Optimizing Sustainability and Profitability: A Multi-Step Approach to the Synthesis of X-Zeolite from Blast Furnace Slag

Abstract

To further unlock the circular economy potential of iron and steel industry and achieve peak carbon and carbon neutrality targets, this study provides a comprehensive analysis of the high value-added use of blast furnace slag (BFS) for the synthesis of X-type zeolite. The thermodynamic and dissolution behaviors during acid leaching are investigated through theoretical analysis, identifying the optimal pH is 0~1.63 and Eh is -1.01~2.00V. Experiments determine that there are obvious improvement in silica gel leaching ratio at 353K, 4mol·L-1 HCl and V(HCl):m(slag) ratio of 12:1. Obtained silica gel has 91.56% whiteness and 86.86% SiO2. The optimal conditions for X-type zeolite synthesis are crystallization at 363K for 6h, with n(SiO2):n(Al2O3), n(Na2O):n(SiO2) and n(H2O):n(Na2O) establishes as 2.8, 2.8 and 45 respectively and resulting material has high crystallinity, purity of crystals and excellent performance. Furthermore, the mechanism is elucidated from the perspective of microstructural and molecular level. Economic evaluation along with carbon tax assessment indicated that it is economically beneficial both in direct profit and potential CO2 capture. These findings emphasize the feasibility, efficacy and economy of X-type zeolite synthesis from BFS, which contributes to turning waste into treasure and promoting the concept of “Green steel”.