Abstract:

Recent studies have shown that zero-valent iron(Fe⁰) may potentially be used as a chemical medium in permeable reactive barriers(PRBs) for groundwater nitrate remediation, and due to the extremely high reactivity, denitrification of nitrate in groundwater using nanoparticles has received increasing interest in recent years. In order to fabricate iron nanoparticles with homogeneous spherical shape and narrow size distribution, we developed a simple and green approach for synthesizing iron nanoparticles. We modified the conventional methods by applying the microemulsion with Span 80 and Tween 60 as mixed surfactants. Water was then titrated into the octanesurfactant mixture and changes were observed by visual inspection and conductivity measurement and the information was used in developing a phase diagram. The maximum content of water in the W/O microemulsion and its appropriate forming condition of the microemulsion were found. And then the microemulsion system consisting of saturated Fe²⁺ solution was used to synthesize α-Fe ultrafine particles by reduction reaction. The nanoparticles were characterized by using the powder X-ray diffraction(XRD), transmission electron microscopy(TEM). The results show that the average diameter of the particle is about 80 nm. The reductive activity of the obtained iron nanoparticles were studied by the denitrification experiment of nitrate. And the results show that under the experimental conditions iron removed mostly 120 mg/L of nitrate within a period of 30 min. And the mass balance of nitrate reduction with nanoscale Fe indicates that endproducts mainly are ammonia and the probable formation of nitrogen gas species during reaction with the new prepared nanoscale iron without pH control.

Key words: Mixed-surfactants; Microemulsion; Iron nanoparticles; Nitrate