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This paper reports the use of synergist-impregnated polyurethane foams for preconcentra-ting trace thorium from natrual waters.The polyether type polyurethane foams were employed,which were loaded with bis (2-ethylhexyl) phosphoric acid/tributyl phosphate/carbon tetrach-loride (2:5:93,V/V/V) mixture.The surplus reagent was removed by filter paper.The loadedfoams prepared in this way were dipped into the water sample and stirred for 20 minutes.Theoptimum conditions for preconcentration are:samples should be adjusted to about pH 1 andtemperature kept within 30°—45℃.The distribution and phase ratios were calculated to be 4.26×10~4 and 2.01×10~4 respe-ctively,assuming that the mixture and water were totally immiscible with each other.Theactural values were all slightly greater than the calculated ones.After removing the foam fromthe sample,the former was washed with water and subjected to wet oxidation with concentratednitric and perchloric acids.The residue was taken up with dilute hydrochloric acid.Theamount of thorium in the water sample was spectrophotometrically determined with ArsenazoⅢ at 665 nm.The method is simple,rapid,accurate and inexpensive.
This paper reports the use of synergist-impregnated polyurethane foams for preconcentra-ting trace thorium from natrual waters. The polyether type polyurethane foams were employed, which were loaded with bis (2-ethylhexyl) phosphoric acid / tributyl phosphate / carbon tetrachioride 2: 5: 93, V / V / V) mixture.The surplus reagent was removed by the filter paper. The loadedfoams prepared in this way were dipped into the water sample and the stirred for 20 minutes.Theoptimum conditions for preconcentration are: samples should be adjusted to about pH 1 andtemperature kept within 30 ° -45 ° C. The distribution and phase ratios were calculated to be 4.26 × 10-4 and 2.01 × 10-4 respe-ctively, assuming that the mixture and water were totally immiscible with each other Theactural values were all slightly greater than the calculated ones. After removing the foam from the sample, the former was washed with water and subjected to wet oxidation with concentratednitric and perchloric acids. The residue was taken up with dilute hydrochloric acid. The thickness of the thorium in the water sample was spectrophotometrically determined with Arsenazo III at 665 nm. The method is simple, rapid, accurate and inexpensive.