Quality improvement of recycled carbon black from waste tire pyrolysis for replacing carbon black N330.

This research aims to improve the quality of recycled carbon black (RCB) obtained from the pyrolysis of waste tires, produced by Pyro Energie Co., Ltd. in Thailand, for use as a replacement for commercial carbon black N330 in rubber products. The study introduces a novel approach by combining chemical and thermal treatments, comparing the effects of two chemical agents: 50% phosphoric acid (HPO) and 5 M potassium hydroxide (KOH). These concentrations were selected based on preliminary evaluations of their effectiveness in removing inorganic impurities and enhancing the porous structure of RCB. A key innovation of this research is the application of Response Surface Methodology (RSM) to systematically analyze and determine the optimal treatment conditions, using the iodine number as a primary indicator of surface area and porosity. The experimental results showed that KOH-treated RCB (KCB_EQ) achieved the highest iodine number of 110.55 mg/g, while phosphoric acid-treated RCB (PCB_EQ) reached 107.3 mg/g. Although the iodine number of KCB_EQ was higher, PCB_EQ exhibited superior properties in other aspects, with the highest BET surface area of 79.98 m/g and the lowest ash content of only 0.13 wt%. When PCB_EQ was blended with N330 in a 50:50 ratio (NR-PCB_EQ/N330) for natural rubber compounding, the resulting material exhibited mechanical properties comparable to pure N330, including a tensile strength of 19.8 MPa and an elongation at break of 366%. These findings demonstrate the potential of PCB_EQ to replace up to 50% of virgin carbon black in rubber applications. This study presents a practical and scalable method to valorize pyrolysis by-products, supporting the circular economy and reducing reliance on fossil-based raw materials.