Mechanistic Insights into the Selectivity for Arsenic over Phosphate Adsorption by Fe³⁺-Cross-Linked Chitosan Using...

Area of Science:

• Environmental Chemistry
• Materials Science
• Computational Chemistry

Background:

• Chitosan-based adsorbents show promise for removing arsenic from water.
• Understanding the selective binding mechanisms of Fe³⁺-chitosan for oxyanions is critical for effective water remediation.

Purpose of the Study:

• To investigate the competitive binding mechanisms of As(V), P(V), and As(III) to neat and Fe³⁺-cross-linked chitosan.
• To elucidate the factors controlling the selectivity of Fe³⁺-chitosan for arsenic oxyanions.

Main Methods:

• Utilized ab initio calculations to model the interactions between oxyanions and chitosan-based materials.
• Analyzed binding energies and charge transfer characteristics to understand bond nature.

Main Results:

• Neat chitosan exhibits weak, non-selective binding of As oxyanions.
• Fe³⁺-chitosan demonstrates selective binding of As(V) over As(III) and P(V) due to distinct Fe³⁺-oxyanion interactions.
• Binding selectivity is influenced by Fe³⁺-oxyanion donor-acceptor characteristics and pH.

Conclusions:

• Fe³⁺-chitosan's selectivity for As(V) is attributed to stronger covalent bonding compared to As(III) and P(V).
• pH significantly affects the binding selectivity, highlighting its importance in environmental applications.
• Findings provide insights into designing advanced adsorbents for selective contaminant removal.