Absorption of Cr(VI) onto amino-modified titanate nanotubes using 2-bromoethylamine hydrobromide through SN2 reaction.
Absorption of Cr(VI) onto amino-modified titanate nanotubes using 2-bromoethylamine hydrobromide through SN2 reaction.
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DOI：
10.1016/j.jcis.2013.03.037
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发表时间：
2013-07
影响因子：
9.9
通讯作者：
Guanjun Niu;Wen Liu;Ting Wang;J. Ni
中科院分区：
文献类型：
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作者：
Guanjun Niu;Wen Liu;Ting Wang;J. Ni
不同于在有害的有机溶剂中接枝氨基的复杂反应，我们提出了一种环境友好的方法，通过纯水溶液中的两步SN2反应，在钛酸盐纳米管（TNTs）上与2-溴乙胺氢溴化物（2-Bh）进行有效的氨基接枝。采用透射电镜、x射线衍射、x射线光电子能谱和傅里叶变换红外光谱对氨基修饰钛酸盐纳米管（TNTs-RNH2）进行了表征。在最佳条件下，步骤1 NaOH/2- bh的摩尔比为1.2，步骤2为1.3，反应时间分别为12h和24h。Cr（VI）在TNTs- rnh2上的吸附等温线符合Langmuir模型，最大吸附量为69.1mg/g，几乎是新鲜TNTs吸附量的5倍。随着no3浓度的增加，吸附容量略有下降，主要原因是离子的竞争、双电层的抑制和Cr（VI）形态的改变。较宽的吸附pH范围是由于更大的零电荷点（8.2）和带正电荷的tnt - rnh2与不同形态的Cr（VI）之间的静电吸引。产物在pH值为10的条件下进行简单解吸，可以很好地重复利用，经过三次循环后，吸附量损失约20%，无需进行任何再生处理。
Unlike the complex reaction of grafting amino groups using harmful organic solvents, we proposed an environmental friendly method for effective amino grafting on titanate nanotubes (TNTs) with 2-Bromoethylamine hydrobromide (2-Bh) through a two-step SN2 reaction in pure water solution. The amino-modified titanate nanotubes (TNTs-RNH2) were characterized by Transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Under optimal conditions, the molar ratio of NaOH/2-Bh was 1.2 for step 1 and 1.3 for step 2 with corresponding reaction time of 12h and 24h, respectively. The adsorption isotherm of Cr(VI) onto TNTs-RNH2well fits Langmuir model with maximal adsorption capacity of 69.1mg/g, which is almost five times larger than that of fresh TNTs. The slight decrease in adsorption capacity with NO3-concentration was attributed to competition from ions, suppression of electric double layer and changes of Cr(VI) speciation. The wide adsorption pH range was due to much larger point of zero charge (8.2) and electrostatic attraction between positively charged TNTs-RNH2and Cr(VI) with different speciations. The products could be well reused due to simple desorption at pH 10 with about 20% loss of the adsorption capacity after three recycles without any regeneration treatment.