| In a variety of dye wastewater treatment technology,microbial treatment technology is favored because of its environmental protection,economic and other characteristics.In this paper,3 strains of bacteria(named S1,S2,S3)and two strains of fungi(named P1 and P2)were screened from samples near the dye wastewater.These five strains have strong decolorization ability for the dye wastewater represented by methylene blue wastewater.In the decolorization experiment of methylene blue wastewater,the decolorization rate of S1 strain to methylene blue was 75.01%(120 h),and the decolorization rate was higher among the three bacterial strains;the decolorization rate of P1 strain to methylene blue was 85.21%(72 h)and the decolorization rate was higher in the two fungi.After 16 S r DNA gene sequence analysis,S1 was Bacillus subtilis strain NW405934,P1 was Pencillum expansum KU162972,and the similarity of gene homology reached 100% and 99%.The effects of Bacillus subtilis and its immobilized microcapsules on the decolorization efficiency of methylene blue wastewater under different single factor conditions were investigated.The results showed that the decolorization efficiency of methylene blue by Bacillus subtilis could reach 83.98% when the concentration of methylene blue was 20 mg/L,inoculation percentage of bacteria was 3%,p H was 5,the concentration of carbon source was10mg/L,and the decolorization time was 120 h.Under the same decolorization conditions as that of Bacillus subtilis,the decolorization efficiency of the immobilized microcapsules prepared by Bacillus subtilis on methylene blue reached 90.12%.At p H 1 and p H 10,the decolorization rate could still reach 45.21% and 43.51%.When the concentration of methylene blue was 100 mg/L,the decolorization rate could reach 66.08%.When the salinity was 10%,the decolorization rate was 50.36%.This indicated that the immobilized microcapsules prepared by Bacillus subtilis had stronger tolerance to adverse environmental conditions than the free Bacillus subtilis.In addition,it could be seen from the analysis and comparison of UV spectrum and infrared spectrum before and after decolorization that the decolorization of methylene blue by Bacillus subtilis mainly depended on the effect of biodegradation.In the process of decolorization of methylene blue wastewater by Penicillium P1,the effects of single factors such as initial methylene blue concentration,inoculation percentage of Penicillium spores,time,p H,salinity,and carbon source concentration on the decolorization efficiency of methylene blue wastewater were investigated.The results showed that when the initial concentration of methylene blue was 20 mg/L,inoculation percentage of Penicillium spores was 3%,time was 24 h,p H was 4,salinity was 2%,and the concentration of carbon source was 6 g/L,the decolorization efficiency of methylene blue wastewater by Penicillium P1 was higher.On the basis of single factor experiment,the response surface optimization method was used to explore the influence of P1 strain on the decolorization efficiency of methylene blue under different conditions.Taking the initial concentration,p H,inoculation percentage and salinity of methylene blue as the investigation factors,and the decolorization rate of methylene blue as the response value,the decolorization conditions of P1 strain were optimized.The results showed that the optimal decolorization conditions were as follows:concentration of methylene blue was 50 mg/L,p H value was 3.61,salinity was 3.7%,inoculation percentage was 3.21%,the decolorization rate of methylene blue by Penicillium P1 was 85.00%(24 h).The experimental study of decolorization mechanism showed that in the decolorization process of methylene blue wastewater,the degradation accounted for 72.85%,and the adsorption accounted for 20.27%,indicating that the decolorization process was completed by both degradation and adsorption mechanisms.According to the UV spectra before and after the decolorization of methylene blue wastewater by Penicillium P1,it could be seen that the UV spectra had obvious changes and new absorption peaks appeared,indicating that other substances were produced in the decolorization process of methylene blue wastewater.Therefore,it could be determined that degradation exist in the decolorization in process of methylene blue wastewater.From the difference between the infrared spectra of methylene blue wastewater and the extracted metabolites,it could be seen that a part of the structure of methylene blue had been transformed.The results of the experiment,UV spectrum analysis and infrared spectrum analysis showed that the decolorization of methylene blue wastewater by Penicillium P1 depended on the combined action of degradation and adsorption.On the basis of the above research,soy protein isolate-sodium alginate microcapsule was prepared by using soy protein isolate and sodium alginate to immobilize Penicillium P1.Investigating the effects of different factors on the decolorization of methylene blue wastewater by soy protein isolate-sodium alginate microcapsule showed that: when the concentration of methylene blue was 20 mg/L,the amount of immobilized Penicillium was 0.2 g/L,p H = 4,and the time was 24 h,the decolorization rate of methylene blue by immobilized Penicillium P1 could reach 98.10%.When p H=1 and p H=9,the decolorization rate of methylene blue wastewater was 75.26% and 53.62%,respectively.When the concentration of methylene blue was 100mg/L,the decolorization rate of methylene blue was 67.5%.When the salinity was 10%,the decolorization rate was 78.12%.According to the experimental data,after immobilized Penicillium with soy protein isolate-sodium alginate microcapsule,the decolorization rate could reach 98.10% under the optimized conditions,and the tolerance to high salt,acid and alkaline conditions was also improved.From the scanning electron microscope picture of the soybean protein isolate-sodium alginate microcapsule,it could be seen that the microcapsule had a loose and porous structure,which was beneficial to the decolorization of the methylene blue dye.On the basis of the above research,soy protein isolate-chitosan polymer was prepared by using soy protein isolate and chitosan to immobilize Penicillium P1.The synthesis mechanism of soy protein isolate-chitosan polymer was investigated.According to the infrared spectrum of soy protein isolate-chitosan polymer,there was an electrostatic interaction between the positively charged amino group of chitosan and the negatively charged carboxyl group of soy protein isolate-chitosan.The effects of different factors on the decolorization of methylene blue wastewater by Penicillium immobilized by soy protein isolate-chitosan polymer was investigated.When the concentration of methylene blue was 20 mg/L,the addition amount of Penicillium immobilized was 0.2 g/L,p H 4,and the time was 24 h,the decolorization rate of methylene blue by immobilized soy protein isolate-chitosan polymer Penicillium could reach99.59%.Under the unfavorable conditions of p H 1 and p H 9,the decolorization rates of methylene blue were 65.45% and 48.75%.When the concentration of methylene blue was 100mg/L,the decolorization rate of methylene blue was 67.50% and 65.23%,respectively.When the salinity was 10%,the decolorization rate was 68.58%.From the above results,it can be seen that under adverse environmental conditions,the decolorization efficiency of Penicillium P1 immobilized by soy protein isolate-chitosan polymer for the decolorization of methylene blue dye could still be higher.From the scanning electron microscope picture of the soybean protein isolate-chitosan polymer,it could be seen that the structure of soy protein isolate-chitosan polymer had loose porous structure.It was beneficial to the decolorization of methylene blue dye. |
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