Column test-based optimization of the permeable reactive barrier (PRB) technique for remediating groundwater contaminated by landfill leachates

Lead is one of the most toxic heavy metals that can create a severe risk to water ecosystem health. Zero-valent iron is an effective material for Pb 2+ removal treatments. In particular, nanoscopic zero-valent iron (nZVI) particles are characterized by high reaction rates; nevertheless, their utilization in water and groundwater remediation techniques requires further investigations. Indeed, it is necessary to define effective methods able to avoid the drawbacks due to the aggregation tendency of nanoparticles and their potential uncontrolled transport in groundwater. In this work, nZVI was supported on magnesium oxide grains (MgO_nZVI) to synthesize an alternative material for lead removal from aqueous solutions. Many experiments were conducted under several operating conditions in order to analyze the effectiveness of the produced material in Pb 2+ abatement. The performance of MgO_nZVI was also compared with those detected using commercial microscopic Fe 0 (mZVI) as a reactive material. The experimental findings showed a much greater reactivity of the supported nanoscopic iron particles. By means of a kinetic analysis of batch tests results, it was verified that, both for MgO_nZVI and mZVI, the lead abatement follows a pseudo-second-order kinetic law. The reaction rates were affected by the initial pH of the treatment solution and by the ratio between the Fe 0 amount and initial lead concentration. The efficiency of MgO_nZVI in a continuous test was steadily around 97.5% for about 1000 exchanged pore volumes (PV) of reactive material, while by using mZVI, the lead removal was approximately 88% for about 600 PV. X-ray diffraction (XRD) and energy-dispersive spectroscopy EDS analyses suggested the formation of typical iron corrosion products and the presence of metallic lead Pb 0 and Pb 2+ compounds on exhausted materials.

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“…This may cause a decrease in the sulfate concentration by its precipitation, such as in the case of Adsorption in column tests. The continuous up-flow column test in the laboratory was used to simulate the reactive effect of the adsorbent materials intended to be used as a permeable reactive barrier (PRB) 3,17,21,68,69 . Figure 8 shows the results obtained using a column setup, until 200 mL per each gram of dregs and grits in the column.…”

Section: Resultsmentioning

confidence: 99%

Kraft pulp mill dregs and grits as permeable reactive barrier for removal of copper and sulfate in acid mine drainage

Farage

Quina

Gando-Ferreira

et al. 2020

Sci Rep

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Mining is an essential human activity, but results in several environmental impacts, notably the contamination of ground and surface water through the presence of toxic substances such as metals and sulfates in mine drainage. permeable reactive barriers (pRB) have been applied to remediate this environmental impact, but the high costs associated with the maintenance of this system are still a challenge. the main objective of this study was to evaluate the use of kraft pulp mill alkaline residues, known as dregs and grits, as material for pRB, and to determine their capacity for retaining copper and sulfate. the work was carried out in laboratory adsorption kinetics assays, batch assays and column tests. tests for elemental characterization, point of zero charge, acid neutralization capacity, total porosity, bulk density and moisture of the dregs and grits were conducted. the results showed high retention of Cu due to a chemical precipitation mechanism, notably for dregs (99%) at 5 min in adsorption kinetics. The grits presented similar results after 180 min for the same assay. Sulfate retention was effective at pH below 5, with an efficiency of 79% and 89% for dregs and grits, respectively. Dregs presented the best results for acid drainage remediation, notably with a solid:liquid (S:L) ratio of 1:10.Acid mine drainage (AMD) is caused by the oxidation of sulfur-bearing materials in the presence of oxygen and water, resulting in sulfate and metals solubilization and forming acidic solutions 1-4 . Active and inactive mining activities for metals, such as copper, lead, zinc, gold, silver and uranium, provoke potential degradation of the environment by the presence of different contaminants, particularly due to metals and sulfates in acid drainage 5 . Indeed, the acid drainage formation is an important environmental aspect of mining practices. The sulfate concentrations may reach 2,400 to 20,800 mg/L 6,7 , well above the limit of 250 mg/L established by the World Health Organization 8 . It might cause damage not only to human health but also to the environment, and depreciation of structures and equipment 2,9 , resulting in high costs for control and management by the mining companies 2,10 . Copper concentration may be in the range from 77 to 615 mg/L, with higher values in the Cu mines 1,11 . Other metals such as Al, Mn, Fe, Mg, and Zn are also commonly found in AMD in these mines 10,12 .AMD remediation can be actively accomplished off-site with the pumping of the contamination plume to a treatment plant, or passively on-site with the use of permeable reactive barriers (PRB), with lower installation and maintenance costs. It can be carried out with the flow directed to the system, by the Funnel model, or the grid-type, by the installation of a perpendicular barrier to the contamination plume 13,14 . The PRB was first proposed in Canada in the 1990s 13,15 , with different materials used as adsorbent media, from single barriers with only one material to composites of different materials, or multiple sequential barrier...

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Column test-based optimization of the permeable reactive barrier (PRB) technique for remediating groundwater contaminated by landfill leachates

Cited by 71 publications

References 64 publications

Studies on the optimum conditions using acid-washed zero-valent iron/aluminum mixtures in permeable reactive barriers for the removal of different heavy metal ions from wastewater

Studies on the optimum conditions using acid-washed zero-valent iron/aluminum mixtures in permeable reactive barriers for the removal of different heavy metal ions from wastewater

Nanoscopic Zero-Valent Iron Supported on MgO for Lead Removal from Waters

Kraft pulp mill dregs and grits as permeable reactive barrier for removal of copper and sulfate in acid mine drainage

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