Liquid polyoxometalate-based catalysts lead to highly efficient desulfurization of waste water

A general, efficient method was developed to selective oxidation of S²⁻ in waste water into sulfur. Sulfur was oxidized from dissolved H₂S using liquid polyoxometalate-based catalysts (LPOMCs). Four room temperature LPOMCs were fabricated from heteropolyanion (SiMo₁₂O₄₀⁴⁻, S₂W₁₈O₆₂⁴⁻, S₂Mo₁₈O₆₂⁴⁻) and cheap organic cations (C₃₃H₃₂N₃⁺, C₃₂H₆₈N⁺). The desulfurization rate of (C₃₂H₆₈N)₄α-S₂Mo₁₈O₆₂ in acetonitrile–water (v:v = 1:1) medium was up to 98.4% after 90 min, 77.3 wt% of LPOMC was recovered and 90.3% desulfurization rate was obtained for the 6th reused of regeneration (C₃₃H₃₂N₃)₄α-SiMo₁₂O₄₀. The desulfurization process can easily be accessed by stirring and lighting while the recycled LPOMC was handled by H₂O₂ regeneration step.