Ann: 99.99%TGC Coated Spherical Graphite Achieved-MNS.AX, page-127

Hi Holmesearth,

Can you narrow your question down at all? It covers a stupendous range at the moment!
What data do you have on the metallurgy of the deposit?
What specific impurities are you trying to remove? Clay? Silica? Iron compounds? Other? This affects both the choice of acids to be used, and the quantities.
Do you want to perform the entire additional concentration job using acids, or do you wish to include some flotation, and possibly a caustic wash? Again, the choice is a function of the other material present in the concentrate.
What about some thermal treatment?
It's probably because of the number of variables involved, and the consequent complexity of the decisions to be taken, that most companies usually farm this work out to specialist consulting groups. Without having any of the above details, the chance that a random response on HC would be close enough to be useful is pretty low.
Lastly, remember that 99.5% is not battery-grade. Most battery makers are looking for a product closer to 99.9%C, meaning that there would be about 400% too much impurity for the major battery producers.

Cheers,

Prime1