Adsorption of Nickel(II) with Composite Filter Material Made of Coal Fly Ash

The regular methods for nickel removal such as activated carbon adsorption are always complicated in process and expensive in construction and maintenance. In this research coal fly ash, usually taken as industrial waste, was synthesized into particle filter material, and then the latter was used as absorbent for nickel removal from aqueous water. The physical and chemical properties of this material were studied by scanning electron microscope (SEM) and energy dispersive X-ray spectrometry (EDS). Results indicated that this material had high porosity and large surface area. The main elements of this material were oxygen, silicon, carbon, aluminum, iron, calcium and magnesium. In the batch experiments for the application of this filter material in nickel removal, the effects of contact time, pH and temperature were studied. The batch experiments showed an equilibrium time of 90 min was required for effective adsorption of nickel. Removal ratio of nickel increased greatly at pH 5.5-6.5. More than 90% of nickel was removed with solution pH above 6.5. Adsorption rate constant (k) increased as temperature (T) rose. The equation describing the relation of k and T complied to Arrhenius equation, which indicated the adsorption of nickel on this filter material had some characteristics of chemical reaction. The adsorption isotherm of nickel accorded with Langmuir model.