In the context of management of the waste streams arising from the reprocessing of spent nuclear fuel, studies have been conducted into the solvent extraction kinetics of lanthanide fission products by the oxygen-donor ligand N,N,N’,N’-tetraoctyl diglycolamide (TODGA) and the effects of solvent phase acidity on the effectiveness of this organic extractant molecule. In this study, we observe a reduction in the rate of cerium extraction as solvent phase acidity increases, attributed to aggregation of the extractant. The effect is shown to be reversible through neutralization while a permanent prevention method is the subject of further work.