Adsorption of aliphatic polyhydroxy carboxylic acids on gibbsite: pH dependency and importance of adsorbate structure

Environmental Sciences Europe

Table 2 Surface and mineralogical properties of gibbsite

Property	Measured and modelled data	Ref. [31]
Purity^a	99.4%
Density^a	2.4 g cm⁻³
Particle size^a (laser diffraction)	D₁₀ 0.3–0.5 µm
	D₅₀ 0.7–1.2 µm
	D₉₀ 1.2–2.7 µm
Surface area^a	10–12 m² g⁻¹	32 ± 25 m² g^−1b
Surface sites [≡SOH] (titration data)	120 mmol kg⁻¹, 2.4 mmol L⁻¹ (in batch)	8.2 ± 0.3 sites nm^−2c
Surface sites [≡SOH] (titration data)	6.02–7.23 sites nm⁻², mean: 6.57 sites nm⁻²	8.2 ± 0.3 sites nm^−2c
Isoelectric point (pH_IEP)	Diffuse double-layer model: pH: 8.28	9.1 ± 0.7^d
Isoelectric point (pH_IEP)	Constant capacitance model: pH: 8.04	9.1 ± 0.7^d
Surface protonation constants	Diffuse double-layer model: pK_intr (+): 6.60, pK_intr(−): − 9.96	pK_intr (+): 7.17^e
Surface protonation constants	Constant capacitance model: pK_intr (+): 5.66, pK_intr(−): − 10.41	pK_intr (−): − 11.18^e
pH (24 h, 5 mM NaClO₄)	9.12 ± 0.01

^aData provided by manufacturer
^bMean of 42 BET/N₂ values, p. 60/61
^cMean of 6 values, p. 64
^dMean of 19 values, p. 64
^eBest fits obtained from double-layer model (including 13 titration curves from several studies)