Extraction and Functional Group Characterization of Fulvic Acid from Hami Lignite

Abstract

This research investigates the extraction of fulvic acid (FA) from Hami lignite from Xinjiang, China, by microwave-hydrogen peroxide and microwave-hydrogen peroxide-formic acid methods. The effects of reaction time, oxidant concentration, oxygen-coal ratio and microwave power on FA yield are determined. Sulfuric acid-acetone was applied to purify the primary FA products. The results indicate that the oxidant concentration is a sensitive factor affecting the yield of FA, while reaction time has little effect. Formic acid can promote the extraction of FA from lignite by hydrogen peroxide, and under optimal experimental conditions, the yields of FA were 5.34% and 9.13%, respectively. UV-Vis analysis shows that FA has a lower aromaticity and degree of carbonyl conjugation in the presence of formic acid. Additionally, Fourier transform infrared spectroscopy was used to characterize the purified FA. The results show that the benzene rings of FA have one, two, three and four substitutions, oxygen-containing functional groups containing -COOH, C=O, -OCH 3 , CÀ OÀ C, Ar-OH, and R-OH and, furthermore, primary oxygen-containing functional groups consisting of C=O and C-OH. The aliphatic functional groups contain symmetrical and anti-symmetrical stretching vibrations of -CH 2 and -CH 3 . Finally, the hydrogen bonds are mainly composed of phenolic hydroxyls and alcoholic hydroxyls, while some hydrogen carboxylate is present.

Characterization of humic acids from original coal and its oxidization production

“…Zhumanova et al 20 reported that sulfuric acid promote the conversion of carbon (C) in coal to a greater extent without increasing the loss of nitrogen (N) and oxygen (O). In addition, by applying hydrogen peroxide (H 2 O 2 ), potassium permanganate (KMnO 4 ) and nitric acid (HNO 3 ), coal oxidation can change the carbon chain structure of HAs and increase the number of active functional groups, such as hydroxyl and carboxyl 21 – 23 .…”

Extraction of fulvic acid by citric acid–ethanol method and its biochemical activity

“…Under the optimum conditions, the extraction yield of FA was ~80‰. The extraction yield of FA in this paper is basically the same as that catalytic oxidation with hydrogen peroxide 46,47 . Compared with the traditional FA extraction process, the citric acid–ethanol method is environmentally friendly.…”

“…The extraction yield of FA in this paper is basically the same as that catalytic oxidation with hydrogen peroxide. 46,47 Compared with the traditional FA extraction process, the citric acid-ethanol method is environmentally friendly. Characterization and analysis of the extracted and purified FA revealed that the molecular structure of FA hardly changed before and after purification and that there were many oxygen-containing functionalitiessuch as carboxyl, phenolic hydroxyl, and alcohol hydroxyl groupsin the structure, which are beneficial to the growth and development of plants.…”

Research of New Cross-Flow Technology with a Gas Heat Carrier for Lignite Pyrolysis

“… 1 − 3 As a thermal processing conversion method, the pyrolysis of lignite is one effective way to efficiently utilize lignite, as the processing conditions are mild, the operation is simple, and the products are retrievable. 4 − 6 …”