High-value utilization of waste tires: A review with focus on modified carbon black from pyrolysis

Recently, the recycling of waste tires has caused widespread concern for its environmental issues. The experience of the producer responsibility and tax system is of great beneficial to developing countries. The article also elaborates on the efforts of Chinese government to focus on establishing and perfecting waste tire treatment system by strengthen legislation. The main reasons such as immature market, non-uniform policy and repeated taxation for the survival difficulties of waste tire recycling enterprises in China are summarized. Among numerous resource methods, pyrolysis has been considered as a promising thermochemical process to deal with the waste tires. Unlike other similar reviews that mainly focus on its liquid phase, special attention has been given to solid char, pyrolysis carbon black, due to its wide application and high-value utilization in the future. We summarize the available research on application of pyrolysis carbon black as an alternative to commercial carbon black in rubber manufacture, as activated carbon in pollution control and as biochar for soil improvement. Analysis of the available data revealed that 1) the influence of temperature and time has been basically established; 2) catalyst type, dosage and reactor selection should be adjusted according to product demand; 3) pickling has become the primary means of improving pyrolysis carbon black; 4) the type of modifier and modification method must be adjusted according to the specific characteristics of the raw materials and needs to be combined with the experimental results to realize resource utilization and give full play to its economic value.