This project has been focused on modelling actinide behaviour using lanthanide analogues. Ternary complexes of Lanthanides-EDTA-Carbonate have been studied with techniques such as potentiometry and ultraviolet-visible absorption spectroscopy.It was found that ternary complexes of Ln-EDTA-Carbonate and Ln-EDTA-OH do exist for La, Eu and Lu. Log K values were calculated from potentiometry titrations which involve the formation of these ternary species. For lanthanum, the log K values for the complexes [La(EDTA)]-, [La(EDTA)(OH)]2- and [La(EDTA)(CO3)]3- were 14.20, -9.22 and 4.70, respectively. For europium, the log K for the complexes [Eu(EDTA)]-, [Eu(EDTA)(OH)]2- and [Eu(EDTA)(CO3)]3- were 13.77, -10.35 and 4.55, respectively. For lutetium, the results for the complexes [Lu(EDTA)]-, [Lu(EDTA)(OH)]2-, [Lu(EDTA)(OH)2]2- and [Lu(EDTA)(CO3)]3- were 17.38, -12.40, -22.97 and 3.30, respectively. The results are useful for helping to understanding solution chemistry of lanthanides with EDTA in aqueous environments, which is applicable to actinide-lanthanide separations and actinide/lanthanide behaviour in storage pond conditions within the area of nuclear waste management.