Study On Extraction Process Of Humic Acid From Weathered Coal

Weathered coal(coal outcrop) is a kind of low calorific value and utilization rate energy material on the surface of ground or exposed in the air. It is produced from the coal through the physical or chemical processes of natural weathering,erosion of the wind and rain and sun burning. As a coal resource, its utilization value is very small. The weathered coal can not be effectively used and treated as solid waste at random in most areas. It results in not only the waste of resources and environment pollution, but also affecting people's quality of life. However, weathering coal can produce a kind of humic substances during its formation process. It is a mixed organic macromolecules that can be used in industrial, agriculture, horticulture, medical, health, food, building materials,electrical materials, environmental protection materials and other industries. It is a very valuable organic raw materials.Humic acid application in the environmental protection industry is mainly the water purification materials preparation by humic acid. Our article study is about the use of Huangling weathered coal in Shaanxi Province as raw material to prepare a suitable kind of water purification material, which is not easily soluble in water and molecular weight of with high adsorption properties of humic acid. The humic acid was extracted through the three basic methods of alkali soluble acid, oxygen and catalytic method from the weathering coal. The humic acid was characterized for finding the best extraction process,which was extracted with high efficiency, high purity and molecular weight and the extracted humic acid could be used to prepare the water purification material. This study can not only effectively use the weathered coal, reduce the waste of resources and reduce environmental pollution, but also be from the waste materials to the useful scarce raw materials to create greater economic benefits. These are in line with the environment of sustainable development strategy and there are the very important economic value and practical significance.In this paper, the single factor analysis method was used to determine the optimum conditions of hydrochloric acid activated 18% boiling hydrochloric acid activated 25 min.The five factors and four levels experiments were used to determine the optimum process conditions of the alkali soluble acid chromatography, oxygen method and catalytic method of humic acid extraction: the optimum highest extraction rate process condition of the acidsoluble alkali chromatography method is 18% hydrochloric acid, 25 min boiling time, 0.8mol?L-1 Na OH concentration, 1:12 ratio of solid and liquid and 60 min boiling water bath.The optimum process condition of the oxygen method is 22% H2O2, 0.5 mol?L-1 alkali solution, 1:8 solid liquid ratio and 30 min boiling water bath. The Optimum process condition of catalytic method is NHPI catalyst used, 0.3 mol?L-1 Na OH, 1:10 solid-liquid ratio and 30 min boiling water bath time.The properties of humic acid are characterized through the ash, infrared chromatography, gel chromatography and E4/E6 method respectively. The results show that the humic acid which is extracted by the alkali solution and acid isolation method has minimum ash content, while the humic acid extracted by the Catalysis method has the most ash content. Infrared analysis of three kinds of humic acid functional group is no significant difference, the wavelength of 1706.7 cm-1and 1613.5cm-1 are caused by the vibration-COOH and-CO relatively strong peaks. It means that the preparation of humic acid containing a large amount of-CO and-COOH and functional groups. The molecular weight of humic acid is characterized through Gel chromatography and E4/E6. The molecular weight of humic acid extracted by catalysis method is the largest, but the disadvantage is that the humic acid has more ash content. The ash content will be mainly controlled in the later experiments. The content of ash could be effectively reduced through using the appropriate catalyst.In summary, the obtained optimal extraction method of humic acid is catalytic method.The optimum extraction process is using NHPI catalyst, 3 mol?L-1 Na OH, 1:10 solid-liquid ratio and 30 min of boiling water bath time. The prepared humic acid could have high molecular weight and good adsorption performance.