Graduation date: 1998

One model system for the investigation of selectivity in inorganic ion exchangers is a group of synthetic analogues of the mineral umbite. Hydrothermally synthesized trisilicates with the general form A2BSi3O9.H2O, where A is a monovalent cation, and B = Ti4+, Zr4+, and Sn4+ have been shown to have ion exchange properties. The extended three dimensional framework structure offers the ability to tune the selectivity based on the size of the cavities and channels. The unit cell volume, and therefore the pore size, can be altered by changing the size of the octahedral metal. The substitution of Ge for Si can also increase the pore size. A variety of cations have been exchanged into the trisilicates including alkali and alkaline earths, lanthanides, and actinides. The reason for the selectivity rests in the pocket of framework oxygens which make up the exchange sites. Close examination of the cation environments shows that the ions with the greatest affinity are those that have the closest contacts to the framework oxygens. For example, among alkali cations, zirconium trisilicate demonstrates the greatest affinity for Rb+ and has the most A-O contact distances approaching the sum of their ionic radii. The origins of selectivity also rely upon the valence of the incoming cation. When cations are of similar ionic radius, a cation of higher charge is always preferred over the lower valence. Ion exchange studies in binary solutions of cations of different valence, but similar size (1.0Å ) have proven the selectivity series to be Th4+ > Gd3+ > Ca2+ > Na+. Through structural characterization, kinetic studies, and use of in situ x-ray diffraction techniques the origins of selectivity in these inorganic ion exchangers has been further elucidated. The principles gleaned from these studies can be applied to other inorganic framework materials. The umbite system has the potential to be altered and tailored for specific separation needs. The trisilicate materials presented in this work are representative of the types of advances in inorganic materials research and prove their potential as applicable compounds useful for solving real world problems.

The aim of this research was to provide a comprehensive evaluation of the heavy metal removal performance of two synthetic zeolites, Zeocros CA150 and Zeocros CG180. Detailed laboratory investigations of the key parameters known to affect zeolitic ion exchange were performed with respect to lead, zinc, copper, cadmium and nickel by means of batch equilibrium tests. The study into the effect of contact time suggests that a near equilibrium state was reached within two hours. As metal hydroxide precipitation was minimal at pH 6.0 and the structural integrity of the zeolite was maintained, metal removal at this pH is predominantly by ion exchange rather than chemical precipitation. Fluctuations in both silicon and aluminium release from the zeolites suggest that partial dissolution may occur under mildly acidic conditions, an observation discussed elsewhere in the literature. Heavy metal removal decreased with increasing metal loading, with the zeolites exhibiting Significantly lower operating exchange capacities compared to the theoretical ones. Exchange capacities varied between 1.3-4.9 meq/g and 0.5-4.6 meq/g for CA 150 and CG180 respectively for the five metals studied. Throughout all of the experimental investigations, lead was removed preferentially (>99%) and nickel removal effiCiencies were the lowest «20%). The results from the mixed metal studies demonstrated that lead removal was the least affected by the presence of other heavy metals whereas cadmium, copper and zinc removal was suppressed in comparison to that from Single metal solutions. The presence of competing ions was not found to adversely affect lead removal by CA 150 and CG180, with copper and cadmium removal showing the most suppression in the presence of calcium, magnesium, potassium and sodium. Zinc uptake by both zeolites proved the most sensitive to the addition of hardness ions even under soft water conditions. The zeolites were also demonstrated to achieve up to 100% removal from real effluents, outperforming a natural zeolite, clinoptilolite. Overall, this research has demonstrated the considerable potential of these synthetic zeolites to selectively remove heavy metals from complex contaminated effluents, indicating their possible application as a tertiary technology for effluent treatment.

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In order to increase the current efficiency in copper electrowinning tankhouses, iron can be removed from the electrolyte using ion exchange. While this is a proven technology, very little data is available for the application of this technology to copper electrowinning electrolytes containing antimony and bismuth. The feasibility of utilizing iron ion exchange for the removal of iron from copper electrowinning electrolytes containing antimony and bismuth was studied in the laboratory. A picolylamine, a sulphonated diphosphonic, an aminophosphonic and three sulphonated monophosphonic resins were tested. The picolylamine resin was found to be completely impractical as it loaded high levels of copper. All the phosphonic resins tested loaded an appreciable amount of antimony, however, only the aminophosponic resin loaded an appreciable amount of bismuth. Tests to determine whether or not the sulphonated monophosphonic Purolite 5957 resin would continue to load antimony with time and, hence, reduce the resin's ability to remove iron gave inconclusive results. In the event that the resin's ability to remove iron is hampered due to antimony loading, testing has shown that the resin performance may be restored via a regeneration with a solution containing sulphuric acid and sodium chloride. A case study for the application of this technology to the CVRD Inco CRED plant has shown that, while iron removal by ion exchange is technically feasible, it will upset the plant's acid balance in electrolyte. Therefore, an acid removal process would need to be implemented in tandem with an iron ion exchange system. Additionally, preliminary calculations suggest that a system with a single ion exchange column may have difficulty removing sufficient iron for the CRED design conditions. Therefore, consideration should be given to the possibility of utilizing a two column system (one column loading, one column stripping).

No description available.

No description available.

In order to increase the current efficiency in copper electrowinning tankhouses, iron can be removed from the electrolyte using ion exchange. While this is a proven technology, very little data is available for the application of this technology to copper electrowinning electrolytes containing antimony and bismuth. The feasibility of utilizing iron ion exchange for the removal of iron from copper electrowinning electrolytes containing antimony and bismuth was studied in the laboratory. A picolylamine, a sulphonated diphosphonic, an aminophosphonic and three sulphonated monophosphonic resins were tested. The picolylamine resin was found to be completely impractical as it loaded high levels of copper. All the phosphonic resins tested loaded an appreciable amount of antimony, however, only the aminophosponic resin loaded an appreciable amount of bismuth. Tests to determine whether or not the sulphonated monophosphonic Purolite 5957 resin would continue to load antimony with time and, hence, reduce the resin's ability to remove iron gave inconclusive results. In the event that the resin's ability to remove iron is hampered due to antimony loading, testing has shown that the resin performance may be restored via a regeneration with a solution containing sulphuric acid and sodium chloride. A case study for the application of this technology to the CVRD Inco CRED plant has shown that, while iron removal by ion exchange is technically feasible, it will upset the plant's acid balance in electrolyte. Therefore, an acid removal process would need to be implemented in tandem with an iron ion exchange system. Additionally, preliminary calculations suggest that a system with a single ion exchange column may have difficulty removing sufficient iron for the CRED design conditions. Therefore, consideration should be given to the possibility of utilizing a two column system (one column loading, one column stripping).