Solubility and hydrolysis of lutetium at different [Lu3+]initial

Abstract

Solubility product (Lu(OH)3(s)⇆Lu3++3OH−) and first hydrolysis (Lu3++H2O⇆Lu(OH)2++H+) constants were determined for an initial lutetium concentration range from 3.72·10−5 mol·dm−3 to 2.09·10−3 mol·dm−3. Measurements were made in 2 mol·dm−3 NaClO4 ionic strength, under CO2-free conditions and temperature was controlled at 303 K. Solubility diagrams (pLuaq vs. pCH) were determined by means of a radiochemical method using 177Lu. The pCH for the beginning of precipitation and solubility product constant were determined from these diagrams and both the first hydrolysis and solubility product constants were calculated by fitting the diagrams to the solubility equation. The pCH values of precipitation increases inversely to [Lu3+]initial and the values for the first hydrolysis and solubility product constants were log10β*Lu,H = −7.92±0.07 and log10K*sp,Lu(OH)3 = −23.37±0.14. Individual solubility values for pCH range between the beginning of precipitation and 8.5 were SLu3+ = 3.5·10−7 mol·dm−3, SLu(OH)2+ = 6.2·10−7 mol·dm−3, and then total solubility was 9.7·10−7 mol·dm−3.