Study on the synthesis mechanism of sodalite, gismondine, and zeolite-P1 zeolite materials from ladle furnace slag and fly ash.

In this study, geopolymers were prepared using ladle furnace slag (LFS) and fly ash (FA), and hydrothermal treatment was then used to synthesize bulk zeolite molecular sieves with gismondine, zeolite-P1, and sodalite phases. The effect of the synthesis conditions on the crystalline phases of the zeolite molecular sieves was investigated by XRD. The results showed that the best zeolite molecular sieves were prepared with an LFS: FA ratio of 4: 6, a curing temperature of 40 °C, a curing time of 12 h, a sodium silicate modulus (Ms) of 1.4, a NaOH concentration of 4 mol/L, a hydrothermal temperature of 120 °C, and a hydrothermal time of 12 h. On this basis, the products were analyzed by SEM, N2 adsorption, and FT-IR. The results showed that the synthesized zeolite molecular sieves had mesoporous properties, and the degree of polymerization and cross-linking of the silica-aluminate gel were enhanced after hydrothermal treatment. In addition, the formation mechanism of the zeolite molecular sieves was explored through the changes of the silica-alumina during zeolite formation. This paper is the first to use the hydrothermal conversion of zeolite molecular sieves from LFS-FA based polymers to provide some guidance for the resource utilization of LFS and FA.

Synergistic effect of hydration and carbonation of ladle furnace aslag on cementitious substances.

Ladle furnace slag (LFS) can undergo hydration and carbonation reactions as cement. This article explores the effect of LFS hydration and carbonation reactions on cementitious substances at different temperatures and different LFS particle sizes, determining the effect of these varying conditions on the microstructure and formation mechanism of cementitious substances. The results show that in the early stages, C2S and C3S undergo hydration to generate C-S-H gel, which then undergoes decalcification and condensation to generate CaCO3 and Ca-deficient C-S-H gel; the hydration reaction and carbonation reaction promote and influence each other. The increase in temperature was found to hinder the formation of CaCO3 from Ca2+ and CO32-, thus reducing the efficiency of hydration carbonation. The increase in particle size was not conducive to the leaching of C2S and C3S to the surface of the reaction phase, which in turn reduced the degree of decalcification and polymerization of the C-S-H gel in the carbonation phase. It was concluded that the optimum LFS hydration and carbonation reactions were achieved at 20 °C and with a LFS particle sizes < 38 µm.

[Characteristics and mechanism of sodium removal by the synergistic action of flue gas and waste solid].

The carbon dioxide (CO2) in flue gas was used to remove the sodium in the red mud (RM) , a kind of alkaline solid waste generated during alumina production. The reaction characteristics and mechanism of sodium removal by the synergistic action of CO2 and RM were studied with different medium pH, reaction time and temperature. It was demonstrated that the remove of sodium by RM was actually the result of the synergistic action of sodium-based solid waste in RM with the CO2-H2O and OH(-)-CO2 systems. The sodium removal efficiency was correlated with pH, reaction temperature and time. The characteristics of RM before and after sodium removal were analyzed using X-ray diffractometer (XRD) and scanning electron microscope (SEM), and the results showed that the alkaline materials in the red mud reacted with CO2 and the sodium content in solid phases decreased significantly after reaction. The sodium removal efficiency could reach up to 70% with scientific procedure. The results of this research will offer an efficient way for low-cost sodium removal.