甲基化MCM-41吸附水中硝基苯类化合物的研究

Uptake of nitroaromatic compounds from aqueous solution by methylated MCM-41

利用三甲基氯硅烷对MCM-41进行表面修饰制得甲基化MCM-41,采用X-射线衍射分析仪(XRD)、透射电镜(TEM)、N2吸附-脱附和红外光谱(FTIR)对样品进行表征,并考察其对水中硝基苯类化合物(NACs)的吸附性能.结果表明,甲基化MCM-41对NACs的吸附速率较快,吸附为放热过程,吸附等温线可以用线性模型拟合.当苯环上存在供电子取代基时,甲基化MCM-41的吸附能力下降,当苯环上存在吸电子取代基时,甲基化MCM-41的吸附能力增加.随着pH值的升高,甲基化MCM-41对分子态NACs的吸附能力保持不变,对电离态NACs的吸附能力逐渐降低.经过分析,推测甲基化MCM-41吸附NACs的机理为吸附剂表面硅氧烷中的氧原子与苯环发生了电子供体/受体配位作用.再生实验表明,甲基化MCM-41可以循环使用.

Surface silylation of MCM-41 with trimethylchlorosilane was carried out to adsorb nitroaromatic compounds （NACs） from aqueous solution based on batch adsorption tests.The methylated MCM-41 was characterized by X-ray diffraction （XRD）,transmission electron microscopy （TEM）,N2 adsorption-desorption and Fourier transform infrared spectroscopy （FTIR）.The results demonstrated that the adsorption rate of NACs was very fast and the adsorption process was exothermic.The linear model could fit the adsorption isotherm of NACs over the methylated MCM-41 well.Substituents with electron donating groups on the aromatic rings decreased the methylated MCM-41 adsorption,whereas substituents with electron withdrawing groups on the aromatic rings strengthened the methylated MCM-41 adsorption.The increase of pH had no noticeable effect on non-ionized NACs adsorption.However,for ionized NACs,the amount of adsorption decreased with the increase of pH.Evidenced from the results given above,the formation of an electron donor-acceptor complex between electron donor functions at the siloxane surface and the aromatic ring system of the NACs may be postulated as a plausible mechanism of the methylated MCM-41 adsorption.The regeneration results showed the suitability of methylated MCM-41 as a reusable adsorbent.