Basic dyes biosorption onto Azolla filiculoides: equilibrium and kinetic modelling
Sustainable process-product development & green chemistry
Environmental Engineering & Management (T1-3P)
Keywords: Azolla filiculoides, non-linear isotherms, biosorption, packed bed column
Biosorption, the uptake of organic/inorganic constituent’s by non-growing or dead microbial mass. During the past two decades, there has been interest in the use of bacteria, fungus etc in treating polluted wastewater. But recently most of researchers focused on algae for the treatment of wastewater. Mainly seaweeds (marine algae), micro fresh water algae and macro fresh water algae were used as biosorbents for the wastewater biosorption treatment. Most studies have been focused on metal sorption by micro and macro algae. In contrary, limited number of studies is available on biological treatment of dyes by algal species in spite of their ubiquitous distribution and their central role in the fixation and turnover of carbon and other nutrient elements. It also offers advantages for biosorption because their macroscopic structures present a convenient basis for the production of biosorbent particles suitable for sorption process applications
Modeling of biosorption isotherm data is important for predicting and comparing biosorption performance. There are various kinds of empirical isotherm models (two, three and even four parameter) are available for modeling adsorption data. Linear regression has been frequently used to evaluate the model parameters. However, transformations of non-linear isotherm equations to linear forms usually result in parameter estimation error and distort the fit.
Azolla filiculoides, a fresh water macro blur green alga, was the focus of the present investigation to remove basic dyes Rhodamine B (RMB) and Methylene blue (MB) from aqueous solutions in batch and column operation. In this work, the influences of different parameters on uptake of dyes, such as initial pH (2-7) and initial concentration (10-1000 mg/L) were investigated. Current research presents a method of direct comparison of the isotherm fit of two and three parameter (Langmuir, Freundlich, Redlich-Peterson and Sips) models to enable the best-fit and best isotherm parameters to be obtained. To evaluate the differences in the biosorption rates and uptakes, the kinetic data were described with Pseudo-first and Pseudo-second order models. The ability of A. filiculoides to biosorb MB in a packed column was investigated and fitted with the Thomas model as well.
