In this study, the influence of pyrolysis time and temperature on yield, fixed carbon and physicochemical properties of the biochar produced from Empty Fruit Bunch (EFB) were investigated. Response Surface Methodology was utilized to optimize the influence of process parameters on the surface area of activated carbon produced from the biochar in the absence and presence of ultrasonication and was coded EFB-AC and EFB-UAC respectively. The EFB-AC and EFB-UAC were characterized using BET, TGA, HRSEM, XRD, FTIR and XPS. The batch adsorption behavior of MB onto EFB-AC and EFB-UAC was evaluated. The results revealed that the optimum surface area (S-BET) of 2114 m(2)/g was achieved for EFB-UAC at activation temperature (600 degrees C), activation time (45 min) and KOH concentration (1.5 M). It was found that EFB-UAC has high surface area, better thermal stability, better pores development and improved surface chemistry compared to the EFB-AC. The maximum adsorption of MB occurred at pH (10), adsorbent dosage (30 mg), contact time (40 min), Temperature (50 degrees C) and MB initial concentration (50 mg/L). The experimental data was best described by Langmuir isotherm model, having an adsorption capacity of 400 mg/g and 435 mg/g for EFB-AC and EFB-UAC, respectively. The kinetic model was best suited by pseudo-second order model for MB adsorption onto EFB-AC and EFB-UAC. The thermodynamics investigation showed that adsorption of MB was endothermic in nature due to strong electrostatic interaction and formation of hydrogen bonding. The study revealed that ultrasonic assisted variations of the adsorption parameters significantly improved the adsorption of MB onto EFB-AC and EFB-UAC. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.