Mechanism Analysis Of Fe²⁺ Activated PS Pretreatment Of Corn Straw And The Effect On Anaerobic Fermentation

Anaerobic fermentation is one of the effective ways to resource corn straw,but the complexity of the structure of corn straw leads to a low biogas production rate,which needs to be improved by pretreatment techniques to destroy the spatial site barrier effect caused by lignin and hemicellulose to achieve efficient use of straw.In this paper,a method of Fe2+ activated PS pretreatment of corn straw is proposed to improve the biogas production rate.The Fe2+ activated PS pretreatment process of corn straw was mainly studied to determine the optimal process parameters,and the mechanism of pretreatment action on corn straw was analysed by SEM,FTIR and GC-MS,and the degradation pathway of lignin was discussed.On this basis,the effect of Fe2+ activated PS pretreatment on the anaerobic digestion performance of corn straw was studied and analysed.The conclusions are as follows:Firstly,the Fe2+ activated PS pretreatment process parameters were optimised by single-factor experiment,which showed that the process could destroy the complex structure of the straw and that the optimum pretreatment conditions were:The reaction time was 24 h,the amount of Na2S2O8 addition was 4.72%,the amount of Fe2+ addition was 0.83%,and the solid-liquid ratio was 1:12.This The degradation rates of straw,lignin and hemicellulose under these conditions were 22.38%,40.86%and 25.70%,respectively;the production of reducing sugars and phenol content were 16.21%and 1.59 ‰,respectively;the ORP and pH values in the system were 480 mV and 2.71,respectively.Secondly,the pretreatment disrupted the physical and chemical structure of corn straw and increased the cellulose crystallinity as shown by SEM,XRD,TG-DTG,FTIR and 13CNMR analyses;ERP analysis showed that the Fe2+activated PS system had both The ERP analysis showed that both ·OH and SO4·radicals were present in the Fe2+ activated PS system.The oxidative degradation mechanism of straw was proposed with degradation products as the entry point.The main roles of ·OH and SO4·-radicals are addition,electron transfer and hydrogen extraction,combined with oxidation reactions such as hydroxylation and decarboxylation to degrade the straw and ultimately degrade the lignocellulose to CO2 and H2O.19 possible degradation pathways were postulated by studying the degradation mechanism of lignin through lignin monomer derivatives.Finally,the effect of pretreatment on the performance of anaerobic fermentation was investigated.the Fe2+activated PS pretreatment could effectively improve the gas production rate.the cumulative methane production after Fe2+/PS pretreatment without elution and Fe2+/PS pretreatment with elution were 2330 mL and 2223 mL,respectively,which were 14.78%and 9.51%higher than the untreated group,respectively.The elution process resulted in the loss of soluble sugars and small organic molecules from the pretreatment solution,which would reduce the methane production rate.Although PS and Fe3+ treatment could also promote gas production,they were poorer than Fe2+/PS pretreatment,and the cumulative methane production was only 4.63%and 2.96%higher.the Fe2+ activation PS pretreatment could improve the TS and VS degradation rates,and the fermentation time T80 was shortened by 1～3 days.