Comprehensive Investigation of Yttrium and Rare Earth Element Complexation by Carbonate Ions Using ICP–Mass Spectrometry

Abstract

Carbonate stability constants for yttrium and all rare earth elements have been determined at 25°C and 0.70 molal ionic strength by solvent exchange and inductively coupled plasma–mass spectrometry (ICP–MS). Measured stability constants for the formation of ${\text{MCO}}_3^ +$ and ${\text{M}}\left( {{\text{CO}}_{\text{3}} } \right)_2^--$ from M³⁺ are in good agreement with previous direct measurements, which involved the use of radio-chemical techniques and trivalent ions of Y, Ce, Eu, Gd, Tb, and Yb. Direct ICP–MS measurements of ${\text{MCO}}_3^ +$ and ${\text{M}}\left( {{\text{CO}}_{\text{3}} } \right)_2^--$ formation constants are also in general agreement with modeled stability constants for the metals La, Pr, Nd, Sm, Dy, Ho, Er, Tm, and Lu, based on linear-free energy relationship (LFER). The experimental procedures developed in this work can be used for assessing the complexation behavior of other geochemically important ligands such as phosphate, sulfate, and fluoride.