Spectrophotometric determination of stability constants of n-butyrate and 2-, 3- and 4-hydroxybutyrate of cobalt(II), nickel(II) and copper(II)

Solubility of Ca(ii), Ni(ii), Nd(iii) and Pu(iv) in the presence of proxy ligands for the degradation of polyacrylonitrile in cementitious systems

“…A limited number of experimental studies are available in the literature reporting on the complexation of Ni(II) with GLU, HIBA and HBA. [57][58][59][60] All these studies were performed in acidic to near-neutral pH conditions, and thus report the formation of 1 : 1, 1 : 2 and up to 1 : 3 complexes of the unhydrolyzed Ni 2+ cation with these ligands. The incorporation of these complexes and corresponding equilibrium constants to the thermodynamic calculations confirm that in the hyperalkaline conditions of interest in this work, these complexes cannot outcompete Ni(II) hydrolysis and thus cannot explain the slight increase in the solubility of β-Ni(OH) 2 (cr) observed at [L] tot ≥ 10 −2 M. This leads to the assumption that hydroxide participates also in the complexation process, and thus the formation of ternary complexes Ni(OH) x L -x (GTA) or Ni(OH) x L −yH 1−x−y (HIBA and HBA, with y = 0 or 1) is proposed on the basis of the observed solubility enhancement.…”

“…In this overall research context, the present contribution evaluates the impact of the aforementioned proxy ligands on the solubility of key elements and radionuclides in porewater conditions representative of the degradation stage II of cement, i.e. pH ≈ 12.5 and [Ca] ≈ 0.02 M. Calcium has been selected as one of the main elements in cement systems, whereas nickel (as 59 Ni and 63 Ni) and plutonium (as 239 Pu) are considered in this study as important contributors to the radiotoxicity of the waste in L/ILW. 17 Neodymium is taken as inactive and redox-stable analogue of key trivalent actinides, e.g.…”