High‐performance liquid chromatography with electrospray ionisation mass spectrometry and diode array detection in the identification and quantification of the degradation products of calix[4]arene crown‐6 under radiolysis

Abstract

The extraction of 135Cs from high-activity liquid waste, arising from reprocessing of spent nuclear fuel, can be achieved by using calix[4]arene crown-6 compounds. The radiolytic degradation of di(n-octyloxy)calix[4]arene crown-6 (octMC6), in aliphatic or aromatic solvent in contact with 3 M nitric acid, was studied by high-performance liquid chromatography directly coupled to electrospray ionisation mass spectrometry (LC/ESI-MS). More than 50 distinct degradation products were observed, and about 30 of these were identified. These compounds can be assigned to three categories, namely, products of reactions involving radical cleavage or addition, of oxidation reactions, or of aromatic substitution reactions. The major product, corresponding to substitution by an NO2 group, was quantified by external standard calibration using a purified synthetic sample. Despite the observation of all these degradation compounds, octMC6 appears to be remarkably stable under these drastic conditions, combining hydrolysis (HNO(3) 3 M) and an extreme exposure to radiolysis (10(6) Gy). Less than 35% degradation of octMC6 was observed in aromatic solvent under these conditions.

The radiolytic behavior and mechanism of calixarene crown ether under γ-irradiation

“…Combining with the radiolytic behavior of IB and BC, the procedure of radiation degradation of BPC6 under -irradiation can be proposed as follows: (1) the breakage of isopropyl structure of BPC6 is the dominant reaction at dose above 300 kGy (Scheme 1), and the dealkylation of BPC6 results in the formation of radiolytic products containing phenolic hydroxyl groups. Several kinds of fragment molecules from the dealkylation of BPC6 have been reported in literatures [20,22], which are consistent with our results. In the presence of oxygen, the radiolytic products containing the carbonyl groups are H NMR spectra of BC before and after -irradiation at 2200 kGy.…”

“…Therefore, the radiation stability of BPC6 is thus of great importance for the assessing application feasibility in nuclear fuel recycle [17][18][19]. Jankowski and co-workers [20][21][22][23] investigated the radiolytic behavior of BPC6 based extraction system under γ-irradiation by ESI-MS and HPLC. Their results suggested that about 40% of neat BPC6 remained unchanged up to 3000 kGy, whereas the radiolytic mechanism of BPC6 have not been clarified because of this system including various components.…”

Review Article: The Effects of Radiation Chemistry on Solvent Extraction: 2. A Review of Fission‐Product Extraction

“…3) in NPOE was irradiated to 1000 kGy in the presence of 3 M nitric acid. [45] Fifty degradation products were observed, including products of oxidation, aromatic substsitution, and radical addition. The major degradation products for the related monocrown calix [4]arene (crown-6) (MC6) (Fig.…”

“…3) were also due to oxidation (hydroxy-derivatives), aromatic substitution (nitrated products) and dealkylation [46] as well as a radical addition to produce higher molecular weight products. [45] The crown ether structure was conserved in these degradation products, although fully 90% of MC6 was decomposed at 3000 kGy and 75% of BC6 was degraded at 1000 kGy. Lower losses were found for samples irradiated in the absence of the acidic aqueous phase.…”

“…As expected, [23] 0.01 M MC6 was more stable in the aromatic diluent NPOE than in dodecane, with degradation yields of 0.003 and 0.008 mmol J 21 , respectively. [45] The only other work involving the irradiation of calixarenes of which we are aware is that of Feng et al [47] The decomposition of calix [4]-, calix [6]-, and calix [8]arenes following e-beam irradiation of their mixtures with polypropylene in the presence of air was examined by multiple analytical techniques. It was concluded that the calixarene skeleton was not decomposed by doses as high as 20 MGy, but that only modification of phenol and alkyl substituents due to radical addition and hydrogen abstraction reactions occurred.…”