Biogenic Synthesis of ZnS Nanoparticles

ZnS nanoparticles were synthesized by delivering a H₂S gas stream produced by a sulfidogenic bioreactor to an aqueous solution of 5 mM ZnSO₄ (Merck Millipore, Burlington, MA, USA). A 2.3 L working volume sulfidogenic bioreactor (Fermac 200; Electrolab Biotech, Tewkesbury, United Kingdom) was operated as an upflow biofilm continuous sulfidogenic bioreactor at pH 7.0, as described elsewhere [24 (link)], housing sulfidogenic bacteria dominated by the SRB genera of Desulfomicrobium, Desulfobacterium and Desulfovibrio that were obtained from different ponds in Salar de Huasco, Chile [25 (link)] having blackened sediments. Enrichments were grown on porous beads of recycled glass of 1–2 mm diameter. The bioreactor was fed 5 mM lactate, 1000 ppm sulfate, autotrophic basal salt (ABS; [26 (link)]), trace elements and yeast extract at pH of 6.5. The H₂S gas was removed by a stream of oxygen-free nitrogen (OFN) at a flux to 100 mL·min⁻¹ and transferred to an off-line vessel containing 50 mL of an aqueous solution of ZnSO₄. After the zinc solution was sparged with gas for 60 min, the precipitate formed (ZnS nanoparticles) was collected from the solution, dried at 30 °C for 24 h and stored for further use.