Fundamental studies on oxidizing roasting of the "bioselenium"

A method has been developed for the recovery and recycling of selenium (Se) from Se-containing wastewater using the Se reducing bacterium, Pseudomonas stutzeri NT-I. The treatment of Se-containing wastewater with strain NT-I produced the bioselenium, which was composed mainly of organic matter and 11-14 mass% of Se. Specifically, the recovery of Se from the bioselenium by oxidizing roasting followed by wet reduction was studied. After thermodynamic calculations were performed to estimate the oxidizing behavior during roasting, experiments were conducted on the bioselenium for various roasting conditions. Selenium in the bioselenium was recovered in the form of solid SeO₂ with a purity of 99% (metal basis) and a maximum yield of 97 mass% after roasting at 700 °C. Wet reduction of SeO₂ to metallic Se was achieved with a purity of 99% (metal basis).