为提高褐煤资源的附加值,探索了NaOH,KOH,LiOH,Na2CO3,NH3·H2O,Na2SO3,NaHCO3,Na4P2O7对萃取褐煤黄腐酸结构的影响。采用碱溶酸析法提取褐煤黄腐酸,以不同弱碱性溶剂为萃取剂再经硫酸酸析,通过容量法测定黄腐酸的纯度,并对提取的褐煤黄腐酸进行光谱表征。结果表明:不同碱液提取褐煤黄腐酸的产率不同,但质量浓度相近,其中LiOH提取黄腐酸的产率(质量分数)最高(5.12%);不同碱液提取褐煤黄腐酸的官能团种类相同,但含量不同,Na2CO3提取的褐煤黄腐酸羰基结构最少,NaHCO3做萃取剂时提取的褐煤黄腐酸的芳香度较高、羟基结构较多;不同碱液提取褐煤黄腐酸的E4/E6值明显不同,相对分子质量差距较大,Na4P2O7可提取出相对分子质量为118157的褐煤黄腐酸;Na2SO3是提取褐煤黄腐酸的最佳萃取剂,提取的黄腐酸中苯环结构较少,芳香聚合度较低,纯度高达0.248g/L。

In order to elevate the value of lignite, the effects of NaOH, KOH, LiOH, Na2CO3, NH3·H2O, Na2SO3, NaHCO3 and Na4P2O7 extraction on the structure of lignite ful-vic acid have been investigated. In this paper, the fulvic acid in lignite was extracted by the alkali-extraction acid-precipitation method, where different weak alkaline solvents were adopted as ex-tractants, followed by acid precipitation using H2SO4. The purity of the fulvic acid was deter-mined by volumetric method, and a spectroscopic characterization was performed. It is found that the yield of lignite fulvic acid varies based on the specific alkaline solvent for extraction, however, their concentrations exhibit noteworthy similarity. The highest yield of fulvic acid of 5.12% is achieved when using LiOH for extraction. The functional groups within the lignite fulvic acid ex-tracted from different alkaline solvents are consistent in type, but their proportions differ consid-erably. Lignite fulvic acid extracted by Na2CO3 has the least carbonyl structure, while a higher aromaticity and a enriched hydroxyl structure are achieved when NaHCO3 is used for extraction. The E4/E6 ratios of lignite fulvic acid extracted from different alkaline solvents are significantly different, accompanied by discernable variations in molecular weight. Na4P2O7 can be used to ex-tract lignite fulvic acid, yielding a molecular weight of 118 157. Notably, Na2SO3 is the best ex-tractant for extracting fulvic acid from lignite, resulting in fulvic acid with less benzene ring structure, fewer aromatic polymerization, and a purity of 0.248 g/L.