Study of a coal fly ash-based integrated CO₂ capture-mineralization material: Preparation method, modification...

Utilizing industrial solid waste for CO₂ mineralization not only reduces CO₂ emissions but also promotes the resource utilization of solid waste. Additionally, it allows for the permanent sequestration of CO₂ and enables green value-added utilization of the products. Coal fly ash (CFA) is one of the most abundant industrial solid wastes with significant carbon mineralization potential. To overcome the challenge of inefficient direct CO₂ mineralization by CFA, this study investigated the preparation of novel integrated CO₂ capture-mineralization materials (ICCM) with flower-like cluster structures through the modification of CFA. The active Al and Si in CFA were activated to form minerals with high specific surface area, such as ettringite (AFt) and calcium silicate hydrate (C-S-H), which were also susceptible to carbonation. These minerals formed a flocculent structure, enabling the ICCM to possess both CO₂ capture and in-situ mineralization capabilities. Experimental studies investigated the effects of CFA content, mineral attractant (MA), and alkaline substances on the physicochemical properties of ICCM, obtaining optimal modification conditions for ICCM preparation. Further orthogonal experiments explored the effects of flue gas temperature, humidity, and CFA content on the capture and mineralization of CO₂ by ICCM, identifying humidity as a primary factor. Under optimal conditions, each gram of ICCM could adsorb and mineralize 48 mg of CO₂. After carbonation, ICCM generated nano-sized calcium carbonate, predominantly in the form of calcite, with minor amounts of vaterite. This study provided a new type of solid waste-based green material and theoretical support for carbon mineralization, serving the development of Carbon Capture, Utilization and Storage technology.