Kinetic and equilibrium studies on the biosorption of textile dyes onto Plantago ovata seeds

The powdered seeds of Plantago ovata (PSPO) were utilized for the removal of Malachite Green (MG) and Rose Bengal (RB) dyes from aqueous media by batch adsorption. The Fourier transform infra red spectroscopy (FTIR) results showed that both the dyes were adsorbed between the cellulose matrices, and this has been verified from the intensifying and narrowing aromatic C-H bending vibration. The morphology of the dye laden adsorbent was studied by scanning electron microscopy (SEM), which showed that the dyes were adsorbed between the cellulose matrices of the adsorbent. The PSPO was found to be very effective for the removal of MG and RB at pH 7, and equilibrium was attained within 200 min. The kinetic study indicated that the rate limiting step for MG and RB adsorption may be chemisorption and intraparticle diffusion. Adsorption equilibrium data were fitted to Langmuir, Freundlich, Redlich-Peterson and Temkin adsorption isotherms. It is inferred from the equilibrium studies that the adsorption of MG follows the Freundlich isotherm and the adsorption of RB follows the Langmuir isotherm. The maximum monolayer adsorption capacity of the PSPO was found to be 86.23 mg/g for MG and 81.23 mg/g for RB, respectively.