【作者】 赵中原；

【导师】 关银燕；

【作者基本信息】 沈阳工业大学 ， 化学工程， 2022， 硕士

【摘要】 城市污水处理厂二级出水作为非常规水源,具有较好的经济效益和环境效益。其中未除去的盐,在回用时需进行处理。电容去离子技术由于其节能高效、无二次污染等优点,近几年受到广泛关注。但传统碳电极脱盐过程中存在同离子吸附问题,使脱附不完全,降低电极使用寿命及电荷效率。膜电容去离子技术,通过引入离子交换膜屏蔽共离子效应,改善离子脱附,克服传统电容去离子存在的问题。本论文以聚乙烯醇为基体,加入聚电解质,制备有离子交换特性的复合水凝胶,研究影响其力学性能主要因素及在含盐水中的结构稳定性。以复合凝胶为离子交换表层,制备具有离子交换特性的复合电极,通过电化学测试及脱盐测试,研究其做为膜电容去离子电极的应用效果。结果表明,复合凝胶的力学性能主要受交联剂用量影响,随着交联剂用量增加,储能模量增加,临近应变减小,凝胶韧性降低。加入聚电解质对复合凝胶的力学性能无显著影响,而对凝胶的离子交换容量及盐浓度响应性具有决定作用。随着聚电解质用量增加,凝胶离子交换容量增加,盐水中溶胀率增加,平衡盐浓度增加。制备的复合膜电极具有明显的双层复合结构,紧密结合的凝胶表层改善电极了亲水性,凝胶层中聚电解质的添加量对电极脱盐性能及电化学性能无显著影响。电化学测试发现,电极的最大比电容为113.55 F/g,50次循环后凝胶电极的比电容为112.73 F/g,无明显变化,表明电极具有较好的循环使用寿命。脱盐实验发现,复合电极脱盐量最大可达15.56 mg/g,电荷效率为64.6%。综上,凝胶膜复合电极有效的屏蔽了脱盐过程中的共离子效应及法拉第反应,改善了膜与电极的亲和性,展现较好的脱盐效果及循环稳定性。本论文的研究结果为开发具有良好循环稳定性和较高电荷效率的膜电容去离子电极提供了新的思路和方法。更多还原

【Abstract】 As an unconventional water source,the secondary effluent of municipal sewage treatment plant has good economic and environmental benefits.The unremoved salts need to be treated when reused.Capacitive deionization technology has received extensive attention in recent years due to its advantages of energy saving,high efficiency and no secondary pollution.However,there is a problem of same ion adsorption in the traditional carbon electrode desalination process,which makes the desorption incomplete,and reduces the service life and charge efficiency of the electrode.Membrane capacitive deionization technology,by introducing an ion exchange membrane,shields the common ion effect,improves ion desorption,and overcomes the problems of traditional capacitive deionization.In this thesis,polyvinyl alcohol was used as the matrix and polyelectrolyte was added to prepare the composite hydrogel with ion exchange properties.The main factors affecting its mechanical properties and the structural stability in saline were studied.Using the composite gel as the ion-exchange surface layer,a composite electrode with ion-exchange properties was prepared,and its application effect as a membrane capacitor deionization electrode was studied through electrochemical tests and desalination tests.The results show that the mechanical properties of the composite gel are mainly affected by the amount of cross-linking agent.With the increase of the amount of cross-linking agent,the storage modulus increases,the adjacent strain decreases,and the gel toughness decreases.The addition of polyelectrolyte has no significant effect on the mechanical properties of the composite gel,but has a decisive effect on the ion exchange capacity and salt concentration responsiveness of the gel.With the increase in the amount of polyelectrolyte,the ion exchange capacity of the gel increases,the swelling rate in brine increases,and the equilibrium salt concentration increases.The prepared composite membrane electrode has an obvious double-layer composite structure.The tightly bound gel surface improves the hydrophilicity of the electrode.The addition of polyelectrolyte in the gel layer has no significant effect on the desalination performance and electrochemical performance of the electrode.Electrochemical tests found that the maximum specific capacitance of the electrode was 113.55 F/g,and the specific capacitance of the gel electrode after 50 cycles was 112.73 F/g,with no significant change,indicating that the electrode has a good cycle life.The desalination experiment found that the maximum desalination capacity of the composite electrode was 15.56 mg/g,and the charge efficiency was 64.6%.In summary,the gel-membrane composite electrode effectively shields the common ion effect and Faradaic reaction during desalination,improves the affinity between the membrane and the electrode,and exhibits better desalination effect and cycle stability.The results of this paper provide new ideas and methods for developing membrane capacitive deionization electrodes with good cycling stability and high charge efficiency.更多还原