Selenium Disulfide from Sustainable Resources: An Example of "Redneck" Chemistry with a Pinch of Salt

Selenium disulfide (often referred to as SeS₂) encompasses a family of mixed selenium-sulfide eight-membered rings, traditionally used as an anti-dandruff agent in shampoos. SeS₂ can be produced by reacting hydrogen sulfide (H₂S) with selenite (SeO₃^2-) under acidic conditions. This chemistry is also possible with natural spring waters that are rich in H₂S, thus providing an avenue for the more sustainable, green production of high-quality SeS₂ particles from an abundant natural source. The orange material obtained this way consists of small globules with a diameter in the range of 1.1 to 1.2 µm composed of various Se_xS_8-x chalcogen rings. It shows the usual composition and characteristics of a Se-S interchalcogen compound in EDX and Raman spectroscopy. Since the mineral water from Bad Nenndorf is also rich in salts, the leftover brine has been evaporated to yield a selenium-enriched salt mixture similar to table salt. As the water from Bad Nenndorf-in comparison to other bodies of water around the world-is still rather modest in terms of its H₂S content, especially when compared with volcanic waters, this approach may be refined further to become economically and ecologically viable, especially as a regional business model for small and medium-sized enterprises.