Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

Simplistically it blocks the carbon pores and thus inhibits the elution of the gold. Hence an acid wash is usually conducted prior to elution.

As said, acid washing "cleans" the carbon improving the contact between the eluent and the carbon. The presence of calcium ions also enhances the adsorption of gold on activated carbon.

Conversely, removing calcium from the carbon by acid washing and using water with a low calcium concentration improves elution efficiency.

Following are links to some papers that you might find useful;

http://is.gd/XOoS3T
http://is.gd/vjZHQ0
http://is.gd/3pNbwf

Calcium ion in the eluent inhibits elution when using AARL elution. Ca>Mg>Na. Basically if you have more than about 100ppm Ca in your eluent it will result in a slower elution

Calcium ion in the eluent inhibits elution when using AARL elution. Ca>Mg>Na. Basically if you have more than about 100ppm Ca in your eluent it will result in a slower elution.

The presence of calcium ions also enhances the adsorption of gold on activated carbon?

Basically Ca ions form into scales at high temp during elution process that blocks the heat exchanger and other pipes, during reagent circulation.It has less effect on the kinetics of the reaction.