The interaction of anions and weak acids with the hydrous goethite (α-FeOOH) surface

A study of sodium silicate in aqueous solution and sorbed by synthetic magnetite using in situ ATR-FTIR spectroscopy

“…A considerable increase in the adsorption of silicate occurred from pH 11 to 9, whereas a decrease in pH from 9 to 7 only contributed a minor change in spectral intensity. It is well known that silicate sorption onto iron oxyhydroxides has a maximum at a pH value around 9 [8,10,21,22], but this is not reflected in our spectra. The observed sorption should already have passed its maximum when reaching pH 7.…”

“…However, in the reversed flotation of apatite from magnetite, Su et al observed that the selectivity of sodium silicate as depressant decreased when the dosage increased from 300 g t −1 (2.4 × 10 −4 mol L −1 ) to 500 g t −1 (4 × 10 −4 mol L −1 ) resulting in a less efficient dephosphorization of magnetite fines and proposed that the dispersion effect of sodium silicate played a key role at such a low concentration rather than the depressant effect [7]. Knowledge about silicate-metal oxide reactions is of course also important to better understand other industrial applications than 0021 flotation such as the synthesis of zeolites and iron oxide-silicate composites as well as interfacial reactions in environmental systems [8][9][10].…”

“…Stumm and colleagues were among the pioneers, who elaborated a ligand-exchange model to explain and predict the adsorption of H 4 SiO 4 on goethite [8]. Other authors [10,19,20] have used but also developed this ligand-exchange model.…”

Kinetics of silicate sorption on magnetite and maghemite: An in situ ATR-FTIR study

“…During the past decades, the study of interaction between silicate and iron oxides as well as other minerals was mainly carried out by batch adsorption experiments, modeling methods, and ex situ spectroscopy techniques [1,3,7,[10][11][12]. However, there are very few if any in situ studies on the sorption of silicate species onto magnetite showing the formation of surface complexes with time.…”

“…Interfacial reactions between soluble silicates and iron oxide surfaces are of great importance in the natural environment considering the content of dissolved silicate in natural waters from mineral weathering [1][2][3] as well as in industrial applications, e.g., flotation of salt-type minerals from metal oxides and other salttype minerals where sodium silicate is usually used as dispersion or depressant agent [4]. Concretely, in the dephosphorizing flotation of magnetite particles, sodium silicate with modulus 3.25 (weight ratio of SiO 2 to NaO 2 ) is used mainly to disperse the agglomerated particles [5], whereas in the flotation of apatite from hematite sodium silicate may be utilized as a selective depressing agent to reduce the flotation of the gangue mineral (hematite) [6].…”