Arsenic stabilization performance of a novel starch-modified Fe-Mn binary oxide colloid

Area of Science:

• Environmental Science
• Geochemistry
• Materials Science

Background:

• Arsenic contamination poses significant environmental and human health risks.
• China faces extensive arsenic-contaminated sites requiring efficient and cost-effective remediation strategies.
• Existing remediation methods often lack efficiency or are prohibitively expensive.

Purpose of the Study:

• To synthesize and evaluate a novel starch-modified FeMn binary oxide (SFM) as a remedial reagent for arsenic stabilization in contaminated soils.
• To investigate the mechanisms of arsenic immobilization by SFM.
• To assess the performance of SFM in reducing arsenic leachability.

Main Methods:

• Synthesis of amorphous colloidal starch-modified FeMn binary oxide (SFM).
• Laboratory batch experiments involving the direct addition of SFM to three arsenic-contaminated soils.
• Analysis of arsenic fractions, leachability (TCLP), adsorption isotherms, kinetics, soil Eh, and microscopic characteristics.

Main Results:

• SFM effectively transformed arsenic from labile fractions to stable forms bound to amorphous iron hydrous oxides.
• Arsenic concentration in TCLP leachates was reduced by up to 93.2%.
• SFM exhibited high adsorption capacities for As(V) (160.63 mg/g) and As(III) (284.64 mg/g) at pH 7.0, following pseudo-second-order kinetics and Freundlich isotherm models.
• SFM increased soil Eh, oxidized As(III) to As(V), and improved the reagent's reactivity and mobility.

Conclusions:

• Starch-modified FeMn binary oxide (SFM) is a novel and effective colloidal material for immobilizing arsenic in contaminated soils.
• SFM enhances arsenic stabilization through adsorption, oxidation, and precipitation mechanisms, significantly reducing leachability.
• This study presents a promising, efficient, and convenient reagent for arsenic remediation, with starch modification improving its field applicability.