Exploring the biosorption of methylene blue dye onto acid treated sugarcane bagasse

The potential of acid treated sugarcane bagasse (ATSB) to remove methylene blue (MB), an azo-cationic dye, from waste waters was explored. Surface characterization of the biomass before and after MB sorption was achieved using FTIR spectrophotometer. The ATSB had surface functional groups, -OH, N-H, -C=O, -C-OH, SiO2 and C-halogen that were involved in removing MB from solution. Batch equilibrium sorption experiments were performed under optimized pH, contact time, biosorbent dosage and varying MB initial concentrations. The Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Halsey adsorption isotherms were used to describe equilibrium data generated from the effect of MB initial concentration. The equilibrium data fitted the isotherms in the order: Langmuir > Freundlich = Halsey > Dubinin-Radushkevich (D-R) > Temkin with R2 ranging from 0.9957 to 0.9621. The Langmuir isotherm based separation factor, RL, (0 < RL < 1) and the Freundlich’s adsorption intensity, n, (1/n < 1) indicated sorption favorability between MB and ATSB with the Langmuir sorption capacity of 64.9351 mg/g. The Freundlich and Halsey isotherms pointed to the surface heterogeneity that the ATSB comprised of both macropores and micropores. The energy of sorption, ED and bT parameters, derived from the D-R and Temkin isotherms respectively indicated that the biosorption was endothermic and physical ion-exchange in nature. ATSB can be used to remove MB from waste waters. However there is need to explore the effects of metal ions, anions and other dyes on the removal of MB by ATSB.