【作者】 孙杰；

【导师】 张涛；

【作者基本信息】 江苏大学 ， 化学工程与技术， 2024， 硕士

【摘要】 “双碳”的战略背景下,废水和固体废弃物的碳排放引起研究者的广泛关注。作为高浓有机废水,含油废水中的甲烷和二氧化碳排放,是污水碳排放增长的主要因素,对生态环境造成严重威胁。农林废弃物,由于数量庞大且处理方法不合理不充分,已经成为环境隐患。农林废弃物的分解,是固体废弃物碳排放的重要来源。以含油废水处理和农林废弃物资源化为背景,如何综合应用物理和化学手段对含油废水进行提质分离和农林废弃物资源化,是资源化工和环境化工领域的一个巨大挑战。基于此,本文以含油废水提质分离和农林废弃物资源化为目标,将生物质资源利用和环境污染防治相结合,开展全木质基复合材料的制备及其油水分离方面的研究工作。以废弃木料为原料,围绕木材的组分选择性拆分、木质素和纤维素重组和油水分离等关键过程展开研究,探索全木质基复合材料的制备工艺和油水分离过程的强化途径,实现含油废水和林业废弃物的资源化。具体研究内容如下:（1）Mg-Al LDHs/纤维素碳杂化凝胶的制备及其油水分离性能的研究以废弃木屑为原料,结合碱处理和漂白工艺提取木质纤维素,从木屑中提取木质纤维素。以木质纤维素为基体,利用原位生长、冷冻干燥和无氧煅烧技术,制备Mg-Al LDHs/纤维素碳杂化凝胶（镁铝双金属氢氧化物/纤维素碳杂化凝胶）。基于形貌结构和化学组成对材料润湿性的影响,详细表征分析了材料的表面形貌、晶体结构、官能团、元素组成和界面润湿性。表征结果证实,制备的Mg-Al LDHs/纤维素碳杂化凝胶具有3D多孔网状结构,LDHs垂直生长在木质纤维表面,增加材料的表面粗糙度。同时,LDHs丰富的羟基官能团协同增强了材料的亲水性能,测得杂化凝胶的空气中水接触角为0°。油水分离结果证实,Mg-Al LDHs/纤维素碳杂化凝胶对水包油型乳液的分离效率高达98.6%以上,分离通量可达7560 L m^-2 h^-1以上。此外,材料在十次循环测试后仍可保持初始分离性能的90%以上,充分表现了其优异的分离性能循环使用性。该研究为废弃木料制备生物质气凝胶提供思路,而且拓展生物质材料在油水分离中的应用。（2）可切换润湿性的木质素基碳层的制备及其油水分离性能研究从废弃木料中提取纤维素过程中,产生大量木质素废水。为资源化利用木质素废水,以木质纤维素提取的副产品黑液为原料,利用水热反应和煅烧制备了木质素基碳层材料。再结合高温煅烧和蒸汽改性技术,制备了润湿性可切换的木质素基碳层。分别测试了材料的润湿性能和油水分离能力,测得煅烧后的木质素基碳层在空气中水接触角为127.28°,表现出超疏水性和水下超亲油性（水下油接触角0°）,使其具有吸附水中微小油滴性能,在分离水包油型乳液时,分离效率高达99.5%上,同时分离通量达到16629 L m^-2h^-1以上;而蒸汽改性后的木质素基碳层则由于高表面能而表现出亲水性,分离油包水乳液时分离效率高达99.9%以上,而且分离通量均高于8000 L m^-2h^-1。材料在十次循环后,分离效率仍达到99.3%以上,具有良好的循环性能。本研究制备润湿性能可切换的木质素基碳层材料,实现了木质素废液的资源化和含油乳液的按需分离,降低废水中的碳排放。（3）全木质基杂化膜的结构设计及其水分离性能研究基于上述两个研究中,纤维素基和木质素基各自在油水分离领域的优势,为了进一步实现废弃木质材料的资源化利用,以木质纤维和木质素碳颗粒为原料,利用组装技术制备全木质基杂化膜材料。通过对全木质基杂化膜材料的表征,证明水热制备的木质素碳微球均匀负载于纤维素纤维上,由此构建了粗糙度更高的表面结构,强化了材料的选择润湿性。同时,对全木质基杂化膜材料的接触角和水包油乳液分离性能进行了研究,测得全木质基杂化膜具有超亲水性（水接触角为0°）和水下疏油性（水下油接触角为140°）。全木质基杂化膜在分离水包油乳液时分离效率可达到98.8%以上,分离通量也高达6673 L m²h^-1以上。全木质基杂化膜具有完全的生物可降解性,无毒无害、绿色环保可持续,同时兼具高分离效率和高分离通量,为含油废水处理和农林废弃物的分解资源化提供研究思路。更多还原

【Abstract】 Carbon emissions from wastewater and solid waste have attracted extensive attention from researchers in the context of the"carbon peaking and carbon neutral"strategy.Methane and carbon dioxide emissions from oily wastewater,which is a highly concentrated organic wastewater,are a major factor in the growth of carbon emissions from sewage,posing a serious threat to the ecosystem.Agricultural and forestry wastes,due to their large quantity and irrationally inadequate treatment methods,have become an environmental hazard.Decomposition of agricultural and forestry wastes is an important source of carbon emissions from solid wastes.Against the background of oily wastewater treatment and agroforestry waste resourcing,it is a great challenge in the field of resource chemistry and environmental chemistry to comprehensively apply physical and chemical means for the upgrading and separation of oily wastewater and the resourcing of agroforestry waste.Based on this,this paper aims at the qualitative separation of oily wastewater and the resource utilization of agricultural and forestry wastes.The research work on the fabrication of all-wood based composites for oil-water separation was carried out by combining the biomass utilization and environmental pollution control.Taking waste wood as raw material,the research focuses on the key processes of component selective separation,lignin and cellulose recombination of wood and oil-water separation,exploring the fabrication process of all-wood-based composites and the enhancement of the oil-water separation process,so as to realize the resourcing of oily wastewater and forestry wastes.The specific research contents are as follows（1）Preparation of Mg-Al LDHs/cellulose carbon aerogels for oil water separationMg-Al Layered Double Hydroxides（LDHs）/cellulose carbon aerogels were prepared from waste wood chips.By combining alkali treatment and bleaching process,lignocellulose was extracted from the wood chips.Then the Mg-Al Layered Double Hydroxides（LDHs）/cellulose carbon aerogels were fabricated by using in-situ growth,freeze-drying,and anoxic calcination techniques on the cellulose.Based on the effects of morphology and structure and chemical composition on the wettability of the materials,the surface morphology,crystal structure,functional groups,elemental composition and interfacial wettability of the materials were analyzed by detailed characterization.The characterization results confirm that the prepared Mg-Al LDHs/cellulose carbon aerogels have a 3D porous mesh structure,and the LDHs grow perpendicularly on the surface of wood fibers which increases the surface roughness of the materials.Meanwhile,the abundant hydroxyl functional groups of LDHs synergistically enhanced the hydrophilic property of the material,and the water contact angle in air of the aerogel was measured to be 0°.The separation results confirmed that the separation efficiency of the Mg-Al LDHs/cellulose carbon aerogel for oil-in-water emulsions is as high as more than 98.6%,and the separation flux can be up to more than 7560 L m^-2h^-1.In addition,the material can still maintain more than 90%of the initial separation performance after ten cycle tests,which fully demonstrated its excellent recyclability of separation performance.This study provides ideas for the preparation of biomass aerogels from waste wood and expands the application of biomass materials in oil-water separation.（2）Preparation of lignin-based carbon layers with switchable wettability for oil-water separationThe process of cellulose extraction from waste wood produces a large amount of lignin wastewater.In order to utilize the lignin wastewater,lignin-based carbon layer materials were prepared by hydrothermal reaction and calcination technology using black liquor,a by-product of lignocellulose extraction,as raw material.After one-step oxygen barrier calcination and steam modification techniques,hydrophobic and hydrophilic switchable lignin-based oil-water separation materials were prepared.The wettability and oil-water separation ability of the materials were tested respectively,and it was measured that the water contact angle of the calcined lignin-based carbon layer is 127.28°in air,which shows superhydrophobicity and superoleophilicity underwater（underwater oil contact angle of 0°）and gives it the performance of adsorption of tiny oil droplets in water.When separating oil-in-water emulsions,the separation efficiency of the materials is as high as 99.5%and the separation flux reaches 16629 L m^-2h^-1.While the steam-modified lignin-based carbon layer shows hydrophilicity due to its high surface energy,with a separation efficiency of 99.9%when separating water-in-oil emulsions,and the separation flux is higher than 8,000 L m^-2 h^-1.The separation efficiency of the material is still above 99.3%after ten cycles which shows a good cycling performance of the materials.This study prepares lignin-based carbon layer materials with switchable wettability performance,which realizes the resourcefulness of lignin waste liquid and on-demand separation of oil-containing emulsion,and reduces the carbon emission from wastewater.（3）Structural design of all-wood-based hybrid membranes for oil-water separation propertiesBased on the respective advantages of cellulose-based composites and lignin-based composites in the field of oil-water separation in the two studies mentioned above,in order to further realize the resourceful utilization of waste wood materials,all-wood-based hybrid membrane materials were prepared by using the assembly technique with cellulose fibers and lignin carbon particles as raw materials.Through the characterization of the all-wood-based hybrid membrane materials,the results show that the hydrothermally prepared lignin carbon microspheres are uniformly loaded on the cellulose fibers,which contributes to the construction of a surface structure with a higher roughness and enhanced the selective wettability of the materials.Meanwhile,the contact angle and water-in-oil emulsion separation properties of the all-wood-based hybrid membrane were investigated.The results show that the all-wood-based hybrid membrane is superhydrophilic（water contact angle is 140°）and underwater superoleophobic（oil contact angle under water is 140°）.The efficiency of the oil-in-water separation of the all-wood-based hybrid membrane could be up to more than 98.8%,and the separation flux could up to more than 6673 L m^-2h^-1.The all-wood-based hybrid membrane is completely biodegradable,non-toxic,harmless,environmentally friendly and sustainable with both high separation efficiency and high separation flux,providing research ideas for the treatment of oily wastewater and the decomposition and resourceization of agricultural and forestry wastes.更多还原