Lignosulfonates as Surfactants to Stabilize Elemental Sulfur Dispersions

The effect of lignosulfonates (LS) of varying molecular weight compositions (\( \overline{Mw} \) 9–50 kDa) on the behavior and aggregation stability of aqueous dispersions of elemental sulfur (S°) was studied under conditions simulating hydrothermal leaching of sulfide ores. A detailed study was conducted of the physicochemical properties of aqueous LS solutions (CLS 0.02–1.28 g/dm³) obtained from various sources (Krasnokamsk, Solikamsk and Norwegian Pulp and Paper Mills). The composition, molecular weight, and concentration of LS were found to significantly affect their specific electrical conductivity, pH, intrinsic viscosity, and surface activity. It has been shown that the introduction of LS during the formation of sulfur sols promotes their stabilization through electrostatic and steric mechanisms. Optimum dispersion stability (293 K, pH 4.5–5.5) was observed at moderate LS concentrations (0.02–0.32 g/dm³), when a stable adsorption layer forms on the surface of sulfur particles. High-molecular-weight LS samples provideed more effective spatial stabilization of sulfur particles. It has been established that increasing temperature (293–333 K) and changing pH (1–7) significantly affect the aggregative stability of systems, namely: with increasing temperature, sol stability decreases, and, the stabilizing effect of different LS types is reversed with changing pH. The obtained results highlight the potential of using naturally occurring polymeric dispersants to control the aggregation stability of sulfur-containing heterophase systems and can be applied to the design of stable colloidal systems in chemical engineering and hydrometallurgy.