an activated carbon , disclosed as useful in purification and decolorization of hydrocarbon fuel , particularly gasoline , is characterized by inclusion therein of polymerized phosphoric acid or reduced transition metals . phosphoric acid may be added to a non - phosphoric acid - activated carbon prior to the subsequent heat treatment or one can take advantage of residual phosphoric acid present in , for example , a phosphoric acid - activated wood - based carbon . similarly , transition metals such as copper may be added to an activated carbon in a salt form in addition to whatever is already present therein as impurities . the conversion of phosphoric acid to a polymerized phosphate content or reduction of transition metals to a reduced form results from the activated carbon having been treated with inert gas or carbon dioxide at from about 1200 ° f . to about 1800 ° f . for at least 5 minutes . alternatively , the conversion of phosphoric acid to a polymerized phosphate content can occur during phosphoric acid activation of carbon at activation temperatures in the range of 1150 °- 1600 ° f .