Antimonate adsorption onto Mg-Fe layered double hydroxides in aqueous solutions at different pH values: Coupling...

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Antimony (Sb) contamination in aqueous solutions poses environmental risks.
• Mg-Fe layered double hydroxides (LDHs) are promising materials for adsorbing contaminants.
• Understanding Sb behavior under varying pH is crucial for effective remediation strategies.

Purpose of the Study:

• To investigate the stabilization of antimony (Sb(V)) in aqueous solutions using Mg-Fe layered double hydroxides (LDHs).
• To determine the influence of pH on Sb(V) adsorption onto Mg-Fe LDHs.
• To elucidate the adsorption mechanisms of Sb(V) on Mg-Fe LDHs through modeling and spectroscopic analyses.

Main Methods:

• Adsorption experiments were conducted at varying initial Sb(V) concentrations and pH values (5.5, 6.5, 7.5).
• Surface complexation modeling (SCM) was employed to predict Sb(V) binding configurations.
• Spectroscopic techniques (XRD, FTIR, XPS) and microscopic techniques (SEM, EDX) were utilized to analyze adsorption mechanisms.

Main Results:

• Sb(V) removal rate and adsorption capacity increased as pH decreased.
• SCM predicted the formation of monodentate mononuclear and bidentate binuclear complexes.
• Adsorption involved chemical adsorption, surface-induced precipitation of brandholzite, brandholzite-like phases, and anion exchange.
• Sb(V) distribution on the Mg-Fe LDH surface was nonhomogeneous across all tested pH values.

Conclusions:

• The combined approach of SCM and solid-state analyses provides a robust method for investigating Sb(V) binding on Mg-Fe LDHs.
• This mechanistic understanding allows for the prediction of Sb(V) adsorption behavior under diverse conditions.
• Mg-Fe LDHs show potential for practical applications in Sb(V) remediation from aqueous solutions.