Modeling the Adsorption of Mercury(II) on (Hydr)oxides: I. Amorphous Iron Oxide and α-Quartz

• Published in: Journal of colloid and interface science 1995-06, Vol.172 (1), p.82-93
• Main Authors: Tiffreau, Christophe, Lützenkirchen, Johannes, Behra, Philippe
• Format: Article
• Language: English
• Subjects: adsorption modeling; Chemistry; chloride ions; diffuse layer model; Exact sciences and technology; ferrihydrite; General and physical chemistry; hydrous ferric oxide; mercury(II); Solid-liquid interface; solid-water interface; surface complexation; Surface physical chemistry; surface precipitation; α-quartz
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.1995.1228

In this study, we provide a single model capable of describing the behavior of mercury(II) at two different solid/water interfaces. Mercury(II) sorption on amorphous ferric oxide (HFO) and α-SiO2 can be simulated using the surface complexation approach. In both cases, experiments are best reproduced when ternary surface complexes between the surface (≡S-OH0), Hg2+, OH- or Cl- are included in the model. Sorption or ternary surface complexes predominates in the case of α-SiO2. In addition, in the case of HFO, additional precipitation reactions of a nonideal Hg(OH)2-Fe(OH)3 solid solution are needed at high sorbate to sorbent ratios. The modeling leads to a new set of surface complexation constants for the interaction between Hg2+ and these oxide surfaces which are described by the following equilibria (298.15 K, I = 0M):≡S-OH0 + Hg2+↔KappSOHg+ ≡S-OHg+ + H+ with log KintSOHg+ = 6.9 ± 0.2 for HFO;≡-OH0 + Hg2+ + H2O ↔KappSOHgOH ≡-OHgOH + 2H+ with log KintSOHgOH = -3.2 ± 0.1 for α-SiO2, log KintSOHgOH = -0.9 ± 0.2 for HFO; and ≡S-OH0 + Hg2+ + Cl-↔KappSOHgCl ≡S-OHgCl + H+with log KintSOHgCl = 7.0 ± 0.1 for α-SiO2, log KintSOHgCl = 9.8 ± 0.4 for HFO.