Hematite surface charge density

Fig. 10.5 Surface charge density of hematite and goethite as a function of pH in an inert electrolyte of various concentrations (KCI for hematite NaNOs for goethite) as obtained by acid/base titration (hematite Atkinson et al., 1967, with permission goethite S. Glasauer, unpubl.).

Fig. 6. Plateau-values, I"P1 /mg m 2, of adsorption isotherms of lysozyme (LSZ), ribonuclease (RNase), a -lactalbumin (aLA), calcium-depleted (X -lactalbumin (aLA(-Ca )) and bovine serum albumin (BSA) on hydrophobic polystyrene (PS) and hydrophilic hematite (a — Fe203) and silica (Si02) surfaces. An indication of the charge density of the surface is given by the zeta-potential, C, and of the proteins by + and signs. Ionic strength 0.05 M T = 25°C. (Derived from Currie et al. 2003).

At equilibrium surfactant concentrations of less than 0.0003 M SDS where the hematite surface is still positively charged, adsorption of surfactant follows its normal pattern due to the electrostatic forces which provide the driving force for adsorption. Sufficient effective surface area must be available for this level of SDS adsorption density. As surfactant adsorption... 

Akhtar and Lai128) infer the adsorption mechanism of a collector on a mineral surface from the mutual position of IPpH and PZC which they determine by electrophoresis. Their deduction is based on experiments performed with hematite in solutions of Na oleate (NaOl) and dodecylamine hydrochloride (DDA-HC1). The surface of hematite is assumed to consist of MeOHj, MeOH and MeO-. Chemisorption of the collector is discussed according to Table 3 which is based on Eq. 72 for charge density at the inner Helmholtz plane ... 

The sorptive capability of solids for charged species is proportional to their surface area per weight and the density of charged sites on their surfaces (their surface-site density or exchange capacity). Explain this statement as it applies to the sorptive capacity of natural hematite versus that of ferrihydrate. 

Based on these equilibria, one can schematically visualize the surface orientation of DFOB species at pH values below and above the isoelectric point of hematite (pH 8), by taking into consideration the charge on the adsorbate species, as illustrated in Fig. 21 [30]. At the low pH value the adsorption density of DFOB is low, due to its flat configuration on the solid surface, which also provides for... 

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