Decoupling of arsenic and iron release from ferrihydrite suspension under reducing conditions: a biogeochemical model

Table 2 Complexation reactions with the constants used in the model

Aqueous and surface reactions	log K (I = 0 M, 25°C)	Reference
H₃AsO₄° = H₂AsO₄^- + H⁺	-2.25	[32]
H₂AsO₄^- = HAsO₄^2- + H⁺	-6.96	[32]
HAsO₄^2- = AsO₄^3- + H⁺	-11.5	[32]
FeH₂AsO₄⁺ = H₂AsO₄^- + Fe²⁺	-2.86	[32]
FeHAsO₄° + H⁺ = H₂AsO₄^- + Fe²⁺	3.42	[32]
FeAsO₄^- + 2H⁺ = H₂AsO₄^- + Fe²⁺	11.04	[32]
H₃AsO₃° = H₂AsO₃^- + H⁺	-9.22	[33]
H₂AsO₃^- = HAsO₃^2- + H⁺	-12.11	[33]
HAsO₃^2- = AsO₃^3- + H⁺	-13.41	[33]
≡(w)FeOH + H⁺ = ≡(w)FeOH₂⁺	7.29	[27]
≡(w)FeOH = ≡(w)FeO^- + H⁺	-8.93	[27]
≡(s)FeOH + H⁺ = ≡(s)FeOH₂⁺	7.29	[27]
≡(s)FeOH = ≡(s)FeO^- + H⁺	-8.93	[27]
≡(w)FeOH + AsO₄^3- + 3H⁺ = ≡(w)FeH₂AsO₄ + H₂O	29.88	[28]
≡(w)FeOH + AsO₄^3- + 2H⁺ = ≡(w)FeHAsO₄^- + H₂O	24.43	[28]
≡(w)FeOH + AsO₄^3- + H⁺ = ≡(w)FeAsO₄^2- + H₂O	18.10	[28]
≡(w)FeOH + AsO₃^3- + 3H⁺ = ≡(w)FeH₂AsO₃ + H₂O	38.76	[28]
≡(w)FeOH + AsO₃^3- + 2H⁺ = ≡(w)FeHAsO₃^- + H₂O	31.87	[28]
≡(w)FeOH + CO₃^2- + H⁺ = ≡(w)FeOCO₂^- + H₂O	12.78	[34]
≡(w)FeOH + CO₃^2- + 2H⁺ = ≡(w)FeOCO₂H + H₂O	20.37	[34]
≡(w)FeOH + Fe²⁺ = ≡(w)FeOFe⁺ + H⁺	-2.98	[34]
≡(s)FeOH + Fe²⁺ = ≡(s)FeOFe⁺ + H⁺	-0.95	[34]

ISSN: 1467-4866