Removal of Rose Bengal dye from aqueous solutions using biosorbent obtained from Mangifera indica

Abstract

Rose Bengal dye is a xanthene class [4, 5, 6, 7-tetrachloro-2', 4', 5', 7'-tetraiodofluorescein] compound with high molecular weight of 1016.7 g/mol. The leaves of Mangifera indica has been used to prepare a homogeneous powdered biosorbent for the removal of Rose Bengal dye from aqueous solution. Maximum dye uptake capacity is achieved for initial dye concentration of 20 mg/L at biosorbent dosage of 0.2 g at neutral pH. Scanning electron microscope (SEM) image, Energy Dispersive X-ray (EDX) and Fourier Transform Infrared (FTIR) spectra display changes in the morphological properties, elemental compositions and functional groups respectively before and after adsorption of RB dye on MI. The maximum monolayer adsorption capacity of MI for RB dye is found to be 0.824 mg per 0.2 g of adsorbent. Freundlich isotherm model best fits the experimental data compared to the results obtained from Langmuir-1 and Langmuir-2 model equations. The pseudo-second order model-1 best describe the kinetics of the adsorption of Rose Bengal dye on MI. The thermal degradation characteristics of Mangifera indica before and after adsorption are studied. The pyrolysis of dye adsorbed biomass at 900°C result in a total degradation of 93.15% with peak weight reduction of 0.0508 mg/min at 528°C.