Investigation of selenium recovery on oxidizing roasting of "Bio-Selenium"

We have developed a method for recycling selenium from Se-containing wastewater using the selenium-oxyanion-reducing aerobic bacterium Pseudomonas stutzeri NT-1. The treatment of Se-containing wastewater with the NT-I strain provided bio-selenium, which is mainly composed of organic matter and 11-14 mass% of Se. In the present study, we investigated the recovery of Se from bio-selenium by oxidizing roasting and chemical reduction. After thermodynamic calculations were performed to estimate the oxidation behavior during the roasting process, roasting experiments were conducted on bio-selenium under varying roasting conditions. The selenium in bio-selenium was recovered in the form of solid SeO₂ with a purity of 99% in a maximum yield of 97% after roasting at 700°C. Furthermore, the chemical reduction of SeO₂ to Se was carried out, and metallic Se with a purity of 99% (based on metal) was obtained.