Acrylic fibers coated with copper hexacyanoferrate to determine 137 Cs activity in coastal seawater of Vietnam
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Acrylic fibers coated with copper hexacyanoferrate to determine 137Cs activity in coastal seawater of Vietnam Nguyen Trong Ngo1 · Le Xuan Thang1 · Nguyen Van Phuc1 · Le Nhu Sieu1 · Phan Quang Trung1 · Nguyen Minh Đao1 · Nguyen Thi Huong Lan1 · Vo Thi Mong Tham1 · Le Ngoc Chung2 Received: 18 March 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract A method employing 137Cs sorption to copper hexacyanoferrate ( Cu2[Fe(CN)6])-coated fibers for determining 137Cs activity in seawater is presented in this paper. The Cu2[Fe(CN)6]-coated fibers were packed into a PVC cartridge and used to treat u2[Fe(CN)6]-fiber samples containing 137Cs 300 L of seawater, exhibiting a 137Cs sorption efficiency of above 99%. The C were subsequently dried and placed into a 500 mL Marinelli beaker to determine the activity concentrations by gamma spectrometry. This method was applied to seawater of the Phuoc Dinh and Vinh Hai coastal areas in Ninh Thuan province, Vietnam. The activity concentrations of 137Cs in the surveyed areas ranged from 1.14 to 1.44 Bq/m3. The activities of 137Cs in the seawater samples of this work were compared with those observed in seawater on the coasts of Vietnam and other countries along the South China Sea. Keywords 137Cs · Copper hexacyanoferrate · Cu2[Fe(CN)6]-coated fibers · Seawater
Introduction 137
Cs is a radioactive isotope that is a common product of U fission in nuclear reactors and nuclear weapons. It is an important indicator of radioactive pollution in nuclear accidents, especially in the ocean. The activity concentration of 137Cs in seawater is too low for direct determination by gamma spectroscopy, which requires a maximum of 1–2 L of seawater per sample. Thus, pre-concentration methods were developed to concentrate this nuclide in large-volume seawater samples before radioactivity analysis. The radiochemical method for determining 137Cs in seawater is often laborious and time-consuming, but improved pretreatment procedures and analytical methods can overcome this difficulty [1–6]. Several techniques have been developed to detect 137Cs in seawater, including cesium adsorption onto ammonium 235
* Nguyen Trong Ngo [email protected] * Le Ngoc Chung [email protected] 1
Dalat Nuclear Research Institute, Dalat, Vietnam
University of Dalat, Dalat, Vietnam
2
molybdophosphate (AMP) and co-precipitation with various insoluble hexacyanoferrate(II) ions [4–6]. Hexacyanoferrates can form compounds with various transition elements, such as Co, Ni, Cu, and Zn, all of which efficiently preconcentrate Cs found in seawater [7]. Copper hexacyanoferrate exhibits excellent stability in seawater and is selective towards Cs (excluding Na and K). This selectivity for cesium ions is strongly influenced by the oxidation state of iron in the copper hexacyanoferrate sorbent. When comparing sorbents comprising CuIIFeII or CuIIFeIII, the iron(III)-form was stable and unaffected by Cs(I) sorption while CuIIFeII presented a high exchange capacity [8]. In this case, Han et al. proposed that C s+ exchan
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