Effective removal of AB24 dye by nano/micro-size zero-valent iron

The removal of AB24 dye in aqueous solution by nano/micro-size zero-valent iron (ZVI) was investigated. Results indicate that the degradation efficiency increases with increasing ZVI concentration and temperature but decreases with particle size of ZVI. Analysis of the results indicates that the reaction follows pseudo-first order kinetics. The rate constant increases linearly with ZVI concentration and decreases with particle size. The activation energy of reaction is 72.3 kJ/mol, indicating that surface reaction controls the rate of degradation. The reaction rate is highly pH-dependent; at pH < 6, the rate constant increases with decreasing pH; between pH 6 and 9, the rate increases with increasing pH; above pH 9 the rate dropped rapidly. Two modes of decolorization of the dye are proposed: a reduction reaction most effective at pH < 6 and adsorption removal most effective at pH 9.