【作者】 张旭；

【导师】 丛海兵；

【作者基本信息】 扬州大学 ， 土木工程， 2025， 博士

【摘要】 人口持续增长加剧了淡水与能源危机的紧张态势,成为制约人类经济社会可持续发展的重要因素。海水淡化被认为是缓解全球淡水短缺的重要解决方案,目前传统淡化工艺受能耗大、碳排放超标,环境污染严重等多重因素的制约,在“新质生产力”背景下,开发可再生能源海水淡化技术被视为最具前景的发展战略。太阳能驱动界面蒸发技术能够直接利用太阳能进行清洁水生产,具有简易高效、低成本和易部署等优点,被认为是缓解淡水短缺的一种可行方案。但海水蒸发过程中,盐结晶问题仍然是影响淡化性能的主要因素,且蒸发产生的浓缩盐水如处理不当也会对环境造成一定程度的污染。针对这些问题,本研究以“耐盐蒸发系统研发-盐水蒸发结晶机理-盐水零液体排放应用”为主线,开发了一系列具有高效耐盐能力的太阳能驱动界面蒸发系统,深入探讨了盐水在蒸发过程中晶体的生长规律及对蒸发传质的影响,并针对性提出控制盐结晶的改进策略,对实现海水淡化零液体排放技术的发展具有积极意义。主要研究成果如下:（1）基于两性离子水凝胶抗聚电解质效应,以磺基甜菜碱、原始棉织物和碳黑粉末为原料,利用冷冻干燥方法制备一种具有仿生水母结构的太阳能蒸发器,并探究了其太阳能驱动界面蒸发海水淡化能力。实验结果表明,太阳能蒸发器内部呈现出纤维互穿网络结构,能够有效输送水分,在1 kW m^-2太阳辐射下实现了2.158 kg m^-2 h^-1的水蒸发速率和88.71%的能量效率;两性离子水凝胶中同时携带的正（-N（CH₃）₂⁺）和负（-SO₃^-）离子官能团,在盐水中表现出抗聚电解质效应,可有效防止盐结晶并提高蒸发系统的稳定性。此外,太阳能蒸发器在净化酸碱废水、重金属废水、含油卤水等复杂水体时也表现出优异的水蒸发和耐污染能力。（2）根据Donnan效应电荷平衡原理,以天然巴尔衫木为原料,通过去除木质素改善渗透性,将PVA和PAA水凝胶原位聚合到木材孔隙中,并进行表面碳化处理,制备一种具有增强Donnan效应的阴离子太阳能蒸发器。由于木材中定向排列的维管束结构及水凝胶超亲水特性,能够有效提高水分输送效率。同时,水凝胶中所携带的-COO-官能团,进一步增强了蒸发器的Donnan效应,提升了系统的耐盐能力。研究结果表明,在1 kW m^-2太阳辐射下对15 wt%Na Cl溶液进行脱盐时,阴离子太阳能蒸发器实现了2.439 kg m^-2 h^-1的水蒸发速率,长时间蒸发过程中没有观察到明显的盐积累现象,并且能够从多种受污染水体中获取清洁水。在户外实验中,通过增强空气对流,可以有效促进水蒸气凝结,系统效率达到83.3%-115%。（3）受温盐环流现象启发,利用PVA海绵作为亲水基材,通过沉积CNTs作为光热层,研发了一种2D平面结构太阳能界面蒸发结晶器,并基于温度、盐度深入探究盐水在连续蒸发过程中盐结晶行为对系统性能的影响机理。实验结果表明:蒸发过程中形成的多孔盐层严重降低了材料光吸收能力,且仅能够在黑暗环境中增强蒸发速率。盐结晶始于温度较低的光热界面边缘区域,受Marangoni效应诱导,盐水从高温中心区域向低温边缘区域移动,导致晶体在边缘积累,低温区域逐渐扩大并最终覆盖整个光热界面;随后盐水优先在盐层内由低温向高温区域输送蒸发,导致盐层在进水端生长,并触发盐晶体的二次成核过程,造成底部盐层结构致密,方形晶核更为明显,孔隙率降低,影响系统蒸发效率。（4）基于上述研究,通过高导热铝板将蒸发界面和光热界面物理分离,在底部和内壁涂覆CNTs浆料作为光吸收涂层,其外壁和棉纤维相结合并作为水蒸发和盐结晶界面,制备得到一种具有反向蒸发能力的3D太阳能蒸发结晶装置,能够有效解决盐晶体对光热界面的不利影响。利用棉纤维亲水和多孔特征,促进了水分的快速输送,并借助交错排列棉纤维之间形成的微半月板状水体结构,增强蒸发速率和Marangoni效应,实现盐水在纤维尖峰处的结晶。对比高浓度Na Cl溶液和浓缩海水溶液（20 wt%）的连续蒸发过程发现,浓缩海水中镁盐形成的玻璃状盐层堵塞了水传输通道,并导致蒸发性能下降。基于此,通过在蒸发过程中投加盐结晶阻垢剂MDC220,产生相对疏松的片状盐层,比表面积和孔隙率得到改善,连续蒸发浓度为20 wt%的浓缩海水溶液48小时,平均水蒸发速率达到1.42 kg m^-2 h^-1,有效提升了蒸发系统的运行稳定性。综上,本课题研究工作以提升太阳能驱动界面蒸发海水淡化技术中盐水关系管理为核心,从高效耐盐蒸发系统研发和盐结晶机理为出发点,深入探索了基于该技术实现海水淡化零液体排放的应用潜力,对利用和促进太阳能热脱盐技术在无害化水处理领域的发展具有重要指导意义。更多还原

【Abstract】 With the continuous growth of the global population,the tension in the freshwater and energy crises has intensified,becoming a major constraint on the sustainable development of human economic and social systems.Seawater desalination is considered a crucial solution to alleviate freshwater shortages.Currently,traditional desalination technologies face multiple challenges,including high energy consumption,excessive carbon emissions,and severe environmental pollution.Under the context of developing"new quality productivity",the advancement of renewable energy-powered desalination technologies is regarded as one of the most promising strategies.Solar-driven interfacial evaporation technology directly utilizes solar energy to produce clean water and has been recognized as a feasible solution to water scarcity due to its simplicity,high efficiency,low cost,and easy deployment.However,salt crystallization during seawater evaporation remains a major factor limiting desalination performance.Additionally,if not properly treated,the concentrated brine produced during evaporation can also cause environmental pollution.To address these issues,this research focuses on the main themes of"salt-resistant evaporation system development-brine evaporation crystallization mechanism-zero liquid discharge applications of brine",developing a series of solar-driven interfacial evaporator systems with high salt resistance.The study investigates in depth the salt crystals growth behavior during the brine evaporation process and its impact on mass transfer,and proposes targeted strategies for controlling salt crystallization.These findings contribute positively to the development of zero-liquid discharge seawater desalination technologies.The main research achievements are as follows:（1）Based on the anti-polyelectrolyte effect of zwitterionic hydrogels,a biomimetic jellyfish-structured solar evaporator was fabricated using zwitterionic hydrogel（sulfonated betaine）,raw cotton fabric,and carbon black powder as raw materials through the freeze-drying method.Its efficiency for solar-driven interfacial evaporation desalination was investigated.Experimental results showed that the solar evaporator exhibited an interpenetrating fiber network structure,which effectively facilitated water transport.Under1 kW m^-2 solar radiation,it achieved a water evaporation rate of 2.158 kg m^-2 h^-1 and an energy efficiency of 88.71%.Additionally,the zwitterionic hydrogel carries both positive（-N（CH₃）₂⁺）and negative（-SO₃^-）ionic functional groups,which demonstrate an anti-polyelectrolyte effect in brine,inhibiting salt crystallization and improved the system’s stability.Furthermore,the solar evaporator also exhibited excellent water evaporation and antifouling capabilities in the treatment of complex wastewater,including acidic and alkaline wastewater,heavy metal-contaminated water,and oil-bearing brines.（2）Based on the Donnan effect charge balance principle,we selected natural balsa wood as a raw material,permeability was enhanced by removing lignin,and PVA and PAA hydrogels were in-situ polymerized within the wood pores,followed by surface carbonization treatment.This produced an anionic solar evaporator with enhanced Donnan effect.The aligned vascular bundle structure in the wood,coupled with the superhydrophilic nature of the hydrogel,significantly enhanced water transport efficiency.Moreover,the-COO-functional groups in the hydrogel further enhanced the Donnan effect,improving the system’s salt resistance.Experimental results showed that,under 1 kW m^-2 solar radiation,the anionic solar evaporator achieved a water evaporation rate of 2.439 kg m^-2 h^-1 when desalting a 15 wt%Na Cl solution.No obviously salt accumulation was observed over prolonged evaporation,and clean water was obtained from various polluted water sources.In outdoor experiments,enhancing air convection effectively promoted water vapor condensation,achieving system efficiency of 83.3%-115%.（3）Inspired by the phenomenon of thermohaline convection,a 2D planar structure solar interfacial evaporator and crystallizer was designed using PVA foam as a hydrophilic substrate and CNTs as the photothermal layer.The behavior of salt crystallization behavior during continuous evaporation was deeply explored to understand its impact on system performance based on temperature and salinity.Experimental results showed that the porous salt layer formed during evaporation severely reduced the system’s light absorption capability,and could only enhance evaporation rate in dark environments.Salt crystallization imitated at the lower temperature edge of the photothermal interface.Driven by the Marangoni effect,saltwater moved from the high-temperature center to the low-temperature edge,causing crystals to accumulate at the edge,expanding the low-temperature region until it covered the entire photothermal interface.Subsequently,saltwater preferentially evaporated within the salt layer from the low-temperature region to the high-temperature region,leading to salt layer growth at the water inlet,triggering secondary nucleation of salt crystals.This resulted in a compact bottom salt layer with more defined square-shaped crystals,lower porosity,and reduced evaporation efficiency.（4）Based on the aforementioned study,a 3D solar evaporator crystallizer with reverse evaporation capability was designed by physically separating the evaporation and photothermal interfaces using a high-conductivity aluminum plate.CNTs slurry was coated as a solar absorption layer on the bottom and inner walls,while the outer walls were combined with cotton fibers as the water evaporation and salt crystallization interfaces.This design effectively addressed the negative impact of salt crystals on the photothermal interface.The hydrophilic and porous characteristics of the cotton fibers allowed for rapid water transport.Micro-meniscus water structures formed between the staggered fiber arrangement enhanced the evaporation rate and Marangoni effect,promoting salt crystallization at the fiber tips.Comparing the continuous evaporation process of high-concentration Na Cl solution and seawater solution（20 wt%）,it was found that magnesium salts in concentrated seawater formed a glassy salt layer that blocked water transport channels,reducing evaporation performance.To resolve this,the addition of salt crystallization inhibitor MDC220 during evaporation resulted in a relatively loose,flake-like salt layer with improved specific surface area and porosity.After 48 hours of continuous evaporation of a 20 wt%concentrated seawater solution,the average water evaporation rate reached 1.42 kg m^-2 h^-1,enhancing operational stability of the evaporation system obviously.In summary,the research focuses on improving the management of the salt-water nexus in solar-driven interfacial evaporation seawater desalination technology.Starting from the development of efficient salt-resistant evaporation systems and the exploration of salt crystallization mechanism,the study thoroughly explores the applications potential of zero liquid discharge seawater desalination on the technology.The findings provide important guidance for the advancement and application of solar thermal desalination in environmentally friendly water treatment.更多还原