In Situ ATR-FTIR Spectroscopic Study of Adsorption of Perchlorate, Sulfate, and Thiosulfate Ions onto Chromium(III) Oxide Hydroxide Thin Films

Abstract

A thin chromium oxide hydroxide colloid film has been used as a model of the passive stainless steel surface for studies of anion adsorption from aqueous solutions. The adsorption of perchlorate, sulfate, and thiosulfate ions has been investigated by in situ attenuated total reflection infrared (ATR-IR) spectroscopy. Surface charge was monitored from the surface excess concentrations of tetramethylammonium ions and of perchlorate ions using the infrared spectroscopic STIRS technique. The colloid film showed a high positive charge at low pH and a low negative charge at high pH. The adsorption of sulfate was only observed for a positive surface charge. The infrared spectrum of adsorbed sulfate was significantly altered by the interfacial electric field, but there was no evidence of sulfate coordination to surface Cr(III) ions. Thiosulfate gave adsorption behavior analogous to sulfate. Adsorption isotherms for sulfate and for thiosulfate were determined from infrared spectral data, and Langmuir binding constants of (2.3 ± 0.4) × 105 and (1.4 ± 0.4) × 105 M-1 were obtained for the respective adsorbates. The lack of chemical binding of sulfate and of thiosulfate to the chromium oxide hydroxide surface may be part of the basis for the corrosion-promoting properties of these ions at stainless steel surfaces.

In situ Fourier-transform infrared spectroscopy studies of inorganic ions adsorption on metal oxides and hydroxides

“…[11,12,16,[23][24][25][26]28,32]. For the first method, the equilibrium of the system solid/solution is reached by a classical batch experiment, then the suspensions are centrificated to obtain a suspension with a high mass/volume ratio.…”

“…No study on the characteristics of the film deposit on the ATR crystal was published, but films of colloids deposited in the same manner into other smooth supports were characterized by Degenhardt and McQuillan [24] who have studied a film of chromium hydroxide sol evaporated onto glass by SEM. It consists of a patchy multilayer of particles whose average diameter was 430 nm, and was about 2.5 µm thick.…”

“…The flow rate value varied from 1 mL.min -1 to 7 mL.min -1 [16,23,24,28,30,32]. Adapted from Peak et al [11] A cell with a horizontal trough configuration was generally used, equipped with a crystal with coated upper face.…”

“….The pH values in the published works were in the range 3 -9 (until 2-11 in a few works [22,24]), correlated to the ZnSe chemical resistance. This range corresponds to the usual pH values of sorption studies, although the ZnSe resistance may limit the study of the surface reactivity at pH values higher than the iep of iron and aluminum oxy-hydroxides (~ 8 -10).…”

“…This water content is required to explain the possibility of using ATR spectroscopy on layers of solids whose refractive indexes (RI) are greater than those of ZnSe (2.4), as hematite (RI ~ [4,11,12,[23][24][25][26][27][28][29][30][31][32], ZnSe was used, the other materials were AMTIR (Amorphous Material which Transmits Infrared Radiation) [33,34],Ge [12,27] and diamond [35]. A summary of the properties of these materials can be seen in Table 2.…”