Innovative oxidative treatment and geopolymer. Encapsulation of spent mixed bed ion exchange resins
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Data di Pubblicazione:
2022
Citazione:
Innovative oxidative treatment and geopolymer. Encapsulation of spent mixed bed ion exchange resins / F. Galluccio, E. Mossini, A. Santi, E. Macerata, G.D. Gatta, P. Lotti, G. Bilancia, A. Ravazzani, P. Peerani, M. Mariani. ((Intervento presentato al convegno EURADWASTE tenutosi a Lyon : 30 Maggio-3 Giugno nel 2022.
Abstract:
Several nuclear industrial applications are currently using ion-exchange resins (IERs).
Organic cationic and anionic resins are mainly employed for chemical control of water
and radioactivity removal during power plant operations, but also for
decontamination of liquid waste streams during decommissioning stages. Upon used,
IERs are usually replaced to reduce the amount of generated radioactive liquid waste.
However, this approach is involving the production of large volumes of exhausted
organic resins. To safely dispose of this low or intermediate level waste, processes
more reliable than direct encapsulation of spent IERs in Ordinary Portland Cement
(OPC) are being developed. They point to overwhelm the challenging nature of the
waste due to swelling, flammability, dispersivity, and potential radionuclides
leachability, and to minimize volumes of the final waste package, processing costs and
environmental footprint.
The focus of this work is on the development of a Fenton-like wet oxidation process
that consists of an exothermic reaction of a catalyst and an oxidant by the production
of reactive radicals that decompose organic matter. It is being considered more
attractive due to low oxidation temperature (< 100 °C), non-toxic catalyst and green
oxidant. The appropriate tuning of catalysts (FeSO4·7H2O, CuSO4·5H2O) and oxidant
(H2O2) amounts allowed the treatment of a mixed resin bed system. The successful
decomposition of about 100 g of a surrogate waste loaded with Cs, Co, Sr, Ni, Cl, and I
as representatives of activation and fission products contamination, has led to a
scaleup of the process (about 200 g of resins). The temperature and colour shift of the
solution have been helpful to monitor the oxidation evolution. The moist and
brownish residue downstream of the evaporation process underwent a geopolymeric
encapsulation. The sustainable formulation involves the activation with sodium
hydroxide of highly zeolitized tuff and recycled industrial by-products, to provide high
pozzolanic reactivity, high durability, chemical and thermal stability in compliance
with the Waste Acceptance Criteria. The process showed promising weight reduction
rates and organic matter decomposition as proved by Chemical Oxygen Demand
measurements. Besides, inorganic compounds have been identified in the final
residues by X-Ray Diffraction, Fourier Transform Infrared, and Raman analyses, while
a satisfactory retention of the contaminants was demonstrated by ICP-MS. In the
future, a new process scale-up will be pursued to manage 1 kg of spent resins.
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Keywords:
geoplymer; ion-exchange resins; zeolitized tuff
Elenco autori:
F. Galluccio, E. Mossini, A. Santi, E. Macerata, G.D. Gatta, P. Lotti, G. Bilancia, A. Ravazzani, P. Peerani, M. Mariani
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