A predictive model (ETLM) for arsenate adsorption and surface speciation on oxides consistent with spectroscopic and theoretical molecular evidence

Fukushi, Keisuke; Sverjensky, Dimitri A.

doi:10.1016/j.gca.2007.05.018

Cited by 90 publications

(108 citation statements)

References 83 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hence, the results suggest that SO 4 ions were mainly adsorbed as outer-sphere complexes on the PO 4 ions was also reported in other minerals [28,29].…”

Section: Adsorption Mechanisms Of Anions On Htsupporting

confidence: 81%

Surface complexation reactions of inorganic anions on hydrotalcite-like compounds

Morimoto

Anraku

Hoshino

et al. 2012

Journal of Colloid and Interface Science

View full text Add to dashboard Cite

Complexation reactions of environmentally important inorganic anions such as nitrate, chloride, sulfate, arsenate, and phosphate on the surface of hydrotalcite-like compounds (HT) were investigated to understand the role of HT in the immobilization of hazardous anions in an alkaline environment. The effects of surface complexation reactions on the solid state properties of HT were also evaluated to understand their stability. Synthetic HT was used for the adsorption and post-adsorption experiments. The obtained adsorption isotherms showed that the order of selectivity of HT for anions was NO 3 < Cl < SO 4 << AsO 4 < PO 4 . To distinguish the adsorption mechanisms (inner-sphere complexes or outer-sphere complexes) of these anions, zeta potential measurements and infrared absorption spectroscopic analysis were performed.The results indicated that NO 3 and Cl were adsorbed as diffuse ions on the outer surfaces of the HT, while SO 4 formed outer-sphere complexes with a strong electrostatic interaction. Moreover, AsO 4 and PO 4 formed inner-sphere complexes via a ligand substitution reaction on the HT surfaces. And it was suggested that oxyanions with low ionic potential, such as AsO 4 and PO 4 , had a tendency to form inner-sphere complexes with the HT surfaces. The formation of inner-sphere complexes shifted the isoelectric point and the surface charge of the HT.Furthermore, the solubility of the HT was reduced by the inner-sphere complexes with PO 4 and AsO 4 . It was revealed that the formation of inner-sphere complexes on the HT surfaces contributed to the stabilization of the HT, as well as a decrease in the mobility of these anions.

show abstract

“…Hence, the results suggest that SO 4 ions were mainly adsorbed as outer-sphere complexes on the PO 4 ions was also reported in other minerals [28,29].…”

Section: Adsorption Mechanisms Of Anions On Htsupporting

confidence: 81%

Surface complexation reactions of inorganic anions on hydrotalcite-like compounds

Morimoto

Anraku

Hoshino

et al. 2012

Journal of Colloid and Interface Science

View full text Add to dashboard Cite

show abstract

“…Alternatively, other aspects of the adsorption process may be affected by ionic strength in ways that do not substantially change the balance of inner-and outer-sphere species. For example, a prior study using the extended triple-layer model suggested a possible reaction stoichiometry involving both inner-and outer-sphere arsenate species in a ratio independent of pH and surface coverage and only sensitive to the activity of water [39]. Alternatively, if applying a charge distribution model then inner-sphere complexes have two O ligands extending to the β-plane, producing an ionic strength-dependence on macroscopic uptake [19].…”

Section: Implications To Arsenate Adsorption Mechanismsmentioning

confidence: 99%

Effects of Ionic Strength on Arsenate Adsorption at Aluminum Hydroxide–Water Interfaces

Catalano

2018

Soil Systems

View full text Add to dashboard Cite

Adsorption processes at mineral-water interfaces control the fate and transport of arsenic in soils and aquatic systems. Mechanistic and thermodynamic models to describe this phenomenon only consider inner-sphere complexes but recent observation of the simultaneous adsorption of inner-and outer-sphere arsenate on single crystal surfaces complicates this picture. In this study, we investigate the ionic strength-dependence of the macroscopic adsorption behavior and molecular-scale surface speciation of arsenate bound to gibbsite and bayerite. Arsenate adsorption decreases with increasing ionic strength on both minerals, with a larger effect at pH 4 than pH 7. The observed pH-dependence corresponds with a substantial decrease in surface charge at pH 7, as indicated by ζ-potential measurements. Extended X-ray absorption fine structure (EXAFS) spectroscopy finds that the number of second shell Al neighbors around arsenate is lower than that required for arsenate to occur solely as an inner-sphere surface complex. Together, these observations demonstrate that arsenate displays macroscopic and molecular-scale behavior consistent with the co-occurrence of inner-and outer-sphere surface complexes. This demonstrated that outer-sphere species can be responsible for strong adsorption of ions and suggests that environments experiencing an increase in salt content may induce arsenic release to water, especially under weakly acidic conditions.

show abstract

“…In the literature there are several reports related to the surface models for arsenate complexation on oxides [1,14]. Inner sphere complexes, Monodentate Mononuclear (MM) and Bidentate Binuclear (BB) have been reported as the most likely adsorption modes of arsenate species when they are coordinated with metal oxides [14].…”

Section: Formation Of Surface Complexesmentioning

confidence: 99%

“…Inner sphere complexes, Monodentate Mononuclear (MM) and Bidentate Binuclear (BB) have been reported as the most likely adsorption modes of arsenate species when they are coordinated with metal oxides [14]. Figure 2 shows the adsorption reaction to form the inner sphere complex, BB, under acidic pH conditions.…”

Section: Formation Of Surface Complexesmentioning

confidence: 99%

See 1 more Smart Citation

Adsorption of arsenate on Fe-(hydr)oxide

Acelas

Flórez

2017

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

Abstract. Adsorption using metal oxide materials has been demonstrated to be an effective technique to remove hazardous materials from water, due to its easy operation, low cost, and high efficiency. The high number of oxyanions in aquatic ecosystems causes serious pollution problems. Removal of arsenate (H2AsO4 -), is one of the major concerns, since it is a highly toxic anion for life. Within the metal oxides, the iron oxide is considered as a suitable material for the elimination of oxyanions. The adsorption of H2AsO4 -on Fe-(hydr)oxide is through the formation of inner or outer sphere complexes. In this work, through computational methods, a complete characterization of the adsorbed surface complexes was performed. Three different pH conditions were simulated (acidic, intermediate and basic), and it was found that, the thermodynamic favourability of the different adsorbed complexes was directly related to the pH. Monodentate complex (MM1) was the most thermodynamically favourable complex with an adsorption energy of -96.0kJ/mol under intermediate pH conditions.

show abstract

A predictive model (ETLM) for arsenate adsorption and surface speciation on oxides consistent with spectroscopic and theoretical molecular evidence

Cited by 90 publications

References 83 publications

Surface complexation reactions of inorganic anions on hydrotalcite-like compounds

Surface complexation reactions of inorganic anions on hydrotalcite-like compounds

Effects of Ionic Strength on Arsenate Adsorption at Aluminum Hydroxide–Water Interfaces

Adsorption of arsenate on Fe-(hydr)oxide

Contact Info

Product

Resources

About