Removal of reactive blue 220 by zero valent iron

Dyes are highly colored polymers with low biodegradability and they constitute an important group of pollutants. Dyes significantly affect the photosynthetic activity of aquatic plants by reducing penetration of sunlight, and they may be toxic to some aquatic organisms. The commonly used dyes include reactive, disperse, acid, and direct dyes. Reactive dyes are widely used in various industries such as textile, paper, plastic, leather, cosmetics, and drug because of their wide variety of color shades, brilliant colors and ease of application. Since reactive dyes are soluble in water, they can't remove by conventional treatment processes. There are various physical and chemical processes such as adsorption, coagulation, flocculation, membrane filtration for removing of dyes from wastewaters. However, low removal efficiency or high costs of these methods limit their application. Therefore, there is a need to find alternative treatments that are effective in removing dyes from wastewater. In recent years, zero valent iron has being explored for treating of toxic and refractory pollutants such as dyes, inorganics, nitro-aromatic compounds, heavy metals because zero valent iron is non-toxic, abundant, cheap, and easy to produce. In this study, the removal of Reactive Blue 220 (RB220) from aqueous solution by micro- and nano scale zero valent iron was investigated. RB220 is a dye that belongs to formazan type of reactive dyes class. The effect on decolorization efficiency of operational parameters such as initial pH of solution, zero valent iron dosage, initial concentration of RB220, and temperature was evaluated. It was seen that decolorization efficiency was significantly depended on pH and higher decolorization efficiency was obtained at lower pH. Under optimal conditions, about 90% decolorization efficiency by micro- and nano scale zero valent iron was achieved. Decolorization kinetics fitted to the first-order kinetic.