Precipitation Of Silicon And Lignin By Lightly Oxidizing And Acidifying Of Bamboo Pulp Black Liquor And Its Application

Due to the lack of forestry resources in China,the wood resources available for papermaking are relatively small,and there is a certain degree of dependence on foreign countries,and the import cost of wood raw materials is high.Therefore,it is an inevitable trend to vigorously develop the pulping and papermaking mode with wood fiber as the main raw materials as well as non-wood fiber as the auxiliary.As a typical representative of non-wood fiber raw materials,bamboo has the advantages of short growth cycle and abundance,but its ash content and silicon content are much higher than those of wood raw materials.High silicon content leads to serious scaling of black liquor in the process of evaporation,transportation and combustion in pulp and paper industry,which damages the stability of alkali recovery system.Therefore,solving the problem of silicon interference with low-cost methods has become the focus of research.At present,acid precipitation is generally used to remove silicon from pulping black liquor,that is,to reduce the p H value of black liquor,but this process will be accompanied by a large amount of lignin precipitation,which seriously affects the stability of alkali recovery system of bamboo pulp black liquor.In this study,acidizing degree and oxidation degree were used as experimental variables to carry out silicon removal experiment.In order to accurately verify the relationship between carboxylate ion and silicon removal rate,simulation experiment was carried out,that is,carbon dioxide and citric acid acidified the mixed solution of sodium silicate and sodium carbonate respectively.The purpose of this study is to solve the problem of silicon interference under the premise of not affecting the stability of alkali recovery system,and explore the preparation of a lignin-based silicon carbon electrode material,so as to realize the resource utilization of silicon dioxide and lignin.The main conclusions are as follows1.When the acidizing degree was the same,with the deepening of light oxidation degree,the silicon removal rate of black liquor gradually increased,and the lignin precipitation and viscosity of black liquor showed a downward trend.The silicon removal rate of black liquor reached 76.41%after oxidizing black liquor to the p H12.45 and acidifying to the p H10.The light oxidation of black liquor changed the structure and molecular weight of lignin.With the deepening of light oxidation,the molecular weight distribution of lignin gradually dispersed.The deeper the degree of light oxidation,the lower the combustion heat of black liquor solid and the lower the lignin precipitation.2.When the oxidation degree was the same,different acidification degree would have a certain impact on the performance of black liquor.With the deepening of acidizing degree of black liquor,the amount of lignin precipitation gradually increased,the molecular weight distribution of lignin precipitation gradually concentrated,the combustion heat of black liquor solid gradually decreased,but the removal rate of silicon gradually increased.3.Oxidation treatment could increase the content of carboxylate ions in lignin molecules.In order to verify the effect of carboxyl content on the properties of black liquor,the viscosity,separated silicon content and combustion heat of black liquor acidified with carbon dioxide and citric acid were compared under the same degree of oxidation and acidification.It was found that the silicon removal rate and combustion heat of black liquor acidified with citric acid increased by5.04% and 6%,respectively.According to the simulation experiment,the mixed solution of citric acid could separate more silicon dioxide,which confirmed the conjecture that the more carboxylate ion content,the higher silicon removal rate.4.In the study of the preparation of silicon-carbon electrode material by lignin and tetraethyl silicate composite,it was found that compared with the material carbonized at 900?,the silicon carbon composite carbonized at 1200?had more C-Si bond and higher crystallinity.According to the three-electrode system,when the current density was 1A/g,the specific capacitance of the material is 74.8F/g,after 1000 cycles,the specific capacitance of the material remained 91.8% of the original.