Liquid-liquid extraction of rare earth elements from sulfuric acid
This thesis is concerned with the liquid-liquid extraction and separation of Y, Ce, La, binary mixtures, and ternary mixtures as well as synthesis of novel amide ligands for the extraction of rare earth elements. Chapter I is the general introduction of the practical process and applications of solvent extraction and its theory. It describes systems involving compound formation, ion-association and solvation as well as solvent loading capacity, dispersion and coalescence. The aims of this thesis are also presented. Chapter 2 presents an introduction to yttrium chemistry and recent developments in yttrium extraction chemistry. It describes the relevant factors affecting the liquidliquid extraction process to determine the optimum conditions for yttriurn extraction from sulfate liquor. These factors include TiOA concentration, contact time, pH value, temperature, aqueous phase composition, diluent and construct of McCabe-Thiele diagram. In addition, the synergistic effect of using TBP, TOPO and D2EHPA and the optimum conditions for the stripping process are deten-nined. Chapter 3 contains introduction to cerium chemistry and recent developments in cerium extraction chemistry. The optimum conditions for solvent extraction of cenum(III) from a sulfate medium, and synergistic effects using TOPO and D2EHPA on the extraction process are studied. Also, the relevant factors affecting cerium(Ill) stripping efficiency are determined. Chapter 4 presents a brief introduction to lanthanum and recent developments in lanthanum extraction chemistry. The optimum conditions for solvent extraction of lanthanum from sulfate media, with synergistic effects using TOPO, D2EHPA and TBP are described. In addition, the suitable conditions for the lanthanum stripping process are determined. Chapter 5 contains the principles of separation and liquid-liquid extraction of binary (Y/La) and ternary (Nd-La-Y) element systems. The optimum conditions for the separation of both systems were investigated. Chapter 6 describes the synthesis and characterization of several novel piperazine and piperidine amide ligands. These ligands have good extraction ability for both light and heavy rare earth elements. The optimum conditions for solvent extraction of yttnum and cerium(III) using these ligands were studied. The chapter also, contains the experimental procedures and characterising data for ligand synthesis in this thesis.