Chromium adsorption by lignin

Hexavalent chromium is a known carcinogen, and its maximum contamination le vel in drinking water is determined by the U.S. Environmental Protection Ag ency (EPA). Chromium in the wastewaters from plating and metal finishing, t anning, and photographic industries poses environmental problems. A commerc ially available lignin was used for the removal of hexavalent as well as tr ivalent chromium from aqueous solution. It is known that hexavalent chromiu m is present as an anionic species in the solution. It was found that ligni n can remove up to 63% hexavalent and 100% trivalent chromium from aqueous solutions. The removal of chromium ions was also investigated using a comme rcially available activated carbon. This absorbent facilitated very little hexavalent and almost complete trivalent chromium removal. Adsorption isoth erms and kinetics data on the metal removal by lignin and activated carbon are presented and discussed.