No abstract

A model of metal extraction based on pH isotherms was generated and applied to a cobalt solvent extraction (SX) circuit. Cyanex 272 (bis-(2,4,4-trimethylpentyl) phosphinic acid) was used as the organic extractant due to its selectivity for cobalt over nickel in the extraction process. Experiments were conducted for cobalt, nickel and magnesium extraction, with the latter two representing impurity elements in Co SX. The methods for determining metal extraction incorporated the effects of temperature, solution composition and pH on the equilibrium constant k, and hence on the overall extraction extent. This information was applied to a multi-stage mixer-settler model consisting of integrated extraction units. The initial mathematical model for cobalt, which was built in Matlab can be further developed to include the impurity elements and incorporate the scrubbing and stripping units. Future work will focus on using the model for process optimisation.

With the publication ofThe Tale of Mr. Tod(1912), Beatrix Potter articulated her impatience with “goody goody books about nice people” (Linder 210) and declared her intention “to make a story about two disagreeable people” (Potter,Tale of Mr. Tod7). Yet although the subjects of the story, Tommy Brock and Mr. Tod, might be the most viciously disagreeable protagonists in Potter's children's stories, her readers were already acquainted with characters who challenged the boundaries of propriety, graciousness, and respectful deference to authority. Throughout her oeuvre, many such characters are not entirely punished for their trespasses, a pattern which often surprises modern readers who blithely assume that the daintily-illustrated books about woodland critters and barnyard creatures affirm conservative Edwardian conventions of behavior and standards of decorum.