I was just wondering. Where do all lamps that go to recycling end up and what materials can be reused if any? 

I'm not sure I think they reuse the mercury and I guess the glass can be melted down and reworked into something new

i think that they can reuse the phosphors. they can probably clean the Hg from the phosphors. endcaps can be re used or melted down into something new.

What about phosphors etc ? Even dirty from a used lamp, they are still in much higher concentration than in nature (source materials from which they are filtered or produced)

What about fill gas ? (especially the more expensive Kr so European types of T8, and Xe so MH and HPS)

What about Tungsten ? (filaments / cathodes)

The mercury is reused, as it is not that cheap metal to produce and it has to be extracted from the waste anyway. Then the glass and construction metal parts (aluminum from caps, brass from pins,...), just because it is quite simple to do so.
The phosphors I doubt: Because there is so wide variety of phosphors in use, unless the lamps would be separated according to the phosphor chemistry, separating them would be more expensive than making new.
However some rare earth elements may be sometimes viable to extract from there. But as these are quite unharmful (once the mercury is extracted), there is no strong need to deal with them.

I read somewhere a while back that the phosphors are sometimes recycled. I'll have to dig up the source.

Even in a "dirty" mix of phosphors from different lamps, i would expect that each type of phosphor is in higher concentration than it's components occur in nature. Then isnt it better to separate it from the mix than separating each of its components from naturally occuring minerals and such ?

Especially for triphosphors for which some components are mined in a limited numbert of places, and could possibly even be "conflict materials"

I think crucial factor is how expensive is separation of phosphor components compared to new material.

 
How about LPS and HPS lamps? is there any need(price of new material) to recycle sodium or ist it even possible?

How about LPS and HPS lamps? is there any need(price of new material) to recycle sodium or ist it even possible?

Sodium is very abundant and not expensive, so there would be no need to recycle it. But it needs controlled disposal, since it will form sodium hydroxide (lye) and hydrogen gas upon contact with water.

They may be able to extract it when they melt the arc tube down (the sodium leeches into the arc tube walls).

They also can scrap the base, the outer envelope, and don't forget the arc tube metal frame that supports it and supplies it power.

I doubt anyone will extract the sodium from the arctube, because the sodium is really harmless in the environment and the alumina is just inert, so no probelem with those when released into the environment (again, I assume the mercury has been already extracted from that). And because manufacture of both sodium and alumina is quite cheap (the sodium come from the table salt or so, with alumina the most expensive part is the processing to get it into the arctube form and that would be paid again anyway), way cheaper than such extraction, there is no economic force to recycle those materials from the old lamps.

If they melted the arc tubes, wouldn't the sodium melt out first or float to the top of molten arc tube since they skim off the imperfections/ slag from the melt pot.

At temperatures of molten alumina the sodium will evaporate very quickly.
And the sodium is highly reactive, so the first thing it will do is just burn.
So you will have to do all that in an inert atmosphere, with extraction from the gases. Not anything cheap.

It is not that it won't be technically possible to extract the parts, the point is it does not make much sense.
It would be more expensive than using "fresh" materials and I would even guess create more load on the environment...

I see your point Medved. Could they at least suck the argon or xenon out from the arc tubes. I know that they'd take the Hg since it's bad for the environment.