Carbon in Pulp (CIP) and Carbon in Leach (CIL) are methods for extracting higher grade ore from underground mining operations. Both methods employ massive stepped tanks aligned in a column whereby gold is dissolved in the slurry (pulp) through a chemical process incorporating agitation, oxygen and cyanide. Given that gold is not soluble in water, earth’s most beautiful metal requires one of earth’s most deadly compounds for the metal’s ultimate capture and presentation. Once dissolved, the gold in aqueous solution requires separation. At this stage, activated carbon pellets are introduced to the circuit. Activated carbon is charged in such a way that it bonds (adsorbs) to the aqueous gold whereby the “impregnated” carbon can then fully solidify and be screened from the circuit. Carbon in Leach simply employs the leaching and loading (impregnation) during the same circuit.
This impregnated carbon is then introduced to a caustic cyanide solution under heat and pressure with the purpose of stripping the gold from the carbon. Ultimately the gold is electroplated onto wounds of steel wool bound to stainless steel cathodes. Loaded heaves of steel wool are then dried and bundled for refining.
Metallurgists strive for the best recovery meaning the least loss of gold from the circuitry through tailings. Different ore compositions will alter the formulae by which reagents are added and subtracted from the system. Lime must be used to counter balance the toxic effect of cyanide. The grind of the pulp exiting the grinding system is continually monitored for the benefit of optimizing the leaching process.
Carbon in pulp is a method that must be deployed with intense environmental scrutiny due to the toxic properties of cyanide. The permitting process in the mining industry is burdensome particularly because of the confidence that governments must acquire in firms through detailed systems of compliance.