Speciation Analysis of ¹²⁹I in Seawater by Carrier-Free AgI–AgCl Coprecipitation and Accelerator Mass Spectrometric Measurement

A rapid and simple method was developed for speciation analysis of ¹²⁹I in seawater by selective coprecipitation of carrier-free iodide and accelerator mass spectrometry (AMS) measurement of ¹²⁹I. Iodide was separated from seawater and other species of iodine by coprecipitation of AgI with Ag₂SO₃, AgCl, and AgBr by addition of only 100 mg/L Ag⁺ and 0.3 mmol/L NaHSO₃ at pH 4.2–5.5. The separation efficiency of iodide was more than 95%, and crossover between ¹²⁹IO₃^– and ¹²⁹I^– fractions is less than 3%. Iodate and total inorganic iodine were converted to iodide by use of NaHSO₃ at pH 1–2 and then separated by the same method as for iodide. Ag₂SO₃ in the coprecipitate was removed by washing with 3 mol/L HNO₃ and the excess AgCl and AgBr was removed by use of diluted NH₃, and finally a 1–3 mg precipitate was obtained for AMS measurement of ¹²⁹I. The recovery of iodine species in the entire procedure is higher than 70%. Six seawater samples collected from the Norwegian Sea were analyzed by this method as well as a conventional anion-exchange chromatographic method; the results from the two methods show no significant difference (<i>p</i> = 0.05). Because only one separation step and fewer chemicals are involved in the procedure, this method is suitable for operation on board sampling vessels, as it avoids the transport of samples to the laboratory and storage for a longer time before analysis, therefore significantly improving the analytical capacity and reliability of speciation analysis of ¹²⁹I. This improvement can stimulate oceanographic tracer studies of ¹²⁹I

Robust microporous metal-organic frameworks for highly efficient and simultaneous removal of propyne and propadiene from propylene

Simultaneous removal of trace amounts of propyne and propadiene from propylene is an important but challenging industrial process. We report herein a class of microporous metal–organic frameworks (NKMOF‐1‐M) with exceptional water stability and remarkably high uptakes for both propyne and propadiene at low pressures. NKMOF‐1‐M separated a ternary propyne/propadiene/propylene (0.5 : 0.5 : 99.0) mixture with the highest reported selectivity for the production of polymer‐grade propylene (99.996 %) at ambient temperature, as attributed to its strong binding affinity for propyne and propadiene over propylene. Moreover, we were able to visualize propyne and propadiene molecules in the single‐crystal structure of NKMOF‐1‐M through a convenient approach under ambient conditions, which helped to precisely understand the binding sites and affinity for propyne and propadiene. These results provide important guidance on using ultramicroporous MOFs as physisorbent materials