Equilibrium and kinetic studies of azo dye molecules biosorption on phycocyanin-extracted residual biomass of microalga Spirulina platensis

Abstract

The capability and mechanism of a model azo dye, C.I. Basic Red 46 removal by phycocyanin extraction residue of Spirulina platensis were investigated in this study. The biosorption data were analyzed using Freundlich, Langmuir, and Dubinin–Radushkevich (D–R) isotherm models. Langmuir model was more adequate to represent the data of biosorption equilibrium. The dye biosorption capacity was obtained as 23.06 mg g−1 for the biosorbent. The dye removal potential of phycocyanin-extracted biomass was very close to that of the virgin alga (25.46 mg g−1). D–R model displayed that the dye was probably to be removed mainly via physical biosorption. The pseudo-first-order, pseudo-second-order, logistic, and intraparticle diffusion models were used for the evaluation of biosorption kinetics. The logistic model presented the best fit to the experimental kinetic data. The intraparticle diffusion model showed that this biosorption process was a complex process involving more than one mechanism. Thus, this waste microalga biomass can be used as a low-cost biosorbent for dye removal.