A paper on their work was published 1 June in the ACS journal Environmental Science & Technology.

A number of technologies have been employed for the capture and disposal of SO₂ from a flue gas stream. Those processes consist mainly of an absorption step and an oxidation step. A typical example is the use of a dilute aqueous sodium hydroxide (NaOH) solution to absorb SO₂ from flue gas, forming an aqueous Na₂SO₃ solution. Before disposal the solution must be purged with air to oxidize Na₂SO₃ into Na₂SO₄. Alternatively, oxidation of an aqueous Na₂SO₃ solution can be carried out for the production of high purity clean hydrogen fuel.

—Huang et al.

Results from using the ultraviolet (UV) photolytic process for production of hydrogen from aqueous Na₂SO₃ solutions showed that the quantum efficiency of hydrogen production can reach 14.4% under illumination from a low pressure mercury lamp.

The mechanism occurs via two competing reaction pathways that involve oxidation of SO₃^2- to SO₄^2- directly and through the dithionate (S₂O₆^2-) ion intermediate. The first route becomes dominant once a photostationary state for S₂O₆^2- is established. The initial pH of Na₂SO₃ solution plays an important role in determining both the hydrogen production rate and the final products of the photolytic oxidation...The highest hydrogen production rate occurs when the initial solution pH is 7.55.

—Huang et al.

Resources

• Cunping Huang, Clovis A. Linkous, Olawale Adebiyi and Ali T-Raissi (2010) Hydrogen Production via Photolytic Oxidation of Aqueous Sodium Sulfite Solutions. Environ. Sci. Technol., Article ASAP doi: 10.1021/es903766w