Reduction of highly concentrated nitrate using nanoscale zero-valent iron: Effects of aggregation and catalyst on reactivity

Simultaneous removal of cadmium and nitrate in aqueous media by nanoscale zerovalent iron (nZVI) and Au doped nZVI particles

“…Without Cd(II), less than 33% nitrate was reduced by nZVI. Reduction of nitrate was catalyzed by the presence of Cd(II) (Ottley et al, 1997), which was similar to the catalytic effect of Cu(II) (Sparis et al, 2013) or Ni(II) (Ryu et al, 2011). Nitrate reduction by nZVI increased with increasing Cd(II) concentration; 100% nitrate reduction was observed at 30e40 mg/L Cd(II) concentration.…”

“…The production of gaseous products (likely N 2 and/or N 2 O) due to nitrate reduction was not expected as previous studies showed that nZVI mainly reduced nitrate to ammonium (Ryu et al, 2011;Hwang et al, 2011). However, certain amount of N 2 gas was observed when nitrate was reduced by nZVI with Pd and Cu deposits (Hosseini et al, 2011;Liou et al, 2009).…”

“…Although ammonium is a toxic pollutant to some organisms (do Amaral et al, 2013;Dai et al, 2008Dai et al, , 2012, it serves as major nitrogen source for plants (Fuertes-Mendizabal et al, 2013;Cabezas and Couto, 2007). Furthermore, nZVI is mainly transformed into magnetite (Fe 3 O 4 ) after reaction with nitrate (Su and Puls, 2004;Sohn et al, 2006;Ryu et al, 2011), which avoids significant increase of Fe 2þ or exchangeable Fe concentration. This vastly reduces the potential environmental impact of nZVI (Adeleye et al, 2013; Keller et al, 2012).…”

“…Several studies showed that nZVI reduces nitrate to ammonium, accompanied by increased solution pH (Eq. (4)) (Sohn et al, 2006;Ryu et al, 2011;Park et al, 2009;Liu et al, 2012), which could enhance Cd removal by nZVI through precipitation (e.g. Cd(OH) 2 ) (Boparai et al, 2013).…”

Effects of nitrate on the treatment of lead contaminated groundwater by nanoscale zerovalent iron

“…Nitrate removal by nZVI generally occurs via reduction to ammonium (Eq. (1)) at very high rate (50 ppm nitrate could be reduced by 1.43 g/L nZVI within 1 h, as modeled by pseudo-first-order reaction kinetics), even at high pH (9)(10) [19][20][21]. Although there are several studies on the use of nZVI for cleanup of Pb 2+ [22][23][24] or nitrate contamination [18,19] individually, little attention has been paid to the treatment of groundwater with different levels of Pb 2+ and nitrate, even though some researchers recommend that studies need to be done in the systems similar to the real environment [25,26].…”