Glycine Leaching Technology

Frequently Asked Questions

IS GLYCINE SAFE? IS IT BIO-DEGRADABLE?

Glycine is a totally non-toxic chemical that is fully bio-degradable. It is used as a feed supplement in animals and is even used therapeutically to reduce inflammation in humans.

IS GLYCINE READILY AVAILABLE?

Glycine is a readily available chemical that is manufactured in large quantities in the USA, Germany, Japan, China, and India. It is manufactured by combining chloroacetic acid and ammonia and is mainly used in producing herbicides, food supplements, and nutrients. Prices vary between manufacturers, but it is generally cheaper than cyanide and readily available from a variety of manufacturers.

WHAT MINERALS CAN GLYCINE LEACH?

Glycine can leach most of the nonferrous transition base metals, specifically copper, but also nickel, cobalt and zinc. It is also capable of leaching precious metals under certain conditions - gold, silver, some of the platinum group metals, and finally lead under special circumstances. Various minerals leach at varying speeds and different chemical conditions. As an example, all copper minerals except silicates and copper that is chemically bound within iron oxides are leached by glycine. Leaching takes place at pH values between approximately 8 and 12.5, with the higher pH values being used to leach the sulphides and in particular chalcopyrite. This supplies the base needed to fix the Fe that is leached from this mineral. In contrast to acid leaching, Fe, Mn, Ca, Mg and many other elements are simply not put into solution. There is no soluble unfixed Fe to deal with, or difficult solids like jarosite to dispose of.

WHY IS GLYCINE SUCH A LOW COST METHOD?

Glycine leaching is low cost because the main reagent, Glycine, is chemically regenerated. Glycine is reacted with a solution of sodium hydroxide to provide sodium glycinate as the major reagent. This has a natural pH value of around 11 to 12. For example, when the copper mineral malachite is put into solution, the released copper is chelated onto the glycine, with each copper molecule sequestering 2 molecules of glycine. This releases Sodium (Na) from the glycine that is then paired with the carbonate ion and hydroxide ions from the malachite. Glycine is completely regenerated when the stripped solution is reacted with lime or calcium hydroxide. This precipitates all of the carbonate and sulphate (from the oxidation of sulphides), and regenerates the caustic which then pairs with the glycine again. Thus it is in a locked cycle, not being consumed. The loss is limited to the glycine that is not physically recovered from the tailings and this will be low.

What’s the minimum ore grade to economically recover metals with GLT?

As a rule of thumb, if it is economical to recover precious and base metals using traditiona leaching methods, then it will most likely also be economical for GLT. However, we could potentially lower the head grade compared to cyanidation because the GlyCat^™ requires less reagent and incurs lower costs compared to cyanidation, even factoring in the cost of glycine. This is particularly true with ores that contain copper, where considerably more cyanide is needed to leach the gold. In this case, the cyanide savings are significant.

Is there any impact on other processes like flotation?

The short answer is no. Glycine is added to the process water, so if it is used in flotation then it will be present during flotation. Our tests have demonstrated that glycine will improve the selectivity and “floatability” of metal sulfides where metal selectivity is achieved through pH. We have observed the use of glycine to clean the sulfide surface to improve flotation.

Unlock tomorrow's metals
with Glycine Leaching Technology

Meet the world’s first truly sustainable solution to metal supply deficits

Current Commercial Applications

GlyCat™ for precious metals

GlyLeach™ for base metals

Reduces processing costs

Reduces reagent consumption

Improves ESG footprint