吸附层中Mg^(2+)在硅胶表面反应的过程

Reaction of Mg^(2+) on the Surface of Silica in Adsorption Layer

利用吸附相反应技术,以纳米SiO_2为载体,将其富集水的表面吸附层作为纳米反应器,研究了Mg^(2+)与富集在吸附水层中的NaOH在硅胶表面的反应。利用X射线衍射(XRD),透射电镜(TEM)和红外光谱(FT-IR)对产物进行分析,发现产物中除了Mg(OH)_2之外,还有MgO-SiO2-H_2O/SiO_2。根据产物的组成,提出了吸附层中发生反应的两种路径,并通过考察NaOH的吸附时问和反应时间对产物的影响证实了这两种路径。其中一条反应路径是吸附层中富集的浓度较高的NaOH与硅胶表面的Si-OH作用,生成一定量的可溶性硅酸盐,在碱性条件下,进一步与MgCl_2反应生成MgO-SiO_2-H_2O类物质;另一反应路径是MgCl_2与吸附层中的NaOH反应生成Mg(OH)_2,在碱性条件下,Mg(OH)_2进一步与硅胶表面反应,形成MgO-SiO_2-H_2O类物质。最后考察了体系中水的量对两种路径的影响,发现水量越多,越容易出现MgO-SiO_2-H_2O。

The reaction of Mg^2＋ with NaOH enriching in the adsorption water layer on SiO2 surface was researched by the adsorption phase nanoreactor technique. The products were analyzed by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and infrared （IR） spectrum. It was found that the products were Mg（OH）2 and MgO-SiO2-H2O/SiO2. Two reaction routes were put forward according to the products and testified by investigation the influence of the adsorption time of sodium hydroxide and the reaction time on the products. The first reaction path was that NaOH reacted with Si-OH and soluble silicate was produced, then the silicate reacted with MgCl2 under basic condition and MgO-SiO2-H2O was produced. The second reaction path was that MgCl2 reacted with NaOH and Mg（OH）2 was produced, then Mg（OH）2 reacted with Si-OH under basic condition and MgO-SiO2-H2O was produced. The effect of water amount in the reaction system was investigated on the two reaction routes and the results showed that the more water was, the more easily MgO-SiO2-H2O was produced.