Complexation of Antimony with Natural Organic Matter: Performance Evaluation during Coagulation-Flocculation Process

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies
• Toxicology

Background:

• Natural organic matter (NOM) in water sources can stabilize toxic antimony (Sb) species, increasing their mobility and posing health risks.
• Understanding the complexation of Sb with different NOM fractions is crucial for effective water treatment.

Purpose of the Study:

• To quantitatively explore the complexation of hydrophobic (humic acid) and hydrophilic (salicylic acid, L-cysteine) NOM with Sb species.
• To evaluate the removal of Sb(III, V) and total organic carbon (TOC) using ferric chloride (FC) as a coagulant.

Main Methods:

• Complexation studies of Sb with humic acid, salicylic acid, and L-cysteine.
• Ferric chloride coagulation experiments to assess Sb and TOC removal.
• Isotherm studies to determine adsorption capacities.

Main Results:

• Hydrophobic NOM, particularly humic acid, exhibited a stronger binding affinity with Sb compared to hydrophilic NOM.
• Higher FC doses were needed for Sb(V) removal than Sb(III) due to stronger NOM complexation with antimonate.
• TOC removal was more efficient with hydrophobic ligands, and high hydrophobic molecule concentrations hindered Sb adsorption onto Fe precipitates.

Conclusions:

• NOM complexation significantly influences Sb mobility and removal during water treatment.
• Ferric chloride coagulation is effective for removing Sb and TOC, but NOM characteristics, especially hydrophobicity, affect treatment efficiency.
• Mechanisms including oxidation, complexation, charge neutralization, and adsorption are involved in Sb removal, providing insights for optimizing water treatment processes.