1. Molecular mechanism of surface recognition. Azo dyes degradation on Fe, Ti, and Al oxides through metal sulfonate complexes
1. Molecular mechanism of surface recognition. Azo dyes degradation on Fe, Ti, and Al oxides through metal sulfonate complexes
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DOI：
10.1021/la9900270
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发表时间：
1999-10-26
期刊：
影响因子：
3.9
通讯作者：
Kiwi, J
中科院分区：
文献类型：
--
作者：
Bandara, J;Mielczarski, JA;Kiwi, J
研究了偶氮染料(橙II、橙I和橙G)在α-Fe_2O_3和α-FeOOH上的吸附，并与在TiO_2和Al_2O_3上的吸附结果进行了比较。当偶氮染料的磺酸基位于萘环上时，偶氮染料的吸附不是很有利，例如橙色G。氧化物的晶面和适当的金属-金属原子距离似乎控制着吸附的程度，而不是表面位置的密度(表面积)。后者的观察结果表明，在不同偶氮染料在特定氧化物表面的吸附过程中，表面分子识别机制是活跃的。在pH小于或等于7时，橙色II(作为模型染料)从溶液中的吸附可以从静电的角度来理解，考虑到氧化物表面的物种和橙色II的电离作为溶液pH的函数。考虑了不同偶氮染料的吸附位置数、平衡常数和比表面积，对吸附过程进行了模拟。最有利的吸附条件是氧化物的M-M原子距离与磺酸基的O-O键距离最接近：橙色IT的-O-S-(O-O)。偶氮染料的吸附是通过橙色II的磺酸基团形成桥联的双齿络合物来实现的。人们使用了多种技术来跟踪吸附，如漫反射红外傅里叶变换光谱(DRIFT)、高压液相色谱(HPLC)、表面Zeta电位(Zeta)、W-Vis分光光度法和N-2(BET)吸附。
The adsorption of azo dyes (Orange II, Orange I, and Orange G) on alpha-Fe2O3 and alpha-FeOOH has been carried out, and the results are compared with those for adsorption on TiO2 and Al2O3 Adsorption of azo dye was less favored when the sulfonic groups were on the naphthalene ring, as in the case of Orange G, suggesting an inner sphere mechanism of complex formation between the dye and alpha-Fe2O3. The crystalline face of the oxide and the appropriate metal-metal atomic distance rather than the density of surface sites ( surface area) seem to control the extent of the adsorption. The latter observations imply a surface molecular recognition mechanism active during the adsorption process of different azo dyes on the particular oxide surface. The adsorption of Orange II (taken as a model dye) from solution at pH less than or equal to 7 could be understood in electrostatic terms taking into account the species found at the surface of the oxides and the Orange II ionization as a function of solution pH. Modeling of the adsorption processes was carried out taking into account the number of adsorption sites, the equilibria constants, and the surface area of the different azo dyes. The most favorable condition for adsorption was the closest matching of the M-M atomic distance of the oxide to the O-O bond distance in the sulfonic group: -O-S-(O-O) of Orange IT. The adsorption of azo dyes was found to occur via the sulfonic group of Orange II through the formation of a bridged bidentate complex. A variety of techniques have been used to follow the adsorption, such as diffuse reflectance infrared fourier transform spectroscopy (DRIFT), high-pressure liquid chromatography (HPLC), surface zeta potential (zeta), W-vis spectrophotometry, and N-2 (BET) adsorption.