Magnetic zeolite NaA: Synthesis, characterization based on metakaolin and its application for the removal of Cu~(2+), Pb~(2+)

摘要

The optimum parameters for synthesis of zeolite NaA based on metakaolin were investigated according to results of cation exchange capacity and static water adsorption of all synthesis products and selected X-ray diffraction (XRD). Magnetic zeolite NaA was synthesized by adding Fe_3O_4 in the precursor of zeolite. Zeolite NaA and magnetic zeolite NaA were characterized with scanning electron microscopy (SEM) and XRD. Magnetic zeolite NaA with different Fe_3O_4 loadings was prepared and used for removal of heavy metals (Cu~(2+), Pb~(2+)). The results show the optimum parameters for synthesis zeolite NaA are SiO_2/Al_2O_3 = 2.3, Na_2O/SiO_2 = 1.4, H_2o/Na_2O = 50, crystallization time 8 h, crystallization temperature 95 ℃ The addition of Fe_3O_4 makes the NaA zeolite with good magnetic susceptibility and good magnetic stability regardless of the Fe_3O_4 loading, confirming the considerable separation efficiency. Additionally, Fe_3O_4 loading had a little effect on removal of heavy metal by magnetic zeolite, however, the adsorption capacity still reaches 2.3 mmol g~(-1) for Cu~(2+), Pb~(2+) with a removal efficiency of over 95% in spite of 4.7% Fe_3O_4 loading. This indicates magnetic zeolite can be used to remove metal heavy at least Cu~(2+), Pb~(2+) from water with metallic contaminants and can be separated easily after a magnetic process.