Viability of adding gypsum and calcite for remediation of metal-contaminated soil: laboratory and pilot plant scales
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The effect of adding waste materials (gypsum and calcite) for the remediation of a soil contaminated by pyritic minerals was examined. Materials were characterised in terms of their acid neutralisation capacity (ANC), sorption capacity and structural components. Their effect on the contaminant leaching in soil + material mixtures over a wide range of pH was also evaluated. Results at laboratory and pilot plant scales were compared to account for the potential variability in the material efficiency when applied at larger scale. The use of gypsum permitted its valorisation, although calcite was a more effective amendment because its addition led to a greater increase in the pH and acid neutralisation capacity, and thus in the sorption capacity in the resulting soil + material mixture. In the same way, when the combination of gypsum + calcite was added to the soil, it led to an increase in the pH from 2.5 to 6.9 and in the ANC from −86 to 1,513 meq/kg. As a result, the concentration of extractable heavy metals and As was reduced, and they were successfully immobilised both at laboratory and at pilot plant scales. Thus, the use of these materials induced a significant reduction in the contaminant mobility and permitted the valorisation of waste materials.
KeywordspHstat leaching test Gypsum Calcite Metal-contaminated soil Remediation
This research was supported by the Ministerio de Educación y Ciencia de España (Projects CTQ2010-14874 and CTM2011-27211) and Generalitat de Catalunya (AGAUR 2009SGR1188). ICP-OES analyses were conducted at the CCiT of the UB. XRD measurements were conducted at the CITIUS of the USA. The authors would like to thank HC Energía for supplying the materials, BEFESA for supplying the contaminated soils and for the access to the pilot plant and in the context of the project funded by the Secretaría General para la Prevención de la Contaminación y el Cambio Climático (Ministerio de Medio Ambiente, contract 300/PC/08/3-01.1).
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