Microwave Catalytic Pyrolysis Preparation Of Biochar And Its Mechanism Of Loading Bacterial Biofilm

Biochar was prepared by microwave catalytic pyrolysis method with apple wood as raw material.Based on Bacillus subtilis SL-44 with the function of desalt and growth promoting,which was independently selected by the previous laboratory,biochar-SL-44 compound bacterial agent was developed.Biochar was prepared with phosphoric acid and potassium phosphate as catalysts,and the effect of microwave catalytic pyrolysis on the structure and characteristics of biochar was investigated;the high density cultivation characteristics of Bacillus subtilis SL-44 were investigated with soybean meal and corn meal as main raw materials;the adsorption mechanism of biochar on SL-44 and the formation mechanism of biofilm were studied with biochar as carrier.The main results are as follows:Phosphoric acid and potassium phosphate can effectively improve the efficiency of microwave pyrolysis and shorten the pyrolysis time.Through the Coats-Redfern model,it is determined that the catalyst and the apple wood exhibit a high degree of synergy during the pyrolysis process,which inhibits the production of volatile substances and effectively reduces the activation energy of the carbonization process,thereby increasing the yield of biochar.FTIR analysis shows that phosphoric acid and potassium phosphate contribute to the formation of aromatic groups and phosphate structure on the surface of biochar.Analysis of the pore structure and morphology of biochar showed that a large number of mesopores were formed on the surface of biochar.The response surface optimization method was used to investigate the effects of corn meal and soybean meal on Bacillus subtilis SL-44’s phosphate solubilization,IAA yield and effective viable cell count.It was finally determined that the cheap medium for SL-44 was corn meal27.7 g/L and soybean meal 19.77 g/L,magnesium sulfate 1.49 g/L,the amount of phosphate solubilized by the strain was 0.59 mg/L,and the yield of IAA was 3.13 mg/L.After optimizing the fermentation process of SL-44,it was finally determined that the optimal inoculum amount was 2%,the optimal growth temperature was 32℃,and the optimal p H was 7.0.After the optimization of the process,the phosphate solubilization,IAA yield,and effective viable count of strain SL-44 in the cheap medium were 0.59 mg/L,3.54 mg/L,and 13.32×10¹⁰ CFU/ml,respectively.The results of adsorption experiments show that biochar can effectively capture a large amount of SL-44 cells.The fitting data of the secondary kinetic model is more in line with the adsorption kinetic behavior.The Langmuir model can better fit the adsorption of SL-44biochar.The Freundlich model shows that biochar has the advantage of adsorbing bacteria.The adsorption thermodynamic parameters indicate that the whole process is spontaneous and exothermic,and low temperature is beneficial to the adsorption of SL-44 by biochar.The growth curve of biofilm showed that the amount of biofilm formed on the surface of biochar was much higher than that of free biofilm,and the protein and polysaccharide content of biofilm increased significantly.