Exploring coconut shell-derived activated carbon black as a green alternative for toner colourants.

Coconut shells (CS) are a promising renewable precursor for carbon black synthesis. By optimising carbonisation parameters for CB synthesis and introducing a low-temperature alkali treatment method using KOH, this study investigates the potential of utilising CS-derived activated carbon black (ACB) as a sustainable black colourant in electrically conductive toner powders. The most efficient synthesis parameters were determined by analysing 36 CB samples that were produced by combining three variables: carbonisation temperature, carbonisation duration, and particle size. The best CB sample was treated using different weight ratios of KOH at 120 °C. The results obtained from FT-IR, XRD, and SEM coupled with EDS, EIS, and TGA revealed that optimised carbonisation and low-temperature KOH treatment caused well-defined porous structures with an amorphous nature. Increasing KOH concentrations result in the formation of large spherical micropores (0.656 µm), however, excessive concentrations lead to smaller or closed pores. The ACB sample synthesised with lower KOH concentration showed the lowest resistance, thermal stability up to 400 °C, and low moisture and ash content. The reduced resistance indicates enhanced electrical conductivity, suggesting the potential of synthesised ACB as a conducting agent, while its high thermal stability indicates suitability for high-temperature printing applications. Moreover, high carbon content (69.2 wt%) and fine particle size (10-15 µm) may ensure good dispersion in polymer matrices while facilitating uniform colour and print quality. Hence the synthesised ACB samples with the lowest KOH concentrations could be used as a black colourant and a conducting agent in the synthesis of toner powders.