DOM不同分子质量组分对石英砂吸附卡马西平的影响研究

为探究溶解性有机质(DOM)不同相对分子质量组分对药物和个人护理品(PPCPs)类污染物吸附过程的影响,以卡马西平(CBZ)为目标污染物,以石英砂代表无机矿物,用商用腐殖酸(HA)制备DOM并进行超滤分级,然后开展吸附实验,并采用荧光光谱和红外光谱表征等手段,研究了DOM不同分子质量组分对石英砂吸附CBZ的影响及机制。结果表明,以3 000和10 000的超滤膜进行分级后的不同相对分子质量HA结构有明显差别,大分子质量HA中苯环等疏水性结构以及羟基的含量较多,芳香构造化程度高,多为分子量较高、稳定性较好的疏水性有机物,但中、小分子质量HA结构差异不大,含有更多羰基、羧基等含氧官能团,主要是一些分子质量较小的亲水物质; DOM不同分子质量组分对CBZ在石英砂上的吸附有明显影响,其中大分子质量组分促进吸附,而中、小分子质量组分抑制吸附,原因在于大分子质量组分可疏水结合于矿物表面,增加介质表面的活性吸附位点,同时其芳香性或脂肪性结构可与CBZ的疏水基团发生疏水作用共吸附或累积吸附于介质表面,从而促进CBZ的吸附;而中、小分子质量DOM的极性官能团可与CBZ酰胺部分通过极性作用结合,对CBZ分子有增溶作用,从而抑制吸附。

Influence of different relative molecular masses of DOM on the adsorption of carbamazepine by quartz sand

In this study, the authors carried out sorption experiment with the purpose of understanding the effects of different relative molecular masses of dissolved organic matter (DOM) on PPCPs adsorption behavior. The authors chose carbamazepine (CBZ) as the target pollutants and quartz sand as the inorganic minerals, and used commercial humic acid (HA) to prepare DOM with ultrafiltration classification. Then the authors studied the impact of HA with different relative molecular masses on CBZ adsorption behavior based on fluorescence spectrum and infrared spectroscopy. It is found that, through ultrafiltration classification technology by 3 000 and 10 000 ultrafiltration membranes, the structures of HA are different. Large molecular weight fractions of HA which contain more hydroxyl and benzene ring are mainly hydrophobic substance with better stability and high degree of aromatic tectonics. However, the structure of HA with medium and small molecular weight is not very different. They contain more oxygen-bearing functional groups such as carbonyl and carboxyl groups which are mainly hydrophilic substances. DOM has a significant effect on the adsorption of CBZ onto quartz sand. Large molecular weight DOM promotes the adsorption of CBZ on quartz sand, while medium and small molecular weight DOM inhibits the adsorption of CBZ on quartz sand. The reason is that the large molecular weight DOM can bind on the mineral surface which increases the activity of adsorption sites on the dielectric surface and its aliphatic and aromatic substances have hydrophobic interaction with hydrophobic groups of CBZ. These effects make CBZ adsorb or accumulate on the surface of the medium, which promotes the adsorption of CBZ in quartz sand. The polar functional groups of small and medium molecular weight DOM can bind to the amide of CBZ through polar interaction and increase the solubility of the CBZ molecules, thus inhibiting the adsorption of CBZ on the quartz sand.