Study On The The Synergistic Action Of Electro-Fenton Technology And White Rot Fungi For Degradation Of Lignin

The key to higher efficient degradation of lignin by white rot fungi is its unique extracellular degrading enzymes system and free radical degradation mechanism.The extracellular degrading enzymes system mianly relies on three lignin-degrading extracellular enzymes including laccase,manganese peroxidase and lignin peroxidase.The manganese peroxidase and lignin peroxidase require hydrogen peroxide to initiate enzymatic hydrolysis.Fenton process is often used for pretreatment of biodegradable lignin.Fenton reagent can increase the activity of sensitive cellulase and promote lignin degradation.Hydroxyl radicals produced by Fenton can non-specifically oxidize various groups of lignin.Exogenous reactive oxygen species can increase the activity of extracellular enzymes to degrade lignin.The NZVI composite cathode Fenton process is continuously producing in situ Fenton reagent and active oxygen species without adding exogenous ferrous ions and hydrogen peroxide.The low molecular weight compounds which are secreted by white rot fungi can reduce Fe3+ to Fe2+ and form a virtuous cycle of Fe2+ during the biodegradation of lignin.(1)The NZVI composite cathode was first prepared and constructed a highly efficient electro-Fenton reaction system in this study.Fe0 and Fe3+ were loaded onto activated carbon fibers to obtain NZVI composite cathode by sol-gel method.A layer of non-crystalline Fe0 and Fe3+ was successfully loaded on the surface of the activated carbon fiber felt by analyzing XRD,SEM,BET and XPS.The performance of NZVI composite cathode was verified by degrading simulated methyl orange wastewater.The experimental results show that the electro-Fenton system with NZVI composite cathode has better performance than traditional electrochemical reaction system under the same reaction conditions.It has higher decolorization rate and removal efficiency of methyl orange with less 30%.power consumption.(2)The white-rot fungi were improved in their adaptability to electric fields,and a best strain was selected by the establishment of a micro-electric field culture system.The experimental results show that the micro-electric field environment can effectively stimulate the growth of white rot mycelium and increase the activity of lignin-degrading extracellular enzymes.The Coriolus versicolor is the most significant and the dry weight of mycelium grows 1.65 times.The activity of Lac was increased by 1.45 times.The manganese peroxidase(Mn P)activity was increased by 1.42 times.The lignin peroxidase(Li P)was increased by 1.37 times.The Coriolus versicolor adaptability to micro-electric field environment is better than that of Phanerochaete chrysosporium,Lentinus edodes,Pleurotus eryngii,Pleurotus ostreatuss,and Ganoderma lucidium.by comparison.Therefore,Yunzhi was selected as the dominant strain for the combination degradation of lignin by electro-Fenton and white-rot fungi.(3)The optimized NZVI composite cathode electro-Fenton system was combined with the best selected strains to establish a synergistic degradation of the woody system between the electro-Fenton and white rot fungi.Alkaline lignin was selected as the main target for subsequent experiments by screening.The experimental results showed that electro-Fenton and white rot fungi showed a good synergistic effect in degrading lignin,which significantly promoted the growth of white rot fungus mycelia.When lignin was the only carbon source,the growth rate of white rot mycelium gradually increased with the increase of electric power.When the voltage was 3 V and the current was 0.3 A,the dry weight of mycelium could increase to 2.3 g.The synergistic system significantly increased the lignin degradation rate which could reach 84.5% In the synergistic system,higher Mn P and Li P activity was detected at a voltage of 3 V and a current of 0.3 A.The maximum activity of Mn P reached 375 U/L at 72 h and the maximum activity of Li P at 400 h was 400 U/L.Mn P and Li P activity changes with current and voltage during the synergistic degradation system of electro-Fenton and white rot fungi,The activity increased with higher electric power.In the synergistic degradation system between electro-Fenton and white rot fungi,the activity of lignin-degrading extracellular enzymes was higher than that of white rot fungi.Two-dimensional heteronuclear single-quantum hydrocarbon-related nuclear magnetic spectroscopy(HSQC)analysis of lignin samples can also prove that the synergistic system can completely degrade aromatic OH and aliphatic OH functional groups in lignin.The NZVI composite cathode electro-Fenton system with the white rot fungus degradation lignin system was organically combined in this experiment.Coriolus versicolor was screened out as the dominant species and the alkali lignin as the target through the micro-electric field experiments The results showed that there was a synergistic effect of electro Fenton and white rot fungi in degrading lignin at the same time.This synergistic effect can be widely applied in the lignin removal process of biopulping,feed,functional sugar preparation and other industries.