Acid-base method for the demineralization of pyrolytic carbon black

The carbon black material used as reinforcing filler in tires was recovered by vacuum pyrolysis at a temperature of 500°C and a total pressure of 20 kPa. The pyrolytic carbon black obtained (CBp) was contamined by various additives of the original tire. Contaminants were also produced by chemical reactions occurring in the pyrolysis reactor. The contamination is reflected by the high content of ash and gritty materials (coke) present in the CBp. A characterization of the recovered carbon black was performed and a possible reduction of the ash content by sulfuric acid and sodium hydroxide treatment was investigated. The variables which were studied included the ratio of reactant to carbon black, the reactant concentration, the treatment temperature and the reaction time. Properties of the commercial carbon black filler grade N539 were compared to those of the CBp recovered before and after the demineralization treatment.