Ultrasonic Enhanced Adsorption of Methylene Blue onto the Optimized Surface Area of Activated Carbon: Adsorption Isotherm, Kinetics and Thermodynamics.

Abstract

tIn this study, the influence of pyrolysis time and temperature on yield, fixed carbon andphysicochemical properties of the biochar produced from Empty Fruit Bunch (EFB) wereinvestigated. Response Surface Methodology was utilized to optimize the influence of pro-cess parameters on the surface area of activated carbon produced from the biochar in theabsence 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 resultsrevealed that the optimum surface area (SBET) of 2114 m2/g was achieved for EFB-UAC at acti-vation temperature (600◦C), activation time (45 min) and KOH concentration (1.5 M). It wasfound that EFB-UAC has high surface area, better thermal stability, better pores developmentand improved surface chemistry compared to the EFB-AC. The maximum adsorption of MBoccurred at pH (10), adsorbent dosage (30 mg), contact time (40 min), Temperature (50◦C) andMB initial concentration (50 mg/L). The experimental data was best described by Langmuirisotherm model, having an adsorption capacity of 400 mg/g and 435 mg/g for EFB-AC andEFB-UAC, respectively. The kinetic model was best suited by pseudo-second order modelfor MB adsorption onto EFB-AC and EFB-UAC. The thermodynamics investigation showedthat adsorption of MB was endothermic in nature due to strong electrostatic interactionand formation of hydrogen bonding. The study revealed that ultrasonic assisted variationsof the adsorption parameters significantly improved the adsorption of MB onto EFB-AC andEFB-UAC.