title: Assessing the efficacy over time of the addition of industrial by-products to remediate contaminated soils at a pilot-plant scale.
abstract: The effect of the addition of industrial by-products (gypsum and calcite) on the leaching of As and metals (Cu, Zn, Ni, Pb and Cd) in a soil contaminated by pyritic minerals was monitored over a period of 6 months at a two-pit pilot plant. The contaminated soil was placed in one pit (non-remediated soil), whereas a mixture of the contaminated soil (80% w/w) with gypsum (10% w/w) and calcite (10% w/w) was placed in the other pit (remediated soil). Soil samples and leachates of the two pits were collected at different times. Moreover, the leaching pattern of major and trace elements in the soil samples was assessed at laboratory level through the application of the pHstatleaching test. Addition of the by-products led to an increase in initial soil pH from around 2.0 to 7.5, and it also provoked that the concentration of trace elements in soil extracts obtained from the pHstatleaching test decreased to values lower than quantification limits of inductively coupled plasma optical emission spectrometry and lower than the hazardous waste threshold for soil management. The trace element concentration in the pilot-plant leachates decreased over time in the non-remediated soil, probably due to the formation of more insoluble secondary minerals containing sulphur, but especially decreased in pit of the remediated soil, in agreement with laboratory data. The pH in the remediated soil remained constant over the 6-month period, and the X-ray diffraction analyses confirmed that the phases did not vary over time, thus indicating the efficacy of the addition of the by-products. This finding suggests that soil remediation may be a feasible option for the re-use of non-hazardous industrial by-products.
authors.affiliation: Departament d'Enginyeria Química i Química Analítica, Universitat de Barcelona, Martí i Franquès 1-11, 3a Planta, 08028, Barcelona, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: González-Núñez
authors.affiliation: Departament d'Enginyeria Química i Química Analítica, Universitat de Barcelona, Martí i Franquès 1-11, 3a Planta, 08028, Barcelona, Spain. annarigol@ub.edu.
authors.forename: Anna
authors.identifier: http://orcid.org/0000-0002-3383-9684
authors.initials: A
authors.lastname: Rigol
authors.affiliation: Departament d'Enginyeria Química i Química Analítica, Universitat de Barcelona, Martí i Franquès 1-11, 3a Planta, 08028, Barcelona, Spain.
authors.forename: Miquel
authors.initials: M
authors.lastname: Vidal
mesh_terms: D002133:Calcium Sulfate / Q000032:analysis; D004784:Environmental Monitoring; D004787:Environmental Pollution / Q000032:analysis; D052918:Environmental Restoration and Remediation / Q000379:methods*; D006256:Hazardous Waste / Q000032:analysis; D007220:Industrial Waste / Q000032:analysis*; D019216:Metals, Heavy / Q000032:analysis; D008903:Minerals / Q000032:analysis; D010944:Plants; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis*; D014131:Trace Elements / Q000032:analysis; D014961:X-Ray Diffraction
chemical_list: D006256:Hazardous Waste; D007220:Industrial Waste; D019216:Metals, Heavy; D008903:Minerals; D012987:Soil; D012989:Soil Pollutants; D014131:Trace Elements; D002133:Calcium Sulfate
keywords: Calcite; Contaminated soil; Gypsum; Heavy metal; Pilot plant; pHstat leaching test