微尺度氧化石墨层状材料过滤过程中的自组装及逾渗现象的影响机制

The seepage phenomenon is the barrier for separation in the purification process of graphite oxide layer carbon materials, during the period of nanostructured carbon materials industrialization. The former research found molecular self-assemble exists in the purification and separation of micro scale graphite oxide layer carbon materials, and the graphite oxide molecular easily combines with water molecular become large molecular clusters through hydrogen bond after self-assembling, the suspension solution become to colloid, that means the seepage happened, when the forces reached to dynamic balance between the outside separation force and the bonding force between the graphite oxide particles, then it makes the filtrating separation process to stop. However, the other purification agents with lower polarity were used in the purification, rarely lead to seepage phenomenon. It means the polarity degree of purification agents molecular, the molecular structure and the surface function groups of graphite oxide, and the interaction between the purification agents and graphite oxide molecular effect the seepage switching threshold. In addition, it will influence the filtrating separation. What is the main influence mechanism needs to be revealed..This project intends to study the self-assembly process, microstructure features after self-assemble, the nature of the surface functional groups and solvation effects of micro scale graphite oxide layer carbon material in the different polarity purifying agents. Adjusting the type and quantity of metal ions in purification agents to change graphite oxide surface properties and research influence of the electric double layer effect on the seepage switching threshold, it will reveal the influence mechanism on filtrating seepage phenomenon of nanostructured carbon materials, establish a suitable theoretical model for the filtration process of micro scale materials, and promote the industrialization of nanostructured carbon materials.

纳米碳材料产业化进程中，氧化石墨层状碳材料分离纯化工艺中的逾渗现象导致分离过程受阻。前期研究发现微尺度氧化石墨层状材料在纯化分离过程中存在分子自组装现象，组装后的氧化石墨分子与水通过氢键紧密结合形成大的分子团簇，当外界分离作用力与氧化石墨颗粒之间的结合力达到动态平衡关系时，悬浮液发生逾渗转变成为胶体，导致过滤分离终止。而采用其它极性较低的纯化剂则不易出现逾渗现象，可见纯化剂分子极性与氧化石墨的分子结构及表面官能团之间的交互作用决定逾渗转变阈值，进而影响过滤分离过程，但具体影响机理亟待揭示。本项目拟研究微尺度氧化石墨层状材料在不同极性纯化剂中自组装过程及自组装后微观结构特性，表面官能团性质和溶剂化作用；调整纯化剂中的金属离子种类及数量和改变氧化石墨表面性质研究双电层效应对逾渗转变阈值的影响，揭示纳米碳材料过滤逾渗现象影响机制，建立适用于纳米微尺度材料过滤过程的理论模型，推动纳米碳材料产业化。

为了解决纳米碳材料产业化进程中，氧化石墨层状碳材料分离纯化工艺中的逾渗现象导致分离过程受阻的问题。本课题应用微观力学理论研究微尺度氧化石墨层状材料在不同溶剂中的分散力，自组装过程分子之间的作用力。将宏观力学理念应用到微观过程中，阐明微尺度氧化石墨材料溶剂化作用，双电层效应与逾渗转变的协同关系，将微尺度氧化石墨层状材料的溶剂化作用、固体颗粒堆积形成的微尺度通道对逾渗转变过程的影响与固液分离效果耦合，发现单个氧化石墨颗粒在不同极性纯化剂中自组装过程及自组装后微观结构特性与氧化石墨片层数、溶剂类型、溶剂数目和分子尺寸有关；其中单个氧化石墨颗粒的片层数随着层数越多，其结构越紧密，溶剂分子不容易进入层间；能够进入氧化石墨颗粒片层间的溶剂分子数目取决于分子三维尺寸的最小值，而混合溶剂中尺寸大的分子在增大氧化石墨层间距中发挥主导作用；在静态条件下随着浓度的增加，氧化石墨体系由独立的颗粒变为大面积连接的网络结构；在外力作用下，体系聚集结构的变化机理不同，低浓度的氧化石墨颗粒碰撞聚集到一起形成了大颗粒絮团，而高浓度的氧化石墨网络结构被破坏，分散聚集为大颗粒絮团；高浓度氧化石墨浆液属于非牛顿流体，呈现剪切变稀行为；对于低浓度的氧化石墨体系，颗粒发生碰撞聚集后相互作用变弱，粘度随着时间的增加而逐渐下降直到稳定状态；金属离子可以使氧化石墨层间距减小，排斥水分子，从而抑制氧化石墨浆液发生逾渗转变；研究氧化石墨在逾渗转变前后物性变化特点，发现电导率是表征逾渗转变的最显著的物性参数之一，通过监测电导率变化率判断体系是否发生逾渗转变；氧化石墨纯化过程中，为了避免体系发生逾渗转变通过添加CPAM减弱颗粒表面的溶剂化作用，形成连续的三维网状结构，导致架桥絮凝，容易实现固液分离纯化；开发了四隔室电渗析小试和中试设备，已经应用于山西煤化所的氧化石墨工业化生产的纯化环节。