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 mu M. According to the established mechanism of surface complexation, the value of anions protonation constant (K-1) 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 K-M(1,2) and the protonation constant of anion K-1. 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 K-d [mL/g] > 4, thereby exhibiting the properties of collective action sorbent.