Phosphate removal from aqueous solution using ZVI/sand bed reactor: Behavior and mechanism

Area of Science:

• Environmental Science
• Water Treatment
• Materials Science

Background:

• Phosphate contamination in aqueous solutions poses significant environmental challenges.
• Zero-valent iron (ZVI) is a promising material for contaminant removal.
• Understanding ZVI performance and optimal conditioning is crucial for effective water treatment.

Purpose of the Study:

• To investigate the efficiency of ZVI/sand packed columns for phosphate removal.
• To evaluate the impact of ZVI preconditioning (pre-oxidation) on phosphate removal efficiency.
• To analyze phosphate distribution within the columns and identify iron species.

Main Methods:

• Phosphate removal experiments using ZVI/sand packed columns.
• Column preconditioning involving ZVI pre-oxidation for varying durations (1, 5, 10 days).
• Analysis of phosphate distribution in column solids and characterization of iron oxidation products using SEM, XRD, and XPS.

Main Results:

• A 1-day preconditioned ZVI column showed higher phosphate removal efficiency compared to un-conditioned, 5-day, and 10-day preconditioned columns.
• Phosphate trapping was heterogeneous before column saturation and became homogeneous upon saturation.
• Iron oxidation products identified as lepidocrocite and maghemite/magnetite; XPS confirmed phosphate sorption and iron phosphate complex formation.

Conclusions:

• One-day pre-oxidation of ZVI enhances its efficiency for phosphate removal from aqueous solutions.
• ZVI and its oxidation products effectively sorb phosphate, forming iron phosphate complexes.
• Column saturation leads to a homogeneous distribution of trapped phosphate, indicating consistent performance over time.