Carbo-Iron as improvement of the nanoiron technology: From laboratory design to the field test.

In a first pilot-scale field test the use of Carbo-Iron® was successfully demonstrated. Carbo-Iron was developed with the goal to overcome significant shortcomings of nanoscale zero-valent iron (NZVI) for in-situ groundwater remediation. The composite material of colloidal activated carbon and embedded nanoiron structures has been tested for the remediation of a tetrachloroethene (PCE) contaminated field site in Lower Saxony, Germany. The results of the two-step field test confirmed the properties intended by its design and the particle performance achieved in the laboratory experiments. The material showed transport lengths of several metres in the field and fast PCE decomposition with no vinyl chloride formation. Extended longevity of the PCE decrease in the treated area and evidence for microbiological participation were found. Carbo-Iron is now under study in the framework of the EU-project NanoREM where its performance is being further optimized at various scales from laboratory via large-scale tank to field testing. Targeted property adjustment was successful for Carbo-Iron performance in both directions: plume treatment and source attack.

Carbo-Iron - An Fe/AC composite - As alternative to nano-iron for groundwater treatment.

Carbo-Iron(®)(1) is a novel colloidal composite consisting of activated carbon colloids (ACC) with a d(50) particle size of 0.8 µm and anchored deposits of zero-valent iron clusters. This study discusses the principal material properties of Carbo-Iron colloids (CIC) relevant for groundwater treatment in comparison to commercially available nano-sized zero-valent iron (nZVI). CIC with 10-25 wt% Fe(0) have been developed and tested in laboratory studies for their suitability as dehalogenation reagent and are especially designed to overcome some limitations known from the utilization of nZVI: CIC combine the sorption properties of ACC and the chemical reactivity of nZVI. In column tests, flushed-in CIC showed an enhanced mobility in sediment material compared to nZVI, without the need for colloid stabilizers. However, adding 1-3 wt-% of carboxymethyl cellulose (CMC) related to CIC as colloid stabilizer was found to assure long-lived stable suspensions under laboratory conditions which may additionally support the already improved mobility of the CIC and the homogeneity of particle deposition on the sediment matrix. The hydrophobic character of the ACC carrier provides a high affinity of CIC to non-aqueous phase liquids (NAPL). In undisturbed flow, the reactive particles are collected at the water-NAPL interface. The reagent accumulation at the organic phase is necessary for a successful source attack.