High immobilization of soil cesium using ball milling with nano-metallic Ca/CaO/NaH2PO4: implications for the remediation of radioactive soils

• Published in: Environmental chemistry letters Vol. 10; no. 2; pp. 201 - 207
• Main Authors: Mallampati, Srinivasa Reddy, Mitoma, Yoshiharu, Okuda, Tetsuji, Sakita, Shogo, Kakeda, Mitsunori
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.06.2012
• Subjects: Analytical Chemistry; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Geochemistry; Original Paper; Pollution; Nano-metallic Ca/CaO; Contaminated soil; Sodium phosphate; SEM/EDS; Ball milling; Immobilization; Cesium
• ISSN: 1610-3653; 1610-3661
• DOI: 10.1007/s10311-012-0357-3

This report shows that cesium can be immobilized in soils with an efficiency of 96.4% by ball milling with nano-metallic Ca/PO 4 . In Japan, the major concern on 137 Cs deposition and soil contamination due to the emission from the Fukushima Daiichi nuclear power plant showed up after a massive quake on March 11, 2011. The accident rated 7, the highest possible on the international nuclear event scale, released 160 petabecquerels (PBq) of iodine 131 I and 15 PBq of 137 Cs according to the Japanese Nuclear and Industrial Safety Agency. Both 137 Cs and 131 I radioactive nuclides are increasing cancer risk. Nonetheless, 137 Cs, with a half-life of about 30 years compared with 8 days for 131 I, is a major threat for agriculture and stock farming and, in turn, human life for decades. Therefore, in Japan, the 137 Cs fixation and immobilization in contaminated soil is the most important problem, which should be solved by suitable technologies. Ball milling treatment is a promising treatment for the remediation of cesium-contaminated soil in dry conditions. Here, we studied the effect, factors and mechanisms of soil Cs immobilization by ball milling with the addition of nano-metallic Ca/CaO/NaH 2 PO 4 , termed “nano-metallic Ca/PO 4 .” We used scanning electron microscopy combined with electron dispersive spectroscopy (SEM/EDS) and X-ray diffraction. Results show that immobilization efficiency increases from 56.4% in the absence of treatment to 89.9, 91.5, and 97.7 when the soil is ball-milled for 30, 60 and 120 min, respectively. The addition of nano-metallic Ca/PO 4 increased the immobilization efficiency to about 96.4% and decreased the ball milling time. SEM/EDS analysis allows us to observe that the amount of Cs decreased on soil particle surface. Use of nano-metallic Ca/PO 4 over a short milling time also decreases Cs leaching. Therefore, ball milling with nano-metallic Ca/PO 4 treatment may be potentially applicable for the remediation of radioactive Cs-contaminated soil in dry conditions.