Zhiyuan Song,Zainab Bibi,Sidra Chaudhary,Qinxiang Jia,Xiaoyong Li,Yang Sun
A water-soluble ternary copolymer bearing carboxyl, sulfonic, and amide functional groups was synthesized using ammonium persulfate-catalyzed free radical polymerization in water, resulting in high monomer conversion. This copolymer was then complexed with aluminum sulfate, forming an admixture containing Al(SO 4 )(OH)·5H 2 O, which was subsequently combined with silica gel. Characterization revealed that the synthesized copolymer formed a large, thin membrane that covered both the aluminum compounds and the silica gel blocks. The introduction of this complex admixture, combining the copolymer and aluminum sulfate, not only reduced the setting times of the cement paste but also enhanced the mechanical strengths of the mortar compared to using aluminum sulfate alone. The complex admixture led to the formation of katoite, metajennite, and C 3 A (tricalcium aluminate) in the mortar, demonstrating significant linking effects, whereas pure aluminum sulfate could not completely transform C 3 S within 24 h. Further addition of silica gel to the complex admixture further shortened the setting times of the paste, slightly reduced compressive strength, but improved flexural strength compared to the initial complex admixture. The silicon components appeared to fill the micropores and mesopores of the mortar, accelerating cement setting and enhancing flexural strength, while slightly decreasing compressive strength. This study contributed to the development of new cementing accelerators with improved hardening properties.
Alum is an important intermediate for the extraction and purification of Cs or Rb chemicals, due to its excellent separation ability for Cs, Rb and K. Although the solubility sequence K-alum > Rb-alum > Cs-alum has been well known, the separation factors among Cs, Rb and K during the formation of alum have not been determined. The formation of solid solution of alum controls the Cs or Rb content and Cs/Rb/K ratio in the sequentially precipitated Cs, Rb and K alums. In this study, the thermodynamic equilibrium separation factors were determined from the solid solution-aqueous solution equilibrium data of the two mixed alum systems: (i) RbAl(SO 4 ) 2 , CsAl(SO 4 ) 2 , and H 2 O, and (ii) KAl(SO 4 ) 2 , RbAl(SO 4 ) 2 and H 2 O. The separation factor β Cs/Rb varied from 48 to 2 with the increase of the Rb/Cs ratio in system (i), and β Rb/K varied from 22 to 0.2 with the increase of the K/Rb ratio in system (ii). This suggests that the purification of Cs or Rb using alums is more efficient from raw materials containing high Cs/Rb or Rb/K ratio than that from low Cs/Rb or Rb/K ratio. In kinetic studies, the apparent separation factors β Cs/Rb and β Rb/K were highly affected by the recrystallization process of cooling or non-cooling and the initial composition of raw alum, showing asymmetric kinetic intensification. The separation factors β Cs/Rb or β Rb/K obtained in the “dissolution by heating and crystallization by cooling (DHCC)” process for the raw alum with high initial Cs/Rb or Rb/K molar ratio is several times larger than the equilibrium value expected from thermodynamics. Finally, CsAl(SO 4 ) 2 and RbAl(SO 4 ) 2 with a metal-based purity of 99.97 % and 99.94 %, respectively, were obtained by using the DHCC process 3–4 times.
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