Mechanistic and kinetic evaluation of biosorption of reactive azo dyes by free, immobilized and chemically treated Citrus sinensis waste biomass

Sorption potential of Citrus sinensis biomass for reactive yellow 42 and reactive red 45 was investigated with variation of pH, biosorbent dose and dye concentration. Biosorbent was treated by organic and inorganic reagents of which acetic acid and acetonitrile enhanced the sorption capacities for reactive yellow 42 and reactive red 45, respectively. Sorption equilibrium was established within 60 min using free and chemically treated biosorbent, while prolonged to 120 min using immobilized biosorbent. Freundlich isotherm and pseudo-second-order rate law described best the sorption mechanism. FT-IR analysis of biosorbent revealed the presence of C=O, C-O, NH and OH groups on the surface of biosorbent. Desorption experiments were performed to regenerate the sorbent, making the process more economical and environment friendly. (C) 2010 Elsevier B.V. All rights reserved.