Extracting rhenium from ammonium thiocyanate mother liquor

I've been trying to figure this out for a while now but all the methods found easily on with google have been tried and rejected.

At the Rhenium recycling facility that I work at we have about 54000L of Ammonium thiocyanate solution that contains about 3g/L Re, reduced from 50-60g/L by cooling to -4C. This stuff has been piling up for over a year now and nobody wants to send it out as waste because there is potentially $1mil worth of product tied up in these things. But it is also starting to take up lots of space.

I will welcome any suggestions on how to either force the solubility equilibrium to favor Ammonium perrhenate, or reduce the oxidation state of the Re+7 to a lower insoluble state.

Anyone interested in knowing the full process leading up to this point can check out www.freepatentsonline.com/y2012/0058029.html.

Thanks

Mac