离子液体预处理对马铃薯茎叶厌氧消化的影响

Effect of Ionic Liquids Pretreatment on Anaerobic Digestion of Potato Stem Leaves

马铃薯茎叶是一种丰富的木质纤维素生物质资源,但其高结晶度、稳定的刚性结构使其不易水解酸化,微生物在短时间内难以直接高效利用。研究了离子液体和助溶剂对马铃薯茎叶进行预处理后其木质纤维素结构组分变化及厌氧消化产沼气的变化。结果表明,预处理后的马铃薯茎叶木质素质量分数降低31.8%~43.9%,离子液体脱除马铃薯茎叶木质素能力由高到低依次为[C_2mim]Ac、[C_2mim]Ac/DMSO、[C_4mim]Cl/DMSO、DMSO、[C_4mim]Cl。离子液体中阴离子可与纤维素羟基上的氢质子形成氢键作用,降低其结晶度,长链分子断裂成短链分子,使厌氧消化的启动滞后期较未处理马铃薯茎叶提前9 d,累积产沼气量提高3.2%~76.3%,最高产甲烷体积分数提高14.3%~25.1%。各处理组累积产沼气量和最高产甲烷体积分数分别为:T5(7.21 L,69.2%)、T4(5.12 L,64.5%)、T2(5.07 L,65.7%)、T3(4.35 L,64.3%)、T1(4.22 L,63.2%)。经无机盐-离子液体双水相体系回收DMSO、[C_2mim]Ac和[C_4mim]Cl,回收率分别为95.1%、91.8%和89.6%。

With the fulfillment of China＇s potato staple food strategy, potato stem leaves gradually become plentiful lignocellulosic biomass resources. However, its cell wall has high-crystalline structure and available surface area which were difficult to hydrolyze and produce biogas by microorganism. Therefore, the effect of lignocellulosic composition, structural and anaerobic digestion from the pretreated potato stem leaf by ionic liquids and dimethyl sulfoxide was evaluated. The potato stem leaf was pretreated with ionic liquids l-N-butyl-3-methyimidazolium chloride （ [ C4 mim] Cl ） , 1-ethyl-3-methlyimidazolium acetate （[ C2mim] Ae） and dimethyl sulfoxide （DMSO） under the condition of 130℃ for 120 min. Compared with untreated group （19.8% lignin content） , the composition and structure of lignocellulosic from the regenerated potato stein leaf was changed and the lignin content was reduced by 31.8% -43.9%. The dissolving capability of the solvents followed the order： [ C2mim] Ac, [ C2mim] Ac/DMSO, [ C4mim] Cl/ DMSO, DMSO, [ C4 mim ] Cl. The anaerobic digestion data demonstrated the lag phase of anaerobic digestion start-up period was shortened by 9 d. Because the solubility of cellulose was risen with the increase of the H-bonds accepting ability of the anions which would form more efficient H-bonds between the hydroxyl protons of cellulose and the anion, meanwhile, the crystalline structure of cellulose became lower and the surface became more porous. In other words, the hydrolytic acidification stage was almost accomplished after pretreatment. Plenty of the small molecular substances, which were easy to be used by methanogens, were dissolved out. The cumulative biogas production and the highest methane content were increased by 3.2% - 76.3% and 14.3% - 25. stem leaf. The cumulative biogas production and the 1%, respectively, compared with untreated potato highest methane content of each pretreated groups were 7.21Land69.2% （[C4mim]Cl/DMSO）, 5.12 L and 64.5% （[C2mim]Ac/DMSO）, 5.07 L and 65.7% （[C2mim]Ac）, 4. 35 L and 64.3% （[C4mim]Cl）, 4. 22 L and 63.2% （DMSO）, respectively. The ionic liquids were almost completely recovered by aqueous biphasic systems （ABSs） with tripotassium phosphate （K3PO4）, the recovery rates of DMSO, [ Czmim]Ac and [ C4mim] Cl were 95.1% , 91.8% and 89.6% , respectively. There were still many issues in putting ionic liquids into practical applications, including the high cost of ILs, regeneration systems and requirements and mechanism of inhibitor generation. Further research was urgently required to dispose such challenges.