The economy of metals extraction from ores depends on scale.  We would need to know how much Sperrylite is available to you.  How much are you planning to process?  On an ongoing basis - like from a mine?  Or do you have a few pounds of mineral or less from which you plan to process one time only?

On a smallish scale, here's an interesting link: http://www.sciencemadness.org/talk/viewthread.php?tid=16067  In his post, the author discusses methods that minimize the toxic and environmental damage that could be caused by the arsenic byproducts.  I'm sure there are others as well.  An interesting book that I own is "Recovering and Refining Precious Metals", by C W Ammen.  There are some errors in it, but for the most part I can find nothing factually wrong with it.  He describes methods to separate Pt from the other platinum metals.  It's available in its first edition on Amazon for $45, used.  The new price is over $130.  There's also a 2nd edition, but I couldn't find it yet.  His methods are a bit complicated, so I would think they wouldn't be economical on the large (multi-tons of ore, mining) scale.  

I've heard of methods of oxidizing sulfide ores by a wet method.  Ore is placed in a closed tank with sulfuric acid, agitated while oxygen is sparged into the solution.  Sulfur oxides and other byproducts can be recovered from the wash during the metal recovery step.  I thought that since Pt ores from formations of the layered complex type, which contain Sperrylite, are smelted (I assume that means some sort of roasting/oxidation), the wet method above or something similar might apply to Pt recovery.  

What are the concentrations of other PGEs in your ore?  It's pretty rare that platinum is found uncontaminated by Pd, Ir, Rh, etc.  If you are going to separate these from your Pt, I think you will have to use some kind of complicated chemo-metallurgy of the type Ammen describes.  Perhaps you can ship your mixed product to another smelter operation for purification.