Impact of Trace Elements and Impurities in Technical Zero-Valent Iron Brands on Reductive Dechlorination of Chlorinated Ethenes in Groundwater - Permeable Reactive Barrier: Sustainable Groundwater Remediation - page 91

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Würth 1 Würth 2Responge GM 1 GM 2 Connelly Peerless

Cr Mn Fe Co Ni Cu

FIGURE 5.3
Normalized average trace element bulk concentrations concerning different ZVI brands
(GM = Gotthart-Maier ZVI), sample workup by aqua regia dissolution and ICP-OES analyses.
Great variations regarding kinds and amounts of trace elements are observed.

concentration level, that vastly differing degradation efficacies have been
encountered when applying different ZVI brands or production batches.
To develop a quality assurance program to address this issue, different
batch experiments using two Gotthart-Maier production batches (“GGG1”
and “GGG3”) were performed in comparison to the column experiment
using the same production batch. It could be verified (Figure 5.7) that a good
correlation between the applied amount of ZVI and the pseudo first-order
rate constant k(obs) (1/h) can be attained. These findings are virtually inde-
pendent of the stirring rate. In the corresponding column experiment, k(obs)
could be determined at 0.05 1/h after around 20 pore volumes (the very first
pore volume show adsorption and not degradation, which is a very common
observation for technical ZVI brands regarding column or batch studies).
As shown in Figure 5.7, GGG1 shows higher degradation as GGG3; the
reactivity of GGG3 was intentionally decreased by soaking with (noncon-
taminated) Rheine groundwater over 1 week (“GGG3 rusted”) as well as by
heating up to 600°C for 6 h in a muffle kiln (“GGG3 calcinated”) in order
to simulate potential failures/malicious conditions while manufacturing or
storing; that is, for example heating scrap iron in a rotary kiln for too long,
or storing in conditions where humidity/water may get access to the freshly
produced ZVI batch.