甘肃某地褐煤中腐植酸的提取工艺研究

Study on the extraction technology of humic acid from the lignite in a place of Gansu province

为研究不同提取工艺对褐煤中腐植酸提取产率的影响,以甘肃某地褐煤为原料,经硝酸活化、碱溶处理、酸析等步骤提取腐植酸.用正交试验法探究了活化处理时硝酸浓度、液固比、硝化时间、硝化温度,以及碱溶处理时碱液浓度、液固比、碱溶时间和碱溶温度对腐植酸提取产率的影响,确定了最佳提取条件,并采用红外光谱、紫外-可见光谱等对所得腐植酸进行了表征.结果表明:提取褐煤中腐植酸的最佳工艺条件是硝酸与煤样的液固质量比为10∶1,硝酸质量分数为14%,硝化温度70℃,硝化时间60 min.再按液固质量比为8∶1在活化处理后的干燥煤中加入质量分数3%的NaOH溶液,在60℃下碱溶反应60 min.然后用质量分数2%的HCl溶液调节体系pH至2,经离心分离干燥得目标产物,其提取产率为60.86%,腐植酸的含量为69.66%.谱图分析证实提取的腐植酸结构中含有羧酸基、醇羟基、酚羟基、芳环基、羰基、稠环芳烃和酰胺基等活性官能团,提取的腐植酸E 4/E 6值为8.27,表观分子量为28477.

In order to study the effect of different extraction technology on the extraction yield of humic acid from lignite,the lignite in a place of Gansu province is taken as the raw material.The nitric acid is used to activate lignite.Then the humic acid is extracted from the lignite through the alkali treatment,acid precipitation and other steps.The effects of nitric acid concentration,liquid-solid ratio at nitrification,nitrification time,nitrification temperature,alkaline solution concentration,liquid-solid ratio,alkaline time and alkaline temperature on the the extraction yield of humic acid were investigated by means of orthogonal test method.The optimum extraction conditions were determined.And infrared spectroscopy and ultraviolet-visible spectroscopy were used to characterize it.The results showed that the optimum technological conditions for extracting humic acid from lignite were as follows:The liquid-solid mass ratio of nitric acid to coal sample was 10∶1,the mass fraction of nitric acid was 14%,the nitrification temperature was 70℃,and the nitrification time was 60 min.Adding 3%NaOH solution to the activated dry coal at a liquid-solid mass ratio of 8∶1,alkaline dissolution reaction was carried out at 60℃for 60 min,and then adjusting the pH to 2 with 2%HCl solution,and finally by centrifugal separation and dry to obtain the target product.The extraction yield of humic acid was 60.86%,and the content of humic acid was 69.66%.And spectra analysis confirmed that the humic acid structure contained the active functional groups such as carboxylic acid,alcohol hydroxyl,phenolic hydroxyl,aromatic ring,carbonyl,polycyclic aromatic hydrocarbons and amide groups.The E 4/E 6 value of humic acid extracted was 8.27,and its apparent molecular weight was 28477.