Cyanide Leaching

SGS has been at the forefront of cyanide leaching technology for decades. We have the equipment and expertise needed to design the most efficient and cost-effective cyanide leaching circuit for your gold processing operation. Our team includes world class professionals who have developed techniques such as CIP (carbon in pulp), CIL (carbon in leach), RIP (resin in pulp) and RIL (resin in leach).

SGS is a leader in gold processing. Our robust technologies and experienced staff ensure improved gold recovery, and an improved bottom line for your mining operation.

Cyanide leaching has been the industry standard for gold processing for more than 100 years. During the cyanide leach process, a cyanide solution, or lixiviant, is percolated through ore contained in vats, columns or heaps. Gold is dissolved by the cyanide and then removed from the heap or columns. It is then extracted from the pregnant leach solution by adsorption on carbon or resins. This cost-effective, proven method of ore extraction provides maximum recovery for many gold ores, including low grade and some refractory ores.  

SGS professionals develop your cyanide leach flowsheet at the bench or laboratory scale using cyanide bottle roll tests to assess leach parameters and optimize the gold recovery. During these tests, aeration, alkalinity, agitation time and grain size are strictly controlled and the resulting data provides an accurate estimate of the gold recovery and rates of acid consumption. Such tests set the parameters for your pilot plant or final site recoveries.

SGS professionals use the results gained from bottle rolls to establish the most appropriate preparation and recovery procedures for your ore. Cyanide leaching processes include:

Vats and Column Leach

In traditional cyanide leaching, ore is placed in vats or columns. The cyanide solution percolates through the ore and dissolves the gold, which is then removed from the lixiviant by adsorption onto carbon or resins. Grain size, oxygen and alkalinity levels are carefully controlled to ensure maximum gold recovery.

Heap Leaching

Heap leaching facilitates the profitable extraction of gold from very low grade ore. Prior to heap leaching, either run of mine (ROM) or crushed ore is heaped into structures 10 to 20m high that are stacked on an impermeable layer. A dilute cyanide solution is sprayed on the heap, percolates through the pile and dissolves the available gold. The solution is then directed into a pond. The cyanide solution, which is said to be “pregnant” with gold, is then pumped through columns where the gold is recovered. Cost-effective heap leaching offers a number of advantages, including:

• Comminution costs are reduced as the ore is only crushed, not ground.
• The cyanide solution is recycled through the heap, reducing the amount of cyanide used in the operation. 
• The process is especially suitable for lower grade ores and ore with a high clay content.

Gold Recovery

Carbon and Resin Adsorption

SGS scientists developed and continue to improve these cost-effective, time-tested processes to extract gold from the pregnant cyanide solutions. Activated carbon effectively removes the gold from the cyanide, as the gold is adsorbed into the pores in the carbon. This has spawned technologies such as CIP (carbon-in-pulp), CIL (carbon-in-leach) and CIC (carbon-in-columns).

More recently, SGS has lead the gold processing industry with the development of resin-based technologies. In this case, the gold is adsorbed onto the synthetic resin particles rather than activated carbon. This process is more efficient, easier to control and more robust than carbon-based technologies.

Variations on this process include:

• Carbon-in-pulp  
• Carbon-in-leach
• Carbon-in-columns

RIL (Resin-in-leach) / RIP (Resin-in pulp)

In recent years, resin is replacing carbon as the phase that gold is adsorbed on. SGS has been a leader in the development of this technology. The process used in resin absorption is similar to carbon absorption, but synthetic spherical resin particles replace the grains of activated carbon. This process brings a number of benefits to gold processing:

• The size of the synthetic resin particles is more consistent that than the natural carbon particles, allowing for easier control when adding adsorbent
• Better results from refractory ores or those containing high levels of clay or organic compounds organic 
• The resin particles are more robust and need not be replenished as often as carbon, thus keeping operating costs down.

Partner with SGS and leverage our internationally recognized experience and technological capabilities into increased recovery rates and maximum growth in your gold recovery operation.