Mix graphene oxide atom-wide sheets with water contaminated with Uranium, and it clumps in minutes: can be strained and removed.
The devil is in the details, of course. The cost is kind of interesting: $200/gram, which when you are talking about tons to clean up a big mess starts to turn into serious money. (Although there may be economies of scale eventually) And different elements are "sorped" differently at different pH: Tc is better sorped in acid (1.5!), but Sr better in neutral or basic solutions, and Uranium between 4 and 8. But it seems to work pretty well. In the lab. Even with contaminants put in to slow it down.