Abstract
Environmental Context.Groundwater is the water that fills the spaces between sand, soil, and rock below the water table. It discharges into ecologically sensitive wetlands and is used as drinking water or in agriculture and industry. Inappropriate waste disposal and poor land management can contaminate groundwater and may minimize its use for decades. The common method for pumping contaminated groundwater to the surface for treatment is costly and labour intensive. Zerovalent iron is a new, more cost-effective method of groundwater remediation. Abstract. Zerovalent iron (ZVI) has been proposed as a reactive material in permeable in situ walls for groundwater contaminated by metal pollutants. For such pollutants that interact with corrosion products, the determination of the actual mechanism of their removal is very important to predict their stability in the long term. From a study of the effects of pyrite (FeS2) and manganese nodules (MnO2) on the uranium removal potential of a selected ZVI material, a test methodology (FeS2–MnO2 method) is suggested to follow the pathway of contaminant removal by ZVI materials. An interpretation of the removal potential of ZVI for uranium in the presence of both additives corroborates coprecipitation with iron corrosion products as the initial removal mechanism for uranium.
Highlights
Groundwater contamination is one of the most difficult and expensive environmental problems.[1, 2] The most common technology used to remediate groundwater is the pump-andtreat technology.[3]
The increasing order of U(VI) removal efficiency for single material systems was FeS2 < MnO2 < Zerovalent iron (ZVI). This observations suggest that, if FeS2 and MnO2 are consider as pure U(VI) adsorbents, their addition to ZVI should primarily increase the number of adsorption sites such that the increasing order of U(VI) removal efficiency should be: FeS2 < MnO2 < (ZVI + FeS2) < (ZVI + MnO 2) < ZVI in both cases, the extent been different due to differences in the kinetics of mass transfer
The proposed method consists in long-term, non-shaken batch experiments with and without appropriated additives for a better comprehension of the mechanism of U(VI) removal by ZVI materials (FeS2-MnO2-method)
Summary
Groundwater contamination is one of the most difficult and expensive environmental problems.[1, 2] The most common technology used to remediate groundwater is the pump-andtreat technology (pump the water and treat it at the surface).[3]. Operating permeable reactive walls treat (degrade or immobilize) contamination as halogenated hydrocarbons, chromium, nitrate, and radionuclides.[1, 8,9,10]. A permeable reactive wall is constructed from appropriate treatment media mixed with sand (to improve permeability) and installed downgradient of a pollutant source. ZVI walls are assumed to be active for several decades,[1, 7] the long-term reactivity of ZVI materials is currently under investigation. [11, 12, 13, Vikesland et al 2003] Even though a considerable amount of work has become available in the field of ZVI application to groundwater remediation, fundamental questions regarding the reaction mechanism remain open.[1, 7, Lin & Lo 2005] For example, field data did not confirmed quantitative U(VI) reduction in ZVI reactive walls.[Gu et al 2002, Matheson et al 2002] ZVI walls are assumed to be active for several decades,[1, 7] the long-term reactivity of ZVI materials is currently under investigation. [11, 12, 13, Vikesland et al 2003] Even though a considerable amount of work has become available in the field of ZVI application to groundwater remediation, fundamental questions regarding the reaction mechanism remain open.[1, 7, Lin & Lo 2005] For example, field data did not confirmed quantitative U(VI) reduction in ZVI reactive walls.[Gu et al 2002, Matheson et al 2002]
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