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.
Degradation of diethyl phthalate (DEP) by ultraviolet/persulfate (UV/PS) process at different reaction conditions was evaluated. DEP can be degraded effectively via this process. Both tert-butyl (TBA) and methanol (MeOH) inhibited the degradation of DEP with MeOH having a stronger impact than TBA, suggesting sulfate radical ( ) and hydroxyl radical (HO ) both existed in the reaction systems studied. The second-order rate constants of DEP reacting with and HO were calculated to be ( 6.4 ± 0.3 ) × 10 7 M −1 s −1 and ( 3.7 ± 0.1 ) × 10 9 M −1 s −1 , respectively. To further access the potential degradation mechanism in this system, the pseudo-first-order rate constants (k o ) and the radical contributions were modeled using a simple steady-state kinetic model involving and HO . Generally, HO had a greater contribution to DEP degradation than . The k o of DEP increased as PS dosages increased when PS dosages were below 1.9 mM. However, it decreased with increasing initial DEP concentrations, which might be due to the radical scavenging effect of DEP. The k o values in acidic conditions were higher than those in alkaline solutions, which was probably caused by the increasing concentration of hydrogen phosphate (with higher scavenging effects than dihydrogen phosphate) from the phosphate buffer as pH values rose. Natural organic matter and bicarbonate dramatically suppressed the degradation of DEP by scavenging and HO . Additionally, the presence of chloride ion (Cl − ) promoted the degradation of DEP at low Cl − concentrations (0.25–1 mM). Finally, the proposed degradation pathways were illustrated.
危险品化学品经营许可证（带存储）