Insights into Antimony Adsorption on {001} TiO₂: XAFS and DFT Study

Abstract

Antimony (Sb) contamination poses an emerging environmental risk, whereas its removal remains a contemporary challenge due to the lack of knowledge in its surface chemistry and efficient adsorbent. In this study, self-assembly {001} TiO was examined for its effectiveness in Sb removal, and the molecular level surface chemistry was studied with X-ray absorption spectroscopy and density functional theory calculations. The kinetics results show that Sb adsorption followed the pseudo-second order reaction, and the Langmuir adsorption capacity was 200 mg/g for Sb(III) and 156 mg/g for Sb(V). The PZC of TiO, which was 6.6 prior to the adsorption experiment, shifted to 4.8 and <0 after adsorption of Sb(III) and Sb(V), respectively, indicating the formation of negatively charged inner-sphere complexes. EXAFS results suggest that Sb(III/V) adsorption exhibited a bidentate binuclear surface complex. The orbital hybridizing of complexes was studied by XANES, molecular orbital theory (MO), and density of states (DOS) calculations. The change in orbital energy derived from orbital hybridizing of adsorbed Sb on surfaces is the driving force underlining the Sb surface chemistry. New bonds between Sb and TiO surface were formed with matched orbital energies. Integrating the molecular and electronic structures into surface complexation modeling reveals the nature of macroscopic Sb adsorption behaviors.

Modulating High‐Index Facets on Anatase TiO2

“…Nano‐ or microcrystals with exposed high‐index facets are of paramount significance to both fundamental research and technical applications by virtue of their copious atomic steps, kinks, ledges, dangling bonds, and abundant unsaturated coordination sites , , . For instance, we observed that high‐index {201} TiO 2 exhibited better adsorption and photooxidation performance than that of three low‐index {001}, {100}, and {101} TiO 2 materials . This observation is ascribed to the surface energy, which follows the order {201} (1.72 J/m 2 ) > {001} (0.90 J/m 2 ) > {010} (0.53 J/m 2 ) > {101} (0.44 J/m 2 ) , .…”

“…For instance, we observed that high‐index {201} TiO 2 exhibited better adsorption and photooxidation performance than that of three low‐index {001}, {100}, and {101} TiO 2 materials . This observation is ascribed to the surface energy, which follows the order {201} (1.72 J/m 2 ) > {001} (0.90 J/m 2 ) > {010} (0.53 J/m 2 ) > {101} (0.44 J/m 2 ) , . {201} facets have more uncoordinated Ti atoms, facilitating the photogeneration of hydroxyl radicals.…”

“…TiO 2 materials have wide‐ranged applications in photocatalysis, photoelectrochemical cells, rechargeable lithium ion batteries, sensors, and dye‐sensitized solar cells . All these applications are rooted in the distinctive physicochemical properties of these materials, which are mainly influenced by the specific facets of the TiO 2 crystals …”

Nanoscale iron (oxyhydr)oxide-modified carbon nanotube filter for rapid and effective Sb(iii) removal

“…This is because the Sb(III) species (i.e., Sb(OH) 3 ) in the aqueous solution remain unchanged from pH 3 to 10. 27…”

Antimonate Sequestration from Aqueous Solution Using Zirconium, Iron and Zirconium-iron Modified Biochars

“…The adsorption capacity of these materials tends to be poor. Only a few sorbents such as metal-loaded Zr(IV), Fe(III) saponified orange waste 13 , zero-valent iron nanoparticles coatings on aluminum and silicon minerals 14,15 , iron oxyhydroxides 5 , zirconium oxide (Zr-O)-carbon nanofibers 7 , reduced graphene oxide/Mn3O4 16 , MnO2 nanofibers 17 , TiO2 18 , and UiO-66NH2 19 have reported promising results for both Sb(III) and Sb(V) adsorption. However, readily available and cost-effective materials are required to remediate Sb from contaminated water.…”