Study on humic acid production from the degradation of Mengdong lignite by two kinds of bacteria
The optimal conditions for extracting biological humic acid from Mengdong lignite by Pseudomonas sp.and Alcaligenes faecalis were obtained through single-factor experiments and orthogonal experiments.The two types of biological humic acids obtained under these conditions were compared and analyzed with the chemical humic acids obtained by alkaline extraction method through UV-vis,FTIR,XPS,and nutrient element detection methods.The research results show that the optimal degradation conditions of Pseudomonas sp.for oxidized coal from Mengdong lignite are coal slurry concentration of 0.5 g/50 mL,extraction time of 14 d,bacterial liquid volume of 2 mL/50 mL,while the optimal degradation conditions of Alcaligenes faecalis include the coal slurry concentration of 0.5 g/50 mL,the extraction time of 12 d,and the bacterial liquid volume of 4 mL/50 mL;the highest yields of the two bacteria on biological humic acid are 35.39%and 38.26%,respectively,showing the better degradation effects of Alcaligenes faecalis on Mengdong lignite than that of Pseudomonas sp.;the highest yield of chemical humic acid by the alkali extraction method in the control group is 42.89%.UV-vis and FTIR analysis show that the molecular weight,aromaticity and total number of oxygen-containing functional groups of the two biological humic acids are smaller than those of chemical humic acid;XPS analysis shows that the number of types of oxygen-containing functional groups in the two biological humic acids is larger than that of chemical humic acid,and the existence form of carbon element in the two biological humic acids is also very different from that of chemical humic acid;nutrient element test shows that the contents of N,P,K,Ca,and Mg in the two biological humic acids are much greater than those of chemical humic acid.
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