Sorption behavior of freshwater aquatic fern Azolla filiculoides on redwine dye

Abstract

The biosorption of redwine dye from aqueous solution onto aquatic fern Azolla filiculoides has been studied. The factors affecting the sorption process, such as solution pH, contact time and initial concentration, adsorbent size, and dosage were determined in the batch mode. Equilibrium sorption isotherms and kinetics were investigated. Sorption isotherm data were fitted with Langmuir and Freundlich models and Langmuir monolayer coverage was determined as 86.21 mg/g. The kinetic data obtained at different initial concentrations were analyzed using pseudo-first-order and pseudo-second-order equations. Biosorption mechanism using Boyd’s plot confirmed the film diffusion was the rate-limiting step. The morphological characteristics and functional groups responsible for the binding of dyes were done using Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy analysis, respectively. The ability of A. filiculoides to remove redwine dye from aqueous solution was also examined in an up-flow packed column (continuous mode) at different experimental conditions. The maximum uptake (5.4 mg/g) was obtained at bed height of 15 cm, flow rate of 2 mL/min, and initial dye concentration of 70 mg/L. The Bed Depth Service Time, Thomas, and Yoon and Nelson models were used to analyze the experimental data and the model parameters were evaluated. Thus, A. filiculoides has a potential to be a biosorbent for the removal of reactive redwine dye from aqueous solutions.

Keywords:

• Azolla filiculoides
• Aquatic fern
• Redwine dye
• Adsorption isotherms
• Biosorption mechanism
• Kinetics