Zhang Yingjie, Gong Guanqun, Zheng Honglei, Yuan Xin, Xu Liangwei
Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education, Xuzhou 221116, China.
School of Chemical Engineering & Technology, China University of Mining and Technology, Xuzhou 221116, China.
ACS Omega. 2020 Mar 19;5(12):6389-6394. doi: 10.1021/acsomega.9b03796. eCollection 2020 Mar 31.
Fulvic acid (FA) has important properties and is used widely in agriculture, industry, medicine, and other fields. However, there is a lack of environmentally friendly and efficient extraction methods for coal-based FA and its molecular structural characterization. In this study, FA was extracted cleanly and efficiently from low-rank lignite via the innovative method of microwave combined with hydrogen peroxide and glacial acetic acid, followed by purification by the sulfuric acid-acetone method. The molecular structures of FA were precisely characterized by UV-vis spectroscopy, infrared (IR) spectroscopy, H nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography-mass spectrometry (GC-MS). The results showed that the microwave combined with hydrogen peroxide-glacial acetic acid method had stronger oxidative degradation ability compared with the conventional method. Under optimized conditions, the yield of FA reached 60.97%. During the oxidation process, the macromolecular network structure of coal was destroyed, resulting in the production of many oxygen-containing functional groups. According to the IR and UV-vis spectra, there were abundant oxygen-containing functional groups such as hydroxyl, carboxyl, carbonyl, and quinone groups in the molecular structure of FA. Determination of the total acid group content in the oxygen-containing functional groups of FA showed that the content of carboxyl groups was much higher than that of phenolic hydroxyl groups. The H NMR showed that there were hydrogen atoms present as part of carboxyl, aromatic, phenolic hydroxyl, and aliphatic groups in FA. The (GC-MS) results suggested that FA is a mixture of dozens of complex compounds, including alkanes, alcohols, esters, etc.
黄腐酸（FA）具有重要特性，在农业、工业、医药及其他领域有广泛应用。然而，目前缺乏针对煤基黄腐酸的环境友好且高效的提取方法及其分子结构表征方法。本研究通过微波联合过氧化氢和冰醋酸的创新方法，从低阶褐煤中高效、清洁地提取了黄腐酸，随后采用硫酸 - 丙酮法进行纯化。利用紫外 - 可见光谱、红外（IR）光谱、氢核磁共振（NMR）光谱和气相色谱 - 质谱联用（GC - MS）对黄腐酸的分子结构进行了精确表征。结果表明，与传统方法相比，微波联合过氧化氢 - 冰醋酸法具有更强的氧化降解能力。在优化条件下，黄腐酸的产率达到60.97%。在氧化过程中，煤的大分子网络结构被破坏，产生了许多含氧官能团。根据红外光谱和紫外 - 可见光谱，黄腐酸分子结构中存在丰富的含氧官能团，如羟基、羧基、羰基和醌基。对黄腐酸含氧官能团中总酸基含量的测定表明，羧基含量远高于酚羟基含量。氢核磁共振谱表明，黄腐酸中存在作为羧基、芳香族、酚羟基和脂肪族基团一部分的氢原子。气相色谱 - 质谱联用（GC - MS）结果表明，黄腐酸是包括烷烃、醇类、酯类等在内的数十种复杂化合物的混合物。
