Removal of nitrate from drinking water using SiO2–FeOOH–Fe core-shell nanostructures

There is increasing global concern about the high concentration of nitrate in drinking water. The high solubility of nitrate in water can lead to widespread groundwater nitrate pollution, representing a serious health risk in drinking water supplies.

In this work, chemical engineers at Shiraz University in Iran report on the synthesis of SiO2–FeOOH–Fe core-shell nanostructures, to overcome some common problems related to the application of nanoscale zero-valent iron (NZVI) in nitrate removal from drinking water.

NZVI was immobilised on SiO2–FeOOH cores using a reduction method with or without the presence of nitrogen gas. The nanostructures were then characterised using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), particle size analysis (PSA), and scanning electron microscopy (SEM).

The experiments revealed that using nitrogen gas leads to a uniform size distribution, and reduced the nanostructure size from 81 to 52 nm.

The researchers also investigated the effects of different parameters, such as the amount of NZVI loading, pH, initial nitrate concentration, amount of nano SiO2–FeOOH–Fe core-shell, contact time, and sonication time. The NZVI loading plays a significant role in nitrate removal; indeed, by doubling the NZVI loading, nitrate removal increases from 69% to 86%.

The results show that nitrate removal increases with decreasing pH and increasing the other parameters. The percentage removal of nitrate was 99.84% under the optimum conditions of pH 3, initial nitrate concentration of 64 mg/L, two-fold loading of Fe0 in nanostructures, sonication time of 3 min, and contact time of 120 min.

Desalination, Volume 347, 15 August 2014, Pages 1–9.