溶液pH条件影响针铁矿对溶解性有机质的吸附机理研究

Study on Solution pH Impacting Adsorption Mechanisms of Goethite for Dissolved Organic Matter

选择酸碱不同的pH条件,研究铁氧化物针铁矿对土壤溶解性有机质(DOM)的吸附模式的变化。批处理吸附实验研究表明,针铁矿对DOM的吸附性强并发生分异现象。而且,针铁矿的表面荷电性的变化,使得DOM针铁矿上的吸附受到显著的影响,随着pH值升高,针铁矿表面从带正电荷变为表面电中性,DOM在铁氧化物矿物表面吸附机制也发生变化,吸附等温线的Freundlich拟合参数n值从0.83升至1.02,表明吸附模式从配体交换为主导转为憎水键和范氏力作用为主导。可见,DOM/矿物界面吸附受多种吸附模式控制,主要包括配体交换、憎水键和范氏力等。

The adsorption experiments of goethite for the dissolved organic matter （DOM） at varying solution pH were investigated using a batch equilibrium technique. The results showed that the adsorption of goethite for DOM was strongly effective along with occurrence of DOM sorption fractionation. The sorption isotherms can be well fitted with good correlation relationships by linear and Freundlich equations （R〉0. 92） and Langmuir equation （R〉0.96）. Moreover, the sorption isotherm curve for DOM adsorbed onto goethite was almost linear at pH≈7. 5 （Freundlich equation fitting n=1. 02）, whereas nonlinear at pH≈4. 3 （Freundlich equation fitting n= 0. 83）. Therefore, the sorption process at DOM/goethite interface was controlled by the coexisted multi-mechanisms, mainly including‘surface ligand exchange＇, ‘hydrophobic force＇ and ‘van der Waals forces＇ models.