Sorption Statics of Cr(VI), Mo(VI), W(VI), Se(IV) Oxygen Anions by Nanostructured Al2O3||C Composite

By the methods of thermodynamic modeling, sorption diagnostics, analysis of particle zeta-potential, and UV-Vis spectrometry the equilibrium conditions of sorption interaction of CrO42–, MoO42–, WO42–, SeO32– oxygen anions in the region of chemical stability of Al2O3||C composite have been analyzed. The anion sorption isotherms are shown to follow the Langmuir model for a monoenergetic sorbent. The Henry region is observed at concentrations less than 1 μM. According to the established mechanism of surface complexation, the value of anions protonation constant (K1) in the investigated pH range determines the sorption activity of the composite to these anions. This explains the correlation found between the ratio of parameters of acid–base sites {Al–O–}, {Al–HO0}, and {Al–OH2+} of composite KM(1,2) and the protonation constant of anion K1. It is shown that the Al2O3||C composite concentrates from dilute solutions both cations of d-, f-elements and oxygen anions of d-elements with the value of log Kd [mL/g] > 4, thereby exhibiting the properties of collective action sorbent.