This might not be turning lemons into lemonade, but it could be close. Microbeads have recently become the cause
While hexavalent chromium ions are a worthwhile and newsworthy target, I imagine the technique could be applied to recovering other ions/elements as well. Arsenic is a problem in many parts of the world as are other metal/metal ions. And I can't see any reason why any particular bead wouldn't be able to recover multiple metals (although a mixture of beads targeting each individual metal could work too).
The article raises but doesn't answer the question of recovering the beads. Making the beads around a magnetic core would be a quick-and-easy option to allow for recovery, but buoyancy would be a concern. Smaller cores would help that, but then a stronger recovery magnet would be needed. Increasing the thickness of the polymeric shell would increase the buoyancy, particularly if it was foamed to any degree. But even if the whole concept of using microbeads fails, the peptoid coatings could still be used to coat other materials to reach the same end. Peptoids are apparently quite resistant to hydrolysis, which is crucial for application like this, so it's just a matter of finding an acceptable substrate with a large surface area and possibly sufficient porosity so that this doesn't end up as a giant filter removing the good (sea life from microbes on up to whales) as well as the bad.
[*] Peptoids are like peptides, oligomers of amino acids, but amino acids have their substituents on the α-carbon, while for peptoids, the substituents are on the nitrogen.