Reduction of Azo Dye from Aqueous Solution using Acid Treated Aquatic Macrophytes

Azo compounds constitute the largest and the most diverse group of synthetic dyes and are widely used in a number of industries such as textile, food, cosmetics and paper printing. They are generally recalcitrant to biodegradation due to their xenobiotic nature. However, aquatic macrophytes are highly versatile in reduction of azo dyes due to their porous nature. In this study, adsorption of an industrial azo dye Metanil Yellow on to acid treated and non-treated biosorbent is investigated. In addition, the study emphasize on identifying the factors exerting the strongest influence on adsorption of dye. The effect of the process parameters such as contact time, adsorbent dose, pH and agitation speed are reported. The contact time of 120 min is found to be sufficient for the adsorption to reach equilibrium. The pseudo first & second order models are used to describe the kinetic data, and the rate constant is therefore evaluated. The dye adsorption to biosorbent is characterized by monolayer isotherm and caused by adsorption with relatively strong uptake. The Langmuir and Freundlich models adsorption are applied to describe the isotherm equilibrium and to determine its constants. The Langmuir and Freundlich models agree well with the experimental data with an adsorption capacity of 91.743 & 85.179 mg of dye per gram of acid treated and non-treated biosorbent respectively. A better fixation was obtained at acidic pH.