Nickel removal by zero valent iron/lapillus mixtures in column systems

The remediation of contaminated groundwater, through permeable reactive barrier (PRB) technology, has raised strong interest in the field of environmental geotechnics. The use of granular mixtures composed of zero valent iron (ZVI) together with an inert and/or porous material is a new strategy for preventing the decrease in hydraulic conductivity of PRBs composed of pure ZVI alone. In this paper, granular mixtures composed of ZVI and lapillus in different weight ratios were tested for nickel removal through column tests. The newly proposed material, lapillus, is a low-cost material (a by-product of pumice mining), readily available and efficient for nickel removal, as is shown by the benchmark column tests carried out in this paper. The weight ratio between ZVI and lapillus, the flow velocity and the initial contaminant concentration were the factors investigated in this paper since they can strongly influence the long-term removal efficiency and hydraulic behaviour of a PRB. The column tests results were analysed in terms of hydraulic conductivity, nickel removal efficiency and the distribution of the removed nickel along the column over time. The test results clearly showed the great potential of the proposed ZVI/lapillus granular mixtures in terms of both removal efficiency and long-term hydraulic conductivity.