| In this study, fly ash ceramsites were firstly synthesized from fly ash (FA) using avoiding-burning stage and then converted to fly ash-zeolite pellets through hydro-thermal method. Orthogonal experiment was taken to determine the optimal parameters on synthesis of fly ash ceramsites. Furthermore, the influential parameters such as reaction time, temperature and concentrations of NaOH solution in the hydro-thermal reaction were investigated in detail. The results showed that the fly ash-zeolite pellet could obtain the best resultant effect with the NaOH concentration of 5 mol/L at 120℃for 12 h. XRD analysis illustrated that the resulting product was combined with zeolite NaX, NaA and hydroxysodalite (HS). Octahedral and cubical crystal morphology as NaX and NaA zeolite were also found from SEM micrographs, respectively. Cation exchange capacity (CEC) of fly ash zeolite pellets was determined to 1.703 mg/g by UV-spectrophotometric method.Besides, the adsorption towards Cd(II) of the as-prepared fly ash ceramsites and zeolite pellets under static adsorption condition were also studied, and the influential parameters to adsorption such as pH, temperature as well as the amount of absorbent were investigated. The results showed that the adsorption isotherm of both fly ash ceramsites and zeolite pellets were well in accordance with Langmuir isotherms and the greatest adsorption capacity were 2.93 mg/g and 2.50 mg/g, respectively. Moving Boundary Model analysis showed that the absorption of Cd(II) was mainly governed by liquid film diffusion and the adsorption processes was well agreed with a pseudo-second-order kinetic model.
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