title: Dynamic immobilization of simulated radionuclide 133Cs in soil by thermal treatment/vitrification with nanometallic Ca/CaO composites.
abstract: Although direct radiation induced health impacts were considered benign, soil contamination with (137)Cs, due to its long-term radiological impact (30 years half-life) and its high biological availability is of a major concern in Japan in the aftermath of the Fukushima nuclear power plant disaster. Therefore (137)Cs reduction and immobilization in contaminated soil are recognized as important problems to be solved using suitable and effective technologies. One such thermal treatment/vitrification with nanometallic Ca/CaO amendments is a promising treatment for the ultimate immobilization of simulated radionuclide (133)Cs in soil, showing low leachability and zero evaporation. Immobilization efficiencies were 88%, 95% and 96% when the (133)Cs soil was treated at 1200 °C with activated carbon, fly ash and nanometallic Ca/CaO additives. In addition, the combination of nanometallic Ca/CaO and fly ash (1:1) enhanced the immobilization efficiency to 99%, while no evaporation of (133)Cs was observed. At lower temperatures (800 °C) the leachable fraction of Cs was only 6% (94% immobilization). Through the SEM-EDS analysis, decrease in the amount of Cs mass percent detectable on soil particle surface was observed after soil vitrified with nCa/CaO + FA. The (133)Cs soil was subjected to vitrified with nCa/CaO + FA peaks related to Ca, crystalline phases (CaCO3/Ca(OH)2), wollastonite, pollucite and hematite appeared in addition to quartz, kaolinite and bentonite, which probably indicates that the main fraction of enclosed/bound materials includes Ca-associated complexes. Thus, the thermal treatment with the addition of nanometallic Ca/CaO and fly ash may be considered potentially applicable for the remediation of radioactive Cs contaminated soil at zero evaporation, relatively at low temperature.
authors.affiliation: Department of Civil and Environmental Engineering, University of Ulsan, Ulsan 680-749, Republic of Korea. Electronic address: srireddys@ulsan.ac.kr.
authors.forename: Srinivasa Reddy
authors.initials: SR
authors.lastname: Mallampati
authors.affiliation: Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, 562 Nanatsuka-Cho, Shobara City, Hiroshima 727-0023, Japan. Electronic address: mitomay@pu-hiroshima.ac.jp.
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Mitoma
authors.affiliation: Environmental Research and Management Center, Hiroshima University, 1-5-3 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8513, Japan.
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Okuda
authors.affiliation: Politehnica University of Bucharest, Department of Organic Chemistry, Bucharest 060042, Romania.
authors.forename: Cristian
authors.initials: C
authors.lastname: Simion
authors.affiliation: Department of Civil and Environmental Engineering, University of Ulsan, Ulsan 680-749, Republic of Korea.
authors.forename: Byeong Kyu
authors.initials: BK
authors.lastname: Lee
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry*; D002588:Cesium Radioisotopes / Q000737:chemistry*; D062406:Fukushima Nuclear Accident; D010087:Oxides / Q000737:chemistry
chemical_list: D017610:Calcium Compounds; D002588:Cesium Radioisotopes; D010087:Oxides
keywords: Nanometallic Ca/CaO; Radioactive cesium ((137)Cs); Remediation; Simulated radionuclide ((133)Cs); Thermal treatment; Vitrification