Nanoscale zero-valent iron flakes for groundwater treatment

Improvements in nanoscale zero-valent iron production by milling through the addition of alumina

“…a Initial iron powder, b after 24 h, c after 48 h, d after 96 h and e detailed image of one flake of an iron particle milled for 48 h This evolution of iron powder with milling in MEG is fully in line with previous studies (Köber et al 2014 ) but it is completely different from the cases in which an aqueous solution was used (Li et al 2009 ;Zhang 2006 ). In the latter case, the iron particles break rapidly and extensively leading to a high particle size reduction with a final individual particle size less than 200 nm and irregular morphology.…”

“…It was found that the other reference products also had high Fe (0) content: N25P had an 87 % ± 1 and A01 a 74 % ± 1. On the contrary, the SSA value for milled M48h-Al O was 14.0 ± 0.1 m g , slightly below the value reported for A01 (18 m g ) (Köber et al 2014 ) and clearly lower than the one for N25P (25 m g ) (Soukupova et al 2015 ). Figure 7 shows the depletion of Cr(VI) in a solution with the amount of nZVI used in the reactivity tests, whereas Table 1 shows the slope of the depletion curve of Cr(VI), the Cr(VI) removal efficiency as weight of Cr(VI) removed by weight of Fe(0) and finally, this Cr(VI) removal efficiency normalized by SSA.…”

“…Unlike other air-stabilized or water aged nZVI particles (Kim et al 2010 ), there was an absence of an oxide layer on the outside of the particles (Fig. 5 b), which can be explained by the protective coating of MEG and argon atmosphere during milling (Köber et al 2014 ). The lack of oxide layer is consistent with the high Fe (0) content of the M48h-Al O suspension which was 92 % ± 1.…”

“…Recently, a new milling method using non-aqueous media (Mono Ethylene Glycol) has been reported (Köber et al 2014 ) and commercialized. The obtained suspensions showed a negligible loss of Fe (0) and a high specific surface area (18 m g ).…”

“…In the light of these results, it seems that the current process is not able to break the flakes even at long milling times and consequently, there is not a more effective particle size reduction. The final flaky product has a very slight thickness less than 100 nm, an interesting SSA, good reactivity against some pollutants and even good mobility (Köber et al 2014 ), although agglomeration and settling of this type of milled particles has been considered to be a major problem for mobility (Velimirovic et al 2015 ).…”