Degradation of Spent Radioactive Ion Exchange Resins and Its Mechanisms by Fenton Process

Spent IERs are released during the operation and decommissioning of nuclear facilities.The safe and efficient treatment of spent IERs is an emergent problem in nuclear industry.IRN77 is a typical ion exchange resin widely used in many nuclear power plants.Fenton process can degrade organic resins and reduce the radioactive residues volume and the disposal cost significantly.In this work,the IRN77 resin was selected as a model ion exchange resin and its treatment via Fenton process was investigated.The influencing factors for resin degradation,including catalyst dosage,reaction time,initial pH,temperature and oxidant dosage were investigated and optimized via the single-factor experimental method.Under the reaction temperature of 100℃ and reaction time of 120 min at initial pH of 2,more than 97%COD was removed with 1.66 g H_(2)O_(2) and 32 mg FeSO_(4)·7H_(2)O added to per gram of wet resin.The catalyst dosage and H_(2)O_(2) dosage can decrease 78%and 50%respectively compared to previous results.SEM,FT-IR and ion chromatograph were employed to characterize the resin beads,soluble organics and intermediates during the degradation reaction.Based on the characterization results,the resin degradation pathway was discussed in detail and it is proposed to three stages including beads dissociation,styrene and divinylbenzene decomposition and carboxylic acids mineralization.During the IERs degradation,formic acid,acetic acid,propionic acid and oxalic acid were quantitatively monitored as main intermediates,and oxalic acid accounted for over 90%of COD in the final residue solution.Fenton process is suggested as a promising resin degradation method.

Effect of chemical and thermal activations on the properties of rice husk ash-based solidified wastes

Strength development, leachability and microstructure of heavy metals from the solidified waste using synthesis rice husk ash （sRHA） and lime blended at the weight ratio of 1：1 were used as binders. The heavy metal-containing sludge was used at the level of 0 wt.%, 30 wt.%, and 50 wt.% dry weight, respectively. The sample specimens with and without 1.5 wt.% of sodium silicate （SiO2/Na2O = 1.0） were cured under the ambient condition and elevated temperature curing at 50℃ for 24 hr. Experimental results showed that the introduction of sodium silicate solution and elevated temperature curing to sRHA-based solidified waste containing 30 wt.% of heavy metal sludge gave one day strength of 20 kg/cme compared to 0.9 kg/cm^2 for the control sample. XRD patterns indicated that most metal-sulfides present in the sludge were appeared in the solidified waste and SEM coupled with EDX techniques reveal these metal-sulfide particles were trapped within the lime-sRHA matrices. In addition, cumulative leaching behavior by tank test （EA NEN 7375：2004） showed that solidified waste containing up to 30 wt.% of heavy metal sludge was suitable to dispose in a secured landfill.

Synthesis, Characterization and Ion Exchange Properties of a New Composite of Inorganic Ion Exchanger： Polyacrylonitrile Cerium（IV） Molybdophosphate

In this work, the synthesis of the composite of cerium（IV） molybdophosphate （CMP） and polyacrylonitrile （PAN） was reported （CMP-PAN）. The material has been characterized by elemental and spectral （FT-IR）, X-ray and thermal （TGA） analysis. Also the size analysis of the composite was done by scanning electron microscopy （SEM）. Its chemical stability in acidic, basic and saline solutions and radiation stability up to 100 kGy total expose dose were assessed. Whereas the synthesized composite has ion exchange properties, its ion exchange capacity and behavior toward several metal ions were also investigated. Further, the distribution coefficients of the metal ions were calculated. Finally, the ability of the synthesized CMP-PAN composite for the decontamination of low level liquid waste （LLLW） was investigated.