Estimate of the optimum weight ratio in Zero-Valent Iron/Pumice granular mixtures used in permeable reactive barriers for the remediation of nickel contaminated groundwater

► Fe0 Permeable Reactive Barriers may have problems in the long term due to the reduction of their hydraulic conductivity. ► The adoption of granular mixtures of Fe0 and pumice has been proposed to reduce clogging problems and increase lifespan. ► In the composition of the mixture a compromise between reactivity and maintaining of hydraulic conductivity must be found. ► Increasing Fe0 content increases reactivity, increasing pumice allows a better maintaining of the hydraulic conductivity. ► For nickel removal the optimal weight ratio between Fe0 and pumice is probably 30:70.