One-step phosphite removal by an electroactive CNT filter functionalized with TiO₂/CeO_x nanocomposites

Area of Science:

• Environmental Science
• Materials Science
• Electrochemistry

Background:

• Phosphite ( +3 valence) is more soluble and resistant to biotransformation than phosphate ( +5 valence).
• Effective removal of phosphite from water bodies is a significant environmental challenge.
• Existing methods for phosphite remediation are often inefficient or complex.

Purpose of the Study:

• To design and evaluate a novel one-step electroactive filter for rapid and efficient phosphite removal.
• To investigate the influence of electric field and flow rate on phosphite removal efficiency.
• To explore the conversion of phosphite to phosphate within the filter system.

Main Methods:

• Fabrication of a filter using carbon nanotubes (CNT) functionalized with nanoscale TiCe binary oxides (TiO2/CeOx-CNT).
• Testing phosphite removal kinetics and capacity under varying electric fields and flow rates.
• Electrochemical characterization to understand the role of CeOx and the electric field in electron transfer and charge capacity.
• Assessment of filter performance across a wide pH range and in the presence of coexisting anions.
• Evaluation of filter regeneration and performance in actual lake water samples.

Main Results:

• The TiO2/CeOx-CNT filter demonstrated increased phosphite removal with higher electric fields (up to 75.6%) and flow rates (up to 81.2%).
• Phosphite was effectively converted to phosphate upon adsorption under an applied electric field.
• The filter maintained high efficacy across a broad pH range with negligible impact from coexisting anions.
• Electrochemical studies confirmed synergistic effects between CeOx and the electric field, enhancing electron transfer and charge capacity.
• The filter exhibited effective regeneration via chemical washing and achieved 72.8% phosphite removal in lake water.

Conclusions:

• The developed TiO2/CeOx-CNT electroactive filter offers a promising solution for efficient and rapid phosphite removal from contaminated water.
• The synergistic effects of electrochemical reactivity, optimized pore size, active sites, and flow-through design contribute to the filter's high performance.
• The technology's ability to convert phosphite to phosphate and its robustness across various conditions make it suitable for real-world environmental applications.