Aqueous Sulfur Sols

Abstract

Sulfur sols are colloidal solutions of elemental sulfur or of sulfur-rich compounds. The particles in these solutions have diameters of 0.1–1.0 μm and consist either of S₈ molecules (hydrophobic sulfur sols) or of chain-like sulfur compounds with hydrophilic end groups like sulfonate or functionalized organic groups (hydrophilic sulfur sols) . Both types of sols are stabilized by the negative charge of the particles which results in mutual repulsion. Therefore, cations and especially multivalent cations are able to precipitate the sol particles. While hydrophilic sulfur sols can be prepared with sulfur concentrations of up to 600 g l⁻¹, hydrophobic sols are much more dilute (<0.1 g l⁻¹). Sols of these types occur both in industrial desulfurization plants where sulfide is oxidized to elemental sulfur as well as in cultures of certain oxidizing sulfur bacteria .