Hi John Lawson,
Biochar can be activated by combining it with a wide range of chemicals, and therefore can absorb many different pollutants, targetted specifically or not. (Metals, arsenic, nitrates, phosphates etc)
The absorption power of biochar is due to its colossal pore surface, inherited from the cellular organic feedstock, which is retained by pyrolysis.
Work on depolluting soil and water is progressing rapidly. Only today I read of work done on mine land remediation, which will be the subject of an international webinar in June.
Thorough scientific studies on Biochar(coals) only really began in earnest about ten years ago, which is not long in terms of bringing new technology to market. And the synthesis of all the very complicated interactions involved have only really begun to be fully clear in the last couple of years.
But the potential is there, and commercial ventures are now under way. And biochar can be recycled to recover the pollutants, including metal ions, but that particular subject has yet to be studied in great detail...