Reducing Occupational Risks and Greening a Traditional Sample Treatment of Industrial Fluorine Containing-materials by Application of Design of Experiments

Abstract

Despite the new technological advances, some traditional methodologies concerning wet chemistry must be used as reference methods when dealing with complex matrices or when no certified reference materials are available. In this context, Willard-Winter distillation is nowadays still employed as a reference technique for fluorine extraction in day-to-day analysis. However, this procedure requires strong acid mixtures, increasing waste treatment procedures/costs and the potential risks associated with their use. The present work reports the application of design of experiments (DoE) to improve the analytical methodology of reference for fluorine extraction through Willard-Winter distillation by substituting perchloric acid. Variables affecting the sample treatment of fluorine-containing compounds, anhydrite, fluorspar, cryolite and aluminium fluoride were studied to ensure complete dissolution and total extraction of fluorine. Volume of sulfuric acid, sample amount, volume of distilled solution including volume of melt and amount of NaOH for fluorspar and the extended fluoroaluminate compounds were the variables studied. Predicted experimental conditions were performed and validated in the target compound, obtaining fluorine concentrations comparable to those obtained by the reference methodology. By this modified approach, not only harmful effect of manipulation of perchloric acid is reduced but also costs of the analytical procedure do so. Besides, a greener performance is achieved by avoiding chlorinated species, reducing waste dangerousness and its treatment.