Chloromethylated activated carbon: A useful new synthon for making a novel class of sorbents for heavy metal separations

The chloromethylation of activated carbon is described. Chloromethylation was found to produce a carbon derivative with a surface area of 1310 m²/g and no significant change in the pore structure. The product was found to contain ~1.5 mmole of -CH₂Cl groups per g of material, similar to the functional density reported in the original Merrifield resin synthesis. Displacement of the benzylic chloride was achieved by treating this material with an excess of sodium thiosulfate in refluxing aqueous methanol. The resulting Bunte salt was then hydrolyzed by treatment with warm 3 M HCl to afford the corresponding thiol ("AC-CH₂-SH") cleanly and in high yield. AC-CH₂-SH was found to be an effective heavy metal sorbent, efficiently capturing Hg, Pb, Ag, and Cu. Sorption kinetics were rapid, with equilibrium achieved in less than 30 minutes.