| Humic acid which have been applied in many fields, widely exist in brown coal of nature. But the humic acids extracted from brown coal directly have large molecular weight, low fulvic acid content and low activity functional groups, how to improve the yield of fulvic acid, humic acid and it s content of active functional groups with Low Rank coals have always been a focal point.Previous research mainly used HNO3 to oxidize brown coal to improve the yield of fulvic and humic acid and the content of active groups in them. But this method isn t friendly to the environment. At the same time, the application of NHA has certain limitations in some fields. Consequently, this paper researches the optimum condition in which we can obtain high yield of fulvic and humic acid by oxidizing brown coal with H2O2, and analyze the physical and chemical properties, spectral characteristics of fulvic and humic acid extracted from brown coal and oxidized brown coal.The main research is follow:1. The experimental investigation of Xundian brown coal, Zhaotong brown coal,Qujing Liaohu brown coal oxidized with hydrogen preside solution in order to prepare fulvic acid carried out in laboratory, The effects of coal-oxidant ratio, oxidization temperature, oxidization duration, oxidant concentration on yields of fulvic acid were investigated by single factor experiment and orthogonal test. The results showed that the coal-oxidant ratio affected the yield markably, the oxidization duration and the oxidization temperature have great influence, the oxidant concentration have no obvious effect. The optimum conditions were determined as follows:Xundian brown coal:coal-oxidant ratio 1:0.38, oxidization temperature 30℃, oxidization duration 180 min., hydrogen yeroside concentration 15%. Under the condition, the yield is up tol9%. Zhaotong brown coal:coal-oxidant ratio'1:65, oxidization temperature 30℃, oxidization duration 180 min., hydrogen yeroside concentration 15%. Under the condition, the yield is about 24%. Qujing Liaohu brown coal:coal-oxidant ratio 1:65, oxidization temperature 30℃, oxidization duration 180 min., hydrogen yeroside concentration 15%. Under the condition, the yield is up to 20%. 2. The fulvic acid produced from Xundian Jinsuo brown coal was fractionated into seven fractions by dialysis, The chemical and structural properties of fulvic humic acid of each fraction were characterized by elemental analyzer, Fourier transform infared spectrometry, ultraviolet-visible light spectrometry; The main part (It's molecular weight< 1K) were characterized 1H and solid 13C-nuclear magnetic resonance spectrometry; The low molecular weight part (molecular weight of it< 500) were analysised by gas chromatography—mass spectrometry(GC-MS). The results showed that the molecular of the main part is relatively low(It s molecular weight< 1K); the content of C and increase with the increasing relative molecular mass, but the content of 0 and oxygen-containing functional groups decrease;The 1H NMR, solid 13C NMR and FT-IR spectra of the main part showed that the main fraction contained much more fatty acid. By the GC-MS results, dicarboxylic acid is predominant of the compounds, oxilic acid, malonic acid and succinic acid are the characteristic compou-nds with higher concent; a-hydroxy carboxylic acid is highest amount in the hydroxyl carboxylic acid compounds; alcohols, aromatic compounds, amino acids are in low c-ontent; Lactone Components, polyring aromatised hydrocarbons are not existed or in a much low amount.3. The humic acids separated from Xundian Jinsuo brown coal original brown coal and residue of oxidation brown coal with H2O2 and from which the fulvic acids were isolated previously were fractionated into different pH fractions based on the acidity of the aqueous solution, and the chemical composition of each fraction was characterized by means of qualitative and quantitative techniques including elemental analyzer, Fourier transform infrared spectrometry. Chemical function group content, and the coagulation value of the main components of humic acids were determined. Results showed that the compositional and structural differences between the OHA from residue of oxidation brown coal and HA from original brown coal is remarkably, the molecular weight of the OHA could be lower than that of HA relatively. The phenolic hydroxyl and carboxyl content of dominate constituents of humic acids increased from 3.68 mmol/g to 4.83 mmol/g, and from3.00 mmol/g to 3.60 mmol/g respectively, and the coagulation values of which decreased from 20.40 mmol·L-1 to 16.80 mmol·L-1; the similar phenomena were observed in the HA and OHA, that is, the total acidic group, carboxyl group, phenolic hydroxyl group, the content of O, the C/H molar ratio increase with the increasing acidity of the aqueous solution, but decrease the content of C and H, the C/O molar ratio.4. The structure of humic acid separated from oxidation brown coal from Zhaotong and Qujing Liaohu were changed greatly, the content of polar groups increased in the FA and OHA.
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