新型多层次孔结构泡沫炭高效吸附材料的制备及形成机制

The investigation of carbon materials with hierarchically porous structure has become the important frontier and hot issue in the field of materials science. At present powdered or granular porous carbon adsorption materials used confront the problems like slow adsorption rate, low separation efficiency, difficult recovery and dust pollution. Therefore, the development of hierarchically porous materials with highly efficient adsorption performance is of important scientific significance and practical value, which possess appropriate porous structure, large specific surface area, high pore volume, easy forming characteristic and relatively high mechanical strength. In this project, a carbon foam with two-stage cell structure and high mechanical strength was prepared with epoxy resin and isocyanate as raw material and nano-MgO as additive by performing a series of procedures including prepolymerization, casting, curing, carbonization and pickling, and then activated by KOH at middle-low temperature to achieve a novel hierarchically porous carbon foam adsorption material with highly efficient adsorption performance. Self-foaming behavior during pyrolysis and carbothermal reduction behavior at high temperature of nano-MgO/epoxy-modified isocyanate resin composite were studied to reveal both the development of two-stage cell structure of the carbon foam and the formation mechanism of cell structure in its cell wall. In addition, influence of preparation process on the structures and properties of the resulting adsorption material was investigated to ascertain the activation mechanism as well as the adsorption mechanism, and thus put forward the theory ofits structural design and controllable preparation.

多层次孔结构炭材料研究是材料学科中的重大前沿和热点问题。目前粉(粒)状多孔炭吸附材料使用过程中存在吸附速度慢、分离效率低、回收难、粉尘污染等问题，开发各级孔道匹配合理、比表面积高、孔体积大、易成形并具有一定机械强度的多层次孔结构泡沫炭高效吸附材料具有重要的科学意义和实用价值。本项目提出以环氧树脂和氰酸酯为原料、纳米氧化镁为添加剂，经过预聚、浇注、固化、炭化、酸洗等步骤制备具有独特两级孔泡结构和较高机械强度的泡沫炭样件，然后采用中低温活化工艺制备新型多层次孔结构泡沫炭高效吸附材料。通过研究纳米氧化镁/环氧改性氰酸酯树脂复合物的热解自发泡行为和碳热反应行为以及制备工艺对多层次孔结构泡沫炭结构与性能的影响规律，揭示泡沫炭两级孔泡结构的演变过程，建立泡沫炭孔壁的孔泡形成机制和高效活化机理，探明这种多层次孔结构泡沫炭的吸附作用及机理，并提出其结构设计与可控制备理论。

多层次孔结构炭材料研究是材料学科中的重大前沿和热点问题。目前粉(粒)状多孔炭吸附材料使用过程中存在吸附速度慢、分离效率低、回收难、粉尘污染等问题，开发各级孔道匹配合理、比表面积高、孔体积大、易成形并具有一定机械强度的多层次孔结构泡沫炭高效吸附材料具有重要的科学意义和实用价值。本项目提出以环氧树脂和氰酸酯为原料、纳米氧化镁为添加剂，经过预聚、浇注、固化、炭化、酸洗等步骤制备具有独特两级孔泡结构和较高机械强度的泡沫炭样件，然后采用中低温活化工艺制备新型多层次孔结构泡沫炭高效吸附材料，在此基础上制备出表面带有石墨烯状纳米片的多层次硬质泡沫炭、两级大孔装填氧化锌颗粒的硬质氧化锌/泡沫炭复合物、双重氧化镁负载泡沫炭和表面氧化的多层次泡沫炭。研究结果表明：环氧改性氰酸酯树脂在热解过程首先形成一级大孔，在一定温度下纳米氧化镁与泡沫炭基体发生碳热还原反应形成二级孔，再经过后期KOH活化后泡沫炭表面形成蓬松多孔的结构；这种多层次泡沫炭具有较高的开孔率和孔隙率（分别为98.9 %和95.7 %），但是其仍然具有较好的骨架结构（极限压缩强度为0.74 MPa），对孔雀石绿(MG)和Pb(II)的实验最大吸附量分别为587.68 mg g-1和157.80 mg g-1，分配系数值分别为17.41 mg g-1 µM-1和14.86 mg g-1 µM-1，且五次循环后对MG和Pb(II)的去除率能够保持在90 %以上，此外，所制备的表面改性泡沫炭及泡沫炭复合物亦兼具良好吸附性能以及循环特性；上述泡沫炭基吸附剂材料的吸附过程均更适合Langmuir等温线模型和准二级动力学模型，说明吸附是以单分子层的化学吸附为主，分离因子RL均在0 ~ 1之间。