Long-Term Efficiency of Zero-Valent Iron - Pumice granular mixtures for the removal of copper or nickel from groundwater.

The use of Permeable Reactive Barriers (PRBs) for in situ remediation of contaminated groundwater represents an attractive technology for both economic and operational reasons. A reactive medium widely used in PRBs is the Zero-Valent Iron (ZVI) which, in several case studies, has proved highly efficient for the removal of both inorganic and organic contaminants. One of the major concerns related to ZVI PRBs is their long-term hydraulic conductivity, which often decreases during operation, potentially compromising the long-term efficiency and durability of the barrier. This paper proposes the use of granular mixtures of ZVI and natural pumice in various weight ratios with the aim of solving this problem. The experimental research was carried out using two different metallic contaminants (nickel and copper) in aqueous solution at two concentrations. The issues related with long-term efficiency of the PRB are examined on the basis of the results of the experimental activity carried out by means of long-term column tests. It is demonstrated how iron-pumice granular mixtures are efficient in contaminant removal and, at the same time, are able to maintain constant the permeability of the PRB.