| Papermaking black liquor is the largest pollutant in the paper industry.There is an urgent need for a black liquor resource utilization of green technology to achieve clean production in the paper industry.Potash alkali pulp technology is to use KOH instead of the traditional NaOH for pulp,the black liquor contains potassium which is necessary for plant growth,and is conducive to the resource utilization of black liquor,which is a potential green technology.In this paper,the black liquor obtained from four kinds of papermaking raw materials using potassium-alkali pulp was extracted to obtain potassium-like humate substances,and the chemical structure of black liquor-like humate and mineral-derived humate were compared,and the physiological activity of black liquor-like humate was further studied,and the practical application effect of black liquor-like humate was determined through field experiments.(1)Comparative study of the composition and chemical structure of black liquor humic substances and mineral-derived humic acids.The chemical analysis showed that the content of xanthate humic acid was higher in the samples prepared from non-wood materials than in the samples prepared from wood materials.Elemental analysis and UV spectroscopic results showed that black liquid humic acids were more aromatic than mineral source humic acids,with the non-wood raw material(wheat grass,bamboo)samples being more aromatic and having a smaller molecular weight.Infrared spectroscopy showed that black liquor humic acid and mineral humic acid had similar humic acid functional groups,but the relative content of the functional groups was different.NMR results also show that the molecular structure is basically the same,but the black liquor humic acid has a more complex molecular structure,more species and more aromatic structures.(2)Effect of black liquid potassium humate on seed germination and growth of cotton seedlings.The germination tests on wheat seeds showed that the black liquor potassium humate had a good ability to promote seed germination and exhibited similar characteristics as phytoestrogens.The optimum concentrations of potassium humate-like plants were 40 mg/L for pine and 20 mg/L for bamboo,respectively.The results of hydroponic tests on cotton seedlings showed that black-liquid potassium humate had a significant effect on the growth of cotton seedlings at appropriate concentrations.The optimum concentration of black-liquid potassium humate of pine origin at 80 mg/L increased the plant height and root length of cotton seedlings by 16.27%and 10.22%,respectively,compared with the control;the optimum concentration of black-liquid potassium humate of bamboo origin at 40 mg/L increased the plant height and root length by 14.49%and 12.23%,respectively.When the concentration of black liquid potassium humate exceeded 100 mg/L,it inhibited the growth of cotton seedlings.(3)Effect of black liquid potassium humate on growth and yield of cottonThe results of field trials on cotton showed that black liquor potassium humate had a significant stimulating effect on the entire growth and development of cotton,increasing the number of bobbins per plant and the weight of bobbins per plant.Black liquid potassium humate also has the effect of stimulating the growth of cotton roots,significantly increased the yield of cotton,the highest yield increase rate of 11.2%.Black liquid potassium humate can also promote the absorption of nitrogen,phosphorus and potassium of the plant,to achieve the efficient use of nutrients.The results of this study can provide a good theoretical basis for the potassium humate like humic acid obtained from the black liquor of potassium-alkali pulp to become a substitute for mineral source humic acid,so that the black liquor of papermaking can be completely resource utilization and realize clean production. |
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