胡敏酸的结构特征及其吸附行为

使用0.5mol/L NaOH和0.1mol/L Na_4P_2O_7溶液分别从土壤中提取胡敏酸,并且对其进行了元素分析、红外光谱、固态13C核磁共振的定性、定量研究。结果表明,两种胡敏酸的性质很相似,但也存在一些微小差异,Na_4P_2O_7提取的胡敏酸比NaOH提取的具有芳香度较大、聚合度较高、极性官能团含量较多的特点。测定了菲在6个胡敏酸上的吸附等温线,Freundlich模型很好的拟合了所有吸附等温线,相关系数r均在0.992以上。有机碳分配系数K_(oc)与胡敏酸中极性碳(POC)之间存在明显的线性相关关系,并受到提取剂类型的影响。

Structure Characterization of Soil Humic Acids and Adsorption Equilibria on Phenanthrene

A better understanding of sorptive behavior in humic acids (HA) will help to determine the sorption mechanisms and fate of organic compounds in soil. Humic acids oxtracted by the 0.5 mol/L NaOH, 0.1 mol/L Na_4P_2O_7 solution from the same soil were characterized by terms of qualitative and quantitative techniques including elemental analysis, Fourier transform infrared spectrometry , solid state ~ 13 C nuclear magnetic resonance etc.. Two types of humic acid have analytical characteristics which are very similar, but have a little difference. The phenanthrene sorption isotherms measured for IA sorbents are nonlinear, with the Freundlich exponents (n) ranging from 0.777 to 0.874. For the same soil, the Na_4P_2O_7-extracted HA exhibits more linear sorption isotherm with larger capacity than that of the NaOH-extracted HA. The plot of K_ oc for phenanthrene vs. percent POC (POC=O-alkyl O-aryl carboxyl acrbonyl) shows a consistent trend between K_ oc and POC. Because sorption of nonionic organic compounds as solutes from water to soil is predominantly controlled by partition to soli organic matter (SOM), the extent of sorption may expect to be governed by the polarity of both the solutes and the sorbent. Data suggest a consistent trend between K_ oc and POC a little affected by two different extractants.