近日，华中农业大学工学院晏水平教授课题组研究成果以“Feasibility and mechanism of an amine-looping process for efficient CO2 mineralization using alkaline ashes”为题在Chemical Engineering Journal发表。研究构建了用于沼气中CO2吸收与矿化固定的“碱性固废-有机胺-水”新体系，系统阐释了有机胺在碱性固废CO2矿化过程中的作用机理，并探究了反应后碱性固废后续利用的可能性，为CO2排放控制提供了新思路。
CO2捕集、利用和封存技术是实现3060双碳目标的重要技术之一。利用工业生产中产生的碱性固废进行CO2矿化，不仅可实现CO2减排，还能实现CO2的永久固化。但传统固废CO2矿化技术存在碱土金属氧化物和CO2在水中溶解过程缓慢且溶解度较低的问题亟待解决。基于此，该研究利用碱性固废作为钙源，利用有机胺溶液作为反应溶剂，构建了“碱性固废-有机胺-水”新反应体系，并用于沼气中CO2吸收，最终实现CO2的高效脱除。
碱性固废CO2矿化性能的有机胺强化新机制示意图
该研究系统阐释了有机胺在碱性固废CO2矿化过程中的作用机理：首先，有机胺可直接与CO2结合生成氨基甲酸酯，实现CO2从气相向液相的快速转移，气液间的CO2传质得到强化，不仅提高了体系对沼气中CO2的脱除效率，还能为碳酸钙沉淀生成提供更高浓度的碳源；其次，有机胺与CO2反应的同时，还会生成质子化的有机胺，可为碱性固废中钙离子溶出提供氢离子，同时，未反应的有机胺可与溶出的钙离子进行弱配位螯合，进一步降低溶液中钙离子的自由度，从而强化钙离子的浸出；最后，有机胺可通过吸附作用，参与碳酸钙结晶沉淀过程，从而调控固废中碳酸钙新生物相的晶型形貌。
此外，通过碳酸钙的沉淀反应，可将体系生成的氨基甲酸酯和质子化有机胺原位再生为有机胺，可实现CO2的循环吸收。
华中农业大学工学院副教授纪龙为论文的第一作者，晏水平教授为通讯作者。该研究得到了国家自然科学基金、湖北省自然科学基金、中央高校基本业务经费等项目资助。
审核人：晏水平
【英文摘要】
Amine-looping-based CO2 mineralization is a promising technology for simultaneous CO2 absorption, mineralization, and carbonate crystallization in a single step. This paper performed a detailed investigation of the feasibility and underlying mechanism of the amine-looping process using industrial alkaline solid wastes, including one Biomass ash (BA) and two coal-fired fly ashes named FA1 and FA2. The CO2 sequestration capacity and CO2 removal efficiency of selected ashes were investigated in five typical amine solutions, including monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), 2-amino-2-methy-1-propanol (AMP), and piperazine (PZ). The physicochemical property of ashes before and after carbonation and the dissolution of alkaline minerals in various amine solutions were systematically determined to explore the underlying mechanism involved in the amine-looping process. Results show that greater improvement in CO2 removal efficiencies and CO2 sequestration capacities were obtained by selected ashes in amine solutions compared to the traditional CO2 mineralization in the water-ash-CO2 system. It also revealed that amines played important roles in promoting CO2 mass transfer, enhancing Ca2+ leaching, and producing small-sized CaCO3. The largest CO2 sequestration capacity (102.9 g/kg) was achieved by FA1 in PZ solution which was suggested as the preferred solvent for the amine-looping process. In addition, the environmental risk of carbonated ashes for agricultural application in terms of amine loss and phytotoxicity was evaluated. Results implied that the phytotoxicity of carbonated BA could be neglected when a simple centrifugal wash was used to remove the absorbed amine on the surface of carbonated BA whilst the phytotoxicity of selected ashes can be significantly reduced after carbonation reactions.
论文链接：
https://doi.org/10.1016/j.cej.2021.133118