Things that absorb toxins useful in aquaria. What about these?

[knifegill]

Worse yet, plastics in the ocean absorb toxins such as DDE and PBCs.

http://www.takepart.com/news/2010/0...te-over-the-age-old-question-paper-or-plastic

And I vaguely remember being told that either silicone or silicon is known for bonding to toxins.

What other affordable/renewable substances can work in this way?