深度共熔溶剂预处理木质纤维素研究进展

深度共熔溶剂(deep eutectic solvent,DES)是两种或多种化合物的低熔点混合物,对不同类型的木质纤维素生物质均表现出良好的预处理性能.由于具有绿色环保、成本低廉、可设计性以及强生物相容性等优势,DES已广泛应用于食品、中药成分提取等诸多领域.DES预处理可以破坏木质纤维素原料中的氢键,断裂木质素-碳水化合物的复合体结构,促使木质素和半纤维素组分溶出或水解,从而增加纤维素的相对含量.该研究从DES预处理作用机理出发,分别对纤维素、木质素和半纤维素的不同作用过程进行了详细综述,综合分析了DES预处理技术的主要影响因素,系统综述了DES对木质类、秸秆类两类生物质预处理的研究进展,并指出应用趋势以及未来研究建议,为DES预处理木质纤维素生物质的研究与应用提供了思路和参考.

Treatment of recalcitrant wastewater and hydrogen production via microbial electrolysis cells

A large amount of real complex wastewaters are generated every year,which leads to a great environmental burden.Various treatment technologies were deployed to remove the contaminants in the wastewaters.However,these actual wastewaters have not been sufficiently treated due to their complex properties,high-concentration organics,incomplete utilization of hard-biodegradable substrates,the high energy input required,etc.Recently,microbial electrolysis cells(MECs),a great potential technology,has emerged for various wastewater treatment,because not only do they demonstrate satisfactory performance during wastewater treatment,but they also generate renewable H2 as a clean energy carrier.Unlike previous reviews,this review introduced the characteristics of every complicated wastewater,and focused on analyzing and summarizing MEC development for wastewater treatment.The performances of MECs were systematically reviewed in terms of organics removal,H2 production,Columbic efficiency,and energy efficiency.MEC performances for treating actual complex wastewaters and producing H2 can be optimized through operation parameters,electrode materials,catalyst materials,etc.In addition,the challenges and opportunities including complexity of wastewaters,instability of H2 production,robust microorganisms,effect of membrane on two-chamber MEC,and integration of MEC with other treatment processes were deeply discussed.Except for the technical feasibility,both environmental feasibility and economic feasibility also need to meet social requirements.This review can indeed provide a basis for high-efficiency treatment and practical commercial applications of recalcitrant wastewaters via MECs in the future.

Anaerobic co-digestion of sodium hydroxide pretreated sugarcane leaves with pig manure and dairy manure

Sugarcane leaves(SL)pretreated by alkali was used as substrate to enhance biogas production via mesophilic anaerobic digestion(AD)in this study.Effectiveness of different concentrations of NaOH pretreatment on AD performance was investigated.Results showed that compared to untreated sample of SL,the lignocellulose(LCH)content of NaOH pretreated group was decreased by 5.79%-16.85%.However,the cumulative biogas production of the pretreated samples increased in the range of 34.54%-82.67%;moreover,T90 was shorten by 5-7 d.The highest anaerobic digestibility of SL was achieved at 6%NaOH pretreatment,which produced 287.30 mL/g TS of biogas.A significant interactive effect of the three parameters(temperature,SL/manure mixing ratio and C/N ratio)was found on the biogasification of anaerobic co-digestion,and a maximum biogas production was achieved at 36.2oC,mixing ratio of 1.6 and C/N ratio of 29.2.These show that the verification experiment confirmed the optimization results.This study provides meaningful insight for exploring efficient pretreatment strategy and optimal condition to stabilize and enhance AD performance for practical application.

Evaluation of different clean heat supply modes based on crop straws in the rural area of Northern China

This study evaluated eight different types of heat supply modes based on crop residues utilization in the rural area of Northern China,including straw densified solid fuel combustion,pyrolysis char combustion,biogas combustion,and pyrolysis gas combustion for single household heating;straw densified solid fuel combustion,baling straw combustion,biogas combustion,and pyrolysis gas combustion for centralized heating;centralized gas supply and centralized pyrolysis gas supply modes.Comprehensively evaluation was the cost of these different eight heat supply modes.The results showed that the cost of straw densified solid fuel combustion,pyrolysis char combustion for single household heating were 2346 RMB/household and 2390 RMB/household.With the heating scale of 200-500 households,the pipe network distance was 8 m/household,and the total annual heating cost was predicted at 2201-2992 RMB/household.Among them,the cost of straw baling combustion for centralized heating was the lowest,the cost of densified solid fuel,biogas,and pyrolysis for centralized heating was the second,and the cost of biogas and pyrolysis gas for centralized gas supply was the highest.For the increase in every 1 m of the pipeline distance,the investment cost will increase by about 645 RMB for each household.This study provides a basis for the implementation of clean heat supply technologies in less-developed areas and guidance of village heat-supply subsidy policies.

Effects of operating conditions and pre-densification on the torrefaction products of sorghum straw

The effects of operating conditions and pre-densification on the torrefaction performance parameters and the properties of the torrefied sorghum straw were studied.A full-factor experiment was performed on a fixed tube furnace,in which sorghum straw powder and pellets were heated to 230℃,260℃,280℃ and 300℃ at 2.5℃/min,5℃/min and 7.5℃/min,respectively.The pyrolysis characteristics of the sorghum straw torrefied under various operating conditions were complemented by thermogravimetric analysis.It was observed that the high temperature led to the high calorific value of the torrefied sorghum straw with an acceptable mass and energy yield.The sorghum straw torrefied at a temperature above 280℃ had a higher heating value(HHV)that was comparable to that of the low rank coal while maintaining its energy yield above 85%.The results suggested that temperature was an important factor determining the properties of the torrefied products,and the heating rate would affect the internal temperature of the torrefied biomass by affecting the heat transfer during the torrefaction.The energy densification index of the pellets decreased uniformly as the heating rate increased proportionally,indicating that pre-densification can be used as a potential method to solve the heat transfer delay in the fixed reactors at high heating rates,especially for high temperatures.

Effects of different heating patterns on the decomposition behavior of white pine wood during slow pyrolysis

This study investigated the effect of different heating rates on the pyrolysis behavior of the white pine wood residues.The raw materials were tested via two heating patterns with variable heating rates and compared with three other heating patterns with constant heating rates.The yields and characteristics of products such as char,pyrolysis oil and non-condensable gases under different heating rates were also determined.The gas,liquid,and solid phase yields of the products via heating with decreasing heating rates were similar to the yields obtained from constant heating rate at 2.3℃/min.The pyrolysis process by decreasing heating rates resulted in 30.04% char,44.53% bio-oil,and 25.43% non-condensable gases,which displayed higher char yield and pyrolysis gas than the other heating patterns.The results of thermo-gravimetric analysis showed that variable heating rate significantly changed the weight loss profiles during pyrolysis.It was observed during gas chromatography test that CO and CO_(2) were released earlier than CH_(4) and H_(2).The analysis of the chemical components confirmed that the bio-oil produced by heating process with decreasing rates contains less macromolecular organic matter content than the other patterns.

Waste bio-tar based N-doped porous carbon for supercapacitors under dual activation:performance,mechanism,and assessment

Bio-tar extra-produced from biomass pyrolysis is prone to pose a threat to environment and human health.A novel N-doped porous electrode from bio-tar was produced under dual-activation of urea and KOH in this study.Onepot dual-activation played significant roles in N-functional group and micro-mesoporous structure,which resulted in the carbon material with the highest of nitrogen content(4.08%)and the special surface area(1298.26 m^(2)·g^(−1)).Specifically,the potential mechanisms of pore formation and N-doping in the one-pot dual-activation strategy were also proposed as a consequence,the one-pot dual-activated carbon material displayed excellent electrochemical performance with the highest capacitance of 309.5 F·g^(−1) at 0.5 A·g^(−1),and the unipolar specific capacitance remained with cyclic characteristics of 80.1%after 10,000 cycles in two-electrode symmetric system.Furthermore,the one-pot dual-activation strategy could create a profit of$1.64-$2.38 per kilogram of bio-tar processed without considering the initial investment and labor costs,which provides new perspectives for the utilization of waste bio-tar.

Heteroatom-doped biochar devised from cellulose for CO_(2) adsorption:a new vision on competitive behavior and interactions of N and S

Biochar,as a potential CO_(2) adsorbent,is of great significance in addressing the problem of global warming.Previous studies have demonstrated that the CO_(2) adsorption performance of biochar can be improved by nitrogen and sulfur doping.Co-doping can integrate the structure and function of two elements.However,the physicochemical interaction of nitrogen and sulfur during doping and the CO_(2) adsorption process remains unclear in co-doped biochar.In this study,the heteroatom-doped biochar was prepared with different additives(urea,sodium thiosulfate,and thiourea)via hydrothermal carbonization,and the physicochemical interaction of nitrogen and sulfur in co-doped biochar was investigated extensively.The findings revealed that nitrogen and sulfur competed for limited doped active sites on the carbon skeleton during the co-doping process.Interestingly,thiourea retained the amino group on the surface of biochar to a great extent due to carbon-sulfur double bond breaking and bonding,which facilitated the formation of pore in the activation process.Significantly,co-doping had no significant improvement effect although nitrogen and sulfur doping separately enhanced the CO_(2) adsorption performance of biochar by 11.9%and 8.5%.The nitrogencontaining and sulfur-containing functional groups in co-doped biochar exhibited mutual inhibition in the process of CO_(2) adsorption.The findings of this study will have pertinent implications in the application of N/S co-doped biochar for CO_(2) adsorption.