Biosorption of methylene blue dye using banana floret:: kinetic, equilibrium, thermodynamic and mass transfer studies

Abstract

Colour removal from effluents remains one of the most challenging requirements faced by indus - tries due to the difficulty of degrading dyes which consequently escape conventional wastewater treatment processes and persist in the environment. This study aimed to assess and optimise the dye adsorption performance of banana floret, a novel biosorbent. Batch experiments were con - ducted to assess the effects of particle size, pH, agitation, temperature, initial concentration and sorbent dose. Kinetic and equilibrium data were modelled, and mass transfer studies were con - ducted to elucidate the mechanisms of biosorption. Equilibrium data were best simulated using the Sips and Langmuir isotherm models. At an optimum pH of 6.0, biosorbent dose of 1.0 mg·L –1 and temperature of 300 K, a maximum sorption capacity of 219 mg·g –1 was observed. The kinetic data were best represented by the pseudo-second-order model. The dominant transport mechanism was attributed to intraparticle diffusion, while the dominant attachment mechanism was phys - ical sorption. The Taguchi method, in combination with analysis of variance, was used to deter - mine the optimum levels of operational parameters for maximising the biosorption of methylene blue by banana floret. The parameter group which produced the highest biosorption capacity and percent removal was determined to be A3-B1-C3 (initial concentration = 200 mg·L –1 , biosorbent dose = 500 mg·L –1 , contact time = 60 min) and A1-B3-C3 (initial concentration = 50 mg·L –1 , biosor - bent dose = 2000 mg·L –1 , contact time = 20 min), respectively. Among these parameters, the initial concentration had the most significant effect on the biosorption capacity, while sorbent dose was most significant on percent removal. A predictive model based on a quadratic equation which incorporates the factor interactions was successfully developed and validated.