칼슘 및 칼륨 용액을 이용한 원자력발전소 주변 스트론튬과세슘 오염토양 세척기술 연구

Abstract

Calcium (Ca) and potassium (K) were introduced to remove Sr and Cs in soil, respectively. Four factor and three levelBox-Bhenken design was employed to determine the optimal washing condition of Ca- and K-based solutions, and theranges tested were 0.1 to 1M of Ca or K, L/S ratio of 5 to 20, washing time of 0.5 to 2 h, and pH of 2 to 7. The optimalwashing condition determined was 1 M of Ca or K, L/S ratio of 20, washing time of 1 h, and pH of 2, and Ca-based andK-based solutions showed 68 and 81% removal efficiency for Sr and Cs, respectively in soil. For comparison, widely usedconventional washing agents such as 0.075 M EDTA, 0.01M citric acid, 0.01M oxalic acid, and 0.05 M phosphoric acidwere tested, and they showed 25 to 30% of Sr and Cs removal efficiency. Tessier sequential extraction was employed toidentify the changes in chemical forms of Sr and Cs during the washing. In contrast to the conventional washing agents,Ca-based and K-based solutions were able to release relatively strongly bound forms of Sr and Cs such as Fe/Mn-oxideand organic matter bound forms, suggesting the involvement of direct substitution mechanism, probably due to thephysicochemical similarities between Sr-Ca and Cs-K.