Synthesis of ZnCl2-activated carbon from macadamia nut endocarp (Macadamia integrifolia) by microwave-assisted pyrolysis: Optimization using RSM and methylene blue adsorption

We report the synthesis of activated carbon from macadamia nut endocarp using ZnCl2 as activating reagent by microwave-assisted pyrolysis. The effects of synthesis conditions and variables were evaluated using the response surface methodology (RSM), which allowed us to obtain an optimized activated carbon (ACop) for efficient adsorption of methylene blue dye (MB). The chemical and textural characteristics of ACop were investigated by using N2 adsorption–desorption measurements, SEM, FT-IR spectroscopy, XPS and the Boehm and pHdrift methodologies. The ACop was obtained with impregnation ratio of 3:1 (ZnCl2:char), microwave heating time of 20 min, and microwave power of 720 W. The ACop possessed microporous structure, with BET surface area (SBET) of ca. 600 m2 g−1, and it had mainly acid functional groups on its surfaces. The adsorption kinetic data exhibited by the material for MB were all well-fitted to the pseudo-second-order model, indicating chemisorption. The adsorption isotherms for MB were well-described by Redlich–Peterson model, and the ACop monolayer adsorption capacity for MB was found to be 194.7 mg g−1, which is comparable to other values reported in the literature.