Processing and purification of carbonaceous materials

A process for processing and/or purifying carbonaceous solids comprising:

• a) providing a mixture comprising a carbonaceous solid and inorganic compounds, wherein the carbonaceous solid comprises carbon black, and the inorganic compounds comprise zinc sulphide, zinc oxide, silicon dioxide, silicates, aluminum oxide, or any mixture thereof;
• b) providing an aqueous fluid comprising a nitrogen hydride, wherein the nitrogen hydride is selected from the group consisting of ammonia, ammonium hydroxide, ammonium halides, guanidine, guanidine derivatives, and ammonium salts thereof;
• c) providing an alkali hydroxide;
• d) contacting the mixture of step a), the fluid of step b) and the alkali metal hydroxide of step c);
• e) subjecting the composition obtained in step d) to an increased temperature and an increased pressure;
• and
• f) separating a carbonaceous solid from the composition obtained in step e).