Removal of methylene blue from aqueous solutions using biochar prepared from Eichhorrnia crassipes (Water Hyacinth)-molasses composite: Kinetic and equilibrium studies

Abstract

A biochar based adsorbent prepared from Eichhornia crassipes-molasses bio-composite was tested for its ability to remove methylene blue from aqueous solutions. Molasses were used as a granulating media for powdered biomass making it easier to prepare the biochar under set conditions. The Biochar adsorbent was prepared by igniting biomass granules at 400°C. A maximum adsorption capacity of 44.13 mg∙g-1 was achieved at an optimum pH 8, with a bio-sorbent dosage of 0.8 g and an initial concentration of 50 mg∙L-1. Experimental data fitted well onto Freundlich adsorption isotherm with an R2 value of 0.9819. Adsorption processes followed pseudo-second order kinetics with an R2 value of 0.9877. FT-IR spectra reveal typical absorption bands around 1563, 1375 and 1028 cm-1. SEM image show the biochar consisted of irregular particles with a microporous structure and appeared to be fibrous. BET results showed that biochar particles had a surface area of 0.8923 m2∙g-1, a pore volume of 0.00246 cm3∙g-1 and a pore diameter of 10.87 nm.   Key words: Bio-sorbent, biochar, Eichhornia crassipes, methylene blue, isotherm.