多孔碳在CO2吸附方面展现出优异性能，是CO2捕集与封存的重要手段之一，对实现“碳达峰、碳中和”目标具有重要意义。以3种典型中药固废——板蓝根渣、甘草渣和大血藤渣为例，探究中药固废掺氮水热碳化-化学活化两步法制备多孔碳及其CO2吸附性能。水热法可省略对中药固废预先干燥的环节，适应中药固废高含水率的特点；化学活化法采用KOH作为活化剂，在高温（试验温度为600、700和800 ℃）下进行活化；制备工艺采用尿素为表面改性剂，将氮掺杂在多孔碳表面以提高吸附性能。采用元素分析和XPS对水热碳和多孔碳进行测试，探究氮在多孔碳表面的掺杂情况，结果表明N已成功掺杂到多孔碳表面，且掺氮多孔碳在相同制备条件下表现出更丰富的孔隙结构和更优异的吸附性能，含氮官能团对多孔碳的吸附性能有积极作用；为比较不同活化温度下制备的多孔碳吸附性能的差异，对其吸附CO2能力进行研究，采用Langmuir和Freundlich模型拟合CO2吸附等温线，结果发现3种试验温度下，600 ℃活化的多孔碳CO2吸附性能最佳，这是由于高温活化导致氮流失对吸附性能产生不利影响。3种原料制得的多孔碳比表面积最大分别为2 516、2 518和1 996 m2/g，孔隙结构丰富；在600 ℃活化温度下，3种原料制备的多孔碳均表现出良好的CO2吸附能力，其吸附容量分别为6.70、6.52和6.43 mmol/g，这表明对于不同种类的中药渣采用水热同步掺氮和化学活化均可获得良好的CO2吸附能力，但原材料对CO2/N2选择性仍有较大影响。

Porous carbon has shown excellent performance in CO2 adsorption which is one of the important methods for CO2 capture and storage. It is important to achieve the goal of "peak carbon dioxide emissions" and "carbon neutrality". Taking three typical traditional Chinese medicine solid wastes that isatis root residue, licorice residue and Caulis Spatholobi residue as examples, the preparation of porous carbon from traditional Chinese medicine solid waste by nitrogen doped hydrothermal carbonization chemical activation two-step method was explored, as well as its CO2 adsorption performance. Hydrothermal method eliminates the pre drying of traditional Chinese medicine solid waste and adapts to the characteristics of high moisture content of traditional Chinese medicine solid waste. KOH was used as activator in chemical activation method, and it was activated under high temperature environment (experimental temperature is 600, 700 and 800 ℃). Urea was used as surface modifier in the preparation process, and N was doped on the surface of porous carbon to improve the adsorption performance. In order to explore whether N is doped on the surface of porous carbon, hydrothermal carbon and porous carbon were tested by elemental analysis and XPS. The results show that N has been successfully doped on the surface of porous carbon. Through the analysis of the experimental results, nitrogen doped porous carbon shows richer pore structure and better adsorption performance under the same preparation conditions, which means that nitrogen-containing functional groups have a positive effect on the adsorption performance of porous carbon. In order to compare the adsorption properties of porous carbon prepared at different activation temperatures, its CO2 adsorption capacity was studied. Langmuir and Freundlich models were used to fit the CO2 adsorption isotherm. The results show that compared with 700 and 800 ℃, the porous carbon activated at 600 ℃ has better CO2 adsorption performance due to the loss of N caused by high temperature activation, which has an adverse effect on the adsorption performance. In general, the porous carbon obtained has rich pore structure, and the specific surface areas of the porous carbon prepared from the three raw materials are 2 516，2 518 and 1 996 m2/g, respectively. At the activation temperature of 600 ℃, the porous carbon prepared from the three raw materials shows good CO2 adsorption capacity, which are 6.70, 6.52 and 6.43 mmol/g, respectively. It means that the effect of hydrothermal simultaneous nitrogen doping and chemical activation on the CO2 adsorption capacity of the prepared porous carbon can be reduced, but the raw materials still have a great impact on the CO2/N2 selectivity.

0 引言

1 试验材料与方法

   1.1 多孔碳的制备

   1.2 样品表征与测试

2 结果与讨论

   2.1 中药固废基多孔碳物理特性

   2.2 化学特性分析

   2.3 中药固废基多孔碳CO2吸附性能

3 结论