Surface complexation reactions in sandy porous media: Effects of incomplete mixing and mass-transfer limitations in flow-through systems

Stolze, Lucien; Rolle, Massimo

doi:10.1016/j.jconhyd.2022.103965

Cited by 8 publications

(2 citation statements)

References 112 publications

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“…The fitted parameters indicated that all models predicted only 13-14% of the adsorption sites in the equilibrium state and that nonequilibrium dominated the adsorption process (similar α). This relatively low fraction in equilibrium is most likely due to relatively high flow velocity in the column 0.375 cm/min, which reduces the residence time to reach equilibrium [51] and is in agreement with previous observations [32,34]. The value of adsorption isotherm coefficient K D depends on the choice of the adsorption isotherm.…”

Section: Inverse Fittingsupporting

confidence: 90%

In Situ Remediation of Arsenic-Contaminated Groundwater by Injecting an Iron Oxide Nanoparticle-Based Adsorption Barrier

Mohammadian

Tabani

Boosalik

et al. 2022

Water

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Arsenic contamination of groundwater occurs due to both geogenic and anthropogenic processes. Conventional arsenic remediation techniques require extraction of groundwater into pump-and-treat systems, which are expensive and require long operational times. Hence, there is a need for cost-effective remediation. In this study, we assessed and validated the in situ remediation of arsenic contamination in groundwater resources using permeable reactive barriers (PRBs) made of injectable, colloidal iron oxide nanoparticles in the laboratory and in field-scale pilot tests. Sand-packed, flow-through column studies were used in order to assess the sorption behavior of the iron oxide nanoparticles using field materials (sand, groundwater) in the laboratory. The breakthrough curves were analyzed using a reactive transport model considering linear and nonlinear adsorption isotherms and were fitted best with a chemical nonequilibrium consideration. The results were used to design a pilot-scale field test. The injected 28 m3 of nanoparticles (ca. 280 kg dry weight of iron oxide) were successfully delivered to the aquifer via an injection well. No mobile iron was detected downstream, confirming that a stable in situ barrier was formed that did not move with the groundwater flow. Arsenic concentrations in groundwater were reduced to the aimed 50% of the background value, despite the relatively short contact time between arsenic and the iron oxide in the barrier, due to the high flow velocity of 1.21 m/day. We compared the results of the laboratory and field tests and concluded that the single-parameter models based on retardation factor and/or adsorption capacity fail to predict the longevity of the barrier and the evolution of arsenic breakthrough with time, most likely because they do not consider the chemical nonequilibrium effects. Therefore, we propose that upscaling the laboratory findings to field design must be carried out with care and be coupled with detailed reactive transport models.

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Section: Inverse Fittingsupporting

confidence: 90%

In Situ Remediation of Arsenic-Contaminated Groundwater by Injecting an Iron Oxide Nanoparticle-Based Adsorption Barrier

Mohammadian

Tabani

Boosalik

et al. 2022

Water

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“…Such enhancement could lower the release of arsenic in both natural and engineered systems. However, fast flow conditions could also decrease the adsorption due to incomplete mixing occurring in pore channels at high flow velocity . Mass transfer limitations such as incomplete mixing and intraparticle diffusion , would, therefore, decrease the arsenic retardation capacity of the porous medium.…”

Section: Results and Discussionmentioning

confidence: 99%

Oxidative Dissolution of Arsenic-Bearing Sulfide Minerals in Groundwater: Impact of Hydrochemical and Hydrodynamic Conditions on Arsenic Release and Surface Evolution

Stolze

Battistel

Rolle

2022

Environ. Sci. Technol.

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The dissolution of sulfide minerals can lead to hazardous arsenic levels in groundwater. This study investigates the oxidative dissolution of natural As-bearing sulfide minerals and the related release of arsenic under flow-through conditions. Column experiments were performed using reactive As-bearing sulfide minerals (arsenopyrite and lollingite) embedded in a sandy matrix and injecting oxic solutions into the initially anoxic porous media to trigger the mineral dissolution. Noninvasive oxygen measurements, analyses of ionic species at the outlet, and scanning electron microscopy allowed tracking the propagation of the oxidative dissolution fronts, the mineral dissolution progress, and the change in mineral surface composition. Process-based reactive transport simulations were performed to quantitatively interpret the geochemical processes. The experimental and modeling outcomes show that porewater acidity exerts a key control on the dissolution of sulfide minerals and arsenic release since it determines the precipitation of secondary mineral phases causing the sequestration of arsenic and the passivation of the reactive mineral surfaces. The impact of surface passivation strongly depends on the flow velocity and on the spatial distribution of the reactive minerals. These results highlight the fundamental interplay of reactive mineral distribution and hydrochemical and hydrodynamic conditions on the mobilization of arsenic from sulfide minerals in flow-through systems.

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Coupling soil/atmosphere interactions and geochemical processes: A multiphase and multicomponent reactive transport approach

Ahmadi

Muniruzzaman

Sprocati

et al. 2022

Advances in Water Resources

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Surface complexation reactions in sandy porous media: Effects of incomplete mixing and mass-transfer limitations in flow-through systems

Cited by 8 publications

References 112 publications

In Situ Remediation of Arsenic-Contaminated Groundwater by Injecting an Iron Oxide Nanoparticle-Based Adsorption Barrier

In Situ Remediation of Arsenic-Contaminated Groundwater by Injecting an Iron Oxide Nanoparticle-Based Adsorption Barrier

Oxidative Dissolution of Arsenic-Bearing Sulfide Minerals in Groundwater: Impact of Hydrochemical and Hydrodynamic Conditions on Arsenic Release and Surface Evolution

Coupling soil/atmosphere interactions and geochemical processes: A multiphase and multicomponent reactive transport approach

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