Microwave-assisted one-step preparation of macadamia nut shell-based activated carbon for efficient adsorption of Reactive Blue

Abstract

In this work, macadamia nut shell-based activated carbon (MNSAC) was prepared using macadamia nut shells (MNS) through KOH activation under microwave radiation. The optimum conditions for preparing MNSAC through the response surface method were as follows: microwave power 600 W, activation time 10 min, and mass ratio 2 : 1 (KOH : MNS). The Brunauer–Emmet–Teller surface area of MNSAC was 876.77 m² g⁻¹, and the total volume was 0.533 cm³ g⁻¹. SEM and FTIR analyses indicated pores and functional groups on the material surface significantly changed after activation. Experimental results revealed the suitability of macadamia nut shells for use as a precursor for activated carbon. The maximum adsorption capacity of RB-19 onto MNSAC reached 376.81 mg g⁻¹ at 293 K. The sorption behavior fitted to the pseudo-second-order kinetic model and the Langmuir isotherm. Thermodynamic parameters, namely, ΔG°, ΔH°, and ΔS°, showed that the sorption process of RB-19 was spontaneous, endothermic, and prone to increase in entropy. Microwave radiation is an efficient and rapid method for preparing a newly developed MNSAC alternative to commercial carbon, which may be used as a cleaner and ecologically compatible adsorbent for effective removal of dye pollutants.