Nitrogen Isotope Separation Using Porous Microreticular Cation-Exchange Resin

Abstract

A long-distance chromatographic operation was carried out in order to study the isotope accumulation of I5 N in the ion-exchange enrichment process by using a porous microreticular cation-exchange resin. Combined bands of ammonium and lithium ions were eluted up to 20 m, and thereafter the ammonium band was eluted up to a total migration distance of 60 m. The constant lengths of the adsorbed bands were maintained throughout the elution, and a sharp boundary at the rear end of the ammonium band was monitored by an electric conductivity meter. The enrichment of both 15 N at the rear end of the ammonium band and 6 Li at the rear end of the lithium band were confirmed in the experiment. The values of HETP in the system were kept almost constant, 0.49 mm, throughout the migration up to a distance of 60 m. Previously reported works on the same process are analyzed, and an empirical relation for HETP in terms of resin diameter and band velocity has been obtained as HETP = c(d p u B ) 0M .

Effects of Cross Linking on the Chromatographic Nitrogen Isotope Separation

“…Previously, Aida et al reported the boron isotope separation by using commercially available anion exchange resin (Diaion WA-21, 60 -80 mesh) and got the value of HETP was 0.18 cm [13]. Ohwaki et al reported nitrogen isotope separation by using HITEC-H1 cation exchange resin (porous strong acid type, cross linking 30%, particle size 37 -77 um) and the value of HETP was 0.019 cm [7,14]. In our previous work [8][9][10], SQS-6 resin (8% cross linking, particle size 60 -80 um) was applied to nitrogen isotope separation and the value of HETP was 0.02 cm.…”

“…The sampled fractions of effluent were subjected to concentration analysis of ammonium ion by YokogawaHokusin IC-100 ion chromatography analyzer (Tokyo, Japan). Nitrogen isotopic abundance ratios of 14 N and 15 N in the samples were measured by two mass spectrometers ESCO EMD-05S double focusing mass spectrometer for gas samples and IsoPrime EA mass spectrometer, which accepts solid samples such as NH 4 Cl. When ESCO EDM-05 was used, the samples collected in the chemical form of NH 4 Cl were converted to N 2 samples by KBrO solutions prior to the analysis by mass spectrometry and the isotopic abundance of 15 N was calculated from the ratio of the peak height.…”

“…Then, a NaOH solution was fed into the columns as an eluent. During this process, the light isotope 14 N was enriched at the front boundary of ammonium ion adsorption band and the heavy isotope 15 N was enriched at the rear boundary region. In general, cation exchange process is a promising technique to produce highly enriched isotope due to the nature of small HETP value.…”

“…Natural nitrogen, however, cannot be used as the material of the nitride fuel, due to the neutron reactivity of the major isotope 14 N. The major isotope 14 N, is converted to the radioactive isotope 14 C in nuclear reactors whose half life is more than 5000 years by the reaction of 14 N (n, p) 14 C. The present urgent problem is lowering the price of nuclear fuel which is mainly affected by the large expense in 15 N enrichment from the natural abundance of 0.365% up to the required 99.9% [3]. For the sake of neutron economy and to avoid environmental risk of 14 C, innovative technologies are needed for the production of highly 15 N enriched nitrogen.…”

Nitrogen Isotope Separation with Displacement Chromatography Using Cryptand Polymer

“…Recently a number of researchers studied isotope separation and enrichment of several metals with cryptands, cryptand polymer and polymers containing crown ethers, [6][7][8][9][10][11][12][13][14][15] but no nitrogen isotope separation has been reported with the macrocyclic compound.…”