本工作研究了在大体积水中用氢氧化镁沉淀浓集钍和用三烷基氧膦萃淋树脂 (TRPO)分离纯化钍的条件,确定了大体积水中微量钍的分析程序。采用本程序,若水中杂质离子分别不超过HPO_4~(2-)(0.4g/1),CO_3~(2-)(0.2g/1),SO_4~(2-)(1.0g/1),Ca~(2+)(1.6g),Mg~(2+)(1.6g),Fe~(3+)(0.2g),U~(6+)(100μg),Y~(3+)(20mg)和Zr~(4+)(10μg)就不会影响钍 In this work, we studied the conditions for the separation and purification of thorium with magnesium hydroxide in a large volume of water and the separation and purification of thorium with trialkylphosphine oxide extraction resin (TRPO). The analytical program for the determination of thorium in large volumes of water was established. With this procedure, if the impurity ions in the water do not exceed the concentrations of HPO_4 ~ (2 -) (0.4g / 1), CO_3 ~ (2 -) (0.2g / 1), SO_4 ~ (2 -) (2 +) (1.6g), Mg2 + (1.6g), Fe3 + (0.2g), U6 + (100μg), Y3 + 20mg) and Zr ~ (4 +) (10μg) will not affect thorium