Activated charcoals have been prepared from the weed like Argemone mexicana L. by using chemical activating agents like Zinc Chloride, Ortho Phosphoric Acid, etc.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/catalytic-study-activated-charcoal-obtained-mexicana-l
[2] http://admin.indiaenvironmentportal.org.in/category/author/pingale-shirish-s
[3] http://admin.indiaenvironmentportal.org.in/category/author/pokharkar-rahunath-d
[4] http://admin.indiaenvironmentportal.org.in/category/journal/research-journal-chemistry-and-environment
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/weeds
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/energy
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/charcoal
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/research