天然有机物在氧化铝表面的吸附机理研究

Adsorption mechanisms of NOM onto the surface of alumina

考察了天然有机物(NOM)的2种分离组份(憎水部分HyO,亲水部分HyI)和一种商用腐殖酸(CHA)在氧化铝表面的吸附解吸行为规律,从芳香性、分子量、极性的角度探讨了NOM自身特性对吸附性能的影响,并通过改变溶液性质(pH值、离子强度、二价阳离子Ca2+),进一步论证了NOM在金属氧化物表面的吸附机理.结果表明,芳香性高、弱极性的有机物吸附性能较强;降低溶液的pH值,有助于增加吸附剂的吸附容量;离子强度和Ca2+对吸附行为的影响,与NOM自身和内部组分的性质有关.NOM吸附于金属氧化物表面的机理,可以归结为配位体交换、静电作用、憎水作用、阳离子架桥等多个因素共同作用的结果.采用原子力显微成像技术,进一步从微观角度证实了憎水作用和阳离子架桥作用的存在.

The adsorption desorption behaviors of the fractions of NOM （ including the hydrophobic fraction, HyO and the hydrophilic fraction, HyI） and CHA onto alumina were investigated, Characteristics of NOM such as the aromaticity, molecular weight and polarity were used to correlate with its adsorption capacity, and the adsorption mechanisms of NOM onto alumina were further verified through changing the solution properties （ the pH value, ion strength and divalent metal ion Ca^2＋ ）. The results revealed that NOM with higher aromaticity and weaker polarity was preferably adsorbed. Decreasing pH value was favorable for increasing the capacity of adsorbate. The effect of ion strength and Ca^2 ＋ was related to the property of NOM and its inner fractions as well. As a result, the mechanisms of the adsorption of NOM onto alumina can be summarized as the corporate effect of ligand exchange, electrostatic interaction, hydrophobic interaction and cation bridging. Besides, the effect of hydrophobic interaction and cation bridging was further verified with the atomic force microscopy.