科研之友
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摘要
Layered double hydroxide (LDH) nanosheets were prepared in formamide by a one-step synthesis method with different concentrations of magnesium (Mg) and aluminum (Al) reactants (LDHns-F1~4), with the aim to produce an effective phosphate adsorbent. The morphology of LDHns-F was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results showed ultrathin LDH nanosheets were successfully synthesized with a lateral size of 30 nm, plate-like morphology and hexagonal shape. The dried LDH nanosheets exhibited the XRD characteristic peak of LDH, and drying will to some extent cause stacking of the nanosheets. The adsorption isotherms showed that the maximum adsorption capacity of LDHns-F3 (the concentration of Mg and Al reactants are 0.08, 0.04 mol?L-1) is 128.0 mg?g-1 by Langmuir fitting, 61% higher than that of conventional layered LDH (LDH-P). The kinetic results showed that LDHns-F3 can quickly adsorb phosphate and reach equilibrium in 15 minutes. The data were well fitted by pseudo second-order model indicated that chemical adsorption may be the rate control step of phosphate adsorption on LDHns-F3.The adsorption mechanism was investigated by Zeta potential analysis and X-ray photoelectron spectroscopy (XPS). The results showed that the hydroxyl groups on the layer surface formed inner-sphere complexes with phosphate. The presence of large amounts of hydroxyl groups on the surface of LDH nanosheets is beneficial for adsorption of oxygen containing anionic pollutants. The LDH nanosheets with good adsorption properties have wide application prospects in high phosphorus containing water treatment.
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