Preparation And Structural Characterization Of Coal-Based Copper Fulvic Acid

In this paper,hydrogen peroxide was used as oxidant to extract fulvic acid from lignite in Huaining County,Yunnan Province.After purification,fulvic acid was reacted with Cu SO₄·5H₂O to prepare coal-based copper fulvic acid.Single factor study was conducted on the preparation conditions and the process parameters were optimized.The structural changes of fulvic acid and copper fulvic acid were studied by means of modern instrument analysis and quantum chemical calculation method,and the structural model of copper fulvic acid was obtained.The effects of reaction time,concentration of NaCl,p H and temperature on the dissociation performance of copper fulvic acid were studied.The thermal stability of copper fulvic acid was studied by thermogravimetric analysis,and the antibacterial activity of copper fulvic acid was studied by antibacterial circle experiment.Coal-based fulvic acid was prepared by oxygen hydrolysis,and the optimum conditions were as follows:hydrogen peroxide concentration 19.76%,reaction time 8min,liquid-solid ratio 7,microwave power 600 W,and the yield of 29.41%.The XPS analysis showed that calcium salt was the main impurity in fulvic acid.The optimal preparation process of copper fulvate is as follows:p H value 7,Cu SO₄·5H₂O input 0.47g,reaction time 50 min,temperature 55 ^oC,copper fulvate yield 47.28%.Cu SO₄·5H₂O input has the greatest influence on the yield of copper fulvate,and the interaction between temperature and Cu SO₄·5H₂O input is obvious.The structures of fulvic acid and copper fulvic acid were characterized by elemental analysis,FT-IR analysis and XPS analysis.The results showed that Cu²⁺combined with the phenolic hydroxyl group and oxygen in the carboxyl group of fulvic acid to form copper fulvic acid.The FT-IR analysis showed that there were benzene ring,ether bond,methyl group,carboxyl group and carbonyl group in fulvic acid and copper fulvic acid.The molecular structure of fulvic acid was obtained by acid functional group titration and liquid ¹H NMR analysis,and its molecular formula was C₂₆H₂₀O₁₆.Through quantum chemistry calculation,it is found that the oxygen in phenolic hydroxyl group has the largest amount of negative charge,and the energy calculation of four possible copper fulvic acid configurations is carried out,and finally the copper fulvic acid structure with energy of-3825.59 a.u.is the most stable,and its configuration is the most consistent with the copper fulvic acid structure.and its molecular formula was C₂₆H₁₈O₁₆Cu.Copper fulvic acid is formed by the adjacent phenolic hydroxyl group and carboxyl group in fulvic acid each losing a hydrogen,and the two oxygen atoms losing hydrogen combine with a copper.The dissociation equilibrium time of copper fulvic in both deionized water and0.9%NaCl solution was about 100 min.The dissociation performance of copper fulvic acid increased with the increase of NaCl concentration.The change of p H value seriously affects the dissociation property of copper fulvic acid.The dissociation property of copper fulvic acid is the strongest in acidic solution,followed by alkaline environment,and the weakest in neutral environment.When p H<7,the smaller the p H value is,the stronger the dissociation property will be.The increase of temperature will promote the dissociation of copper fulvic acid.When the temperature is higher than 50^oC,the change of temperature has little effect on the dissociation performance of copper fulvic acid.Copper fulvic acid can maintain good thermal stability within 150 ^oC.Copper fulvic acid showed significant antibacterial activity against B.albicans,E.coli and Staphylococcus aureus.This paper has a total of 45 figures,33 tables,101 references.