【作者】 吴宇雄；

【导师】 赵仁杰；

【作者基本信息】 中南林业科技大学 ， 木材科学与技术， 2010， 博士

【摘要】 木质素是大量存在的、一种可再生的生物质资源。其开发和利用有着重要价值。目前工业木质素的主要来源是制浆造纸T业。制浆造纸工业的木质素通常作为燃料使用,有的甚至未经处理直接排放,造成严重的资源浪费和环境污染。如何合理利用木质素这一宗自然恩赐给我们的可再生资源,减少环境污染,变废为宝,具有重要而现实的意义。越来越多的研究表明各种工业木质素及其改性产物表现出对重金属离子良好的吸附性能。吸水树脂作为‘种新型的高分子功能材料,不仅可用作吸水和保水材料,而且还可用于各种金属离子的吸附分离富集。结合木质素基吸附材料、高吸水性树脂及废水污染处理的发展方向,整合木质素的吸附功能和高吸水性树脂的吸水吸附特性,本工作以工业副产物木质素(磺酸盐)等为原料,合成了三种木质素基吸水吸附材料,研究了木质素基吸水吸附材料的吸水保水性能及对于重金属离子Pb2+、Zn2+、Cd2+的吸附性能。采用溶液聚合法,成功将可再生生物质资源木质素磺酸盐与丙烯酰胺及部分中和的丙烯酸接枝共聚,合成了木质素基吸水吸附材料LS-g-P(AA-co-AM)；同时,通过田口实验设计优化和miniTab软件分析,获得了LS-g-P(AA-co-AM)的最佳合成条件为：交联剂N,N’-亚甲基双丙烯酰胺浓度CNMBA为7.5×10-4mol/L,引发剂过硫酸钾浓度CKPS为4.0×10-3mol/L,木质素磺酸镁用量cLS为2.5g/L,丙烯酸中和度N为60及丙烯酰胺与丙烯酸的摩尔用量比rAM/AA为1：1,程序升温：55℃反应2.5 h,65℃反应2.5 h,75℃反应3 h。在最优条件下合成的LS-g-P(AA-co-AM)具有良好的吸水性能,重复吸水性能,在自然状态及高温下的保水性能。LS-g-P(AA-co-AM)的平衡吸蒸馏水倍率为1156g/g,平衡吸0.09%盐水倍率为451g/g,吸0.9%盐水倍率为122g/g。在LS-g-P(AA-co-AM)的基础上,成功地将木质素基吸水吸附材料LS-g-P(AA-co-AM)与价廉的无机矿物膨润上(BT)复合,合成了LS-g-P(AA-co-AM)/BT复合吸水吸附材料。膨润土的最佳用量为15g/L。LS-g-P(AA-co-AM)/BT的平衡吸蒸馏水倍率为1020g/g,平衡吸0.09%盐水倍率为397g/g,吸0.9%盐水倍率为109g/g。LS-g-P(AA-co-AM)与膨润土的复合,改善了吸水吸附材料的吸水凝胶强度,提高了材料的重复吸水性能、保水性能和热稳定性,降低了材料的生产成本。在LS-g-P(AA-co-AM)的基础上,进一步将另一种价廉的可再生生物质资源淀粉引入到了吸水吸附材料中,合成了(木质素／淀粉)接枝部分中和丙烯酸、丙烯酰胺吸水吸附材料(LS/St)-g-P(AA-co-AM)。淀粉的最佳用量为5g/L。(LS/St)-g-P(AA-co-AM)的平衡吸蒸馏水倍率为1299.6g/g,平衡吸0.09%盐水倍率为292.6g/g,吸0.9%盐水倍率为85 g/g。淀粉的引入,提高了材料的吸蒸馏水倍率,改善了材料的重复吸水性能、保水性能并降低了成本。形貌分析表明LS-g-P(AA-co-AM)、LS-g-P(AA-co-AM)/BT、(LS/St)-g-P(AA-co-AM)三种木质素基吸水吸附材料均形成了多孔性网络结构：LS-g-P(AA-co-AM)呈多孔性海绵状网络结构,LS-g-P(AA-co-AM)/BT的膨润土成剥离状态分散在LS-g-P(AA-co-AM)多孔海绵状网络结构中,(LS/St)-g-P(AA-co-AM)则形成了蜂窝状三维网络结构。热稳定性研究表明,LS-g-P(AA-co-AM)、LS-g-P(AA-co-AM)/BT、(LS/St)-g-P(AA-co-AM)三种木质素基吸水吸附材料最大失重阶段的起始失重温度均高于330℃,其最大失重温度均高于360℃,说明三种木质素基吸水吸附材料均具有较好的耐热性能。吸水性材料中木质素磺酸盐的引入,提高了材料网络内的离子强度。多孔性网络结构的形成和离子强度的提高正是LS-g-P(AA-co-AM)、LS-g-P(AA-co-AM)/BT、(LS/St)-g-P(AA-co-AM)三种材料显示优良性能的根本原因。LS-g-P(AA-co-AM)、LS-g-P(AA-co-AM)/BT、(LS/St)-g-P(AA-co-AM)三种木质素基吸水吸附材料吸蒸馏水及吸盐水的动力学行为都可以较好地用方程：dQ/dt=k(Q-Qt)2进行拟合。LS-g-P(AA-co-AM)、LS-g-P(AA-co-AM)/BT、(LS/St)-g-P(AA-co-AM)三种木质素基吸水吸附材料作为吸附剂对Zn2+、Pb2+、Cd2+离子均显示了良好的吸附性能,具有极快的吸附速率和较高的吸附容量。在吸附剂用量为1.000g/L,起始离子浓度为2.000 mmol/L时,LS-g-P(AA-co-AM)对Zn2+、Pb2+、Cd2+的平衡吸附密度分别为1.3552 mmol/g、1.6021 mmol/g、1.1902 mmol/g, LS-g-P(AA-co-AM)/BT对zn2+、Pb2+、Cd2+的平衡吸附密度分别为1.1239 mmol/g、1.5612 mmol/g、1.4413 mmol/g, (LS/St)-g-P(AA-co-AM)对Zn2+、Pb2+、Cd2+的平衡吸附密度分别为1.2339 mmol/g、1.4456 mmol/g、1.4690 mmol/g。三种材料吸附金属离子的吸附机理包含化学吸附、离子交换吸附、物理吸附等多种机理。Lagergren准二级动力学方程可以较好地拟合LS-g-P(AA-co-AM)、LS-g-P(AA-co-AM)/BT、(LS/St)-g-P(AA-co-AM)三种木质素基吸水吸附材料作为吸附剂对Zn2+、Pb2+、Cd2+的动力学吸附数据；吸附质浓度和吸附剂浓度均影响LS-g-P(AA-co-AM)、LS-g-P(AA-co-AM)/BT、(LS/St)-g-P(AA-co-AM)吸附Zn2+、Pb2+、Cd2+体系的吸附行为,平衡吸附密度随起始离子浓度增大而增大,随吸附剂浓度增大而降低；除Freundlich吸附等温方程基本可以用来拟合LS-g-P(AA-co-AM)吸附zn2+体系的吸附行为外,Langmuir吸附等温方程和Freundlich吸附等温方程均不能用来描述LS-g-P(AA-co-AM)、LS-g-P(AA-co-AM)/BT、(LS/St)-g-P(AA-co-AM)吸附Zn2+、Pb2+、Cd2+体系的吸附行为。LS-g-P(AA-co-AM)、LS-g-P(AA-co-AM)/BT、(LS/St)-g-P(AA-co-AM)三种木质素基吸水吸附材料具有良好的综合性能：优良的吸水性能、保水性能和耐盐性、良好的对Zn2+、Pb2+、Cd2+等重金属离子的吸附性能。因此,三种木质素基吸水吸附材料有望应用于吸水保水、盐碱地的治理改良、吸肥保肥、废水处理等领域。更多还原

【Abstract】 Lignin is an abundant and renewable biomass resource and its development and utilization is of great value. The main source of industrial lignin is pulping process & paper making industry. Most of the lignin from pulping process & paper making industry is incinerated and discharged directly without any treatment, which makes great resource waste and severe pollution. Thus, rationally utilize the natural renewable resource lignin and decrease the environment pollution is of great significance. Increasing researches on lignin show that many kinds of industrial lignin and their modified products feature high adsorption for many heavy metal ions. Superabsorbent resin is a new functional material with high water absorbency and water retention capability and can also be used to adsorb heavy metal ions. To combine the features and functions of lignin-based adsorbents and superabsorbent resins and the development tendency of wastewater treatment, three lignin-based water absorbent and heavy metal ion adsorbent materials were synthesized and their water absorbency, water retention and adsorption for Pb2+, Zn2+, Cd2+ were studied.The lignin-based water absorbent and heavy metal ion adsorbent material (LS-g-P(AA-co-AM)) was synthesized by graft-copolymerization of renewable biomass resource lignin with acrylamide and partially neutralized acrylic acid through solution polymerization. The optimized synthesis conditions, acquired through Taguchi experimental design and miniTab software analysis were as follows. Crosslinker N,N’-methylene-bisacrylamide CNMBA 7.5×10-4 mol/L, initiator potassium persulfate CKPS 4.0×10-3 mol/L, magnesium lignosulfonate CMgLS 2.5 g/L, neutralization degree of acrylic acid NAA 60 and mole ratio of acrylamide to acrylic acid RAM/AA 1:1. Reaction duration and temperature were programmed as 55℃for 2.5 hrs, then 65℃for 2.5 hrs and followed by 75℃for 3 hrs to guarantee complete copolymerization and therefore, good products. The optimized final (LS-g-P(AA-co-AM)) features good water absorption, repeat water absorption and water retention under natural condition and/or high temperature. The confirmed maximum water absorbency,0.09% saline absorbency and 0.9% saline absorbency of the optimized final (LS-g-P(AA-co-AM)) is 1156 g/g,451 g/g and 122 g/g, respectively.On the basis of synthesis of (LS-g-P(AA-co-AM)), the cheap inorganic Bentonite (BT) was employed to in-situ react with (LS-g-P(AA-co-AM)) to prepare LS-g-P(AA-co-AM)/BT composite water absorbent and heavy metal adsorbent material. The optimal dosage of Bentonite is 15g/L. The maximum water absorbency,0.09% saline absorbency and 0.9% saline absorbency of the optimized final (LS-g-P(AA-co-AM)/BT) is 1020 g/g,397 g/g and 109 g/g, respectively. After composition, the material’s strength after water absorbing, repeat water absorption, water retention and thermal stability are improved while its cost is lowered.Again, on the basis of synthesis of (LS-g-P(AA-co-AM)), the cheap, renewable biomass resource-starch (St) was introduced into the lignin-based water absorbent and heavy metal ion adsorbent material to synthesized lignin/starch-graft-acrylic acid-co-acrylamide (LS/St)-g-P(AA-co-AM). The optimal dosage of starch is 5 g/L. The maximum water absorbency,0.09% saline absorbency and 0.9% saline absorbency of the optimized final (LS-g-P(AA-co-AM)/BT) is 1299.6 g/g,296.9 g/g and 85 g/g, respectively. After the introduction of starch, the material’s equilibrium water absorbency, repeat water absorption, water retention are also improved while its cost is lowered.SEM photographs shows that the three kinds of lignin-based water absorbent and heavy metal ion adsorbent materials, LS-g-P(AA-co-AM), LS-g-P(AA-co-AM)/BT and (LS/St)-g-P(AA-co-AM) have formed porous network structure. LS-g-P(AA-co-AM) shows a porous sponge net structure. For LS-g-P(AA-co-AM)/BT, Bentonite is stripped and dispersed in the porous sponge net structure of LS-g-P(AA-co-AM). However, (LS/St)-g-P(AA-co-AM) has formed honeycomb three-dimensional net structure.Thermogravimetric analysis indicates that LS-g-P(AA-co-AM), LS-g-P(AA-co-AM)/BT and (LS/St)-g-P(AA-co-AM) feature good thermal stability. Their initial weight-loss temperatures at the maximum mass-change stage are higher than 330℃and their maximum weight-loss temperatures are higher than 360℃.The introduction of lignosulfonate into the superabsorbent resin has increased the ion strength in the network of superabsorbent resin. High ion strengths and porous network structures are the foundations for good performances of the three lignin-based water absorbent and heavy metal ion adsorbent materials.The kinetic behaviors of LS-g-P(AA-co-AM), LS-g-P(AA-co-AM)/BT and (LS/St)-g-P(AA-co-AM) absorbing distilled water and 0.09% saline can be simulated by equation dQ/dt=k(Q-Qt)2.LS-g-P(AA-co-AM), LS-g-P(AA-co-AM)/BT and (LS/St)-g-P(AA-co-AM) all shows good adsorption for Zn2+, Pb2+ and Cd2+ cations with fast adsorption rates and high adsorption capabilities.As the adsorbent dosage is 1.000 g/L and initial ion concentration is 2.000 mmol/L, the equilibrium adsorption density of LS-g-P(AA-co-AM) for Zn2+, Pb2+ and Cd2+ is 1.3552 mmol/g,1.6021 mmol/g and 1.1902 mmol/g, respectively. Under the same conditions, the equilibrium adsorption density of LS-g-P(AA-co-AM)/BT for Zn2+, Pb2+ and Cd2+ is 1.1239 mmol/g,1.5612 mmol/g and 1.4413 mmol/g, respectively, and the equilibrium adsorption density of (LS/St)-g-P(AA-co-AM) for Zn2+, Pb2+ and Cd2+ is 1.2339 mmol/g,1.4456 mmol/g and 1.4690 mmol/g, respectively. The adsorption mechanism for lignin-based water absorbent and heavy metal ion adsorbent materials-heavy metal ion adsorption systems is not unique and may include chemical adsorption, ion-exchange adsorption, physical adsorption and other mechanisms.The kinetic behaviors for LS-g-P(AA-co-AM), LS-g-P(AA-co-AM)/BT and (LS/St)-g-P(AA-co-AM) adsorbing Zn2+, Pb2+ and Cd2+ can be well simulated by Lagergren quasi-secondary kinetic equation. Both the adsorbent concentration and adsorbate concentration show influences on the adsorption of lignin-based water absorbent and heavy metal ion adsorbent materials-heavy metal ion adsorption systems. Equilibrium adsorption density increases with initial ion concentration (adsorbate concentration) and decreases with adsorbent concentration.Except Freundlich adsorption isotherm equation can be barely used to simulate the adsorption of LS-g-P(AA-co-AM)-Zn2+ adsorption system, Langmuir adsorption isotherm equation and Freundlich adsorption isothermal equation can not be employed to describe the adsorption of lignin-based water absorbent and heavy metal ion adsorbent materials-heavy metal ion adsorption systems.Since the three lignin-based water absorbent and heavy metal ion adsorbent materials, LS-g-P(AA-co-AM), LS-g-P(AA-co-AM)/BT and (LS/St)-g-P(AA-co-AM) feature good comprehensive performances, i.e., high water absorbency, good water retention, high salt resistance and good adsorption for Zn2+, Pb2+, Cd2+ ions, these three lignin-based water absorbent and heavy metal ion adsorbent materials may be hopefully used in water absorption & retention, saline and alkaline land treatment & improvement, fertilizer absorption & retention, wastewater treatment and other fields.更多还原