稀酸酸析对褐煤腐植酸结构的影响

Effects of dilute acids on structures of humic acids extracted from lignite

为了促进褐煤非燃料化利用,探索硫酸、硝酸、盐酸、磷酸酸析对褐煤腐植酸结构的影响。采用碱溶酸析法提取腐植酸,以氢氧化钠为萃取剂、不同稀酸酸析沉淀,通过容量法测定褐煤腐植酸的纯度,并对提取腐植酸进行紫外可见光谱、傅里叶变换红外光谱、核磁共振氢谱表征。结果表明,不同稀酸酸析对褐煤腐植酸产率影响很小,而对纯度和腐植酸结构影响较为明显;褐煤腐植酸均含有羟基、甲基、亚甲基、羰基、羧基、醚键和苯环等官能团;硝酸酸析的褐煤腐植酸芳香度较低、纯度(质量分数)最高,达到82.54%;盐酸酸析的褐煤腐植酸芳香度最高、相对分子质量最大,达到79211。硝酸是提取褐煤腐植酸的最佳酸析稀酸,提取的褐煤腐植酸中苯环结构较少、芳香聚合度较低。

To promote the non-fuel utilization of lignite.The effects of sulfuric acid,nitric acid,chlorhydric acid and phosphoric acid precipitated on the structures of humic acids in lignite were explored.Humic acids were extracted by alkali-extraction acid-precipitation method.Sodium hydroxide was used as extractant and different dilute acids were used to precipitate.The purity of lignite humic acids was determined by the volumetric method.The extracted humic acids were characterized by UV-Visible spectroscopy,Fourier transform infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy.The results show that different dilute acids precipitated have little effect on the yield of humic acids,but have obvious effects on the purity and structures of humic acids.Lignite humic acids with different dilute acids precipitated contain hydroxyl,methyl,methylene,carbonyl,carboxyl,ether bond and benzene ring functional groups.The humic acids of lignite precipitated by nitric acid have low aromaticity and the highest purity(mass fraction),reaching 82.54%.The humic acids of lignite precipitated by chlorhydric acid had the highest aromaticity and the largest relative molecular mass,reaching 79211.Nitric acid is the best dilute acid for extracting humic acid from lignite,and the extracted lignite humic acids have less benzene ring structures and lower aromatic polymerization degrees.