Preparation of Activated Carbon from Macadamia Shells for Efficient Removal of Organic Pollutants from Wastewater

Abstract

Activated carbon was prepared from macadamia nutshells by chemical activation using KOH and K₂CO₃ as activating agents and was characterized by Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscopy (SEM), and determination of the point of zero charge (pHₚzc) using the pH drift method in KNO₃ solution. For the KOH-activated sample, the resulting carbon exhibited a larger micropore volume, with pore diameters predominantly smaller than 3 nm, and a higher specific surface area (1599.73 m² g⁻¹). In contrast, the K₂CO₃-activated carbon was dominated by pores in the 3.5–4.5 nm range, with a comparatively lower specific surface area (988.91 m² g⁻¹). The point of zero charge (pH_PZC) of the prepared activated carbons was found to be in the range of 6.8–6.9. Adsorption experiments for Rhodamine B, chloramphenicol, and phenol demonstrated the superior adsorption performance of the KOH-activated carbon. The adsorption kinetics for all three adsorbates were well described by the pseudo-second-order kinetic model.