Key Laboratory of Plant Nutrition and Fertilizer, Ministry of Agriculture/Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China; College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
Key Laboratory of Plant Nutrition and Fertilizer, Ministry of Agriculture/Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
Chemosphere. 2017 Jan;166:334-342. doi: 10.1016/j.chemosphere.2016.09.095. Epub 2016 Oct 1.
To reduce the compositional and structural heterogeneity of humic acids (HAs) and achieve better use of HA resources, in this study, we report a new sequential dissolution method for HAs derived from Chinese weathered coal. This method was used to separate HAs into seven fractions by adjusting the pH (3-10) of the extraction solution. The results showed that the HA fractions derived from Chinese weathered coal were concentrated up to 90.31% in the lower pH solutions (3-7). The compositional and structural characteristics of the HA fractions were determined by elemental analysis; ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), and solid-state C-nuclear magnetic resonance (NMR) spectroscopies; and other techniques. The results showed significant differences among the HA fractions. The concentrations of the total acidic groups and the carboxyl groups decreased with the increasing pH of the extraction solution. However, the HA fractions derived from extraction solutions with pH 3-4 had relatively lower aromaticity but a higher protonated carbon content. The HA fractions derived from extraction solutions with pH 6-7 had the highest aromaticity and the greatest abundance of COO/N-C=O. This study demonstrated that adjusting the pH of the extraction solution is one way to fractionate HAs from Chinese weathered coal and to obtain HA fractions with compositions and structures that could serve as useful material for study and utilization.
为了降低腐殖酸（HA）的组成和结构异质性，并更好地利用 HA 资源，本研究报告了一种从风化煤中分离 HA 的新顺序溶解方法。该方法通过调节提取溶液的 pH 值（3-10）将 HA 分离成 7 个级分。结果表明，源自风化煤的 HA 级分在较低 pH 值（3-7）的溶液中浓缩高达 90.31%。通过元素分析；紫外可见（UV-Vis）、傅里叶变换红外（FTIR）和固态 C-核磁共振（NMR）光谱以及其他技术确定了 HA 级分的组成和结构特征。结果表明，HA 级分之间存在显著差异。总酸性基团和羧基的浓度随提取溶液 pH 值的增加而降低。然而，源自 pH 为 3-4 的提取溶液的 HA 级分具有相对较低的芳香度，但质子化碳含量较高。源自 pH 为 6-7 的提取溶液的 HA 级分具有最高的芳香度和最多的 COO/N-C=O。本研究表明，调节提取溶液的 pH 值是从风化煤中分离 HA 并获得具有组成和结构的 HA 级分的一种方法，这些级分可作为研究和利用的有用材料。
