| The extraction of fulvic acid from low-rank lignite can not only obtain high activity fulvic acid products,but also improve its utilization efficiency to reduce the harm to the environment caused by direct use,which is of great significance to the construction of environment-friendly society.in view of the complexity of coal-based fulvic acid production and the lack of in-depth study on the mechanism of biological function and activity,taking Hegang coal in Heilongjiang Province as raw material,fulvic acid is extracted by citric acid ethanol method and glacial acetic acid ethanol method,and the macrokinetics of the extraction process was analyzed.it is purified by acetone sulfate method,and its molecular structure was characterized by elemental analysis,UV-Vis and FTIR.Finally,the effects of characteristic structure functional groups of fulvic acid on the physiological activity of Cucumber Seed Germination and seedling quality were investigated.Fulvic acid from lignite was extracted by citric acid ethanol method and glacial acetic acid ethanol method.Combined with single factor and orthogonal test data analysis,the optimum process conditions were obtained.It was concluded that reaction temperature,acid-coal ratio and ethanol concentration had significant effects on the yield of fulvic acid in citric acid-ethanol process.The results show that the optimum yield is 7.93%when the reaction temperature is 70,the ratio of acid to coal is 0.03,the ratio of liquid to solid is 10,and the concentration of ethanol is 15%.The effect of reaction temperature and acid coal ratio on extraction of fulvic acid by glacial acetic acid ethanol was significant.The results show that the optimum yield of fulvic acid is 5.90%when the reaction temperature is 70,the ratio of acid to coal is0.09,the ratio of liquid to solid is 10 and the concentration of ethanol is 20%.The extraction of fulvic acid was purified by acetone sulfate method.The interaction among various factors was investigated by response surface central composite design and data variance analysis.The results showed that the optimum process combination for purifying fulvic acid was:acid-coal ratio is 0.025,liquid-solid ratio is 11.35,temperature is 56.The structural parameters of fulvic acid molecules before and after purification were calculated by elemental analysis,ultraviolet-visible spectroscopy and infrared spectroscopy,including aromatic hydrogen ratio,aromatic carbon ratio,hydrocarbon atom ratio and aliphatic chain length.According to Fick's law dissolution diffusion model,the reaction kinetics of extracting fulvic acid by citric acid ethanol under conventional water bath conditions was analyzed.Based on the differential method and MATLAB programming data processing,the reaction order and rate constant were obtained,and then the activation energy,pre-exponential factor and rate equation of the reaction were calculated.The reaction order n=1.4749,the Arrhenius activation energy Ea=57.453 kJ/mol and the pre-exponential factor A=8.13×10~5 were obtained.Finally,the expression of reaction rate for extracting fulvic acid from Lignite by citric acid ethanol method was obtained.Fulvic acid is widely used as plant growth regulator because of its low molecular weight and high activity.In this experiment,purified fulvic acid was applied to study the biological activity of Cucumber Seed Germination and seedling quality.Response surface design experiment was used to eliminate the insignificant influencing factors,and nine response index model equations were fitted by variance analysis of data,the optimum combination of soaking concentration and soaking time was 258.5~340.17mg/L and 6.39~10 h. |
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