Characterization of CFB-Coal Fly Ash Zeolitic Materials and Their Potential Use in Wastewater Treatment

Two different fly ash (FA) samples were tested for their ability to give synthetic zeolitic products. Polish bituminous (PB) and South African (SA) coal fly ash (FA) samples, derived from pilot-scale circulated fluidized bed (CFB) combustion facilities, have been utilized as raw materials. The two FAs underwent a hydrothermal activation with 1M NaOH solution at 90°C for 24 h. Two different FA/NaOH solution/ratios (50, 100 g/L) were applied for each sample and the following zeolitic materials were formed: Na-Al-Si Zeolite A (Na), K-Al-Si Zeolite A (K), Erionite, ZSM-18, K-Ca-Al-Si-Hydrate Unnamed Zeolite, Erionite and Linde (L). The experimental products were characterized by means of X-Ray Diffraction (XRD) and Energy Dispersive X-Ray coupled-Scanning Electron Microscope (EDX/SEM), while X-Ray Fluorescence (XRF) was applied for the determination of their chemical composition. The zeolitic products were also evaluated in terms of their cation exchange capacity (CEC), specific surface area (SSA), specific gravity (SG), particle size distribution (PSD), pH and the range of their microand macroporosity. The current work focuses on testing the synthesized zeolitic materials for their potential of retaining heavy metals from industrial wastewater. Therefore, the aforementioned products were tested for their ability of adsorbing Cr, Pb, Ni, Cu, Cd and Zn from contaminated liquids, by the use of instrumental analytical methodologies. It must be noticed that the main goal is the treatment of liquid waste with such by-products and the capability of the zeolitic material to inhibit the leaching of the metals. Main parameters, as it is concluded from the experimental results, are the mineralogical composition of the initial fly ashes, as well as the type and the amount of the produced zeolite and specifically the mechanism by which the metals ions are hold on the substrate. 2009 World of Coal Ash (WOCA) Conference May 4-7, 2009 in Lexington, KY, USA http://www.flyash.info/