Study On Microwave-assisted Extraction Of Fulvic Acid From Lignite Oxidated By Hydrogen Peroxide

Oxidative disaggregation is an effective means to extract coal-based fulvic acid from lignite. In order to obtain an efficient method of extracting fulvic acid, hydrogen peroxide, microwave and hydrogen peroxide, hydrogen peroxide-glacial acetic acid, microwave and hydrogen peroxide-glacial acetic acid were used to extract fulvic acid by oxidation Hulunbeier lignite, then purify it by sulfuric acid- acetone method for the low extract rate and efficiency of traditional extract mothed. Various means were used to analyze and characterize the macro- and micro-structure of the high purity fulvic acid. In order to obtain the related kinetic parameters of oxidative depolymerization process, coal composite structure model and dynamic model of the unreacted shrinking core were combined to analysis oxygen reaction kinetics by using molecular chemistry and mathematics.Although the reserve of Hulunbeier lignite is very rich, high moisture and high ash characteristics limit its effective industrial exploitation. In this paper, single factor and orthogonal experiment of hydrogen peroxide and microwave combined with hydrogen peroxide in extracting fulvic acid from Hulunbeier lignite were studied and the optimal yield of fulvic acid were 15.22% and 16.58%, respectively. The reaction time were 60 min and 7min, separately. It showed that the microwave enhance the reaction rate, shorten the reaction time and increase the yield of fulvic acid. There were still lot of organic matter residual in oxygen solutions residual coal. So it is needed to enhance the oxidation of the oxidizing agent. Peracetic acid with stronger oxidizing ability was generate by the react between glacial acetic acid and hydrogen peroxide. single factor and orthogonal experiment of hydrogen peroxide- acetic acid and microwave joint hydrogen peroxide- acetic acid method were studied and the optimal yield was 57.83% and 62.30%, respectively. This indicating that the yield of fulvic can be significantly increased by adding glacial acetic acid in peroxide hydrogen.There was small amounts of inorganic salts and other humic substances in the extracted fulvic acid, so sulfuric acid- acetone method was used to purify the fulvic acid obtained by the four methods. Elemental analysis, total acid group and a carboxyl group content, E4/E6, UV-Vis, FTIR and 1H NMR were used to analyze the four different kinds of fulvic acid. The results show that the carboxyl content increased under microwave conditions. When weak oxidants, oxidized organic in coal is small molecules embedded in macromolecular structure. With the upgrading of the reaction conditions, the coal macromolecular structure is destroyed, aromatics regular dissolution.Reaction kinetics of important guiding significance to the achievement of industrial application. In this paper, composite structural model was used to explain the dissolution law of fulvic acid. The unreacted-core shrinking model were used to analyze the reaction kinetics of microwave combined with hydrogen peroxide-glacial acetic acid oxidative depolymerization lignite innovation. The correlation kinetic parameters of the reaction were calculated. The relevant kinetic parameters: the reaction activation energy E=38.04 k J/mol, reaction order n =1.1, the frequency factor A =2.67 × 103. The reaction rate expressions of microwave combined with hydrogen peroxide-glacial acetic acid oxidative depolymerization lignite was gave by the above parameters.