Recovery of high pure pyrolytic carbon black from waste tires by dual acid treatment

Pyrolytic carbon black (CBp) is one of the products from waste tires through the pyrolysis process having potential business prospects. However, any impurities in CBp tremendously limit its further applications, such as rubber reinforcers, fuels, and other functional materials. The existing processes for CBp purification suffer from low purification efficiency, high cost, and severe environmental pollution . In this work, hydrochloric acid (HCl) and the phosphate fertilizer acid (PFA) which is a by-product waste acid from the phosphate fertilizer plant are employed as leaching agents for recovery of high pure CBp. In this process, the former is used to remove metal and sulfur compounds , and the latter can effectively dissolve silicon oxide in CBp. The high purity (99.63%) of the treated CBp product is achieved, well meeting the standard of commercial carbon black (99.3%). Moreover, the HCl solution can be recycled and reused for several times, realizing the continuous enrichment of zinc ion in the leaching solution , while the used PFA can be directly transferred into value-added H 2 SiF 6 as new production due to the desirable enhanced silicon amount. The obtained CBp shows the same internal structure and sulfur state as that of commercial carbon black, suggesting the possibility of application as rubber reinforcing filler . Therefore, this approach for the recovery of high-purity CBp is efficient, economical and suitable for large-scale production. Furthermore, an amplified production installation with 50 L scale was successfully designed and operated, verifying its good universality and stability with the proposed purification technology. This work provides a sustainable method to refine CBp derived from waste tires, contributing to the development of the upstream pyrolysis industry and effective utilization of solid waste resources. • A new value-added dual-acid leaching method is proposed for the recovery of CBp. • The recovered CBp has high purity of 99.63% higher than commercial carbon black. • The structure tests reveal the recovered CBp can be reused for tire manufacture. • A 50 L amplification device was set up to verify its economy and stability.