Sorption of P(V), As(V), and Sb(V) Oxyanions on Goethite and Hematite During their Thermal Transformation

Abstract

Sorption of pentavalent oxyanions P(V), As(V), and Sb(V)was studied on goethite and hematite prepared by its thermal transformation. The surface properties of goethite and products of its thermal modification at different temperatures were studied by BET method, FT-IR, XRD, and DTA-TGA. Amounts of immobilized ions reached their maxima on sorbent prepared at 250 C. Changes of the specific surface area (32.5 m 2 .g −1 at 150 C, 82 3 m 2 g −1 at 250 C and 34 8 m 2 g −1 at 350 C) during the thermal transformation at different temperatures were observed. Further analysis confirmed the complete transformation of goethite to hematite at temperatures 200−250 C accompanied with the disappearance of hydroxyl absorption bands at ∼800 and ∼900 cm −1 in FT-IR spectrum and significant loss of weight observed on TGA curve. The study of adsorption isoterms revealed that antimony has higher affinity for all studied sorbents.

The Effect of High Selenite and Selenate Concentrations on Ferric Oxyhydroxides Transformation under Alkaline Conditions

“…Negligible structural changes and rearrangements of iron during maturation of ferric precipitates are also illustrated by ATR-FTIR spectra in Figure 3a. There are two strong absorbance bands at 885 and 796 cm −1 in the hydroxyl deformation region, labelled as δ(OH) and γ(OH), respectively, that can be assigned to goethite's characteristic vibrations [45,46], and provide some information on its crystallinity and substitution in mineral structures [45]. δ(OH) and γ(OH), respectively, that can be assigned to goethite's characteristic vibrations [45,46], and provide some information on its crystallinity and substitution in mineral structures [45].…”

“…There are two strong absorbance bands at 885 and 796 cm −1 in the hydroxyl deformation region, labelled as δ(OH) and γ(OH), respectively, that can be assigned to goethite's characteristic vibrations [45,46], and provide some information on its crystallinity and substitution in mineral structures [45]. δ(OH) and γ(OH), respectively, that can be assigned to goethite's characteristic vibrations [45,46], and provide some information on its crystallinity and substitution in mineral structures [45]. Since the vibrational bands between 1800 and 1000 cm −1 generally belong to water bending modes, the bands observed at ~1650 cm −1 can be assigned to the bending vibration of weakly adsorbed molecular water [47].…”