Converting pyrolysis carbon black derived from waste tires into a highly efficient adsorbent for dye wastewater treatment

Abstract

Conversion of pyrolysis carbon black (CBp) derived from waste tires into activated carbon for industrial wastewater treatment could be a sustainable waste reuse opportunity. However, untreated CBp has low surface activity and contains large amounts of ash and carbonaceous deposits. In this study, a highly efficient multifunctional adsorbent was successfully synthesized by converting CBp into hierarchical porous carbon featuring micro-, meso-, and macropore structures via a facile and scalable one-step KOH high-temperature molten chemical activation approach. The acid pretreatment was not as effective as KOH activation in removing ash from the adsorbents produced. The adsorption capacities and mechanism of the direct activated carbon black (ACBp) for methyl orange (MO) and methylene blue (MB) adsorption were also examined. ACBp with a hierarchical porous structure showed a high S_BET value of 789 m² g⁻¹, far higher than CBp (49 m² g⁻¹), which enables ACBp to exhibit rapid adsorption kinetics for MO and MB. Batch adsorption experiments demonstrated that ACBp achieves maximum adsorption capacities of 390.6 mg g⁻¹ for MO and 444.4 mg g⁻¹ for MB. In addition, the removal of MO and MB was 90% and 80% after 5 cycles, respectively, indicating the good regeneration performance of ACBp, which has great potential for industrial applications. This work offers a feasible pathway to realize high-value recycling of waste tires and reduce the contamination of dye wastewater.