Partial Stabilization of Mo-Containing Hazardous Wastes Using a Ferrous Sulfate-Based Additive as a Redox Agent
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ORIGINAL PAPER
Partial Stabilization of Mo‑Containing Hazardous Wastes Using a Ferrous Sulfate‑Based Additive as a Redox Agent G. Mancini1 · F. Palmeri1 · A. Luciano2 · P. Viotti3 · D. Fino4 Received: 31 December 2019 / Accepted: 18 May 2020 © Springer Nature B.V. 2020
Abstract Bottom and fly ashes from a hazardous waste incineration plant, which showed a high concentration of Mo in a leaching test, have been treated to decrease its leachability to below the limit set by the laws in force for admittance to a non-hazardous waste landfill. Both ashes have a basic pH, that is, of around 11–13, therefore most of the molybdenum species were expected to be in the form of molybdate ions (MoO42−), the most soluble molybdenum compound. The aim of the study was to immobilize the molybdate ions using the reducing properties of the Fe2+ ion, in compliance with specific pH and redox potential conditions, which resulted to be crucial for the partial stabilization and immobilization of Mo. The bottom ash was treated both by adding a cost-effective ferrous sulfate-based additive alone and by adding it together with calcium oxide. The fly ash was initially tested with the same ferrous sulfate-based additive; a mix of the former additive and a concentrated solution of sulfuric acid (96%) was then tested to increase the stabilization efficiency. The conducted experiments revealed that the molybdenum leaching behavior can be controlled efficiently by adding ferrous sulfate, under specific pH and redox potential conditions, thereby providing further insight into the sustainable chemical conditions necessary to partially stabilize Mocontaining hazardous waste. Graphic Abstract
Keywords Molybdenum · Hazardous waste treatment · Solid waste stabilization · Redox precipitation · Immobilization Extended author information available on the last page of the article
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Waste and Biomass Valorization
Statement of Novelty This research fully supports the implementation of the European directives and policies pertaining to sustainable waste management strategies and BAT (Best Available Techniques) for industrial waste treatments. The novelty of the approach is that it focuses on the partial stabilization of Mo-containing hazardous wastes and on the need to treat these wastes separately, in order to avoid a diffused practice that is based more on a dilution effect than on a real efficient treatment. The advantages and limitations of the proposed approach are presented. The research, by proposing a low-cost but effective reagent, may have an impact on the industrial waste treatment sector, as it has dealt with the strategies that are needed to treat heavy metals with oxoanionic behavior, thereby providing a more complete and sustainable approach for their partial stabilization and, therefore, for their safe disposal in non-hazardous waste landfills.
Introduction The characterization of waste, which is required for its disposal in a non-hazardous waste landfill, is aimed at ensuring that the behavior of the waste, aft
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