The Rapid Measurement and Monitoring of Selenite Concentration by Turbidimetry Following its Conversion to Colloidal State by Sulfite Reduction and Acidification

Abstract

In this study, the rapid reduction of selenious ions using sulfite species at negative pH is described and its use as analytical technique in combination with turbidimetry is proposed. It was found that Se(IV) can be reduced quantitatively at ambient temperature via a combination of sulfite reduction and ultra-acidification with sulfuric acid to a colloidal form that can be determined using turbidimetry. The developed analytical procedure can accurately and reproducibly measure Se(IV) concentrations down to 1 mg/L. For concentrations above 20 mg/L dilution is necessary. Common transition metal ions such as iron(II), copper(II), or zinc(II) up to 10 g/L concentration were found not to have noticeable influence on the precision of the method. Finally the developed technique was shown to be equally effective with real Se(IV)-bearing industrial solutions generated in a zinc concentrate roasting operation, hence making the method particularly useful as a fast and simple process monitoring and control tool.