基于新型石墨烯/碳量子点复合材料的微污染饮用水电吸附深度脱砷铅研究

Low concentration of arsenic and lead in micro-polluted drinking water sources can harm human health. Compared with the traditional treatment methods on advanced removal of arsenic and lead, the capacitance deionization electrosorption technology has the advantages of high efficiency, low cost and low energy. Preparation of electrosorption materials with high conductivity, large specific surface area and high activity, improvement in wettability of electrodes and clearing the structure-activity relationship between the microstructure of the electrode and the ion adsorption are the research hotspots. Starting from the design of the micro graded porous structure and electrochemical activity of the electrode, this project will controllable construct the new type of graphene / nitrogen loaded carbon quantum dots nano-material with zero-dimensional / two-dimensional structure. On the basis of using this material to mix ink, we precisely bionic construct the electrode interface and establish a new method based on inkjet printing technology to prepare low ionic transport resistance and interface polarity controllable electrode. Additionally, this electrode is used to assemble the capacitance deionization system and the influence rules of hydrodynamics, electrochemical conditions and the same ion effect on the removal performance of arsenic and lead by electrosorption are thoroughly analyzed. Meanwhile, a theoretical model is built to simulate the electrosorption process. Based on these studies, the mechanism between the electrode microstructure regulation and the electrosorption performance response is obtained. This work will not only realize the large-scale and integrated construction of capacitance deionization electrode with high ion removal performance, but also provide theoretical basis and technical support for the safety of drinking water.

微污染饮用水水源中存在的低浓度砷、铅会危害人体健康。与传统的深度脱砷、铅技术相比，电容去离子电吸附技术具有高效、低成本、低能耗等优势。制备高导电性、大比表面积、高活性的电吸附材料，改善电极润湿性，理清电极微观结构与离子吸附之间的构效关系是国内外研究热点。本项目从设计电极微观分级多孔结构和电化学活性入手，可控构筑零维/二维结构精密复合的石墨烯/氮负载碳量子点新型纳米材料。用此材料调配油墨，仿生构建电极微界面，建立基于喷墨打印技术制备低离子运输阻力和界面极性可控电极的新方法。将电极组装进电容去离子系统，全面分析流体力学、电化学条件、同离子效应等因素对电吸附去除砷、铅性能的影响规律，结合模型模拟电吸附过程，阐明电极微观结构调控与电吸附性能响应间的作用机理发展规律。为实现大规模、集成化，高性能的电容去离子电极构筑和饮用水安全保障提供了理论依据和技术支撑。

本项目以电容去离子（CDI）技术高效、低成本深度处理微污染饮用水中低浓度砷、铅为目标，从精确构筑新型石墨烯基复合电极材料，构建电极微界面仿生形貌，探究吸附性能影响因素及吸附机制等方面重点开展了研究工作。（1）以柠檬酸和聚酰胺-胺树枝状聚合物为原料合成氮负载碳量子点，与氧化石墨烯混合后水热法构筑“点-面”新型石墨烯/碳量子点（rGO/NCDs）复合材料。通过形貌结构、电化学性能表征，证明NCDs的掺杂有效改善复合材料孔隙结构和电化学性能，提高离子传输速率，rGO/25%NCDs比表面积达到347.65m2/g，孔容0.342cm3/g，比电容达到284F/g（扫速10mV/s）。（2）采用静电纺丝技术制备“点-线-面”柔性自支撑CDI电极，电极表面呈现微/纳尺寸“鱼鳞状”仿生分级粗糙结构。rGO/25%NCDs电极具有超亲水性和双电层电容特性。（3）外加电压、初始离子浓度、循环流速、温度和电极间距等因素均对电吸附容量产生影响。rGO/25%NCDs电极对铅、砷的吸附量可达到19.26mg/g，15.07mg/g，远优于文献报道。rGO/25%NCDs电极具有优异的循环再生吸附性能，循环10次性能降低<7%。同离子电吸附选择性影响顺序为：浓度>价态>水合半径。rGO/25%NCDs电极脱除微污染（5mg/L）饮用水中砷、铅能耗低于0.4kWh/kg，低于文献报道结果。（4）采用等温吸附模型、吸附动力学、热力学模型、分子模拟等方法分析吸附过程，探究砷、铅CDI吸附机制。结果表明rGO与rGO/25%NCDs电极脱铅、砷为单分子层均匀吸附行为，以物理吸附为主。电吸附过程放热，可自发进行，并且是一个混乱度减小的过程。N参与了砷、铅的吸附，伴随着轻微氧化反应。大部分高毒性As（III）在阳极吸附后被氧化成低毒性As（V），在电极表面同时存在As（III）和As（V）的吸附。本项目研究成果对推动CDI技术大规模、集成化、高性能深度处理微污染水、保障饮用水安全提供技术支撑。