The removal characteristics of para-nitrophenol from aqueous solution by fly ash were investigated under various conditions of contact time, pH and temperature. The influence of pH on the para-nitrophenol uptake by the fly ash was carried out between pH4 and pH 10. The level of uptake of para-nitrophenol by fly ash increased at higher pH values. The effect of temperature on the uptake of para-nitrophenol was investigated between 30 and 60oC; the adsorption increased at lower temperature. Rate constants were evaluated in terms of first-order kinetics. The rate constants k for uptake of different concentrations of para-nitrophenol was 1.10x10-2 s-1 and 1.14x10-2 s-1, respectively. The experimental results underlined the potential of coal fly ash for recovery of para-nitrophenol from waste water. The main mechanisms involved in the removal of para-nitrophenol from solution by fly ash were electron – withdrawing effect of NO2 group of benzene ring and adsorption at the surface of the fly ash.
Key words: Fly ash, para-nitrophenol, adsorption, kinetics, mechanism.
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