Theoretical And Applied Research On Separation Of Precious Metals By High Performance Ion Exchange Chromatography

Precious metals are very important in national economy due to their special physical and chemical performance. However, it is their particular physical and chemical properties that result in the complexity of their extraction process. As a result, except for solvent extraction being limitedly adopted in industrialized process, many enterprises are using conventional precipitation technique, which is tedious, with low recovery, high costs, and heavy pollution. It is necessary to carry out theoretical and applied research on high efficiency, economical short flow and friendly environment technique for the extraction of precious metals using ion exchange chromatography.The dissertation is aimed at establishing a new process for highly efficient separation of platinum, palladium, iridium, rhodium and gold, in which some representative samples such as platinum and palladium concentrates, copper and lead anode muds, crude copper and lead and alloys of precious metals were tested. In order to achieve the above goal, the dissertation focuses on the following studies, static separation by ion exchange resins, dynamic separation by high performance ion exchange chromatography, practical samples separation, reaction kinetics and thermodynamics, adsorption and elution mechanism.Static separation by ion exchange resins, in which D301R anion exchanger was employed as the principal resin for separation, was the basis of dynamic separation by ion exchange chromatography, so the main factors that influence ion exchange reaction were investigated. Great efforts have been made to solve the problem of selectivity for adsorption and elution, which restricted the application.Achieving dynamic separation by high performance ion exchange chromatography is the core of the dissertation. Based on the results of static experiments, the factors influencing dynamic separation were studied. The problems of selectively elution and regeneration in ion exchange chromatography were solved by the selection of stationary and mobile phase, and the stage elution technique. The flow chart for dynamic separation by high performance ion exchange chromatography is established, in which D301R anion exchanger chromatographic column is used to carry out the separation of precious metals from base metals, and the separation among precious metals. Combined with a 001 X 7cation exchanger chromatographic column, rhodium could be separated. The flow chart was tested by simulated samples, showing that it is practical and highly efficient.To solve the practical separation problems is the final object of the dissertation, so several kinds of precious metal samples such as platinum and palladium concentrates, copper and lead anode muds, crude copper and lead and alloys of precious metals were tested by the proposed method. Satisfactory results were obtained with high recovery of precious metals, good resolution, and wide application scope. The recoveries for platinum, palladium, iridium, rhodium and gold are in the range of 93.72~100.16% 91.25~101.48 %, 93.15~99.33%, 97.00~98.99%, 92.94~101.55% respectively. The separation between precious and base metals, the separation among precious metals are so complete that baseline resolution effect has been achieved, with the resolutions being in the range of 1.50~2.17. The purities, of the concentrated precious metals solution in the scaled-up experiments are 97.04% for platinum, 98.28% for palladium, 97.14% for iridium, and 98.67% for gold.The goal of kinetics and thermodynamics research is to get more information about the main factors, which influencing the reaction course and degree, and benefiting the control in practice. My kinetics studies focused on the relationships between reaction rate and temperature, the calculation of activation energy and thermodynamics studies focused on the distribution coefficients and reaction enthalpy. The higher the temperature, the faster the reaction. The 'exchange reaction would be carried out completely for gold and platinum with the increase of temperature, while th...