Manal,
I am not sure, but my guess would be that the iron is not removed from the food and that it leaves the body through the digestive tract. I don't think that it leaves as oxidative, free iron so in my opinion it does not need to bind anything - it is simply not aborbed by the body.
In fact some people have conditions in which they cannot absorb iron and it leaves their body unabsorbed.
This is just a thought, it may require further resesarch,
Sharmin