Competition between sodium oleate and sodium silicate for a silicate/oleate modified magnetite surface studied by in situ ATR-FTIR spectroscopy.
Competition between sodium oleate and sodium silicate for a silicate/oleate modified magnetite surface studied by in situ ATR-FTIR spectroscopy.
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DOI：
10.1016/j.jcis.2009.12.002
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发表时间：
2010-03
影响因子：
9.9
通讯作者：
Payman Roonasi;Xiaofang Yang;A. Holmgren
中科院分区：
文献类型：
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作者：
Payman Roonasi;Xiaofang Yang;A. Holmgren
利用衰减全反射(ATR)红外光谱技术研究了在pH=8.5条件下油酸钠和硅酸钠在合成磁铁矿上的吸附行为。油酸盐在0.01-0.5 mM的浓度范围内被吸附。在0.1 mM的溶液中，随着油酸浓度的增加，对油酸的吸附呈线性增加。油酸盐的红外光谱在1535 cm−处有一个较宽的单峰，归属于羧酸盐的不对称伸缩振动，表明油酸盐在磁铁矿表面上有化学吸附。油酸盐的吸附动力学符合拟一级反应，表观速率常数K1=0.030±0.002min−1。在初始平衡的磁铁矿薄膜中加入硅酸盐溶液，或在浓度为0.1-5 mm的磁铁矿中加入油酸盐溶液，均可实现对硅酸盐和油酸盐的竞争吸附。结果表明，在合理的时间内，硅酸盐对磁铁矿表面已吸附的油酸盐量影响不大。另一方面，如果硅酸盐物质已经吸附在氧化铁上，油酸盐就不能有效地与硅酸盐竞争。
Attenuated Total Reflection (ATR) IR spectroscopy was utilized to monitor adsorption of sodium oleate and sodium silicate onto synthetic magnetite at pH=8.5, both individually and in a competitive manner. Oleate was adsorbed within a concentration range of 0.01–0.5mM. It was observed that adsorption of oleate increased linearly with increasing concentration of oleate in solution up to a concentration of 0.1mM. The infrared spectrum of oleate showed a broad single band at 1535cm−1assigned to the asymmetric stretching vibration of carboxylate, implying chemisorption of oleate to the magnetite surface. The kinetics of oleate adsorption followed a pseudo first-order reaction with an apparent rate constant of k1=0.030±0.002min−1. Competitve adsorption of silicate and oleate was performed either by adding silicate solution to a magnetite film initially equilibrated with 0.1mM oleate or adding oleate solution to magnetite treated with silicate solutions in the concentration range 0.1–5mM. It was shown that silicate, within reasonable time, had only minor effect on the amount of oleate already adsorbed on magnetite. On the other hand, oleate did not efficiently compete with silicate if the latter substance was already adsorbed on the iron oxide.