’s proprietary formula and to collect key operational data such as leach kinetics, chemical reusability, reagent consumption and costs, the company said. The bulk test produced no tailings effluent, as all filtrate/liquids were reused in the process.

The test results report an overall average estimated gold recovery of 97% and three gold bars were produced having a combined gold content of 277.8 oz.

Duane Nelson, EnviroLeach CEO, said: “This successful bulk test on these high-grade gravity tails clearly validates the proficiency of our patented formula to offer a cost-effective, sustainable and environmentally friendly extraction alternative to the gold mining sector.

“Thousands of gold mines around the world rely on gravity-based concentration. This bulk test demonstrates that many of these mine operations could benefit from our eco-friendly extraction alternative.

“The adoption of the EnviroLeach process could reduce the industry’s reliance on the conventional cyanide and smelting methods used today and contribute to environmental sustainability across the gold mining sector.”

Golden Predator, EnviroLeach hit on the right gold extraction and recovery formula

Golden Predator Mining says tests have successfully confirmed that EnviroLeach Technologies’ environmentally friendly technology can effectively extract and recover more than 95% of the gold from sulphide concentrates produced at the 3 Aces gold project, in the Yukon of Canada.

The concentrate is produced using Golden Predator’s Secondary Recovery Unit (SRU™).

With this environmentally friendly technology confirmed in successive tests both in the EnviroLeach facility and at the Golden Predator bulk sample processing plant (pictured), the companies have initiated a larger material test run to process up to 5 t of gold-bearing sulphide concentrates to be completed onsite at Golden Predator’s plant in the Yukon, they said.

This testing follows an earlier agreement between the two companies to use EnviroLeach’s proprietary cyanide-free hydrometallurgical technology to extract gold from gravity concentrate produced at 3 Aces.

As part of this testing, a sample of gold-bearing sulphide concentrate recovered in 2018 was shipped from Golden Predator’s plant to the EnviroLeach facility in Surrey, British Columbia, in August of 2019.

Some 55.9 kg of the material was processed using EnviroLeach solution and 96.5% of contained gold was leached in six hours; and gold in solution was extracted by electrowinning and poured into a 91.3 g bar.

A sample of gold-bearing sulphide concentrate recovered in 2019 was also sent to and processed by EnviroLeach at the facility, with 30.4 kg of the material processed using EnviroLeach solution with 96.7% gold recovery in 29 hours; and gold in solution extracted by electrowinning in four hours and poured into a 77.8 g bar.

Following completion of test work in the EnviroLeach facility in Surrey, on-site testing was initiated to leach material at the plant during the week of September 23, 2019. This saw 121 kg of gold-bearing sulphide concentrates produced during 2019 processed in 21 hours with a 96.2% gold recovery; and electrowinning completed in 14 hours, with 255 g of gold recovered from the electrowinning cell and poured into a bar.

Janet Lee-Sheriff, Chief Executive Officer of Golden Predator, said: “Working with EnviroLeach provides us a unique opportunity to lead the way for safe and responsible new cyanide-free extraction methods in processing gold bearing concentrates which has immediate value on our 3 Aces project as well opening up other commercial opportunities.”

The Golden Predator-EnviroLeach working relationship has enabled the companies to successfully demonstrate the first “in the field” recovery of gold from gold-bearing sulphide concentrates, using EnviroLeach’s environmentally friendly formula and Golden Predator’s SRU processing equipment, according to the companies.

EnviroLeach cyanide-free tech to be tested on Golden Predator’s 3 Aces gold

EnviroLeach Technologies and Golden Predator Mining have entered into an agreement that will see EnviroLeach’s proprietary cyanide-free hydrometallurgical technology extract gold from gravity concentrate produced at Golden Predator’s 3 Aces project in the Yukon of Canada.

This working relationship provides both companies with the first on-site bulk test of EnviroLeach’s new cyanide-free technology, they said.

Initial laboratory, pilot scale and production scale testing was successfully conducted at EnviroLeach’s facility in Surrey, British Columbia, prior to on-site testing at Golden Predator’s processing plant in the Yukon. All tests were conducted under the supervision of EnviroLeach and Golden Predator personnel with results to be released shortly, they said.

The initial 5 t bulk test will be conducted in phases and completed at the plant, they added.

Golden Predator operates the plant for the purposes of bulk sample testing of gold concentrate from its 3 Aces project. As part of its processing plant, Golden Predator developed a mobile batch recovery unit (Secondary Recovery Unit or SRU™) for the recovery of gold from its sulphide concentrate. Golden Predator intends to use the EnviroLeach proprietary cyanide-free technology in the SRU, it said.

Duane Nelson, President and Chief Executive Officer of EnviroLeach, said: “The gold recovery from Golden Predator’s arsenopyrite concentrate confirms the ability of our new eco-friendly formula to extract gold into solution from sulphide ores and recover it using conventional technologies.

“EnviroLeach is the only commercial-scale, economically viable and safe hydrometallurgical gold extraction process in the world. Our unique and eco-friendly process will change the way the world produces and recycles gold.”

Janet Lee-Sheriff, Chief Executive Officer of Golden Predator, added: “The plant and SRU are examples of the continuing ways that Golden Predator works to be innovative, testing new methods that have the ability to change how we operate at projects like 3 Aces.

“Working with EnviroLeach provides us a unique opportunity to lead the way for safe and responsible new cyanide-free extraction methods in processing gold bearing concentrates.”

The EnviroLeach process can effectively dissolve gold into aqueous solution with similar leach kinetics and economics to that of cyanide but is sustainable, safe and environmentally friendly, according to the company. This water-based process has a broad applicability spectrum and is effective on most gold ores and concentrates, the company said, potentially unlocking the value of many deposits located in environmentally sensitive areas that cannot be developed using current extraction methods.

Golden Predator’s test processing plant (pictured), the first of its kind in Yukon, Canada, commenced operations in 2016 providing increased metallurgical and geological understanding of its 3 Aces project. The plant is a relatively simple gravity circuit using a closed-circuit water system with no added chemicals due to the free-milling nature of 3 Aces gold.

The 50 t/d closed circuit plant recovers gold from #1 concentrates realising over 85% recovery of contained gold with doré bars sent to a commercial refinery for final processing. Golden Predator is currently testing EnviroLeach’s patent pending technology in it’s SRU for the extraction of gold from their #2 concentrates.

The 3 Aces Project is an orogenic gold project in southeast Yukon which provides the testing material for the processing plant. Golden Predator has to date focused exploration on a broad gold-in-soil anomaly, where numerous orogenic gold-bearing quartz veins have been discovered.

Golden Predator made an early decision to bulk sample at its 3 Aces project when it realised that much of the gold contained in its veins is high grade (not uncommonly over 30 g/t gold) and nuggety. The best way to determine the true gold value of a nuggety gold system is to conduct large scale bulk sampling which also allows Golden Predator the opportunity and ability to conduct on-site bulk metallurgical and processing tests.

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.

GreenGold’s ReCYN to detoxify tailings, recover cyanide and copper at Martabe

Technology provider GreenGold says it has been awarded a ReCYN™ design and install contract with PT Agincourt Resources to detoxify tailings and recover cyanide and copper at its Martabe gold-silver operation in Sumatra, Indonesia.

Jakarta- and Perth-based GreenGold will deliver the project with preferred fabricators for specialist equipment packages, the company said.

In a report published last year, Whittle Consulting called the ReCYN process “a world-leading approach” in cyanide recovery, metal recovery and tailings detoxification. “Based on an innovative resin-bead absorbent, ReCYN reduces cyanide consumption by 50%, capturing free cyanide from the plant tailings and recycling it back into the leach circuit while recovering metal complexes and making them available for sale,” Whittle said.

Whittle also said adopting the technology could provide a $126.9 million upside to the project.

GreenGold said it had received the contract following a record influx of enquires for the technology.

GreenGold CEO, Malcolm Paterson, said of the Martabe contract: “We have come up with an elegant design to fit the space constrained site. We also will be recovering cyanide and copper which previously was destroyed or sent to tails, turning a cost into an economic benefit for the mine.

“We are looking forward to delivering on this strategically important project, and continuing to build on our proven metallurgy and process capability within the precious/base metals sector globally.”

The Martabe mine has a resource base of some 7.4 Moz of gold and 69 Moz of silver.

Goldcorp’s Éléonore gold mine cleans up its act with novel wastewater treatment

The latest winner of Goldcorp’s Global Excellence Awards 2019 to be featured in its online blog is the Éléonore gold mine and a novel system that proved its worth removing ammonia and residual cyanide by-products at the company’s Éléonore gold mine in Quebec, Canada.

Goldcorp said: “For any mining operation, effective wastewater treatment to remove contaminants is an indispensable step needed to minimise environmental impacts and maintain the mine’s social license to operate.

“When elevated concentrations of ammonia and residual cyanide by-products were detected in mill effluent at Éléonore, in 2014, the mill and environmental team took decisive action by introducing a novel wastewater treatment process that rectified the problem and secured Éléonore a Global Excellence Award for Sustainability Stewardship.”

Following Éléonore’s mill start-up in 2014, the new process water bleed (discharge) to water treatment plant (WTP) and paste backfill process resulted in increased concentrations of contaminants in water effluent, according to Goldcorp.

Even though the cause of the ammonia and residual cyanide toxicity couldn’t readily be identified, the Éléonore team immediately notified all major stakeholders, such as the Quebec Environment Ministry, Environment Canada and the Cree Nation Government – Environment Committee of Opinagow Collaboration Agreement, informing them on the extent of the problem and plans to rectify the situation.

France Trépanier, Environmental Coordinator at Goldcorp, said: “From the outset, we wanted to be very open and transparent with key stakeholders on steps we were taking to identify the source of the toxicity and plans to resolve the problem. Through ongoing dialogue and regular reporting, we were able to maintain a collaborative climate and establish strong partnerships based on mutual trust.”

During 2015 and 2016, the Éléonore team developed an action plan, investigated various water treatment options, and executed a series of projects including cyanide detox and leaching circuits optimisation to reduce effluent contamination, the company said.

The team also worked on mill water balance through its zero-bleed project with the objective of reducing contaminant process water discharge to the WTP, which involved reducing fresh water consumption by replacing water-sealed pumps used in the mill with mechanical seal pumps. “These projects increased control of process water contaminant concentration but didn’t resolve toxicity issues,” Goldcorp said.

A consultant working on the toxicity problem recommended the Éléonore team consider zeolite treatment and a Moving Bed Bacteria Reactor (MBBR) system to process wastewater effluent. Zeolite is a mineral well known for its ability to absorb a variety of heavy metals and ammonia. MBBR, more commonly used for municipal water treatment, is an activated bacteria aeration system, where bacteria collected on porous plastic carriers breaks down organic matter from wastewater, according to Goldcorp.

A pilot project found that zeolite treatment removed ammonia but did not eliminate the toxicity. MBBR, on the other hand, could remove ammonia and cyanide by-products delivering non-toxic results at low water temperatures (8°C).

In Spring 2016, the Quebec government granted approval for Éléonore to expand its water treatment plant by adding MBBR treatment while continuing to reduce its process water discharge to reach a zero-bleed operation.

Construction got underway in the fall of 2016, and the MBBR treatment plant was commissioned in May 2017.

“Energy efficiency was one of the critical plant design considerations to minimise heating requirements in winter,” Goldcorp said. “The addition of a heat exchange system and an insulated water circuit ensured that process water could feed the MBBR to keep the bacteria-activated treatment as stable as possible during cold winter months. Now, at the second winter, treatment is achieved without any heating at a temperature around 5°C.”

From concept to completion, Éléonore workers were kept up to date on the project’s progress through regular on-site presentations and stakeholders informed of the mine’s plans through monthly reports, quarterly presentations and site visits, the company said.

Trépanier said: “Consistent communication really enabled us to demonstrate how serious we were about solving this problem, which was essential in helping secure support for this project among stakeholders and regulators.”

Following the MBBR ramp up, Éléonore reduced ammonia and cyanide by-product concentrations in its effluent by more than 90% and was designated 100% in compliance with water quality regulations in October 2017. Since MBBR has been in steady operation, mandatory effluent sampling frequency returned from weekly to monthly.

The Éléonore team recently shared its experience in implementing this novel water treatment technology at a symposium on mining and the environment. Since then, it has received numerous enquiries from other mining companies and have hosted site visits to demonstrate the water treatment process, according to Goldcorp.

“There was a lot of people from different departments working on this project over the last two-and-a-half years,” Trépanier said. “It’s very gratifying to be recognised both externally and by our peers at Goldcorp for a successful outcome. We’re very happy to share what we’ve learned with other mining companies to help improve the industry’s environmental performance.”

BQE Water moves a step closer to first SART application in China

BQE Water has signed agreements with two of the top 10 gold producers in China to complete engineering feasibility studies to integrate the sulphidisation, acidification, recycling and thickening (SART) process and modernise cyanide destruction and residue management at existing operations in Shandong Province.

These studies are being undertaken in response to advancing environmental regulations and to enable the processing of feedstock with elevated levels of cyanide soluble copper, BQE said.

The feasibility studies will see BQE Water, which focuses on management of mine wastewater and metallurgical bleed streams, complete metallurgical and wastewater treatability test work in China and develop a sufficient level of engineering to confirm overall project economics, construction budget and schedule for possible implementation, the company said.

BQE Water calls itself a global leader in the SART process, which enables cyanide consumed by base metals to be recovered and recycled, lowering the cost of gold extraction and reducing the environmental footprint of gold mining projects.

David Kratochvil, President and CEO of BQE Water, said: “There is no question these new contracts were enabled by the success of the water treatment plant we designed and commissioned last year at the nearby Guoda gold smelter. That project has made all the major metallurgical operations in Shandong Province take notice of our capabilities.”

Shandong Province is home to some of China’s top gold producers. In the region alone where BQE Water’s new Guoda water treatment plant recently began operation, there are over 12 metallurgical plants that focus on gold extraction and refining, according to BQE.

Songlin Ye, Vice President for Asia at BQE Water, added: “If these new projects move forward to implementation, we will be able to leverage our operations base at Guoda and our partnership with MWT, the Beijing based company with construction capabilities we formed a joint venture with for the Guoda project, to build what would be the first SART application in China and provide ongoing operations services to ensure performance excellence.”

Cyanide regulations around the world are advancing and target not only residual cyanide contained in wastewater and tailings produced by mining and metallurgical operations but also place strict limits for cyanidation and cyanide destruction by-products such as ammonia, cyanate, thiocyanate and nitrite, according to BQE.

“The goal is to ensure all discharges are non-toxic and do not cause impacts to the receiving environment. As such, proper cyanide management is key to the permitting of new projects and securing a social licence for gold producers.”