High nitrate removal by starch-stabilized Fe⁰ nanoparticles in aqueous solution in a controlled system

Area of Science:

• Environmental Science
• Environmental Chemistry
• Nanotechnology

Background:

• Nano zero valent iron (nZVI) is prone to agglomeration, reducing its reactivity in environmental applications.
• Stabilizers are crucial for improving nZVI stability and maintaining its effectiveness.
• Biodenitrification is a key process for removing nitrates from aqueous solutions.

Purpose of the Study:

• To investigate the efficiency of starch-stabilized nano zero valent iron (S-nZVI) as an electron donor for biodenitrification.
• To evaluate the impact of S-nZVI on nitrate removal in the presence of thiosulfate (S2O3) under anaerobic conditions.
• To determine the optimal conditions for S-nZVI-enhanced biodenitrification.

Main Methods:

• Synthesis of S-nZVI using a chemical reduction method with starch as a stabilizer.
• Characterization of S-nZVI using Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and Fourier-Transform Infrared Spectroscopy (FTIR).
• Investigation of biodenitrification efficiency under varying temperatures and S-nZVI concentrations in aqueous solutions.

Main Results:

• S-nZVI nanoparticles exhibited a size range of 5-27.5 nanometers.
• Optimal biodenitrification was observed at 35°C and 500 mg/L S-nZVI, increasing efficiency from 40.45% to 78.84%.
• Biodenitrification rates improved with decreased initial nitrate concentration, reaching 94.07% in a bioreactor.

Conclusions:

• S-nZVI effectively enhances biodenitrification efficiency in aqueous solutions.
• Temperature and S-nZVI concentration are critical factors influencing nitrate removal.
• Fe2+ from S-nZVI can serve as a primary or supplementary electron donor to boost denitrification.