Enhanced thermal decomposition of CF4 by CaO over HCl-treated red mud/γ-Al2O3 composite

A composite material synthesized from HCl-treated red mud and γ-Al 2 O 3 (Al 1 HRM 2 ), was developed to enhance CF 4 decomposition in our previous study. However, its catalytic performance requires improvement, as it suffers from poor stability. In this study, the low-cost and anti-HF-corrosive CaO was utilized to further boost the material's CF 4 decomposition efficiency and stability. Specifically, decomposition efficiency and stability increased by 30% and 2.25 times than that of Al 1 HRM 2 , respectively. At the microscopic level, it was observed that after CaO uniformly distributed across the catalyst surface, it enhanced the Al-O (Al-O-Al) stretching vibration, increased the number of oxygen vacancies, and simultaneously prevented the phase transition from γ to α. Additionally, CaO intensifies the characteristic peaks of strong L-acid sites, enhancing their CF 4 adsorption capacity and strength. Specifically, Al Ⅲ sites facilitate C-F bond cleavage to form AlF 3 , which undergoes fluorine-oxygen exchange with CaO to produce CaF 2 . This process effectively inhibits F + occupation of γ-Al 2 O 3 active sites, thereby promoting CF 4 decomposition. This study utilizes RM as a high-performance material for CF 4 pollution control, achieving the goal of treating waste with waste across the aluminum industry supply chain. It provides a new technological foundation for purifying difficult-to-treat Perfluorocarbons greenhouse gases.