Preferential removal and immobilization of stable and radioactive cesium in contaminated fly ash with nanometallic Ca/CaO methanol suspension

• Published in: Journal of hazardous materials Vol. 279; pp. 52 - 59
• Main Authors: Mallampati, Srinivasa Reddy, Mitoma, Yoshiharu, Okuda, Tetsuji, Sakita, Shogo, Simion, Cristian
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 30.08.2014; Elsevier
• Subjects: Applied sciences; Calcium - chemistry; Calcium Compounds - chemistry; Cesium; Cesium - chemistry; Cesium - isolation & purification; Cesium Isotopes - chemistry; Cesium Isotopes - isolation & purification; Cesium Radioisotopes - chemistry; Cesium Radioisotopes - isolation & purification; Coal Ash - analysis; Contaminated fly ash; Contamination; Exact sciences and technology; Fly ash; Immobilization; Incineration; Methanol; Methanol - chemistry; Methyl alcohol; Microscopy, Electron, Scanning; Nanometallic Ca/CaO; Nanostructure; Oxides - chemistry; Pollution; Refuse Disposal; Remediation; Removal; Stable and radioactive cesium; Suspensions; Washing; Removal; Immobilization; Contaminated fly ash; Nanometallic Ca/CaO; Stable and radioactive cesium; Methanol; Cesium 137; Scanning electron microscopy; Elution; Radioactive pollution; Cesium 134; Combustion; Washing; Radioisotope; Fly ash; Amendment; Decontamination; Ash content
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2014.06.044

Schematic representation of possible mechanisms determining the Cs extraction and immobilization in fly ash during water, methanol or n-MCaS extraction. •nMCaS suspension for cesium extraction and immobilization in fly ash was developed.•Enhanced cesium immobilization was done by nanometallic Ca/CaO methanol suspension.•By SEM analysis the amount of cesium detectable on soil particle surface decreases.•Leachable cesium concentrations reduced, lower than the standard regulatory limit.•nMCaS unique and a highly potential amendment for the remediation of Cs. In this work, the capability of nanometallic Ca/CaO methanol suspension in removing and/or immobilizing stable (133Cs) and radioactive cesium species (134Cs and 137Cs) in contaminated fly ash was investigated. After a first methanol and second water washing yielded only 45% of 133Cs removal. While, after a first methanol washing, the second solvent with nanometallic Ca/CaO methanol suspension yielded simultaneous enhanced removal and immobilization about 99% of 133Cs. SEM-EDS analysis revealed that the mass percent of detectable 133Cs on the fly ash surface recorded a 100% decrease. When real radioactive cesium contaminated fly ash (containing an initial 14,040Bqkg−1134Cs and 137Cs cumulated concentration) obtained from burning wastes from Fukushima were reduced to 3583Bqkg−1 after treatment with nanometallic Ca/CaO methanol suspension. Elution test conducted on the treated fly ash gave 100BqL−1 total 134Cs and 137Cs concentrations in eluted solution. Furthermore, both ash content and eluted solution concentrations of 134Cs and 137Cs were much lower than the Japanese Ministry of the Environment regulatory limit of 8000Bqkg−1 and 150BqL−1 respectively. The results of this study suggest that the nanometallic Ca/CaO methanol suspension is a highly potential amendment for the remediation of radioactive cesium-contaminated fly ash.