Borate complexes of X-ray iodinated contrast agents: Characterization and sorption studies for their removal from aqueous media

Boric Acid Induced Transient Cross-Links in Lactose-Modified Chitosan (Chitlac)

“…At variance, when the convex curvature regime of the Scatchard plot was reached, Hill plot displayed an α H of 0.90, pointing to an anti-cooperative binding of the boric acid and the association constant resulted to be 165. As expected, the two (limiting) association constants were found to be very similar and in line with values reported both for binding of divalent ions on pectin and of boric acid to a synthetic polymer containing deoxylactitol, while being higher than the binding constants between diols and boric acid previously reported . Similarly, the present K assoc results were larger than those reported by Pezron et al for the formation of complexes between borax and galactomannan. , Figure S3 in the Supporting Information shows the effect of the temperature over the association constant, K assoc , as determined by 11 B NMR, i.e., in conditions where the positive cooperative process is likely to prevail.…”

“…As expected, the two (limiting) association constants were found to be very similar and in line with values reported both for binding of divalent ions on pectin and of boric acid to a synthetic polymer containing deoxylactitol, while being higher than the binding constants between diols and boric acid previously reported . Similarly, the present K assoc results were larger than those reported by Pezron et al for the formation of complexes between borax and galactomannan. , Figure S3 in the Supporting Information shows the effect of the temperature over the association constant, K assoc , as determined by 11 B NMR, i.e., in conditions where the positive cooperative process is likely to prevail. The calculation according to a simple van’t Hoff model of the Δ H and Δ S for the initial binding process (i.e., in conditions of an excess of polymer) provided the following data: Δ H b = −23.3 ± 1.2 kJ/mol and Δ S b = −37.7 ± 2.1 J/(mol K), thus being comparable with those of complexes between diols and boric acid at slightly higher pH values .…”

“…The calculation according to a simple van't Hoff model of the ΔH and ΔS for the initial binding process (i.e., in conditions of an excess of polymer) provided the following data: ΔH b = −23.3 ± 1.2 kJ/mol and ΔS b = −37.7 ± 2.1 J/(mol K), thus being comparable with those of complexes between diols and boric acid at slightly higher pH values. 27 The free energy variation of initial binding at 25 °C was ΔG b = −12.7 kJ/mol, which corresponds to a K assoc of 168, in line with the one experimentally determined by CD and UV−vis at 25 °C, thus demonstrating that the linear interpolation was acceptable. In fact, the bare application of the van't Hoff treatment corresponds to arbitrarily setting the α H parameter of the Hill treatment equal to 1.…”

“…Similarly, the present K assoc results were larger than those reported by Pezron et al for the formation of complexes between borax and galactomannan. , Figure S3 in the Supporting Information shows the effect of the temperature over the association constant, K assoc , as determined by 11 B NMR, i.e., in conditions where the positive cooperative process is likely to prevail. The calculation according to a simple van’t Hoff model of the Δ H and Δ S for the initial binding process (i.e., in conditions of an excess of polymer) provided the following data: Δ H b = −23.3 ± 1.2 kJ/mol and Δ S b = −37.7 ± 2.1 J/(mol K), thus being comparable with those of complexes between diols and boric acid at slightly higher pH values . The free energy variation of initial binding at 25 °C was Δ G b = −12.7 kJ/mol, which corresponds to a K assoc of 168, in line with the one experimentally determined by CD and UV–vis at 25 °C, thus demonstrating that the linear interpolation was acceptable.…”