Chemical Speciation of Environmentally Significant Metals With Inorganic Ligands. Part 5: The Zn2+ + OH–, Cl–, CO3 2–, SO4 2–, and PO4 3– Systems

Different binding modes of Cu and Pb vs. Cd, Ni, and Zn with the trihydroxamate siderophore desferrioxamine B at seawater ionic strength

“…Values of [H + ] T 0 vary randomly between a proton deficiency of~42 μM and an excess of~18 μM. Powell et al (2013) give pK S2 ≈ -12 (Table 1) in 0.2 M NaClO 4 for various polymorphs of Zn(OH) 2 (s). Solution compositions calculated by FITEQL indicate that undersaturation of at least a factor 5 was maintained with respect to these solids throughout all titrations.…”

“…Most were titrated with 0.1001 M NaOH, but several with M:L ratios of ≥1 were titrated with 1.0005 M NaOH to shorten the runs. Because Cd forms comparatively stable chloride complexes (Powell et al, 2011), an ancillary experiment was done in 0.7 M NaCl at a nominal M:L ratio of 0.5 for comparison with the titrations in NaClO 4 .…”

“…Within a set, 2 titrations each were performed at nominal M:L ratios of 0.25, 0.5, and 0.7, using 0.1001 M NaOH as the titrant. Two sets of 5 titrations were conducted for Pb, which forms comparatively stable chloride complexes (Powell et al, 2009;Easley and Byrne, 2011), one in 0.7 M NaClO 4 and one in 0.7 M NaCl. Within either set, 3 titrations were performed at a nominal M:L ratio of 0.5 and one each at M:L ratios of 0.25 and 0.7, using the Pb stock standard in 0.7 M NaClO 4 and 0.1001 M NaOH as the titrant.…”

“…The stability constant for the first hydroxide complex of Cd (Table 2) was taken from Powell et al (2011). Experiments with Cd were used for most of our method development.…”

“…Nonetheless, relative uncertainties of b1% in average log L β j values derived from the six titrations convey their good agreement. The stability constant for the first hydroxide complex of Zn (Table 2) was taken from Powell et al (2013). Six titrations with M:L ratios ranging from 0.25-0.7 are listed in Table S3.…”