Tag Archives: precious metals

EnviroGold to expand tailings remediation with patent application for proprietary electrochemical process

EnviroGold Global Ltd has filed a patent application for a proprietary electrochemical process designed to achieve advanced metal recoveries from refractory ores with reduced capital expenditure compared with industry-standard solutions, adding to the company’s suite of solutions for metal recovery and environmental remediation.

“We are very pleased with this development that we believe increases the value of our intellectual property portfolio and expands the company’s opportunities to remediate legacy tailings dumps.”, Dr Mark Thorpe, EnviroGold Global’s CEO, said. “The residual metals contained in tailings are commonly encapsulated in refractory ores and it is estimated that the value of precious metals currently locked up in tailings storage facilities and old mine sites exceeds $1 trillion, increasing by $20 billion per annum. Further, as the proportion of refractory gold reserves continues to increase globally, we believe the ability to achieve advanced metal recovery rates and attractive economics from the processing of refractory ores provides better environmental outcomes, expands the company’s addressable market and creates an enduring, competitive advantage.”

Commenting on the patent filing, EnviroGold Global’s Chief Technology Officer, Brock Hill, said: “Refractory ores resist conventional metal extraction due to an impervious mineral matrix surrounding super-fine metal particles. The complex processes required to significantly improve extraction from these ores can drive substantial increases in a project’s capital expenditure and operating expenditure, often rendering otherwise attractive resource recovery opportunities uneconomic. EnviroGold Global’s patent pending process is designed with advanced electrochemical technology to induce changes in the metal-bearing matrix and achieve superior metal recovery rates.”

This process, in conjunction with other proprietary solutions developed for the removal of environmental contaminants, including cyanide, allows EnviroGold Global to provide a compelling value proposition for mine site owners while reclaiming and recharging natural resources, ultimately positioning the company to actively increase its significant tailings reprocessing pipeline, it said.

Curtin University ups glycine gold leaching rates with permanganate agent

Curtin University researchers say they have improved their award-winning glycine leaching technology by “significantly enhancing” the leaching rates for gold ore by using a low concentration of a strong oxidising agent known as potassium permanganate.

The Curtin team is currently working with minerals industry partner, Mining and Process Solutions Pty Ltd (MPS), to commercialise the new process.

The research, published in Hydrometallurgy and led by Professor Jacques Eksteen and Dr Elsayed Oraby both from the Western Australia School of Mines: Minerals, Energy and Chemical Engineering, found that adding potassium permanganate to the process could solve the problems currently associated with leaching gold with glycine (in the absence of cyanide), such as the need for higher temperatures, glycine concentrations and oxygen addition levels.

Professor Eksteen said the research team evaluated various oxidants for their new alkaline glycine gold leach system, with the most successful results observed with potassium permanganate.

“Traditionally, leaching or separating gold and other precious metals from an ore deposit or e-waste materials requires the use of cyanide – a highly toxic chemical compound that is known to have detrimental effects to the environment and to the human body,” Professor Eksteen said. “Industrially, it is very expensive to detoxify cyanide, but it still does not eliminate the risks associated with transporting, handling and processing the chemical.”

Professor Eksteen said glycine is naturally produced by the human body and is essential for life, while cyanide, on the other hand, is dangerous.

“Permanganate and glycine partially decompose to form insoluble manganese dioxide, insoluble calcium oxalate, and nitrogen all of which are naturally occurring, low-toxicity chemical compounds,” Professor Eksteen said. “Whereas cyanide retains its toxicity, even in the waste solution of the extraction process.”

With low concentrations of potassium permanganate being added to the alkaline glycine system, the researchers were able to leach 85.1% of gold from the ore deposit (similar to the extraction by cyanidation) at ambient temperature and using a substance known as a benign reagent, according to Professor Eksteen. This is “quite an achievement” compared with the industry standard, he said.

Dr Oraby said the new process builds on Curtin University’s important work in this space, which has been ongoing for the past eight years.

“Researchers at Curtin University have spent years developing a new leaching process and our work broadens the use of this patented technology, making it more suitable for extracting gold deposits,” Dr Oraby said. “We believe this new process will bring many benefits to gold extraction industries, which, from an environmental point of view, is a much friendlier extraction method.”

The full paper from Hydrometallurgy is titled: ‘Gold leaching from oxide ores in alkaline glycine solutions in the presence of permanganate’.

Kwatani collaborating with EPCMs, miners on bespoke screening options

Mineral process plant designs are favouring higher-capacity vibrating screens and a more holistic approach to plant optimisation, according to screen specialist Kwatani.

“These trends hold great potential for the mining sector, and Kwatani has been at the forefront of technologies driving this direction,” Annelize van der Walt, Kwatani’s Business Development Manager for Mining and Minerals, says.

Vibrating screens are essentially the “glue” that integrates various unit processes, from bulk materials handling to optimally liberated comminution and pre-concentration, according to the company.

“Larger, engineered-for-tonnage screens are growing in popularity, as they reduce the number of processing modules and hence the level of infrastructure required, especially on mega-projects,” van der Walt says. “Higher capacity is becoming the new design standard for greenfields projects.”

There is also an ever-greater demand for reliability and uptime in these mission-critical machines, as well as an expectation of longer lifespans. All this requires bespoke solutions that address site-specific conditions, van der Walt says, while leveraging digital technology for real-time monitoring and control.

“Kwatani’s metallurgists and engineers use their extensive on-site experience and in-house laboratory facilities to innovate from our proven technologies,” she says. “A cornerstone of our philosophy is close collaboration with engineering, procurement and construction management contractors and end-customers to customise solutions, from concept to construction, commissioning and operation.”

Annelize van der Walt, Kwatani’s Business Development Manager for Mining and Minerals

Specific conditions include waterless beneficiation in arid Mauritania, where Kwatani’s screens operate completely dry in an iron ore plant. In South Africa and Botswana, meanwhile, the company has retrofitted dewatering screens to reduce water consumption, while increasing output by 40% with the same footprint.

“We also recently designed screens for exceptional ore characteristics in a precious metal beneficiation facility in Canada,” she said. “This required a high level of customisation, not only in the screening media but in the mechanical design.”

Remote mine locations – which are difficult to access for maintenance and replacement purposes – also guide the design parameters. In a recent project, Kwatani innovated by selecting special hard-wearing materials for the construction of the screening equipment. The design included components that would provide early warning of wear.

Embracing a more holistic plant design approach, customers often invite Kwatani to participate in optimising the screening side of their chosen beneficiation technology, van der Walt says. A different screening approach would be taken, for instance, in a dry pre-concentration application than in wet dense medium separation.

“This holistic approach is also facilitating greater synergy between original equipment manufacturers,” she says. “This is a very positive trend, allowing us to consider the impact of different equipment on the performance of each – from mineral processing apparatus to transfer chutes.”

Underpinning Kwatani’s responsiveness to customer’s specific needs is its ongoing research and development.

“Our R&D unit is currently working on projects to suit our designs to novel crushing and grinding technologies, which are changing the whole approach to the process flow of future plants,” van der Walt says. “These are significant innovations for the mining sector, and we are excited to be at the forefront with our evolving screen designs.”

Kwatani is incorporating digital technologies to facilitate remote monitoring and control of its vibrating screens. It is also piloting a service app for mobile phones, which helps operations predict their maintenance needs more accurately. The app also helps to drive down the total cost of ownership by gathering data that can be used in future design improvements.

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.”

Outotec processing expertise and tech on its way to Mexico precious metals project

Outotec has won a contract for the delivery of a complete minerals processing plant for a precious metals project in Mexico, as part of wider €30 million ($34 million) order.

The company will also deliver process equipment for upgrades of two other sulphide silver ore processes for the same customer.

The total value of the contracts booked in Outotec’s December quarter order intake is approximately €30 million ($34 million), Outotec said.

The scope of the delivery includes the entire process flowsheet of grinding mills, flotation machines, concentrate and tailings thickeners, as well as concentrate filters, automation, and various spares and supervision services for the new precious metals concentrator.

For the upgrade of existing silver processes, Outotec will deliver additional flotation machines and multiple fine grinding equipment for improved recovery.

The deliveries will take place in the end of 2019, Outotec said.

Kimmo Kontola, Head of Outotec’s Minerals Processing Business, said: “We are pleased that we were chosen to deliver our leading technologies and services that enable our customer to improve their profitability in a sustainable way.”

The company was also recently awarded a pressure leaching and solvent extraction technologies for a battery chemicals plant to be built in Sotkamo, Finland. The total order value booked in the December quarter order intake for this contract is some €34 million.