There is not enough information.
How big and heavy are the objects?
How many are there?
What is the shape of the objects?
How are objects discriminated from the surface?
How large is the surface?
Where are the object to be thrown away?
How is the surface discriminated from non-surface?
Is there a weight limitation for the robot?
Have other robots done the same thing before, and if so, how quickly, and how were they designed?
What is your price budget?