Study On The Effect Of Sodium Persulfate Pretreatment On Structure And Anaerobic Digestion Of Corn Stover

Due to the complex and dense structure of straw,it is difficult to be efficiently degraded by microorganisms,and it is necessary to use effective pretreatment to destroy the connection between lignocellulose,thereby improving the accessibility of the microorganisms to the straw,and realizing the efficient biological transformation of the straw in the anaerobic digestion.Utilizing the oxidative properties of oxidants to degrade lignin in straw,and degrad some of the cellulose and hemicellulose macromolecules into small molecular soluble sugars,destroying the winding and wrapping structure between cellulose,hemicellulose and lignin,which is convenient for anaerobic microbes efficiently convert sugars into products such as methane.Through a large number of experiments in this paper,it was found that both pretreatment with sodium persulfate at room temperature and heat-activated sodium persulfate can damage the structure of straw.Among them,heat-activated sodium persulfate has the best pretreatment effect,which can obviously destroy the complex structure of lignocellulose,thereby promoting the progress of anaerobic digestion.In this paper,the influence of two different pretreatment methods of Na2S2O8 pretreatment at room temperature and heat-activated Na2S2O8 pretreatment on the corn stover pretreatment effects were investigated.The influence of different influencing factors on the pretreatment effects were compared through the single factor test,and the optimal pretreatment conditions were obtained by using a combination of orthogonal test and single factor test,and then the thermally activated Na2S2O8 pretreatment with the best pretreatment effect was selected as pretreatment of anaerobic digestion,to explore the effect of heat-activated sodium persulfate pretreatment on anaerobic digestion performance.The results showed that:(1)The effects of Na2S2O8 dosing ratio,pretreatment time,solid-liquid mass ratio,and solution pH on the pretreatment effect of Na2S2O8 at room temperature were investigated through a single factor test.The results showed that the pretreatment effect is better when the Na2S2O8 dosing ratio was 1%,the pretreatment time was 32 h,the solid-liquid ratio was 1:10,and the solution pH was 6.In addition to the above factors,the activation temperature is also one of the important factors affecting the pretreatment effect of thermally activated Na2S2O8.The influence of each factor on the heat-activated Na2S2O8 pretreatment effect were investigated through the single factor experiment,and the optimal pretreatment conditions were obtained by orthogonal experiments:the solid-liquid mass ratio was 1:10,the pretreatment time was 16 h,the activation temperature was 50?,the solution pH was 5,and the sodium persulfate addition ratio was 0.5%.At this time,the straw degradation rate reaches 23.43%,and the reduction sugar yield is 16.75%.Comparing the effects of Na2S2O8 pretreatment at room temperature and thermally activated Na2S2O8 pretreatment,the results showed that the heat-activated Na2S2O8 pretreatment effect is better.The highest straw degradation rate that can be achieved by pretreatment with sodium persulfate at room temperature is 17%?18%,and the highest reduction sugar yield is 13%?14%,while the straw degradation rate can reach about 23%,the highest reduction sugar yield can reach about 21%under thermal activation conditions,and the time to achieve the optimal pretreatment effect is shortened from 32 h to 16 h.(2)Methanol(MeOH)and tert-butanol(TBA)were introduced into the straw/Na2S2O8 system and combined with EPR technology,the hydroxyl radicals(·OH),sulfate radicals(SO4·-),and organic radicals in the sodium persulfate reaction system at room temperature were determine.Under the condition of thermal activation,the symmetrical cleavage of the peroxide bond forms SO4·-.At the same time,it is judged that OH and SO4·-coexist in the solution during the thermal activation process based on the EPR spectrum results.(3)Observe the microstructure of straw after heat-activated Na2S2O8 pretreatment and Na2S2O8 pretreatment at room temperature,and compare with unpretreated straw,it can be found that the two sodium persulfate pretreatment methods can play a significant role in destroying the straw structure.However,thermally activated Na2S2O8 has better pretreatment effect,more thorough structural destruction,increased porosity,and can effectively break the chemical bonds between lignocellulose;the crystallinity of straw cellulose increased after pretreatment.(4)Heat-activated Na2S2O8 pretreatment can effectively improve the anaerobic digestibility of corn stover.The cumulative methane production of the heat-activated Na2S2O8 pretreatment for 48 h without elution and the 16 h without elution was 4944 mL and 4787 mL,respectively,which were 26.80%and 22.12%higher than those of the untreated group.The loss of soluble organic matter after the elution operation has an adverse influence on increasing gas production and cumulative methane production.The system stability of the pretreated group was better than that of the non-pretreated group,and the system stability of the pretreatment group with the elution operation was the best.