Seminar: Developing a Method for the Bulk Preparation of Highly Pure Calcium Compounds

Student: Diana Ha

Supervisor: Dr. Eric Da Silva

Abstract

Bulk purification and synthesis of highly pure calcium compounds for phantom and bone dosimeter preparations is extraordinarily challenging and has been known to be as such for the better part of a century. This is due to strontium and calcium being in the same periodic group and behaving very much alike chemically and biologically. Various methods have been proposed for the separation of calcium from strontium (and other elements) and include: 1) precipitation of calcium in bulk through chelation with 8- hydroxyquiniline; 2) precipitation of strontium (and other group II element) contamination in fuming nitric acid; 3) ion exchange of strontium from solution using a crown ether-based resin; and 4) hydroxide precipitation of calcium from solution in the presence of very high excess calcium concentrations. These methods are, however time consuming, require large quantities of hazardous reagents, are extremely expensive and wasteful, and are not suitable for the separation of calcium compounds in bulk (kilogram quantities) needed for most applications. In this work, we aim to design and assess a novel method for the preparation of large quantities (kilograms) of highly pure calcium compounds using a continuous reactor system. In this proposed design, a cheap source of calcium as carbonate (i.e., oyster shells) is used to prepare dilute Ca2+ solutions that are treated with hydroxide and the resultant pure calcium hydroxide is removed through continuous centrifugation with the remaining calcium-rich supernatant continuously reused thus extracting as much calcium as possible.