Comparative Adsorption Characteristics of Methylene Blue on Raw Leaves and Biochar of Guinea Grass (Megathyrsus maximus)

Wastewater discharged from textile industries leads to severe impact on aquatic ecosystem and public health. Methylene blue (MB), commonly found in textile wastewater systems, would cause many health problems on humans and lead to undesirable ecological changes in the environment. Hence, removal of MB from contaminated water is a priority to safeguard the environment. This study thus aims to explore the practicability of utilizing both raw biosorbent and biochar of guinea grass ( Megathyrsus maximus ) for removal of MB cationic dye from synthetic contaminated water. The raw biosorbent and biochar were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. Effect of adsorbent dosage, shaking time, settling time and pH of the MB solution were investigated in batch experiments. Adsorption kinetics investigated under pre-equilibrium conditions leads to the validity of the pseudo second-order kinetics model according to linear regression analysis, which can be attributed to the presence of two or more functional groups involved in the adsorption process. Moreover, adsorption equilibrium data of both biosorbents show the validity of the Langmuir adsorption isotherm over the Freundlich isotherm according to the linearized relationships, indicating the monolayer adsorption of MB molecules. Both raw biosorbent and its biochar exhibit more than 95% removal of MB under the experimental conditions employed. Another desirable factor is that the raw biosorbent could easily be modified to further improve adsorption characteristics. Although both biosorbent types are cost-effective, ecofriendly and sustainable, it is more economical to use the raw biosorbent for the removal of MB from aqueous systems.