KAu(CN)2 must be used to ensure that the gold is present in the adsorption solutions as the Au(CN)2- complex.

If you use gold analytical standard solutions these are HCl/HNO3 based and the Au will be present as Au(III) in the AuCl4- complex.

In the Au(CN)2- complex, Au is present as Au(I).

When activated carbon is added to AuCl4- solution the gold is reduced to metallic gold at the carbon surface. http://is.gd/1WvzIH

The reduction of AuCl4- at the activated carbon surface is very rapid and this reaction doesn't have any relationship to the rate of adsorption of Au(CN)2- complex by activated carbon.

You can obtain 1000 mg/L Au standards in NaCN or KCN matrix (NIST certified) from several vendors; these cyanide standards are actually made w/a starting solution of AuCl3; my understanding is that the presence of alkali metals such as Na or K monovalent ions are not an issue during adsorption of the MAu(CN)2 complex onto activated carbon.

Thanks for the information. They are very useful information for me.

I am looking for a company that manufacture an equipment to produce active carbon by steam process.

Presuming you are referring to stripped C requiring thermal regeneration, multiple global suppliers exist for Indirect or Direct Fired rotary kilns including Metso, Kemix, Denver Minerals, FLSmidth etc.

I am referring to the manufacture (by steam) of the active carbon, from charcoal. What you mentioned is how to recover the quality of the stripped C. unless is the same technology the production of active carbon and the recovered of the striped one?

Rotary kilns or Open hearth furnaces both work....check out:

http://is.gd/Z6dumO

http://is.gd/8iBJAQ

You may want to touch base w/some of the earlier mentioned vendors.

The processes are very different (regeneration versus re-activation or virgin material activation). Regeneration is essentially a pyrolysis of the non-volatile organics and a thermal desorption of the volatile constituents (at some 600 deg C or so). This may not necessarily create or regenerate the micro-pores required for the high loadings. Only the controlled oxidation of the internal structure at 1200 dec C and steam/oxygen controlled environment will do that. To run this is no trivial matter though - especially is different grade types must be manufactured etc. Equipment manufacturers are many, but successful producers of activated carbon not. Check with the manufacturers and get throughput data and limitations. You might find that the economics are quite challenging.