Crane and Harvard Consulting Engineers P/L has teamed up with an Asian company to introduce an environmental friendly gold extraction reagent to replace the toxic cyanide currently in use in the gold extraction industry.
CraneHarvard Environmental Gold leaching agent, CH_0103 is applied to various types of gold ores to extract the AU metal.
CraneHarvard Eco-friendly reagent is suitable for most gold leach processes like heap leach methods, CIL & CIP (carbon in Leach & Carbon in Pulp ) including Dust and Zinc wire replacement methods.
The production methods including plant & equipment remains the same as used during sodium cyanide process. There is no need to purchase additional equipment to accommodate the eco-friendly reagent.
Transport and Storage of CraneHarvard Lixiviant
CraneHarvard Eco-friendly reagent is classified as non-hazardous. It is non-combustible, non-explosive, non-corrosive and non-radioactive. No special requirement for transportation and storage is required.
The lixiviant should be stored in a dry place, away from other reagents like acids and bases. Consumption by animals and humans alike should be avoided.
Preparation method
The product is a pale white powder whose main ingredients are sodium oxide, Iron nitride, Ammonium bicarbonate, calcium oxide and Ferric oxide (an international patent is registered on the formulation).
This product is fully soluble in water and is prepared in a stirred tank at room temperature to give a 15-20% solution that is applied directly to the process.
pH Adjustment
Generally, lime or caustic soda is used to adjust and maintain the pH value at about 11.2 (the recommended optimum pH level).
Too high a pH value for an extended time (greater than pH 12) is likely to produce an alkali scale that might affect adsorption of activated carbon, or liquid passivation; when the pH value is lower than 10.5 for an extended period then leaching rates are negatively affected. pH control is critical for the process.
Reagent Dosages
It is common practise that oxidized ores are treated with sodium cyanide at a rate of 1000g~2000g/ ton ore. It is not unusual to treat the same ore with 1000g ~ 1200g of CraneHarvard reagent CH 0103 per ton of ore. This equates to huge savings in reagent consumption. It goes without saying that different ore grades containing different types and forms of other complex minerals in them require adjusted dosage rates as determined during laboratory test-works.
Laboratory Test-Works
A number of laboratory test runs at certain gold processing plants have been carried out to evaluate superiority of CH_0103 over sodium cyanide. The attached reports will show that the eco-friendly reagent CH_0103 produces process tails containing far much less cyanide residues and at the same time , the leach rates observed are higher than seen during sodium cyanide leach process.