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用硫酸铵对镁铝水滑石进行改性,研究了镁铝水滑石的溶解性及硫酸铵的改性机理。结果表明,镁铝水滑石在pH 1.0-11.0范围内呈现出完全溶解、部分溶解和基本不溶三种溶解特性。硫酸铵的改性即为镁铝水滑石的部分溶解过程,层板中镁以Mg~(2+)形态进入溶液,导致羟基铝(Al(OH)_6~(3-))进入溶液形成Keggin结构(Al_(13)聚集体),Al_(13)聚集体附着在镁铝水滑石层板表面形成无定形Al(OH)_3,从而阻止镁离子进一步溶出。改性镁铝水滑石对Pb~(2+)的吸附率提高了18.3%,是比表面积的增加、化学键合及静电吸附能力的提升所致。
Ammonium hydrotalcite modified with ammonium sulfate, magnesium aluminum hydrotalcite solubility and ammonium sulfate modification mechanism. The results show that the Mg-Al hydrotalcite exhibits three kinds of dissolution characteristics: completely dissolved, partially dissolved and almost insoluble in the range of pH 1.0-11.0. The modification of ammonium sulfate is the partial dissolution process of MgAl2O4. The magnesium in the coating enters the solution in Mg2 + form, resulting in the formation of Keggin (Al (OH) 6 ~ (3-)) into solution (Al_ (13) aggregates). The Al_ (13) aggregates adhere to the surface of the MgAl 2 O layer to form amorphous Al (OH) _3, which prevents the further dissolution of magnesium ions. The adsorption rate of modified Mg-Al hydrotalcite on Pb 2+ increased by 18.3%, which was due to the increase of specific surface area and the improvement of chemical bonding and electrostatic adsorption.