Abstract
A new, faster and more reliable analytical methodology for S(IV) species analysis at low pH solutions by bichromatometry is proposed. For decades the state of the art methodology has been iodometry that is still well justified method for neutral solutions, thus at low pH media possess various side reactions increasing inaccuracy. In contrast, the new methodology has no side reactions at low pH media, requires only one titration step and provides a clear color change if S(IV) species are present in the solution. The method is validated using model solutions with known concentrations and applied to analyses of gaseous SO2 from purged solution in low pH media samples. The results indicate that bichromatometry can accurately analyze SO2 from liquid samples having pH even below 0 relevant to metallurgical industrial processes.
Highlights
Sulfur dioxide (SO2) is a compound present in various processes in industry, in metallurgical processes with sulfuric minerals
This paper aims at accurate low and high concentrated S(IV) analysis from acidic solutions relevant to metallurgical sulfuric acid and SO2 depolarized electrolyzer (SDE) processes and the new method is compared with currently used state-of-the-art method, iodometry, evaluating the strengths and weaknesses of each method
These results imply that when S(IV) species come from Na2SO3 salt the deviation is smaller than what reported with gaseous SO2 in water
Summary
Sulfur dioxide (SO2) is a compound present in various processes in industry, in metallurgical processes with sulfuric minerals. At these industries, the detailed detection of SO2 from liquid media is vital for process control and for creating thermodynamical equilibrium data for SO2 –H2O –H2SO4 systems. SO2 has been widely used as a preservative agent at food industry, where operation is at milder pH conditions than in process industry. S(IV) species has been analyzed from liquid media with a 2-step method by iodometry [1] where S(IV) species are oxidized by iodine with Bunsen reaction: SO23À þI2þH2O $ SO24À þ2IÀ þ2Hþ ð1Þ.
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