Speciation of Al and Cd in Aqueous Solutions: Association Quotients of Oxalate and Malonate Complexes

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9317075 Kettler Despite the importance of Al and Cd chemistry to the geological sciences there are few measurements of the association quotients of their oxalate and malonate complexes. The investigator will measure the association quotients of Al-oxalate, Al-malonate, Cd-oxalate, and Cd-malonate complexes in solutions with ionic strengths ranging from 0.1 to 5m and at temperatures ranging from 0-125 C. These measurements will be made using potentiometric methods by titrating oxalate or malonate solutions into aqueous solutions of Cd or Al. Na-trifluoromethanesulfonate will be used as a non-complexing supporting electrolyte. The data obtained during these titrations will be regressed and equations relating the relevant association constants to temperature and ionic strength will be derived. Al is the third most abundant element in the earth's crust. Problems related to the dissolution of silicate minerals and the environmental and public health effects of acid rain are fundamentally problems of al speciation in aqueous solutions. Although Cd is a trace metal, its toxicity and its ubiquity in landfill leachates, sewage sludge, sulfide ore deposits, and fossil shells give it great environmental and geologic importance. Oxalate and malonate are difunctional carboxylic acid anions that form strong complexes with metals. These acid anions are ubiquitous in soils and the by-product waters produced during enhanced oil recovery and synthetic fuels operations. They may also be present in large amounts in some sedimentary basin brines. This work should be of interest to a wide variety of researchers in the geological and environmental sciences.